Anaesthesia: Active Threads

Speed of Spinal Vs General Anaesthesia

vijayendrakc — Mon, 17 Jun 2013 07:33:20 GMT

We wish to congratulate Kathirgamanathan et al. on their well conducted study of the time taken for surgical readiness in category-1 caesarean section [1]. While we do not disagree with their finding that spinal anaesthesia is slower than general anaesthesia, we believe that in actual category-1 caesarean section the median (range) time of 8:52 (3:31 – 17:22) minutes for spinal anaesthesia may be much greater.

The authors have studied the performance of a group who were probably experts in obstetric anaesthesia practice and the study participants may not have been representative of resident obstetric anaesthesia cover, at least not in the United Kingdom, which typically relies on basic and intermediate level trainees who are competent, but neither proficient nor expert [2 - 4]. Attendance at a category-1 caesarean section is acutely stressful, and typically occurs out-of-hours when experts are not immediately available. The negative impact of acute stress, distraction and fatigue on cognitive capacity and psychomotor performance are known [5 - 7], and we believe that this further widens the performance gap between the study participants and actual practice. With this is mind, we feel that the authors’ pessimistic estimation of total time for spinal anaesthesia (17 min 22s) is perhaps closer to the mark.

Although the total spinal time reported in this manuscript may appear to strengthen the case in favour of spinal anaesthesia for category-1 caesarean section we advise caution in its interpretation. As the authors rightly point out, category-1 caesarean section is a process with a number of predictable, well recognised steps to achieving that end. We believe that improvements in the decision-delivery time may be more reliably and safely achieved by focussing on interventions to modify systems within the maternity suite and to improve non-technical skills within the multi-disciplinary team.

V. Chikkabbaiah

R. McCahon

Nottingham University Hospitals NHS Trust

Nottingham, U.K.

Email: vijayendra.kc@gmail.com

No external funding and no competing interests declared.

References.

Kathirgamanathan A, Douglas MJ, Tyler J, et al. Speed of spinal vs general anaesthesia for category-1 caesarean section: a simulation and clinical observation-based study. Anaesthesia 2013; 68: 753 – 59.
Hawthorne L, Wilson R, Lyons G, Dresner M. Failed intubation revisited: 17-yr experience in a teaching maternity unit. British Journal of Anaesthesia1996; 76: 680–4.
Rahman K, Jenkins JG. Failed tracheal intubation in obstetrics: no more frequent but still managed badly. Anaesthesia 2005; 60: 168 – 71.
McCahon RA, Catling S. Time required for surgical readiness in emergency caesarean section: spinal compared with general anaesthesia. International Journal of Obstetric Anaesthesia 2003; 12: 178 – 82.
Byrne AJ, Oliver M, Bodger O, et al. Novel method of measuring the mental workload of anaesthetists during clinical practice. British Journal of Anaesthesia 2010; 105: 767 – 71.
Stiegler MP, Neelankavil JP, Canales C, Dhillon A. Cognitive errors detected in anaesthesiology: a literature review and pilot study. British Journa of Anaesthesia 2012; 108: 229 – 35.
Kahol K, Leyba MJ, Deka M, et al. Effect of fatigue on psychomotor and cognitive skills. The American Journal of Surgery 2008; 195: 195 – 204

We need smarter simulators

Mahdi Najafi — Sat, 15 Jun 2013 10:11:41 GMT

We read with interest the recent article by Lee et al [1], who used four training manikins to compare forces generated during intubation with the GlideScope^® and Macintosh laryngoscopes. Their results demonstrate that average forces generated by 16 practitioners during intubation with the Macintosh laryngoscope had a wider range compared with the GlideScope. The authors compared forces generated in this manikin study with forces generated in humans published as an earlier study [2]. The range of the forces generated in humans was wider than that in manikins using both types of laryngoscopes. Peak forces, however, were not compared.

An increase in force applied during laryngoscopy by higher Mallampati class has been reported before by Lee et al. [3] and we would expect to see a significant rise in the peak force when we use cricoid pressure. Although the forces exerted by different practitioners vary, especially with the Macintosh laryngoscope, current and previous studies indicate that average and peak exerted forces are lower during the intubation of manikins compared with humans [1,2]. Furthermore, there is a larger variability in the force applied by practitioners in humans in comparison with manikins, which is supported by previous studies [2,4,5].

In our opinion, the manikins which we currently utilize for training and research probably need modifications to better reflect the variations of normal and difficult airway anatomy. Findings about forces applied on teeth and oral soft tissue may serve as helpful input data in such smarter airway simulators and manikins.

M. Najafi,

Tehran University of Medical Sciences

Tehran, Iran

M. Najafi-Koopaie

Shahed University

Tehran, Iran.

Email: najafik@sina.tums.ac.ir

No external funding and no competing interests declared.

References.

1. Lee C, Russell T, Firat M. Cooper RM. Forces generated by Macintosh and GlideScope^® laryngoscopes in four airway-training manikins. Anaesthesia 2013; 68: 492–6.

2. Russell T, Khan S, Elman J, Katznelson R, Cooper RM. Measurement of forces applied during Macintosh direct laryngoscopy compared with GlideScope^®
videolaryngoscopy. Anaesthesia 2012; 67: 626–31.

3. Lee RA, Van Zundert AA, Maassen RL et al. Forces applied to the maxillary incisors during video-assisted intubation. Anesthesia and Analgesia 2009; 108: 187–91.

4. Russell T, Lee C, Firat M, Cooper R. A comparison of the forces applied to a manikin during laryngoscopy with the GlideScope^® and Macintosh laryngoscopes. Anaesthesia and Intensive Care 2011; 39: 1098–1102.

5. Carassiti M, Zanzonico R, Cecchini S, Silvestri S, Cataldo R, Agro FE. Force and pressure distribution using Macintosh and GlideScope laryngoscopes in normal and difficult airways: a manikin study. British Journal of Anaesthesia 2012; 108: 146–51.

Extubation over a bougie in difficult airways: are we missing a trick?

tanyasmith — Fri, 14 Jun 2013 21:12:15 GMT

Following publication of the DAS extubation guidelines [1], we performed an audit to evaluate extubation over a standard bougie for patients undergoing maxillofacial and ENT procedures. Although the use of Airway Exchange Catheters (AEC) to maintain airway access post extubation has been described [2], the use of simple bougies has not. Bougies may confer important advantages over AEC in that they are smaller in diameter (and are therefore potentially better tolerated), cheaper and readily available. Also, anaesthetists are familiar with standard bougies and feel comfortable with their use.

In our audit of 18 patients, a standard bougie (Frova Intubating Introducer; Cook® Medical, Bloomington, USA) was inserted immediately prior to extubation. In order to minimise the risk of trauma associated with endobronchial placement, the centimetre markings on the bougie were used to ensure that insertion was no more than 1-2cm further than the tip of the endotracheal tube. The bougie was then secured to the face of the patient.

Ease of extubation over the bougie and patient tolerance of the bougie were evaluated by the anaesthetist (scored out of 10). Extubation over the bougie was considered easy in the majority of cases (median score 10/10 [IQR 9 to 10]) and the use of a bougie was very well tolerated by patients during emergence (median score 10/10 [IQR 7 to 10]). The bougies remained in situ for a median (IQR) time of 9 (5-12) min and one patient tolerated a bougie overnight in level 2 care. In 14 of 18 patients, the bougie was easily removed once the airway was deemed to be secure. The bougie was not tolerated in 2 patients and became dislodged in the remaining 2 patients. In the one case that needed re-intubation, this was successfully and easily performed over the bougie.

Although further studies are needed, our findings suggest that the use of a bougie to maintain airway access in patients waking from head and neck surgery is feasible and surprisingly well tolerated. We believe that this simple manoeuvre should be considered more often in routine anaesthetic practice.

T. Smith

D. Vaughan

Northwick Park Hospital

Harrow, U.K.

Email: tanyasmith@doctors.org.uk

No external funding and no competing interests declared.

References.

1. Popat M, Mitchell V, Dravid R, Patel A, Swampillai C, Higgs A. Difficult Airway Society Guidelines for the management of tracheal extubation. Anaesthesia 2012; 67: 318-340.

2. Mort TC. Continuous airway access for the difficult extubation: the efficacy of the airway exchange catheter. Anesthesia and Analgesia 2007; 105:1357-62.

Inadvertent Perioperative Hypothermia

johnaski — Sun, 09 Jun 2013 17:02:59 GMT

Karalapillai et al are to be congratulated on highlighting again the subject of inadvertent perioperative hypothermia and its effect on perioperative morbidity [1]. I am concerned that the conclusion, as it stands, may lead some clinicians to think that preventing postoperative hypothermia is somehow of less importance than the NICE guidelines of 2008 implied [2].

It should be noted by readers that some morbidity from hypothermia is ‘masked’ by anaesthesia. For example it is only after emergence that patients who are hypothermic are found to have elevated catecholamine levels and an increased potential for morbid cardiac events [3,4]. It would be interesting to know how many of the patients had continuing sedation whist they were hypothermic since this might have protected them from some of the side effects.

The results may also be a reflection of the excellent care that hypothermic patients received in the ICU environment and the ability to rapidly address any complications of hypothermia such as coagulopathy or arrhythmias as well as timely treatment of sepsis.

