Professor and Head of Department Anaesthesiology University of Auckland New Zealand.
It is widely claimed that anaesthesia today is very safe. As a teacher, I often ask trainee anaesthetists two questions: "What is the risk of dying from an anaesthetic today?" and "What risk would be acceptable?" The answer to the second question is really the starting point for thinking about safety in anaesthesia.
The answer depends on context. If a surgical procedure could be done under local anaesthetic, and / or is not really essential to preserve life or limb, then the risk of dying from the anaesthetic has to be very low indeed. If, on the other hand a surgical procedure has the potential to save life, a higher risk would be acceptable; if the odds faced by the patient (perhaps expressed in quality-adjusted life years or QALYs) are better with the procedure and anaesthetic than without, it would make sense to proceed.
What then is the answer to the first question? The astonishing fact is that we don't really know. In developed countries, estimates of avoidable anaesthetic mortality vary from as low as 1:2,00,000 to as high as ~1:10,000. Australia probably provides the best data in the world about anaesthesia mortality, but even there it is difficult to determine a true rate with confidence. A rate of 1 in 79,509 was cited in the "Review of Anaesthesia Related Mortality" published by the Australian and New Zealand College of Anaesthetists for triennium 1997-1999. However, the rate for the next triennium (2000-2002) was 1 in 56,000. Does this mean that anaesthesia was becoming more dangerous over time? No! In fact, the apparent increase in risk in the second report is attributable to improved collection of denominator data. Of course, this implies that the rate in the first report is wrong, which raises the question as to whether further refinements in data collection will show that the current rate is not reliable either. In reality, there has been a wide variation in reported rates from many countries over the last 30 years. Difficulties in data collection certainly contribute to this variation, but a more significant factor is the lack of an agreed international definition of anaesthetic mortality.
Most current estimates of anaesthetic mortality pertain to the first 24 or 48 hours after an anaesthetic (with perhaps a few extra deaths after that), but there is no particular reason to choose either of these time periods. In developed countries, it is quite unusual for a patient to die on the operating table, and relatively few die within 24 hours of an anaesthetic. On the other hand, families are probably interested in having their loved ones leave hospital and come home in good health and the rates for in-hospital death or 30-day mortality have not been widely evaluated.
The risk of death attributable to anaesthesia also depends on the condition of the patient. For a fit young patient undergoing minor surgery in countries like Australia, this risk is obviously very low (although not zero). However, the risk to patients at the extremes of life, with co-morbidities, and undergoing major surgery is much higher. As I have said, this may be acceptable from a pragmatic standpoint, but it is not ideal. