November 2013

CPD Update

November’s Journal articles have been added by Dr Philippa Webb , Locum Consultant in Neuroanaesthesia and Dr Judith Dinsmore, Consultant in Neuroanaesthesia at St George’s Hospital, London. Al-Tamimi YZ, Sinha P, Chumas PD et al. Ventriculoperitoneal Shunt 30-Day Failure Rate: A Retrospective International Cohort Study The British Pediatric Neurosurgery Group (BPNG) Audit Committee. Neurosurgery 2013; E pub ahead of print. Many of us will have been involved in providing anaesthesia for insertion of new and revision of ventriculoperitoneal shunts (VPS). In fact ventriculoperitoneal shunt surgery is the most common procedure undertaken by paediatric neurosurgeons. However much of this surgery, especially revision surgery occurs out of hours and, in my experience, is rarely performed by a consultant neurosurgeon. Historically failure rates are assessed at one year and range from 25- 60%. This wide range is hardly surprising as most of the literature is based on single centre experiences, from a range of countries with differing underlying aetiologies and surgical techniques. This cohort study from The British Paediatric Neurosurgery Group (BPNG) Audit Committee enrolled all, except one (Belfast), paediatric neurosurgical centres in the UK and Ireland. All new and revision shunts were recorded for 2008 and 2009 and a 30-day failure rate was obtained for each procedure. This information was compared with the 30-day failure rate obtained from 2 large RCTs. The overall 30-day failure rate and 1 year failure rate for new shunts in the study was 12.9% and 28.8% respectively, comparable to that of the 2 RCTs (14% and 16%). Subsequent revision rates for these new shunts were 20.7% at 30 days and 40.4% at 1 year. The authors conclude that VPS survival in this study was comparable to that of published data. There was no difference in failure rates of new shunts performed by non paediatric neurosurgeons compared to consultant paediatric surgeons and there was no regional variation. However trainee neurosurgeons and consultant “adult” neurosurgeons were grouped together and compared with consultant paediatric neurosurgeons. I would have been interested in a further breakdown of figures to distinguish consultant and trainee grade. They did find a lower failure rate of revision shunts when performed by consultant paediatric surgeons. They suggest that the 30-day failure rate may present a better barometer of surgical outcome and should be used in the design of future studies. Bilooa F, Titi L, Lanni F, Stazi E, Rosa G. Training anaesthesiology residents in providing anesthesia for awake craniotomy: learning curves and estimate of needed case load. Journal of Clinical Anesthesiology 2013; 25: 359-66. These authors attempted to determine how long it would take for anaesthetic trainees to achieve good-excellent competency in provision of anaesthesia for awake craniotomy. They sub-divided the process into three separate components:

  1. Provision of local anaesthesia
  2. Provision of sedation / analgesia
  3. Intraoperative haemodynamic management

They then went on to produce a learning curve for each resident for each of the three components over ten consecutive procedures. Quantitive assessment was based on both the resident’s own self assessment score and the attending’s judgement and then reported as an ability score on a VAS ranging from 1-12. They found that each component had a specific learning rate and went on to calculate the number of procedures they thought would be necessary to achieve good- excellent competency:

  1. Provision of local anaesthesia                                    10
  2. Provision of sedation / analgesia                                15-25
  3. Intraoperative haemodynamic management                   20-30

The authors concluded that a dedicated training programme with specific learning tasks and confidence building would be necessary to provide good- excellent ability. One wonders how this number of procedures could possibly be achieved within our current neuroanaesthesia training programmes in the UK. Georgiou AP, Manara AR. Role of therapeutic hypothermia in improving outcome after traumatic brain injury: a systematic reviewBritish Journal of Anaesthesia 2013; 110:357-367. There is much interest in the concept of therapeutic hypothermia for neuroprotection in traumatic brain injury (TBI). However, despite evidence of efficacy following cardiac arrest and in neonatal hypoxic brain injury, clinical trials have so far had inconclusive results in TBI. This review was undertaken to look at the current evidence and re-evaluate the risks and benefits in traumatic brain injury. 18 randomized controlled trials were identified involving 1851 patients. The authors looked specifically at:

  1. Does therapeutic hypothermia improve survival
  2. Does therapeutic hypothermia improve subsequent neurological function in patients who survive traumatic brain injury
  3. Is therapeutic hypothermia safe in the context of traumatic brain injury

Unfortunately they could identify no benefit on mortality or neurological morbidity from high quality trials to date. In addition hypothermia was associated with cerebrovascular disturbances on rewarming and possibly an increased incidence of pneumonia. However due to the paucity of high quality studies the possibility of these conclusions changing on completion of current trials cannot be excluded. Hopefully the large on going trials such as the Eurotherm3235Trial will provide us with some answers. 

XENON in medical area: emphasis on neuroprotection in hypoxia and anesthesia

Ensencan E, Yuksel S, Tosun YB, Robinot A, Solaroglu I, Zhang JH

Medical Gas Research 2013, 3:4. Available from

Introduction Medical gases are utilised across a broad field in medicine. Xenon is a noble gas with properties that have proven to be particularly applicable in the areas of anaesthesia and neurodegeneration. This paper aimed to review these. Discovery and chemical properties of Xenon Sir William Ramsay discovered Xenon in 1898 and it is still produced by a similar method – the fractional distillation of air in its liquefied form. Albert R Behnke Jr. then proposed that it could be used as an anaesthetic following his studies that included Xenon in deep sea divers’ breathing mixtures. It was not until 1951, however, that it was used as a surgical anaesthetic for the first time. Xenon was deemed very effective in view of its low blood-gas partition coefficient, minimal effect on the cardiovascular system and lack of fetotoxic or teratogenic properties. Neuroprotective role The authors collated 9 recent studies (in vivo and in vitro)that demonstrated elements of neuroprotection exhibited by Xenon. Fundamental to these studies is the ability of Xenon to act as an NMDA receptor  antagonist. As NMDA receptors are key in the process of neural tissue apoptosis, Xenon is proposed to protect against neuronal hypoxia and ischaemia. The authors also referred to studies using Xenon as a pre-conditioning agent where it was concluded that animal brain infarct size was reduced in addition to improved neuronal recovery following administration of the gas. Combination therapy studies Xenon is suggested an agent to be used in combination with hypothermia to further protect neuronal tissue following hypoxia and ischaemia. Several animal studies are quoted to conclude that Xenon acts synergistically with hypothermia to improve neuronal survival  with one purporting an increase in neuroprotection from 37% (with hypothermia alone)to 76% (with combination therapy). Anaesthesia In 2000, Russia approved the use of Xenon in anaesthesia. Germany followed in 2005 with an extension to all of Europe in 2007. The authors describe Xenon as having qualities befitting the title of an ideal anaesthetic agent; rapid onset and offset owing to a low blood gas partition coeffiecient, cardiovascularly stable, neuroprotective, associated with decreased postoperative pain, lack of hepatic/renal side effects and absence of induced  coagulative or immunological dysfunction. As it occurs naturally in the earth’s atmosphere, it is also non-toxic to the environment. Other medical uses Xenon continues to be used in lasers for eye surgery and to enhance CT scans when measuring cerebral blood flow. Cost efficiency The authors finally highlight the unfortunate downside of Xenon in being its cost. As it is a trace element and requires fractional distillation, its expense is elevated to 30 times that of other volatiles used for the same length of time. Conclusion This is a comprehensive review covering all aspects of Xenon’s properties and investigated uses. It paints an extremely favourable picture of its potential as an anaesthetic agent, especially in those patients at risk of, or following neurological insults. It would appear that only the cost of its production prohibits its elevation to regular use. The authors feel that this would be outweighed by their expected improvement in clinical outcome.

Comparison of the effect of lignocaine instilled through the endotracheal tube and intravenous lignocaine on the extubation response in patients undergoing craniotomy with skull pins: A randomized double blind clinical trial

George SE, Singh G, Matthew BS, Fleming D, Korula G.