Karalapillai’s paper shows that postoperative hypothermia is common (46%). Patients with postoperative hypothermia may be under-warmed post operatively and/or sent to a ward with a lower nursing and medical staffing ratio, with less invasive haemodynamic monitoring and fewer investigations. It is, perhaps, these non-ICU patients who are at greater risk of complications secondary to their postoperative hypothermia.

J. Andrzejowski

Sheffield Teaching Hospitals NHS Trust

Sheffield, U.K.

Email: johnirra@gmail.com

No external funding and no competing interests declared.

References.

1. Karalapillai D, Story D, Hart G et al. Postoperative hypothermia and patient outcomes after major elective non-cardiac surgery. Anaesthesia 2013; 6: 605-11.

2. Clinical Practice Guideline. The management of inadvertent perioperative hypothermia in adults. National Collaborating Centre for Nursing and Supportive Care commissioned by National Institute for Health and Clinical Excellence (NICE): April 2008. Available from http://www.nice.org.uk/nicemedia/pdf/CG65Guidance.pdf.

3. Frank SM, Higgins MS, Breslow MJ, et al. The Catecholamine, Cortisol, and Hemodynamic Responses to Mild Perioperative Hypothermia: A Randomized Clinical Trial. Anesthesiology 1995; 82: 83–93

4. Frank SM, Fleisher LA, Breslow MJ, et al. Perioperative maintenance of normothermia reduces the incidence of morbid cardiac events. A randomized clinical trial. Journal of the American Medical Association 1997; 277: 1127-34

TAP block – or general anaesthesia?

Dr Stu White — Thu, 06 Jun 2013 14:00:38 GMT

Whilst I would agree that transversus abdominis plane (TAP) block as the sole method of anaesthesia for hip hemiarthroplasty is worthy of further research, I would suggest that Stuart-Smith’s patient effectively received general anaesthesia, augmented by TAP block [1].

Reliable regional anaesthesia for hip hemiarthroplasty requires not only that the sensory innervation of the peri-incisional skin, subcutaneous tissues and muscle is blocked, but also that of the hip joint and capsule, including branches of the sacral plexus which supply the posteroinferior aspects of the capsule [2]. Whilst Stuart-Smith is correct in noting that high-volume TAP blocks can extend caudad beyond L1 to involve the sacral plexus, the patient described was only assessed as having loss of pain and cold sensation as far caudad as L3, suggesting sensation may have been retained below this level.

Peri-operatively, the patient received a relatively high-dose infusion of propofol (6.4 mg.kg^-1.h^-1) for sedation during surgery, in addition to the 2 mg midazolam and 20 mg ketamine administered before TAP block insertion. Outwith the co-administration of midazolam and ketamine, the Summary of Product Characteristics for propofol states that general anaesthesia can usually be maintained using rates of infusion "in the region of 4-12 mg.kg^-1.h^-1" and that "maintenance of sedation … (for) most (adult) patients will require 1.5–4.5 mg.kg^-1.h^-1’, although in elderly patients ‘the rate of infusion … should … be reduced. Patients of ASA grades 3 and 4 will require further reductions in dose and dose rate" [3], hence my assertion that the patient effectively received general anaesthesia. As Sieber et al. have noted, general anaesthesia occurs frequently in elderly patients during propofol-based sedation [4].

Furthermore, anaesthesia is an important element of the prehabilitative continuum that aims to return hip fracture patients seamlessly to their pre-fracture functional status. Compared with light sedation (1.9 mg.kg^-1.h^-1) in elderly patients undergoing hip fracture under spinal anaesthesia, heavy sedation (6.6 mg.kg^-1.h^-1) increases the risk of postoperative delirium, which in turn is associated with poor functional recovery after surgery [5].

Finally, I do not agree with Stuart-Smith’s justification for avoiding spinal anaesthesia in favour of TAP block in the first instance, namely that the former ‘might result in dangerous levels of hypotension’. Even given the procedural difficulties assessing the patient’s left ventricular function echocardiographically, the administration of low-dose, unilateral intrathecal anaesthesia (<1.5 ml hyperbaric bupivacaine 0.5%) is associated with only small (< 20%) mean reductions in systolic blood pressure [6], and may have reduced left ventricular work by reducing ventricular preload through arteriolar vasodilation. The pre-induction insertion of a radial arterial line would have facilitated beat-to-beat diagnosis of hypotension, enabling early vasopressor intervention.

Use of TAP blockade during the repair of hip fractures is very intriguing, and I would encourage Stuart-Smith to conduct further research formally assessing the reliability of motor and sensory blockade of the hip together with bispectral index-guided propofol sedation, in order to assess the utility of this method as an alternative to intrathecal anaesthesia for frail, elderly patients with hip fracture.

S. White

Royal Sussex County Hospital

Brighton, UK

Email: stuart.white@bsuht.nhs.uk

Dr. White sat on the Working Party for the AAGBI Management of Proximal Femoral Fracture guidelines, and is an Editor of Anaesthesia. No other funding or conflict of interests declared.

References

1. Stuart-Smith K. Hemiarthroplasty performed under transversus abdominis plane block in a patient with severe cardiorespiratory disease. Anaesthesia 2013; 68: 417-20.

2. Maxwell L, White SM. Anaesthetic management of patients with hip fractures: an update. Continuing Education in Anaesthesia, Critical Care and Pain 2013; 13: doi:10.1093/bjaceaccp/mkt006

3. Electronic Medicines Compendium. Summary of Product Characteristics for propofol. http://www.medicines.org.uk/emc/medicine/2275/SPC (accessed 19/04/2013).

4. Sieber FE, Gottshalk A, Zakriya KJ, Mears SC, Lee H. General anesthesia occurs frequently in elderly patients during propofol-based sedation and spinal anesthesia. Journal of Clinical Anesthesia 2010; 22: 179-83.

5. Sieber FE, Zakriya KJ, Gottschalk A, et al. Sedation depth during spinal anesthesia and the development of postoperative delirium in elderly patients undergoing hip fracture repair. Mayo Clinic Proceedings 2010; 85: 18-26.

6. Wood R, White SM. Anaesthesia for 1131 patients undergoing proximal femoral fracture repair: effects on blood pressure, fluid administration and perioperative anaemia. Anaesthesia 2011; 66: 1017-22.

Magnesium for chronic back pain with a neuropathic component

gas324 — Wed, 05 Jun 2013 16:50:57 GMT

I congratulate Yousef and Al-deeb on an interesting article related to a new treatment for chronic back pain with a neuropathic component [1]. This is a common and debilitating condition and their research may prove a cost effective and significant step forward.

I wondered whether the authors measured serum magesium concentrations in any patients, although the fact that no patients had side effects attributable to significant magnesium overdose is reassuring. Also, why did the authors choose such an onerous intravenous dosing schedule? Onerous, that is, to the patients and the administering staff so that, although they have shown magnesium to be useful, the applicability of their work is surely limited by the administration schedule.

P. Fernandes

Email: dr_fernandes@hotmail.com

No external funding and no competing interests declared.

Reference.

1. Yousef A, Al-deeb, A. A double-blinded randomised controlled study of the value of sequential intravenous and oral magnesium therapy in patients with chronic low back pain with a neuropathic component. Anaesthesia 2013; 68: 260-5.

RE: Epidural anaesthesia and analgesia for liver resection

leighkelliher — Tue, 04 Jun 2013 17:25:32 GMT

We were interested to read the comprehensive review by Tzimas et. al. [1] regarding epidural anaesthesia and analgesia for liver resection. The authors address the key issues concerning the use of epidural analgesia in this population of patients – efficacy, safety, perioperative fluid management and the overall effect on patient outcomes.

As a regional hepatobiliary centre our unit performs over 100 hepatic resections every year and we have been using thoracic epidural analgesia as a component of our standard perioperative care since 1996, with no significant epidural-related morbidity (haematoma, abscess, permanent neurological damage) to date and published outcome data from our unit is amongst the best in the UK [2].

On the subject of safety, it is well recognised that the majority of patients exhibit some degree of coagulopathy following liver resection [3] although the magnitude of the disturbance in clotting profiles varies. In a small study of our own patients we found that mean INR remained below 1.4 and platelet counts above 150 x 10⁹/L for up to 10 days postoperatively [4] however other authors have reported a more profound derangement. This phenomenon has given rise to concerns that the risk of epidural haematoma formation may be increased. However, as the authors indicate, the incidence of epidural haematoma is extremely low (1:150,000) [5] and there is no single reported case of epidural haematoma related to thoracic epidural following elective liver resection [3]. In a recent study of enhanced recovery (ER) for liver resection conducted at our unit [6] the trial protocol dictated that epidural catheters were removed on postoperative day (POD) two, provided INR ≤ 1.4. Only four patients (out of 91) failed the protocol, but all catheters were removed by POD six and there were no haematomas.

The range of reported failure rates for epidural analgesia is wide; indeed the authors quote one study where the failure rate was 38% [1]. In our institution we have a great deal of experience in the use of thoracic epidurals and we manage all of our postoperative liver resection patients in an HDU setting. Subsequently we have found epidural failure rates to be low (2.2% in our recently published study [6]) although we accept that this may not be universally achievable. The recent evidence emerging for alternatives to epidural analgesia, including the use of intrathecal morphine and wound catheters, is very interesting although these approaches are not without potential problems (e.g. the risk of late respiratory depression with intrathecal morphine) and more comprehensive studies are required.

