Joint Meeting Manchester Medical Society, Manchester Town Hall
The meeting was opened by Dr Paul Cook, the President of the section of Anaesthesia of the Manchester Medical Society who introduced the first speaker.
1) In the footsteps of Featherstone
Dr David Whittaker, Consultant Anaesthetist, Manchester Royal Infirmary
Dr Whittaker introduced his talk by giving a background of the major events happening in and around Manchester in the 1830s. The Manchester Medical Society was formed in 1834 at which time the medical profession was disorganised and it was not until 1858, when the Medical Act was introduced, were doctors given unique prescribing rights. The cost of joining the society was a guinea per year and one of the principal aims was the development of a library. The venue of the meeting, Manchester Town Hall, was built in 1887 for one million pounds at a time when Manchester and its surrounding areas were responsible for more than 50% of GDP in Britain.
1896 saw the first society for anaesthetists which was formed in London followed 11 years later by the formation of the Royal Society of Medicine. The first female graduate of Manchester Medical School was Catherine Chisholm who qualified in 1904 and four years later joined the Manchester Medical Society.
1932 saw the establishment by Henry Featherstone of the Association of Anaesthetists of Great Britain and Ireland with the aim of establishing an examination which was to be called the Diploma of Anaesthesia. 1945 saw the establishment of the Section of Anaesthesia of the Manchester Medical Society. The next important date in the development of anaesthesia was 1951 when Charles Suckling discovered halothane in the ICI laboratories in Widnes. After animal testing, Michael Johnston used halothane for the first time on humans in St Mary’s Hospital Manchester. The popularity of halothane funded further drug development such as beta and H2 blockers and latterly Propofol.
Dr Whittaker then talked about his experience of being President of the AAGBI with trips overseas and compared his insight with UK practice. In particular, he looked at aspects of patient safety particularly in the third world. He finished by hoping that Manchester anaesthetists would continue to take a role in the development of anaesthesia.
2) How Green Is Your Anaesthetic?
Dr Nigel Harper, Consultant Anaesthetist Manchester Royal Infirmary
Dr Harper started his lecture by looking back to 1974 when the destructive potential of CFCs were discovered followed in 1985, by the description of their effects on the ozone layer. In 1987, the Montreal protocol for the use of CFCs was agreed with their discontinuation including isoflurane and enflurane. These will be both banned from 2030. 1992 saw the first UN convention on climate change which was followed in 1997 by the Kyoto Agreement where it was agreed that CO2 emissions would be 5% below those in 1990 by 2012. This was followed in 2008 by the Climate Change Act which committed the UK to a reduction in CO2 emissions by 26% by 2020.
The IPCC 2007 report documented the rises in temperature and sea levels and reduction in snow cover over the northern hemisphere since 1850. The concentration of CO2 has risen from 320 to 380 parts per million since 1960. He showed a slide of the massive rise in carbon emissions from the burning of fossil fuel since the 1950. He also stated that 11 of the last 12 years were the warmest since records have begun and there has been a 3 mm per year rise in sea level since 1993.
Dr Harper then asked the question “Why should we worry?” He explained that the increase in atmospheric temperature would cause changes in the food and water supply as well as changes in eco-systems with an increase in extreme weather events which is likely to lead to irreversible change. He then looked at greenhouse gases which comprise water, ozone, carbon dioxide, methane, nitrogen oxides and hydrocarbons. He explained that the greenhouse effect was essential as without it, the average temperature of the earth would be -19ºC. He said that water vapour was the largest greenhouse gas and was more potent than CO2. Ozone, which is important for absorbing ultraviolet light in a self-regenerating reaction, is susceptible to depletion by nitrogen oxides and chlorine. Isoflurane may increase this due to its atmospheric breakdown which releases chlorine. Dr Harper then looked at CO2 which had increased in the atmosphere by 30% since the industrial revolution. As well as increasing in the atmosphere it was also causing the acidification of oceans. UK CO2 emissions had changed little in the last 20 years. He pointed out that the National Health Service was actually responsible for a significant amount of emissions. Methane has 21 times the warming effect of carbon-dioxide although it has a much shorter atmospheric life. The UK emissions of methane are falling because it is being utilised better although consequently being turned into CO2. Nitrous oxide is also a very potent greenhouse gas and destroys ozone. It has 200 times the greenhouse effect of CO2 however has a thousand times lower concentration. Most of the emissions of nitrogen oxides are from agricultural fertilizer and the contribution from anaesthesia is very small. Finally, he looked at hydra-carbons which have a potent warming effect. Sevoflurane and desflurane had no ozone depleting effect because they lack chlorine.
Dr Harper finished by asking whether Xenon could be the ultimate green anaesthetic. It is a by-product of the fractional distillation of air and is an excellent anaesthetic agent.
3) Will I be asleep?
Professor Brain Pollard, University of Manchester
Professor Pollard started with the findings from studies which have shown that the incidence of awareness is between 1:500 and 1:1000 patients. This would indicate that between 3500 and 7000 patients were aware under anaesthesia every year. With his involvement in medical litigation, he thought this number was unrealistic as there was very little litigation in this area. The spectrum ranged from awareness with or without recall to vivid dreaming. The causes of awareness were principally inadequate anaesthesia. Sequelae included anxiety, depression, sleep disorders and nightmares. Prevention is the maintenance of adequate anaesthesia but how much is adequate?
Professor Pollard said that it was easy to measure anaesthetic concentrations such as MAC and TCI but every patient is different and these are not measures of depth of anaesthesia. Indeed anaesthesia is a continuum and we rely on the monitoring of autonomic reflexes and patient movement. Professor Pollard looked at the more objective monitoring of anaesthetic depth; firstly, he looked at the EMG which is only useful in the non-paralysed patient. He then went onto the EEG which is very difficult to interpret as different agents cause different waveform changes. Other methods include evoked responses and heart rate variability. Finally Professor Pollard looked at bi-spectral index which was a combination of EEG analysis and frontalis muscle EMG and gave a read-out of a single number between 0-100. This is currently used in approximately 60% of patients undergoing anaesthesia in the USA. Its accuracy is still debatable but Professor Pollard felt it was an additional tool to use in gauging depth of anaesthesia and may help prevent anaesthesia becoming too deep as well as too light. Finally, he commented upon functional imaging of cerebral metabolic rate and said that this correlated with CMR reduction during anaesthesia.
In conclusion, he said that more monitors were now available to gauge the depths of anaesthesia and he used bi-spectral index routinely for high risk patients.
The vote of thanks was given by Professor Jennifer Hunter and the meeting closed at 5pm.
6th April 2009