J Anaesthesiol Clin Pharmacol. 2013; 29(2): 168-172.

Introduction During anaesthesia for neurosurgical procedures, it is prudent to avoid coughing on the removal of skull pins and emergence through to extubation.  Lignocaine is an agent that can be used and may be administered either directly to the airway or intravenously. The authors sought to compare the effect of intratracheal (IT) lignocaine, which was instilled via the endotracheal tube, and intravenous (IV) lignocaine on coughing at pin removal and extubation. Methods 114 patients were enrolled in the study. Ages ranged from 18 -65 years and all were American Society of Anesthesiologists (ASA) grade I or II with a Glasgow Coma Score of 15 preoperatively. The subjects were all elective patients for supratentorial tumour (<5cm) surgery in the supine or lateral position. Exclusions were as follows: history of Asthma or chronic respiratory disease, history of tracheal or laryngeal pathology, current respiratory infection, local anaesthetic allergy, planned post op ventilation and vascular or additional infratentorial tumours. A computer randomly assigned each patient to one of three groups. 1. IT placebo and IV lignocaine 2. IT and IV placebo 3. IT lignocaine and IV placebo The lignocaine was prepared as a 1mg/kg quantity of 2% lignocaine in vials of the same appearance as the placebo. Aside from the pharmacy, all involved were blind to the contents of each vial. Each patient received an identical anaesthetic that included Propofol 2mg/kg, Fentanyl up to a maximum 7mcg/kg, Vecuronium 0.15mg/kg and maintenance with oxygen/air/isoflurane. Lignocaine was avoided for scalp incision but was administered at a maximum dose of 40mg for arterial and venous cannulation. When the wound dressing was about to be applied the study drug was administered. Following oropharyngeal suctioning and reversal, the patients were stimulated  by verbal commands only. Endotracheal tolerance was then graded and noted (Grade 1– no/mild cough during extubation, Grade 2- coughing when breathing regularly, Grade 3- coughing before breathing regularly). Time taken to extubate, physiological parameters following study drug, sedation levels after extubation and plasma levels of lignocaine were also documented. The data was subsequently statistically analysed using Chi-squared tests for categorical data and ANOVA for continuous data with Kriskal-Wallis testing applied to that which was not normally distributed. The accepted P value for statistical significance was <0.05. Results The three groups of patients were not significantly different with regards to any of the resulting recorded data. The only exception being negligible plasma lignocaine levels in the group treated with placebo. The grade of coughing and number of coughs in all three groups were listed as the table below. Discussion The authors concluded that their study showed no attenuation of coughing when 1mg/kg of 2% IT lignocaine was given 20-30 minutes before extubation.  They had hoped that if the effect of lignocaine on preventing coughing was by a local effect, then it should be superior to, and incur less sedation, than IV administration. In fact, they discovered that the plasma concentrations of lignocaine were not significantly different between groups 1 and 3. The serum levels were also noted to be far lower (mean concentration 0.63 mcg/ml and 0.79 mcg/ml in IV and IT groups respectively) than those stated by Hamaya and Dohi (4.3 +/- 2.5 mcg/ml at five minutes) which were shown to inhibit coughing on extubation reliably [1,2]. The authors felt that overall, the grade of coughing and total number of coughs was low, although they did attribute this to moderate to severe levels of sedation in all their patients just after extubation. Conclusion This double blind, randomized trial is inconclusive as to the action of lignocaine in blunting coughing on emergence through to extubation. The timing of lignocaine administration prior to extubation was far earlier than in previous studies and did not show any significant difference between the IT and IV routes.

  1. Jee D, Park SY. Lidocaine sprayed down the endotracheal tube attenuates the airway circulatory   reflexes by local anaesthesia during emergence and extubation. Anesth Analg.2003;96:293-93:95-103
  2. Hamaya Y, Dohi S. Differences in cardiovascular response to airway stimulation at different sites and blockade of the responses by lidocaine. Anesthesiology. 2000;