Commonly, intravenous fluids are administered in response to the hypotension often seen in patients with on-going epidural analgesia. In many cases the hypotension seen is a result of a reduction in systemic vascular resistance, which requires treatment with a vasopressor, not fluids. The result is fluid overload. In our institution we have found that the incidence of this problem may be reduced by the use of trained and experienced staff, managing the patient in an HDU setting with the help of non-invasive cardiac output monitoring to guide therapy.

Finally we have recently published the results of a study on ER for liver resection performed at our unit [6] in which we found epidural analgesia was not a barrier to early mobilisation. Length of stay was reduced by four days (from 9 days previously), almost 90% of patients were mobilising with assistance up and down the ward by POD two and over 80% of patients in the ER group were independently mobile on POD three.

In summary we would suggest that a working, properly managed, epidural is safe for patients undergoing elective liver resection, offers excellent analgesia and is not a barrier to early mobilisation and enhanced recovery. However there remains significant variability between centres in terms of experience and success rates with epidurals and we accept the need to find alternative options.

L. Kelliher

C. Jones

M. Dickinson

M. Scott

N. Quiney

Royal Surrey County Hospital NHS Foundation Trust

Guildford, U.K.

Email: lkelliher@nhs.net

No external funding and no competing interests declared.

References.

1 Tzimas P, Prout J, Papadopoulos G, Mallett SV. Epidural anaesthesia and analgesia for liver resection. Anaesthesia 2013; 68: 628-35

2 Karanjia ND, Lordan JT, Fawcett WJ, Quiney N, Worthington TR. Survival and recurrence after neo-adjuvant chemotherapy and liver resection for colorectal metastases – a ten year study. European Journal of Surgical Oncology 2009; 35: 838-43

3 Stamenkovic DM, Jankovic ZB, Toogood TJ, Lodge JP, Bellamy MC. Epidural analgesia and liver resection: postoperative coagulation disorders and epidural catheter removal. Minerva Anestesiologica 2011; 77: 671-9

4 Patel A, Quiney N, Fawcett W. Perioperative coagulation changes following hepatic resection surgery and consequent thoracic epidural risk. European Journal of Anesthesiology 2006; 23: 88A-335

5 Cook TM, Counsell D, Wildsmith JA. Major complications of central neuraxial block: report on the Third National Audit Project of the Royal College of Anaesthetists. British Journal of Anaesthesia 2009; 102: 179-90.

6 Jones C, Kelliher L, Dickinson M, et al. Randomized clinical trial on enhanced recovery versus standard care following open liver resection. British Journal of Surgery DOI: 10.1002/bjs.9165

Colour Coding of Drug Packaging

jwatts — Mon, 03 Jun 2013 13:37:02 GMT

I read the letter regarding the lack of colour coding of drug ampoules with interest [1].

Whilst manufacturers are correct in stating that the proper checking of the ampoule irrespective of the packaging is the most important factor in preventing errors in drug administration, there is little justification in the persistent failure in adopting a system of international colour coding of ampoules and packaging reflecting that already adopted for syringe labels.

In my theatre drug cupboards and fridge this morning, I found the following: orange packets containing glycopyrrolate; both suxamethonium and tramadol in green boxes ; purple boxes containing either suxamethonium, atracurium or midazolam; blue boxes containing glycopyrrolate/neostigmine and cyclizine; rocuronium in a brown box; furosemide in beige packaging; and a range of vasopressor drugs in boxes with a variety of prominant packaging colours, including white, blue and purple.

The NPSA published a report which showed that at least 1 anaesthetic fatality, and three serious incidents, resulted from the administration of incorrect medication [2]. Glavin [3] classified most drug administration errors as slips and lapses, and specifically identified similarities in labelling and packaging as a possible causative factor.

Whilst individuals do indeed have a responsibility to optimise practise and prevent such mistakes, it is surely reasonable to expect manufacturers to maximise their contribution to the reduction in human error

J. Watts

East Lancashire Trust

Burnley, U.K.

Email: james.watts@elht.nhs.uk

No external funding and no competing interests declared.

References.

1. van Hamel C, Sant P. Colour-coding of drug packaging. Anaesthesia 2013; 68: 649.

2. NPSA 2009 Safety in Doses: Improving the use of medicines in the NHS http://www.nrls.npsa.nhs.uk/resources/?entryid45=61625

3. Glavin RJ. Drug errors: consequences, mechanisms, and avoidance British Journal of Anaesthesia 2010; 105: 76-82.

Residual anaesthesia drugs – silent threat, visible solutions

Kieran Oglesby — Sat, 01 Jun 2013 14:51:59 GMT

We read Bowman et al’s editorial [1] regarding retention of anaesthetic drugs in intravenous lines with great interest and commend the standards of care proposed.

We have taken an interest in this topic ourselves due to a recent incident. A patient in our hospital underwent rapid sequence induction using an indwelling intravenous cannula sited on the ward and after induction a new cannula was inserted for use during surgery. Several hours later, the original cannula and connector (total dead space of 0.7ml) was flushed prior to antibiotic administration on a surgical ward. The patient experienced a rapid loss of motor function, leading to respiratory arrest, presumably from inadvertent administration of retained suxamethonium. After approximately five minutes of bag-valve-mask ventilation, the patient recovered neuromuscular function and reported explicit awareness of events with no physical sequelae. Clinical psychology interviews were conducted and the patient’s overriding concern was that measures be taken within our hospital to prevent a recurrence. In our review of this incident we have become aware of the need to not only flush all intravenous cannulae but also to remove any unnecessary cannulae after anaesthesia. This reduces the risk of both administration of retained drugs and also of cannula- associated infections.

Before instigating a safety campaign, we conducted a local survey of practice using visible propofol as a surrogate for an unflushed cannula or connector. This was seen in 32% of cases. In 26% of cases, unnecessary connectors or cannulae remained in place after anaesthesia. Flushing of cannulae was not documented on the anaesthetic record or drug chart of any patient.

We have addressed the problem with a local protocol, post-anaesthesia handover documentation and regular repeat audit. A range of safety posters – designed to be intentionally eye-catching (Figures 1 and 2) have been placed in areas where anaesthesia is administered or where anaesthetists gather (Figure 3). These have been found to be particularly effective in maintaining awareness amongst anaesthetists and theatre staff. A subsequent re-survey has demonstrated that only 1.6% of patients had visible propofol in a cannula, no TIVA connectors were left attached to lines and both written documentation and verbal handover
to recovery staff has increased by 36%. Recovery nurses now routinely remove any unused cannulae.

As described in Bowman et al’s article, it is well recognised that the occurrence of critical incidents in general [2] and anaesthesia specifically, is underestimated due to under-reporting and misclassification [3]. The danger posed by retained anaesthetic drugs in cannulae has long been recognised as a problem [4]. Given this, and the potentially devastating sequelae, it would seem imprudent to view this issue as rare and not take firm action as an anaesthetic community. Analogous to the ‘Stop Before You Block’ campaign regarding wrong site or wrong side nerve blockade, the development of a highly-visible national patient safety initiative to help prevent the inadvertent administration of anaesthetic drugs would improve patient safety.

K.J. Oglesby

T.M. Cook

L. Jordan

Royal United Hospital,
Bath, UK

Email: oglesbyk@doctors.org.uk

No external funding and no competing interests declared.

The posters are published by permission of the Royal United Hospital Bath NHS Trust. Copies are available by contacting the author.

References.

1. Bowman S, Raghavan K, Walker IA. Residual anaesthesia drugs in intravenous lines – a silent threat? Anaesthesia 2013; 68: 557-61.

2. Sari AB, Sheldon TA, Cracknell A, Turnbull A. Sensitivity of routine system for reporting patient safety incidents in an NHS hospital: retrospective patient case note review. British Medical Journal 2007; 334: 79-82.

3. Cassidy CJ, Smith A, Arnot-Smith J. Critical incident reports concerning anaesthetic equipment: analysis of the UK National Reporting and Learning System (NRLS) data from 2006–2008. Anaesthesia 2011; 66: 879–88.

4. Fielden J, Cook TM, Day C. Retention of drugs in venous access port chamber. British Medical Journal 1996; 312: 1477.

5. Safe Anaesthesia Liaison Group. Wrong site blocks during surgery. Royal College of Anaesthetists 2010. http://www.rcoa.ac.uk/node/631 (accessed 30 May 2013).

Figure Captions

Figures 1 and 2 Awareness posters that are placed in clinical areas reminding anaesthetists and theatre staff of the need to either flush or remove intravenous cannulae

Figure 3 Awareness poster placed in areas where anaesthetists and theatre staff may gather in non-clinical areas, reinforcing the need to either flush or remove intravenous cannulae

Preservative-free bicarbonate for epidural top-up

sunihalder — Wed, 29 May 2013 21:59:51 GMT

Ferguson and Woodcock describe the increasing problem of drug shortages in anaesthesia [1]. Like other UK obstetric anaesthetic services, ours has had to deal with several shortages of drugs in recent years, though none have had the effect of the latest one.

In our unit, the current standard top-up solution for extending epidural analgesia for emergency caesarean section (emCS) for the last five years is a mixture of lidocaine 2% and bicarbonate 8.4% with adrenaline 1:200 000 [2]. This has led to a halving of our general anaesthesia conversion rate since its adoption (unpublished internal audit data).

