Minutes of the Liverpool Society of Anaesthetists Joint Meeting with the Section of Anaesthesia of the Manchester Medical Society
Thursday 19th March 2015
The meeting was opened by Dr Richard Wadsworth, the President of the Section of Anaesthesia of the Manchester Medical Society. He introduced the first speaker.
‘Anaesthesia for Liver Transplantation’
Dr John Isaac, University Hospital Birmingham
Dr Isaac began his talk by describing the liver transplantation service which occurs in seven UK centres. There are 900 cases per year and this figure is rising. The sources of these organs are mainly cadaveric of which 70% are from patients with a diagnosis of brain death and the other 30% from those already having had a circulatory arrest. A small proportion come from living related donors. Liver transplantation is the treatment of choice for end stage liver disease with this being their only chance of survival. The principle causes of chronic liver failure are hepatitis C, alcoholic liver disease and autoimmune illness, such as primary biliary cirrhosis. A small number of patients present with acute liver failure due to paracetamol poisoning or seronegative hepatitis.
Dr Isaac looked at the consequences of end stage liver disease which was a multi-system disorder. These patients seemed to have a very high output cardiac output syndrome for which the reason is still unclear, the problems of portal hypertension with splenomegaly ascites and oesophageal varices, renal impairment and coagulopathy. This could all be reversed following a transplant and he quoted figures of 92% survival after one year and 79% after five years.
Dr Isaac described the trends in liver transplantation in this country. Numbers on the waiting list had been steady in the early to mid-2000’s at about 300-400 per year, but this figure was steadily rising in the current decade. The number of transplants was also increasing, although patients could have to wait up to two years for a suitable donor. The median wait however was 4-5 months and 10% of listed patients died whilst waiting for an organ.
Dr Isaac discussed the indications and contraindications for liver transplantation. This surgery was physiologically stressful and therefore patients with poor cardiac reserve, pre-existing pulmonary hypertension and current sepsis were clearly not suitable, however age was no bar and recently they had transplanted a 76 year old man with good results.
Dr Isaac spoke about the donor types, the commonest being donation after brain death which was the optimum way of donation. Those who donated after circulatory death may have had a prolonged time of organ hypoperfusion prior to circulatory arrest and then the required transfer to the operating theatre. This period of hypoperfusion caused increased re-perfusion instability which could lead to cardiac arrest, a longer postoperative stay in intensive care, a greater occurrence of acute kidney injury and poorer graft and therefore patient outcomes. This was certainly reflected in the 30-day mortality which was 2% in the donation group from brain dead patients and 9% in the donation from patients having had a circulatory arrest.
Dr Isaac discussed patient management in the operating theatre. Donor livers tolerated cold ischemic time relatively poorly and therefore liver transplantation was truly emergency surgery often occurring during the night because of the time pressure related to the organs. The practical conduct of anaesthesia often required major vascular access. He described the liver circulation which via the portal venous and hepatic arterial circulation accounted for 30% of the cardiac output so bleeding could be a major problem. The median time for surgery was 6-8 hours with median blood transfusion of 5 units of red cells. He described the issues around liver reperfusion which centred around a hyperkalaemic acidotic cold volume load going straight to the right atrium and pulmonary circulation. This caused vasoparesis, myocardial depression, right ventricular failure, dysrhythmia and ultimately, ventricular fibrillation on occasions. At best there was cardiovascular instability which at worse was life-threatening. This syndrome was worsened by donor factors such as age, donation after circulatory death and prolonged cold ischemic times. Recipient factors included patient age and significant comorbidity. He stressed the importance of good communication with the surgeon and being ready once the caval clamp had been released. There could often be a second hit once the hepatic artery anastomosis had been completed and this additional blood flow was put into the mix. Monitoring coagulation at the bedside had become a very useful innovation and had helped to more rapidly normalise it. Postoperatively patients were transferred to critical care and ventilated for 12-24 hours until their condition had stabilised. Most stayed in ITU for 3 days with a median length of stay in hospital of 14 days. There were, however, postoperative problems related to life-long immunosuppression but also other issues such as hepatic artery thrombosis, biliary stricture, graft failure and rejection.
Dr Isaac looked at future innovations which were currently being used in renal transplantation. This included machine perfusion to prevent and reverse ischaemic damage to organs and possibly prevent reperfusion injury. These machines also helped to predict which organs were viable and certainly made renal transplantation a daytime only activity. Currently there is a trial which may answer this question but Dr Isaac looked to the holy grail of liver transplantation. This would be sufficient good organs to meet the need, a tolerance of a variable ischemic time so that transplantation could become a more elective daytime procedure and an ability to predict graft function prior to transplantation.
Dr Isaac closed his talk by returning to the editorial in anaesthesia (Shaw and Gardiner, Anaesthesia 2015,70 1-17) which he thought highlighted the moral responsibility of critical care doctors to act upon the wider benefit of patients requiring organs rather than the narrower needs of a single patient and the practical management of an Intensive Care Unit.
‘An Update on Head Injury’
Dr Richard Protheroe, Salford Royal Hospital
Dr Protheroe introduced his talk by stating that 1.5 million patients suffer head injuries in the UK every year, of which 2500 were severe. Severe head injuries account for 1% of all UK deaths and around 15% of deaths between the ages of 15-45 years. In the older age group, patients on antiplatelet and anticoagulant drugs had worsened the complications from severe head injuries. Severe head injury could be classified as a Glasgow Coma Score of between 3 and 8 on arrival and this was associated with a mortality rate of >35%. Of those that survive a severe head injury, 85% were disabled at 1 year and only 15% returned to work by 5 years. Figures for those with a mild head injury, which is someone with a Glasgow Coma Score of 13-14 on admission, showed that 50% of these patients had a disability at 1 year and only 45% returned to full functional activity. Consequently, head injury had a high economic and social cost.
Dr Protheroe spoke about the pathophysiology of head injury, starting with the primary injury which then could be compounded by secondary injury from hypotension, hypoxia, pyrexia and seizures. He showed figures demonstrating the deleterious effects of hypoxia and even worse hypotension and the very poor outcomes associated when both have occurred. Hypoxia and hypotension still remain major problems, with odds ratio for death or poor outcome doubling for a single episode of hypotension and increasing eight-fold after multiple episodes.
Dr Protheroe looked at the consequences of delay in evacuation of intracranial haematoma. For subdural haematoma, a delay of more than four hours was associated with a much poorer outcome. In those with an extradural haematoma, any delay was even more critical with one of more than 2 hours causing a poorer outcome. He then looked at local transfer times in Manchester which averaged between 5 and 6 hours. He discussed ways of improving transfer times but even with air transfer, there remained very significant logistical problems.
Dr Protheroe described a paper from TARN (Lancet 366 October 2005), which looked at the outcome of patients with and without head injuries, treated either in Neurosurgical Centres or in the districts. It demonstrated that patients treated in regional neurosurgical centres had better outcomes. Therefore, the case was made for these patients all being treated in neurosurgical centres. He then talked about the Rain Study (Risk Adjustment in neuro-critical care). This was a prospective study to validate risk prediction models for patients with acute traumatic brain injury in order to evaluate optimum location and the comparative cost of neuro-critical care. The results demonstrated a 26% mortality. In those that survived a severe head injury, 44% had severe disability, 30% moderate disability and only 26% had achieved a good recovery. It showed no difference in the outcome from dedicated neurosurgical critical care units compared to combined units. Dr Protheroe then looked at how best to treat this group of patients. He spoke about protocols, which generally doctors do not like but they have actually been demonstrated to improve outcome. He then discussed five interventions that were no longer used. These included the regular use of mannitol, which was only now used as a rescue therapy to buy some time, hyperventilation because it vasoconstricted areas of normal brain only, barbiturate-coma, CSF drainage which was technically very difficult in a swollen brain and the use of steroids which had been discredited following the CRASH Trial. He talked about decompressive craniectomy which had come back into fashion and the current trial assessing its use was due to report later this year. He discussed therapeutic hypothermia in head injury. There was good evidence that pyrexia was associated with an increase in neuronal damage, however hypothermia had significant side-effects. These affected the cardiovascular system causing a fall in cardiac output and dysrhythmias, renal and gastrointestinal dysfunction as well as metabolic and haematological consequences. He though that the problem was the target temperature and 35oC and below was too low. The evidence suggested the best temperature to which to cool people was no lower than 35.5oC.
In conclusion, he thought the most important aspects were an early transfer to the local Neurosurgical Centre, the avoidance of hypotension and hypoxia, early operative intervention for haematoma evacuation and the prevention of pyrexia.
‘Measuring Outcomes after Surgery’
Professor Ben Bridgewater, University Hospital of South Manchester
Professor Bridgewater started his talk by describing the background that began his interest in this area. He had been asked by a family friend, who had a close relative with oesophageal cancer, about who would be the best surgeon to consult for an oesophagectomy. He started to make enquiries and by pure chance found that the surgeon at the patient’s local hospital had an excellent reputation in this field. It brought home to him the paucity of data that patients have on the quality of care offered in different hospitals.