Because of concerns over the risk of neurological damage and the potential neurotoxicity of preservatives [3], we have used preservative-free sodium bicarbonate (BP Minijet 10 ml, International Medication Systems (UK) Ltd, Dunstable, UK) and preservative-free lidocaine 2% (Antigen Pharmaceuticals, Tipperary, Ireland or Hameln Pharmaceuticals, Gloucester, UK). The adrenaline solution used (Martindale Pharmaceuticals, Romford, UK) does contain preservative but we maximise dilution by adding 0.1 ml to 20 ml local anaesthetic solution.

Production of preservative-free bicarbonate has suddenly ceased because the manufacturer is developing a new design of Minijet (personal communication). This has left us pondering our options when a parturient with an epidural catheter in situ presents for emCS:

(i) Use an alternative top-up solution such as: a) lidocaine 2% + adrenaline without bicarbonate, although the only head-to-head comparison of lidocaine with and without bicarbonate for emCS found that the onset time of anaesthesia was halved when bicarbonate was used [4]; b) levobupivacaine 0.5%, although we have found this solution markedly inferior to our preferred lidocaine/bicarbonate/adrenaline solution [2]; or c) ropivacaine 0.75%, although we have found this broadly equivalent to bupivacaine 0.5% [5] (and by extension, therefore, levobupivacaine).

(ii) Use preservative-containing bicarbonate from ampoules suitable for intravenous injection. (Currently commercially available formulations contain EDTA as an antioxidant/chelator which has been shown to cause neurological injury when given intrathecally [6]).

We are aware that the actual neurotoxicity of preservatives is uncertain, even given intrathecally [7], but remain concerned that even a small but very real risk may go unnoticed because the incidence of important neurological injury post-epidural is low. Further, by not using our preferred method of management are we vulnerable to claims of substandard care? And how should we address the issue of consent when faced with a parturient requiring emCS? Should we resort to preservative-containing bicarbonate but only in the most urgent of cases (and what should we tell these women – and those not deemed urgent enough)?

We wonder whether readers of Anaesthesia would consider our concerns unfounded or exaggerated, or whether they share them, and also what units where bicarbonate is/was routinely used are currently doing.

S. Halder

M. Butcher

S.M. Yentis

J. Allam

C. Cormack

M. Cox

D. Dob

J. Durbridge

B. Norman

E. Pickering

Chelsea and Westminster Hospital

London, UK

Email: sunihalder@icloud.com

SMY is Editor-in-Chief of Anaesthesia. No other external funding or competing interests declared.

References.

Ferguson K, Woodcock T. Ensuring a sustainable supply of drugs for anaesthesia and peri-operative care. Anaesthesia 2012; 67: 1313-6.
Allam J, Malhotra S, Hemingway C, Yentis SM. Epidural lidocaine-bicarbonate-adrenaline vs levobupivacaine for emergency Caesarean section: a randomised controlled trial. Anaesthesia 2008; 63: 243-9.
Rowlingson JC, Neal JM. Adjuvant and preservative toxicity. In: Neal JM, Rathmell JP, eds. Complications in Regional Anesthesia and Pain Medicine, 2nd Edn. Philadelphia: Lippincott Williams & Wilkins, 2013: 85-95.
Lam DT, Ngan Kee WD, Khaw KS. Extension of epidural blockade in labour for emergency Caesarean section using 2% lidocaine with epinephrine and fentanyl, with or without alkalinisation. Anaesthesia 2001; 56: 790-4.
Sanders RD, Mallory S, Lucas DN, Chan T, Yeo S, Yentis SM. Extending low-dose epidural analgesia for emergency Caesarean section using ropivacaine 0.75%. Anaesthesia 2004; 59: 988-92.
Wang BC, Li D, Hiller JM, et al. Lumbar subarachnoid ethylenediaminetetraacetate induces hindlimb tetanic contractions in rats: prevention by CaCl2 pretreatment—observation of spinal nerve root degeneration. Anesthesia and Analgesia 1992; 75: 895–9.
Hodgson PS, Neal JM, Pollock JE, Liu SS. The neurotoxicity of drugs given intrathecally (spinal). Anesthesia and Analgesia 1999; 88: 797-809.

Target BIS for anaesthetist?!

malcolmbroom — Fri, 24 May 2013 08:17:12 GMT

I enjoyed reading Dr.Russell's excellent article about bispectral index targets during intravenous anaesthesia [1], which was fascinating and thought provoking. However, one sentence in the Discussion particularly caught my attention:

"Not only do patients expect to be unconscious during general anaesthesia, but a survey of anaesthetists indicates that they too wish to be unconscious during general anaesthesia."

I wonder if an area for further study would be the ideal target BIS for the anaesthetist during cases (and the, presumably, opposing effects of caffeine and sudoku on this)?!

M. Broom

Email:malcolmbroom@doctors.org.uk

No external funding and no competing interests declared.

Reference.

Russell, I. F. The ability of bispectral index to detect intra-operative wakefulness during total intravenous anaesthesia compared with the isolated forearm technique. Anaesthesia 2013; 68: 502–11

How aware is your operating table?

clhalligan — Thu, 23 May 2013 15:59:09 GMT

During apparently adequate remifentanil and propofol total intravenous anaesthesia, E-Entropy (GE Healthcare, Chalfont St. Giles, UK) RE/SE values rose from 45/40 to 97/89 after a short transfer from the anaesthetic room to the operating theatre. Anaesthesia was deepened and the patient showed no other signs of awareness. Sequential assessment of presumed faulty E-Entropy equipment revealed that a charging cable for the Eschmann MD20 (Eschmann, Lancing, UK) operating table remained attached, removal of which (as normally occurs pre-operatively) resulted in a return to expected Entropy values compatible with deep anaesthesia (Figure 1 on left), and re-insertion of which reproduced the same erroneous readings (Figure 1 on right). We wonder whether such interference might contribute to errors when calculating the prevalence of intraoperative awareness [1].

C.L. Halligan

M. Slattery

W.A. McFadzean

Morriston Hospital,

Swansea, UK

Email: clairelouise.halligan@wales.nhs.uk

No external funding and no competing interests declared.

Reference.

1. Pandit JJ, Cook TM, Jonker WR, O'Sullivan E, on behalf of the 5th National Audit Project (NAP5) of the Royal College of Anaesthetists and the Association of Anaesthetists of Great Britain and Ireland. A national survey of anaesthetists (NAP5 Baseline) to estimate an annual incidence of accidental awareness during general anaesthesia in the UK. Anaesthesia 2013; 68: 343-53

Closing the door on fire

katyedmonds — Tue, 21 May 2013 15:47:10 GMT

We read with interest the article by Dr Kelly et al. [1]. Although fires can have tragic outcomes in any situation, in a hospital environment it is particularly problematic where many individuals are unable to evacuate themselves unaided. Whilst extreme care should always be taken when handling oxygen cylinders in any hospital situation, we think it is important to remember that oxygen cylinders are also used in inter hospital patient transfers. In 1997 it was estimated that more than 11,000 critically ill patients were transferred between intensive care units within the UK [2]. This figure is likely to be far higher today, with the majority of patients receiving oxygen therapy.

Oxygen enrichment in a confined space such as an ambulance can pose a serious fire hazard. Indeed, the Health and Safety Executive have considered oxygen concentrations >24% as potentially dangerous [3]. Whilst we support the excellent guidelines proposed by Dr Kelly et al., we would also suggest that whilst connecting and disconnecting oxygen cylinders during ambulance transfers, the ambulance doors should remain open. As well as minimizing confined-space oxygen enrichment, we would also like to emphasize the importance of regular fire education and fire evacuation drills.

The out-of-hospital transfer situation is particularly difficult and complex regarding fire prevention and management. The transfer team should be sufficiently educated and equipped to deal, not only with medical, but other emergencies including fire that could arise during inter hospital transfer

K. Edmonds

R. John

M. John

London, U.K.

Email: katyjohn1@gmail.com

No external funding and no competing interests declared.

References.

1. Kelly FE, Hardy R, Hall EA, et al. Fire on an intensive care unit caused by an oxygen cylinder. Anaesthesia 2013; 68: 102-4

2. Mackenzie PA, Smith EA, Wallace PG. Transfer of adults between intensive care units in the United Kingdom: postal survey. British Medical Journal 1997; 314: 1455-6.

3. Health and Safety Executive. Take care with oxygen-fire and explosion hazards in the use of oxygen. HSE 8, revision 2, C150 4/100 London HSE, Subury 1999

4. The Association of Anaesthetists of Great Britain and Ireland. Safety Guideline Interhospital Transfer Feb 2009

The unknown endpoint of the landmark TAP block

S. Ford — Thu, 16 May 2013 10:20:05 GMT

We read with interest the article by Dr. Stuart-Smith et al. [1] who describe a landmark-based Transversus Abdominis Plane (TAP) block for anaesthesia for an emergency hemiarthroplasty. However, we have a number of concerns; we agree with the posted comments regarding the anatomy and the likely alternative explanation for femoral nerve block encountered in this case but what hasn’t been commented on is the practice of performing "blind" TAP blocks. The exact anatomical planes used by the blind TAP block as described by McDonnell et al.[2] have not been clarified. The fascial planes at the point of injection all lie very close together [3] making it very easy to transgress a fascial layer unintentionally, creating a very different pattern of local anaesthetic spread and nerve blockade. This paper reinforces the uncertainty of blind needle placement and corroborates the inaccuracy found in clinical studies [4]. Whilst we recognize the potential benefits of the blind TAP block over an ultrasound-guided approach, we would not recommend this until the anatomy is clarified and results replicated under ultrasound guidance. The patient in this report was fortunate that the block was misplaced and received appropriate anaesthesia.