In 2001, Sir Ian Kennedy, who chaired the enquiry into the Bristol paediatric cardiac surgery services, recommended that outcome data should be provided in the public domain. This was acted upon but only within cardiac surgery. This was highlighted, yet again, in the Francis Report more than ten years later. He then spoke about the case of Ian Patterson, a breast surgeon who had a high recurrence rate for breast cancer due to poor operative technique. This was well known among his colleagues but appropriate action was not taken and Professor Bridgewater said there were many more examples of this failure to act.
Professor Bridgewater demonstrated that doctors were still very trusted members of society, however with the increasing use of social media, patients were turning to their peer group to ask for opinions about treatment options given by doctors. On average, people spend 36 hours on their computers per month so information can be readily found by patients. Similarly one patient having a bad experience in a hospital can, through the power of social media, cause damage to the reputation of that institution.
Professor Bridgewater thought the drivers of more open data were the failures of clinical governance which had been repeatedly demonstrated through regular medical scandals as well as the change in expectations and attitudes of society in general. The government had reacted to this and NHS England had recently mandated that outcome data should be published. However Professor Bridgewater thought there was absolutely no point in publishing any data unless it could be meaningful. He thought that this was a world-wide issue because people expect doctors on a medical register to be competent.
Professor Bridgewater demonstrated the cardiac surgery model. He thought that the first thing to do was to define the outcome measurement, for example mortality. A standard should then be set for example all surgeons should have a similar mortality and then acceptable variations should be defined. Data entered must be validated to ensure its accuracy and then any outliers must be informed prior to the publication of data. Over a long period sudden trends can be identified with causes then rapidly investigated and prevented from further worsening. Outcome measurements must be contemporaneous because standards are always changing and risk stratification can be improved. For example, a 50 year old with a good left ventricle will have a very different risk profile from a 95 year old having a double valve replacement with a poor left ventricle. Consequently, predicted outcomes can be compared with those observed.
Professor Bridgewater then looked at the NHS Choices website. He demonstrated the level of detail for his own outcome data. Cardiac surgeons have led the way in this field and the level of detail is high. However, it had taken some time to get this detail correct. He then showed a video of a patient and how this data had been very reassuring for the patient in his selection of surgery. Professor Bridgewater highlighted 3 important points that came from the video. Firstly the patient could know a great deal about the surgeon before he had actually met him. Secondly, a lot of the data that the patient valued could be easily produced such as qualifications, training and experience and thirdly, this data should be easy to find for patients.
In summary, Professor Bridgewater thought transparency was increasingly demanded by society. Outcome data disclosure was still unpopular with medical professionals however, the process must be medically let for reliable meaning to be made of disclosed data. The future possible issues were significant. These included the possibility of doctors becoming increasingly risk averse, team versus individual performance, what to do about outlining outcomes and whether or not outcome data will determine revalidation.
In questions, Professor Bridgewater thought that more data should be available about anaesthetists and he thought that patient feedback was very helpful to clinicians. He also thought that all revalidation data should be made public because having a large amount of data about an individual’s practice empowers them.
Dr James Palmer, Salford Royal Hospital.
Dr Palmer started his talk by thanking the audience for taking part in this national audit and therefore making it possible. He then summarised the report by stating that accidental awareness under general anaesthesia was often brief, usually occurred in dynamic phases, commonly caused distress and was frequently associated with neuromuscular blockade. The sequelae from accidental awareness were common and long-lived and associated with patient distress because of the association with neuromuscular blockade. Therefore, paralysis should be avoided wherever possible and when required should be managed better. NAP5 had identified both high risk groups and situations. The management and monitoring of neuromuscular blockade was one of the main messages, particularly when used with total intravenous anaesthesia because this combination seemed to be associated with a higher incidence of accidental awareness. NAP5 also recommended the use of an anaesthesia specific checklist.
Dr Palmer looked at studies that had preceded NAP5. He looked at three studies, all of which had relatively small numbers with an apparently high incidence of accidental awareness. All studies had highlighted the increased incidence during cardiac and obstetric operations and these had frequently occurred during maintenance of anaesthesia rather than during induction and emergence. NAP5, in contrast, had included 269 UK centres and the total estimated number of anaesthetics as the denominator figure was approximately 2.7 million. 300 cases of accidental awareness had been accepted for further analysis.
Dr Palmer discussed memory and its association with post-traumatic stress disorder. He said that memories are reconstructed and not replayed and events may come back due to unique retrieval cues. Traumatic experience seemed to block normal memory formation and triggers which may be related in some way to the original experience can cause uncontrolled flashbacks.
Dr Palmer described the figures. The overall figure from NAP5 demonstrated that 1 in 19,000 anaesthetics was associated with accidental awareness. However, when no neuromuscular blockers were used, this figure was 1 in 136,000 whereas with the use of neuromuscular blockade the incidence is 1 in 8,200. Reports were however quite heterogeneous and some were actually associated with sedation. The timing of awareness seemed to be most commonly during induction with nearly half the cases were associated with this period of anaesthesia. Almost a third had occurred during maintenance of anaesthesia and the remainder associated with emergence. The experience of awareness was commonly an inability to move or to communicate and a feeling of an inability to breathe and that of suffocation. Other sensations reported were that of hearing noise or voices, awareness of tracheal intubation, pain or just touch without pain. The distress of awareness could be made worse after the event assuming that it is reported by the professionals involved having a lack of understanding. Similarly, it can be subsequently reduced by a sensitive explanation and apology. Generally the period of awareness was relatively short but its length did not affect its long-term impact. Distress is always worse when associated with paralysis. In NAP5, as in previous studies, patients undergoing obstetric and cardiothoracic surgery were overrepresented. For anaesthesia for cardiothoracic surgery, the figure of 1 in 8,000 was the same as for other surgery requiring neuromuscular blockade, however for caesarean section the instance was much higher at 1 in 670.
Dr Palmer then discussed the modes of anaesthesia where TIVA seemed to be overrepresented in cases of awareness. He looked at induction of anaesthesia where the use of thiopentone and etomidate has a greater association particularly when used during rapid sequence induction. He highlighted the issue of awareness being more common with TIVA. He described the unholy trinity of neuromuscular blockade being used with no nerve stimulator and no reversal, meaning that patients were transferred to the recovery room and woke up still with a very significant degree of neuromuscular blockade.
Dr Palmer then described various causes such as accidental syringe swabs, for example between thiopentone and cefuroxime. Another example was the gap between the offset of induction agents and the rise in the concentration of volatile agents, leading potentially to lightening of anaesthesia and transitory awakening. This was far more common in prolonged or difficult airway management, particularly when using thiopentone as well as delay during the transfer of patients from the anaesthetic room to the operating theatre, particularly if the volatile agent is not immediately switched on.
Dr Palmer then spoke about various solutions. These included appropriate dosing, particularly in the obese and considering alternatives to thiopentone for rapid sequence induction. He thought that the risk of accidental awareness should be communicated to patients prior to rapid sequence induction or anticipated difficult airway management. He then spoke about the anaesthetic checklist which looked at the different aspects of anaesthesia at the various stages of the WHO checklist. He stressed the importance of the monitoring of the degree of neuromuscular blockade to prevent premature awakening in partially paralysed patients. He thought that patients should be warned about the experience of awake extubation during the preoperative consent process, this being the commonest timing of extubation in the recovery room leading to potential distress.
Dr Palmer discussed the use of TIVA and a deeper analysis of why patients appeared to be at greater risk. This was particularly a problem when TCI was not used although even with TCI, there appeared to be a significantly increased risk. It also seemed a problem when intubated patients were transferred from the operating theatre to critical care, the volatile agent being exhaled prior to a sufficient plasma concentration of propofol being available. Patients were at greatest risk from awareness during TCI when neuromuscular blocking agents were used. He looked at depth of anaesthesia monitoring which was still used relatively infrequently. Its use seemed to be greatest when TIVA was being administered and patient benefit seemed to be greatest in this situation. However, there were cautions and awareness could still occur despite is use.
Dr Palmer then looked at the issue of sedation because 20% of reports were from patients who had not actually had a general anaesthetic, however their experiences appeared to be just as bad. This is because patients misunderstood the intention of sedation and their dissatisfaction with the achieved level of consciousness. Therefore, during the consent process it needs to be made quite clear to patients the difference between anaesthesia and sedation.
In summary Dr Palmer said that awareness was often brief but commonly associated with distress and the use of neuromuscular blockade. When associated with distress, sequelae can be common and long-lived, however distress can be reduced by a sympathetic understanding of the patient experience. Neuromuscular blockade should be avoided wherever possible and when used managed better. The incidence of awareness has implications for the consent process and with this information patients can have a better understanding of the actual risk.
20th March 2015