We cannot agree with Dr. Stuart-Smith et al. that this technique is a safe and appropriate method of anaesthesia for hemiarthroplasty. In our institution this patient would have received a spinal catheter for careful development of spinal anaesthesia and a fascia Iliaca block provided by a more classical approach.

L. French

S. Ford

Morriston Hospital

Swansea, U.K.

Email: smford1@gmail.com

No external funding and nocompeting interests declared.

References.

1. Stuart-Smith K. Hemiarthroplasty performed under transversus abdominis plane block in a patient with severe cardiorespiratory disease. Anaesthesia 2013; 68: 417–20.

2. McDonnell JG, Laffey JG. Transversus Abdominis Plane Block. Anesthesia and Analgesia 2007; 105: 883 –883–a.

3. Tobin CE. The renal fascia and its relation to the transversalis fascia. The Anatomical Record 1944; 89: 295–311.

4. McDermott G, Korba E, Mata U, Jaigirdar M, Narayanan N, Boylan J, et al. Should we stop doing blind transversus abdominis plane blocks? British Journal of Anaesthesia 2012; 108: 499–502.

Dumbing down pain management!

cynaam — Mon, 06 May 2013 09:33:48 GMT

We read with interest the recent article by Moore et al. [1]. The laudable intent of only being satisfied with minimal or no pain we respectfully suggest is overly simplistic and risks sabotaging the very aim they seek to achieve. Excellence in clinical care is not whether a pain score of 6 is treated or not, but is listening to the patient, making a thorough assessment and identifying realistic and acceptable goals. By definition [2] a painful experience, unlike a blood pressure reading or a serum glucose level cannot be reduced to a number with any real meaning. The authors state that “a pain score of 6/10 is not mild, but borderline between moderate and severe, and the patient did need something for that.” ‘6/10’ means different things to different people – not least the patient and their health care provider [3,4]. What if that patient was mobilizing well, not bothered by his healing wound and didn’t feel he needed further medication? Alternatively, what if, on receiving further medication to reduce a 6/10 pain score, the patient then suffered a respiratory arrest – would the system not have failed him? Whilst we agree that the patient may have “needed something” – listening to patients and acknowledging their concerns may be the ‘something’ that is needed and this should be recognized. It is not enough to say that a pain score of 6 needs treating whilst a pain score of 3 does not.

Promoting the idea that pain scores are the ‘be all and end all’, ignores the reality that psychosocial factors play a major role in determining how patients express their pain. Many clinicians lack skills in this area and inevitably default to pharmacological management with its attendant risks. Good quality care supports patient choice and autonomy and not just a default pain score of 3 or less. For many patients functional outcomes such as the ability to cough and deep breathe or patient centred outcomes such as the ability to walk to the local shops, can be more important than pain score reports. These inevitably vary with time and are highly context specific.

The authors state that “the system surely failed this patient” but did they actually ask the patient?

S.G.M. Tan

Nepean Hospital

New South Wales, Australia

A.M. Cyna

Women’s and Children’s Hospital

Adelaide, Australia

Email: allan.cyna@health.sa.gov.au

No external funding and no competing interests declared.

References.

1. Moore RA, Straube S, Aldington D, Pain measures and cut-offs - no worse than mild pain as a simple, universal outcome. Anaesthesia 2013; 68: 400-12.

2. IASP. Task Force on taxonomy. Part III: Pain terms: a current list with definitions and notes on usage. In: Merskey H, Bogduk N, eds. Classification of chronic Pain. Seattle: IASP Press, 1994; 209–14. Available from http://www.iasp-pain.org/AM/Template.cfm?Section=Pain_Defi...isplay.cfm&ContentID=1728
(accessed 6th May 2013).

3. Nguyen T, Slater P, Cyna AM. Open vs specific questioning during anaesthetic follow-up after Caesarean section. Anaesthesia 2009; 64: 156–60.

4. Chooi CSL, White AM, Tan SGM, Dowling K, Cyna AM. Pain vs comfort scores after Caesarean section: a randomized trial. British Journal of
Anaesthesia 2013; 110: 780–7.

The ability of bispectral index to detect intra-operative wakefulness during total intravenous anaesthesia compared with the isolated forearm technique

johnaski — Thu, 02 May 2013 21:11:23 GMT

We read with great interest the recent study by Dr Russell [1] in which he attempted, in vain, to titrate total intravenous anaesthesia to a target bispectral index (BIS) of 55 to 60. Regular users of BIS monitoring will appreciate that such tight control is almost impossible to achieve even in a single investigator study such as this one. The high intraoperative BIS levels reported in the study (up to 80 in one participant) were not only entirely predictable but also potentially consistent with pain and/or memory formation; this raises significant ethical concerns. We would be interested to know if the participants recruited to the study were informed that, as part of the anaesthetic technique, they would deliberately have their anaesthetic reduced with the sole aim of achieving a response to command or a BIS of greater than 60; both are endpoints which could be associated with postoperative recall. There is also a distinct possibility that such response to command could have occurred during painful parts of the procedure since not only were the doses of propofol and remifentanil low, but epidurals were not inserted in all patients and no mention is made as to whether or not the epidurals were tested for block efficacy prior to induction. We are most surprised, and somewhat relieved, that more patients did not recall intraoperative events. It is widely accepted that, in order to accurately detect awareness with recall, patients should have follow-up interviews at three and seven days postoperatively [2]. Perhaps if this had been done, the rate of awareness may have been even higher.

The recent NICE guidelines [3] relating to depth of anaesthesia (DOA) monitors specifically mention that training needs to be undertaken to ensure that users fully understand the strengths and weaknesses of these monitoring modalities. If a manuscript like this is to contribute to our understanding of this technology, it must explain why a technique that involved the use of a muscle relaxant and a surgical field distant from the BIS sensor, could result in such consistently high (30%) EMG activity shown in the in the two detailed cases presented. Similarly, it should be pointed out that the large BIS variability seen in the study figures (known as ‘trend spikes’) should warn the anaesthetist that the underlying opiate dose is relatively low and a climbing/rising BIS trace seen in figure 3 should be addressed immediately. The study protocol however, involved waiting a little longer to see if the patient woke further and had a ‘hand squeezing conversation’ with the attending clinician. This we feel is unacceptable since, if light anaesthesia is a possibility, a cause should be sought (e.g. inadequate analgesia) and the anaesthetic adjusted accordingly, without delay. We feel that the author should have made it clear in his discussion that accepting a BIS value of greater than 60 is not to be encouraged unless the patient is haemodynamically stable and the anaesthetic concentrations are clinically adequate (which is questionable in this study when one example shows a propofol target concentration of less than 2 mcg.ml^-1)

The isolated forearm technique, if used for its original purpose and not simply to test the boundaries of probability, is undoubtedly the gold standard for monitoring wakefulness under anaesthesia; it is, however, unlikely to ever be widely adopted into routine clinical practice. As routine users of intraoperative BIS monitoring, we would urge all readers not to take the findings of Dr Russell’s study in isolation. He has correctly concluded that patients may respond to command with a BIS value of less than 60. He has gone on to demonstrate that by deliberately giving an inadequate anaesthetic this becomes more likely. Our final question for Dr Russell (and perhaps other depth of anaesthesia monitoring sceptics) is this: what kind of monitoring would they like to be used on themselves if they were undergoing major surgery using total intravenous anaesthesia with neuromuscular blockade?

In common with all the other monitoring devices utilised by anaesthetists, BIS has the potential for error and artifactual readings. Pulse oximetry does not preclude the possibility of unrecognised hypoxaemia, nor can train-of-four monitoring prevent occurrences of postoperative residual curisation; the likelihood of either event is, however, diminished when they are used by a competent anaesthetist who is trained in their use and is aware of their potential flaws. BIS does not aim to replace the vigilant attending anaesthetist, but rather provides them with additional information that has the potential to benefit the patient under their care.

J. Andrzejowski

M. Wiles

Royal Hallamshire Hospital

Sheffield, UK.

Email: johnirra@gmail.com

JA was a member of the NICE Diagnostics Advisory Committee that published the DOA guidelines in Nov 2012. No other competing interests or external funding declared.

References.

1. Russell IF. The ability of bispectral index to detect intra-operative wakefulness during total intravenous anaesthesia compared with the isolated forearm technique. Anaesthesia 2013; 68: 502-11.

2. Sandin RH, Enlund G, Samuelsson P, Lennmarken C. Awareness during anaesthesia: a prospective case study. Lancet 2000; 355: 707-11.

3. National Institute for Health and Clinical Excellence. Depth of anaesthesia monitors – Bispectral Index (BIS), E-Entropy and Narcotrend-Compact M. Nice diagnostic guidance 6; November 2012. http://publications.nice.org.uk/depth-of-anaesthesia-monitors-bispectral-index-bis-e-entropy-and-narcotrend-compact-m-dg6. (accessed 02/05/2013)

Remifentanil PCA use in labour

keithkelly — Wed, 01 May 2013 14:19:51 GMT

We read with interest the recent articles in Anaesthesia regarding remifentanil in labour [1-5]. Whilst we realise that the merits of remifentanil in labour is a debate for obstetric anaesthetists, we would like to ask whether our colleagues have considered measuring maternal carbon dioxide levels, by means of a transcutaneous electrode, as an additional safety measure to guard against critical incidents related to remifentanil PCA?

Within our own department we have looked specifically at transcutaneous PCO₂ (PtcCO₂) measurements in the first 24 hours following major colorectal surgery and the effect that morphine PCA and epidural analgesia has on ventilation [6]. Our findings revealed a mean (95% confidence intervals) postoperative PtcCO₂ of 5.56 (5.0-6.12) kPa in the epidural group compared with 6.73 (6.22-7.22) kPa in the PCA group. This represented a significant rise over baseline of PtcCO₂ in the PCA group of 1.8 (1.5-2.1) kPa compared with 0.7 (0.5-0.9) kPa in the epidural group. Others have also measured PtcCO₂ after laparotomy for 8 hours and obtained broadly similar results [7].

Importantly, we found that despite the rise in PtcCO₂, which suggests hypoventilation, the mean (IQR) respiratory rate in both groups was maintained within normal limits; the epidural group recorded 15 (14-16) breaths.min^-1 compared with 12 (11-13) for the morphine PCA. We would therefore ask whether monitoring only conscious level, respiratory rate, and Sp0₂, as guidelines recommend [8], may be lulling the observer into a false sense of security.

Monitoring PtcCO₂ in parturients has been performed previously although there is still a relative paucity of information about its use in humans in labour. Work from the 1990s [9] together with a recent Japanese group [10,11] have shown that maternal hyperventilation during labour results in a decreased PtcCO₂ whilst further studies have shown that PtcCO₂ can return to non-labouring baseline levels with the administration of central neural analgesia.

Currently there is no published data on PtcCO₂ levels in parturients receiving remifentanil PCA but given the ease with which it can be measured and the simultaneous measurement of SpO₂ by modern machines perhaps this is a topic to be investigated further.

O. Daly

K.P. Kelly

Western General Hospital

Edinburgh, Scotland

J.G. McCormack

Royal Hospital for Sick Children

Edinburgh, Scotland.

B.H. Heidemann

Simpson Centre for Reproductive Health

Edinburgh, Scotland.

Email: oliver.daly@gmail.com

No external funding and no competing interests declared.

References.

1. Muchatuta NA, Kinsella SM. Remifentanil for labour analgesia: time to draw breath? Anaesthesia 2013; 68: 231-5

2. Shen MK, Wu ZF, Zhu AB et al. Remifentanil for labour analgesia: a double-blinded, randomised controlled trial of maternal and neonatal effects of patient-controlled analgesia versus continuous infusion. Anaesthesia 2013; 68: 236-244.

3. Jost A, Ban B, Kamenik M. Modified patient-controlled remifentanil bolus delivery regimen for labour pain. Anaesthesia 2013; 68: 245-52.

4. Marr R, Hyams J, Bythell V. Cardiac arrest in an obstetric patient using remifentanil patient-controlled analgesia. Anaesthesia 2013; 68: 283-87.

5. Hughes D, Hodgkinson P. Remifentanil PCA for labour analgesia. Anaesthesia 2013; 68: 298.

6. McCormack JG, Kelly KP, Wedgwood J, Lyon R. The effects of different analgesics regimens on transcutaneous CO₂ after major surgery. Anaesthesia 2008; 63: 814-21.

7. Kopka A, Wallace E, Reilly G, Binning A. Observational study of perioperative PtcCO₂ and SpO₂ in non-ventilated patients receiving epidural infusion or patient-controlled analgesia using a single earlobe monitor (TOSCA). British Journal of Anaesthesia 2007; 99: 567-71.

8. http://www.oaa-anaes.ac.uk/content.asp?ContentID=333 (accessed 01/05/2013)

9. Bergmans MGM, van Geijn HP, Hasaart THM, Weber T, Nickelsen C. Fetal and maternal transcutaneous PCO2 levels during labour and the influence of epidural analgesia. European Journal of Obstetrics, Gynecology and Reproductive Biology 1996; 67: 127-32.

10. Tomimatsu T, Kakigano A, Mimura K, et al. Maternal Hyperventilation During Labor Revisited: Its Effects on Fetal Oxygenation. Reproductive Sciences 2012; 19: 1169-74.

11. Tomimatsu T, Kakigano A, Mimura K, et al. Maternal carbon dioxide level during labor and its possible effect on fetal cerebral oxygenation: Mini review. Journal of Obstetrics and Gynaecology Research 2013; 39: 1-6.

The ability of the bispectral index to detect intra-operative wakefulness during total intravenous anaesthesia compared with the isolated forearm technique.

ubrigue — Sun, 28 Apr 2013 22:06:12 GMT

Dr Russell is to be congratulated on conducting a very worthwhile but difficult study on the risk of intra-operative wakefulness during TIVA [1]), but the devil is unfortunately in the lack of detail, particularly when a small number of patients were so intensively studied. Some of the important missing factors in determining depth of anaesthesia are highlighted in the review article on MAC [2]. The essential presumption is that all factors were held constant, except for the request to respond to a verbal command at different levels of BIS. This may not have been so.

There is no information on ethnicity of the patients (which may affect pharmacogenetics), preoperative anxiety or sleep deprivation, opioid analgesia, alcohol and recreational drugs (affecting depth of anaesthesia and analgesia); pre- and per-operative haemoglobin and albumin levels (which may affect drug binding); temperature; nor on surgical incision and nature of surgery. In addition, responders were, on average, 10 kg lighter than non-responders, which may reflect the Marsh model’s use of weight rather than BMI and age in calculating an estimated effect site concentration. These points may appear to be “nit-picking”, but even a three degree core body temperature difference has been associated with a 28% difference in propofol concentration, due to reduced hepatic blood flow, which could have affected outcomes [3].

A variable response to verbal, but not noxious, stimuli is perfectly understandable in Russells study, when epidural top-up doses were given at variable intervals of 90 to 120 minutes. Variation in the density, duration and spread of the top-up epidural doses, delivered into patients with variable epidural fat volume and epidural blood flow will also have occurred [4]. The response of the patient to a “noxious stimulus” at a given (apparently steady state) propofol effect site concentration would then depend on the adequacy of the epidural providing analgesia and anaesthesia, rather than a particular BIS value.

While it is clearly impossible to completely control for all these factors in advance, a post hoc analysis might usefully guide further research. An epidural infusion, following an initial loading dose, might also have reduced the variability in response to surgical stimulation.

U. Brigue

C. Lanigan

Lewisham Hospital

London, UK.

Email: ubrigue@yahoo.com

No external funding and no competing interests declared.

References.

1. Russell IF. The ability of the bispectral index to detect intra-operative wakefulness during total intravenous anaesthesia compared with the isolated forearm technique. Anaesthesia 2013; 68: 502-11.

2. Aranake A, Mshour GA, Avidan MS. Minimum alveolar concentration: ongoing relevance and clinical utility. Anaesthesia 2013; 68: 512-22.

3. Leslie K, Sessler DI, Bjorksten AR, Moayeri A. Mild hypothermia alters propofol pharmacokinetics and increases the duration of action of atracurium. Anesthesia and Analgesia 1995; 80: 1007-14.

4. Higuchi H, Kazama T, Adachi Y. Factors affecting the spread and duration of epidural anaesthesia with ropivacaine. Anaesthesiology 2004;101: 451-60

An alternative explanation for the reported success of a TAP Block for hip surgery

michligsam — Sun, 28 Apr 2013 11:59:53 GMT

We were interested to read the case report by Dr Stewart-Smith on the use of the transversus abdominis plane (TAP) block for a high risk emergency hemiarthroplasty due to a fractured neck of femur [1]. The author proposes that high volume infiltration may have led to spread beyond the classically described T10-L1 areas and partially anaesthetised the lumbosacral plexus.

We believe that it is likely the patient did not, in fact, receive a TAP block at all, but that the needle was inadvertently passed one layer deeper, to rest between the transverse abdominis and transversalis fascia. This plane is continuous with the space deep to the fascia iliaca anteriorly, where the femoral nerve and lateral cutaneous nerve of thigh are situated.

A previous cadaveric study identified spread of dye to the femoral nerve after injection into this layer, and explains the high incidence of accidental femoral nerve blockade on performing percutaneous ilioinguinal blocks [2].

We suggest that Dr Stewart-Smith is actually describing a novel approach to the fascia iliaca block.

S. Michlig

G. Walker

Horton Hospital

Banbury, UK

Email: michligsam@doctors.org.uk

No external funding and no competing interests declared.

References.

1. Stewart-Smith K. Hemiarthroplasty performed under transversus abdominis plane block in a patient with severe cardiorespiratory disease. Anaesthesia 2013; 68: 417-20

2. Rosario DJ, Jacob S, Luntley J, Skinner PP, Raftery AT. Mechanism of femoral nerve palsy complicating percutaneous ilioinguinal field blocks. British Journal of Anaesthesia 1997; 78: 314-6

Was this really a TAP block or spread of LA into fascia Iliaca compartment from supra-inguinal block?

shiv1985 — Sun, 28 Apr 2013 05:37:23 GMT

We read the case report on hemiarthroplasty under TAP block with great interest [1]. There are several issues that we should like to raise.

The author has used 400mg.hr^-1 (6.7mg.min^-1) propofol infusion in a cachetic patient (BMI of 21). If 4mg.min^-1 is enough to provide deep anaesthesia in order to intubate the trachea, then 6.7mg.min^-1 is not light intra-venous sedation, as the report suggests, but, in combination with 2mg midazolam and 20mg ketamine, is total intravenous anaesthesia (TIVA).

The author has used lidocaine along with bupiviacine above its recommended maximum dose (>3 mg/kg), a practice that should be condemned especially when local anaesthetic is injected blindly into a neurovascular plane such as in a TAP block. As Sibata’s study results indicate, a TAP block can potentially result in systemic toxicity of local anaesthetic and the analgesic effect of the TAP block may partially be due to the resultant rise in serum concentration of local anaesthetic [2].

The author argues that because TAP blocks have been used for to provide analgesia in radical prostectomy cases, and because the prostate gland is supplied by the sacral plexus, TAP block must be spreading to the sacral nerves. However;

1. The prostate gland is a visceral organ and a somatic block such as a TAP block cannot be assumed to provide analgesia for visceral pain. [3]

2. The prostatic plexus is derived from sacral parasympathetic nerves.

3. A TAP block is used in radical prostectomy to provide analgesia from pain arising from the incision site, that is in the T10 – L1 region. [3]

4. Of the few anatomical studies on TAP blocks, none have been able to demonstrate spread below the L2 level, even with the most posterior approach through the lumbar triangle of Petit (LTOP) [4,5].

5. Carney’s study demonstrated that using landmark, or ultrasound-guided, blocks in volunteers resulted in posterior spread around the quadratus lumborum to the paravertebral space from T5 to L1 levels only [4].

We would argue that large volumes of local anaesthetic are accidentally deposited beneath the fascia transversalis and can tract down the fascia iliaca which is in continuation with the transversalis fascia [6]. We do not believe that large volumes of local anaesthetic can track to the lumbar plexus because it lies within the psoas compartment and is surrounded by the tough thoraco-lumbar fascia. The only reliable way to achieve a lumbar plexus block is by performing a lumbar paravertebral or posterior psoas compartment block.

We do not believe that a TAP block should be employed for hip hemi-arthroplasties in compromised patients, when simpler and safer alternatives exist and feel that the case described was not a TAP block but an accidental injection of local anaesthesia under the transversalis fascia that spread to the fascia iliaca compartment to cause a femoral nerve block.

S.K. Singh

T. Dixit

Royal Liverpool University Hospitals

Liverpool, UK.

Email: shvkmrsngh@aol.com

No external funding and no competing interests declared.

References.

1. Stuart-Smith, K. Hemiarthroplasty performed under transversus abdominis plane block in a patient with severe cardiorespiratory disease. Anaesthesia 2013; 68: 417–20

2. Shibata Y, Harada J and Komatsu T. Serum concentration of lidocaine after transverses abdominis plane block. British Journal of Anaesthesia 2009; 23:298-300.

3. Rodrigues AO, Machado MT, Wroclawski ER. Prostate innervation and local anaesthesia in prostate procedures. Reviews of Hospital Clinics 2002; 57: 287–92.

4. Carney J, Finnerty O, Rauf J, Bergin D, Laffey JG, McDonnell JG. Studies on the spread of local anaesthetic solution in transversus abdominis plane blocks. Anaesthesia 2011; 66: 1023– 30.

5. Barrington MJ, Ivanusic JJ, Rozen WM, Hebbard P. Spread of injectate after ultrasound-guided subcostal transverses abdominis plane block: a cadaveric study. Anaesthesia 2009; 64:745-50.

6. Derrick JL, Aun CST. Transient femoral nerve palsy after ilioinguinal block. Anaesthesia and Intensive Care 1996; 24: 115.

The McGrath Series 5 videolaryngoscope vs the Macintosh laryngoscope: a randomised, controlled trial in patients with a simulated difficult airway

A. M. Taylor — Wed, 24 Apr 2013 05:29:58 GMT

We thank Dr. Westwood and colleagues for their interest in our study [1]. We agree that the Cormack and Lehane grading system [2] is not entirely adequate when using videolaryngoscopes; as addressed in previous correspondence [3, 4] it was originally developed for direct laryngoscopy, not indirect laryngoscopy. Furthermore, as discussed in our article, the view obtained with videolaryngoscopes does not necessarily give an indication of ease of intubation. However, the Cormack and Lehane grading system is widely recognised and is currently one of the only validated scoring systems for grading the laryngeal view. We note the development and preliminary evaluation of the “Fremantle Score” by Dr. Westwood and colleagues and will follow their clinical trial report with interest.

We believe the poor rate of successful tracheal intubation using the Macintosh blade in our study was understandable given that we deliberately simulated a difficult airway using manual in-line stabilisation, did not allow the usual external rescue manoeuvres, and restricted the number of intubation attempts to one attempt. These strict restrictions were necessary in order to standardise the intubation technique between the two devices.

We agree with Dr. Westwood and colleagues that the laryngoscopic view obtained by the McGrath Series 5 videolaryngoscope cannot be directly correlated with the rate of intubation success. We clearly stated in our discussion that our study was not powered for the secondary outcome, tracheal intubation success. Our study found that in a simulated difficult airway, using manual in-line stabilisation without rescue manoeuvres, the McGrath Series 5 videolaryngoscope
was superior in terms of view of the laryngeal inlet, and also in terms of intubation success.

We welcome further research in this area, and hope that a more appropriate validated scoring system for videolaryngscopes will be developed.

A.M. Taylor

M. Peck

S. Launcelott

O.R. Hung

J.A. Law

K. MacQuarrie

D. McKeen

R.B. George

J. Ngan

Dalhousie University,
Halifax, Canada.

Email: hungorla@dal.ca

This study was funded by the Department of Anaesthesia, Dalhousie University. Two McGrath Series 5 videolaryngoscopes were provided by Vitaid Canada for the purposes of this study. The investigators did not receive any other funding. Dr Hung is a consultant to Covidien Canada the distributor of the McGrath Mac
videolaryngoscope.

References.

1. Taylor AM, Peck M, Launcelott S, et al. The McGrath Series 5 videolaryngoscope vs the Macintosh laryngoscope: a randomised, controlled trial in patients with a simulated difficult airway. Anaesthesia 2013; 68: 142-7.

2. Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 1984; 39: 1105-11.

3. Mines R, Ahmad I, Teoh WHL, Shah MK, Sia ATH. Can you compare the views of the videolaryngoscopes to the Macintosh laryngoscope? Anaesthesia 2011; 66: 315-7.

4. Angadi SP, Frerk C. Videolaryngoscopy and Cormack and Lehane grading. Anaesthesia 2011; 66: 628-9.

Hemiarthroplasty performed under transversus abdominis plane block- Is it really a block for the future?

seemajpai — Fri, 19 Apr 2013 17:13:41 GMT

I read with interest the case report by Stuart-Smith et al. [1]. It is impressive to see yet another use for transversus abdominis plane (TAP) block which has been described in several clinical settings [2]. There is evidence that transversalis fascia comprises the fascial plane deep to the rectus abdominis muscles and this fascial plane is continuous with the fascia iliaca so local anaesthetic solution can track down resulting in femoral nerve block [3]. The fascia iliaca block is commonly used for providing analgesia in hip fracture patients as it can block up to 3 nerves that supply the hip and provide good analgesia intraoperatively. Also, there is evidence to show that the analgesia provided depends on the spread of local anaesthetic solution and that when the injection is sited via a posterior approach paravertebral spread blocks dermatomes from T12-L2 [4].

I think that the addition of propofol sedation is vital in this case and that a TAP block alone may not be sufficient to perform the procedure as it may block the lower thoracic and lumbar segments but there is insufficient evidence regarding the sacral segments. I believe that there is a need for a carefully designed study.

S.J. Pai

Royal Sussex County Hospital,

Brighton, UK.

Email: seemajpai@yahoo.com

No external funding and no competing interests declared.

References.

1. Stuart-Smith K. Hemiarthroplasty performed under transversus abdominis plane block in a patient with severe cardiorespiratory disease. Anaesthesia 2013; 68 : 417-20.

2. Finnerty O, McDonnell JG.Transversus abdominis plane block. Current Opinion in Anaesthesiology 2012; 25: 610-4.

3. Young MJ, Gorlin AW, Modest VE, Quraishi SA. Clinical implications of transversus abdominis plane block in adults. Anaesthesiology Research and Practice 2012; 22: 831-40.

4.Carney J, Finnerty O, Rauf J, Bergin D, et al. Studies on the spread of local anaesthetic solution in transversus abdominis plane blocks. Anaesthesia 2011; 66: 1023-30.

Obstetric Early Warning Scores: much more work required

garybsmith — Fri, 19 Apr 2013 10:46:57 GMT

Carle et al. are to be congratulated on beginning the work required to develop a scientifically-based Early Warning Score (EWS) for pregnant women [1]. However, the EWS that they describe is only applicable to those obstetric patients who have been admitted to an ICU and only discriminates the risk of in-ICU death. The data were collected from obstetric patients after their admission to critical care units and not from the general obstetric inpatient population. How representative is this ICU population of patients on a general obstetric ward? We are surprised at the effort that has been applied to developing escalation criteria for their EWS before it has been tested statistically against data from the general obstetric inpatient population. This is surely an essential step before consideration of implementation in the general obstetric ward, and would be informative about the efficiency of the EWS[2] and the appropriate escalation trigger points.

The accompanying editorial by McGlennan and Sherrat [3] contains inaccuracies in their description of the recommended National Early Warning Score (NEWS) and vital signs chart for adult patients [4]. It states that “...The weightings assigned...(in NEWS)...were not steeped in science, rather mainly based on NEWSDIG’s members’ clinical opinions and their views of existing EWS...” This is incorrect. NEWS is derived from the VitalPAC Early Warning Score (ViEWS), the scoring bands of which were deliberately adjusted to maximise its ability to discriminate in-hospital death within 24 h of a vital signs dataset [2]. Members of the RCPL National Early Warning Score Design and Implementation Group made only minor adjustments to ViEWS,
based on clinical opinion, to develop NEWS [4]. McGlennan and Sherrat also state that “...evaluation of the NEWS chart was performed by Professors
Smith and Prytherch...” This is also incorrect. We provided only the analysis of the National Early Warning Score. We had no involvement in the
development of the associated NEWS chart.

G.B. Smith

Visiting Professor

School of Health & Social Care

University of Bournemouth

Bournemouth, UK

D.R. Prytherch

Visiting Professor

Centre for Healthcare Modelling and Informatics

University of Portsmouth

Portsmouth, UK

Email: gbsresearch@virginmedia.com

VitalPAC is a collaborative development of The Learning Clinic Ltd (TLC) and Portsmouth Hospitals NHS Trust (PHT). PHT has a royalty agreement with TLC to pay for the use of PHT intellectual property within the VitalPAC product. Professor Prytherch is employed by PHT; Professor Smith was an employee of PHT until 31/03/2011. The wives of Professors Smith and Prytherch are shareholders in TLC. Professors Smith and Prytherch are unpaid research advisors to TLC, and have both received reimbursement of travel expenses from TLC for attending symposia in the UK.

Professors Smith and Prytherch were members of the clinical team that developed the VitalPAC Early Warning Score (ViEWS). Professor Smith
was also a member of the Royal College of Physicians of London’s National Early Warning Score (NEWS) Development and Implementation Group. Professor Prytherch assisted the Royal College of Physicians of London in the analysis of data validating NEWS. Professor Smith is a member of a multiprofessional group, based at Bournemouth University, investigating early warning scores in Obstetrics.

No other external funding or competing interests declared.

References

1. Carle C, Alexander P, Columb M, Johal J. Design and internal validation of an obstetric early warning score: secondary analysis of the Intensive Care National Audit and Research Centre Case Mix Programme database. Anaesthesia 2013; 68: 355–8.

2. Prytherch DR, Smith GB, Schmidt PE, Featherstone PI. ViEWS—towards a national early warning score for detecting adult inpatient deterioration. Resuscitation 2010; 81: 932-7.

3. McGlennan AP, Sherratt K. Charting change on the labour ward. Anaesthesia 2013; 68: 338–42.

4. Royal College of Physicians. National Early Warning Score (NEWS): Standardising the Assessment of Acute Illness Severity in the NHS. Report of a Working Party. London: RCP, 2012.

One dose fits all? Local Anaesthetic dosing, clinical trials and safety

patrick.tapley — Tue, 16 Apr 2013 22:53:20 GMT

We read with interest Fredrickson and Danesh-Clough’s study on ultrasound guided femoral catheter placement [1]. The investigators administered a total of 60mls 0.5% ropivicaine (300mg) via three different nerve blocks: sciatic, obturator, and femoral (catheter technique). Lidocaine with adrenaline (50-100mg) was administered prior to femoral catheter placement.

An issue this study raises is the dosing of local anaesthetic (LA) agents for nerve blockade, and whether it is appropriate to apply a ‘one dose fits all’. Traditional teaching suggests a 3mg.kg^-1 dose for ropivicaine with a maximum dose of 300mg [2] dependent on indication and intended block (this is not evidence based), but emphasises the importance of individualising doses.

A risk with larger doses is Local Anaesthetic Systemic Toxicity (LAST). Various factors influence plasma concentrations of local anaesthetics, including injection site, comorbidities, and the dose used, with multiple reports after 300mg ropivicaine (4.28-8mg.kg^-1) [3]. Toxic plasma levels have been demonstrated 24hrs after a 300mg ropivicaine bolus with continuous 0.2% ropivicaine infusion via femoral and sciatic catheters [4].

Fredrickson and Danesh-Clough’s cohort of patients weighed a mean (SD) of 82.4 (16.4) kg and, assuming their patients’ weights followed a normal distribution, over half of study subjects received a potentially toxic dose of greater than 3 mg.kg^-1. Whilst no patient demonstrated symptoms or signs of LAST, onset can take 10-30minutes [3,5], with peak plasma ropivicaine concentrations reported 30 minutes following injection [5]. As study patients received a general anaesthetic, reporting delayed minor neurological symptoms associated with LAST may not have been possible. Had they occurred, would the LA infusion be commenced post operatively?

The American Society of Regional Anaesthesia’s guidance [6] states that evidence suggests most peripheral nerve blocks are performed using excessive doses of local anaesthetic, and that when using ultrasound and catheter techniques (as in this study) adequate blocks may be achieved with much smaller doses of properly placed local anaesthetic.

So what is the correct dose? In reality the type of block, the injection site, patient co-morbidities and pharmacokinetic factors should influence dosing. Therefore we question whether a ‘one dose fits all’ approach for patients is appropriate, even in the setting of a clinical trial.

P. Tapley

V. Fong

North Shore Hospital

Auckland. New Zealand

Email: paddytap@hotmail.com

No external funding and no competing interests declared.

References.

1. Fredrickson MJ, Danesh-Clough TK. Ultrasound-guided femoral catheter placement: a randomised comparison of the in-plane and out-of-plane techniques. Anaesthesia 2013; 68: 382-90

2. New Zealand Medicines and Medical Devices Safety Authority. Naropin New Zealand data sheet. http://www.medsafe.govt.nz/profs/datasheet/n/Naropininj.pdf (Accessed 25/03/2013)

3. Kimura Y, Kamada Y, Kimura A, Orimo K. Ropivicaine-induced toxicity with overdose suspected after axillary brachial plexus block. Journal of Anesthesia 2007; 21: 413-6

4. Bleckner LL, Bina S, Kwon KH et al. Serum Ropviciaine Concentrations and Systemic Local Anaesthetic Toxicity in Trauma Patients Receiving Long Term Continuous Peripheral Nerve Block Catheters. Anesthesia and Analgesia 2010; 110: 630-4

5. Griffiths JD, Le NV, Grant S Bjorksten A, Hebbard P, Royse C. Symptomatic local anaesthetic toxicity and plasma ropivicaine concentrations after transversus abdominis plane block for Caesarean section. British Journal of Anaesthesia advanced access doi:10.1093/bja/aet015.

6. Neal JM, Bernards CM, Butterworth JF, et al. ASRA Practice Advisory on Local Anaesthetic Systemic Toxicity. Regional Anesthesia and Pain Medicine 2010; 35: 152-61

Frova introducer and double lumen tubes

bougiedlt — Fri, 12 Apr 2013 19:46:22 GMT

We read with interest the report of a fragment of a Frova intubating introducer (Cook Medical, Brisbane, Australia) becoming dislodged in the airway after use with a double lumen tube (Covidien-Mallinkrodt, Mansfield, MA, USA) [1] and the reply from the manufacturer [2]. We recently reported the same complication which has occurred on two occasions with the same two pieces of equipment [3]. The second incident occurred some time after the first and despite efforts to inform department staff not to use the Frova intubating introducer with double lumen tubes.

As we described in our report we have added a bright pink label with the instruction ‘NOT FOR DOUBLE LUMEN TUBE’ to the outside of the packaging of the Frova intubating introducers. Posters have been placed in the appropriate operating theatres advising of this problem and suggesting alternative ways to manage the patient with a difficult airway who requires a double lumen tube to be placed. We have also bench tested the other bougies available in our department.

We are concerned that, despite literature reports and product information recommendations, the Frova intubating introducer continues to be used for double lumen tube placement by clinicians unaware of the possibility of fragments being deposited in the airway. We suggest that the packaging should display this contraindication.

J. Graham

C. Von Heldreich

W. Howard

C. Fiddes

Austin Health

Melbourne, Australia

Email: jon.graham@austin.org.au

No external funding and no competing interests declared.

References.

1. Huitink JM, Bisschops M. A complication with an intubating introducer and a double-lumen tube: tip of the iceberg? Anaesthesia 2012; 67 :926-7.

2. Ogilvie L. Intubating introducers and double-lumen tubes. Anaesthesia 2012; 67 :1408-9.

3. Graham J, Von Heldreich C, Howard W, Fiddes C. Frova intubating introducers and double-lumen tubes. Anaesthesia and Intensive Care 2013; 41 :127-8.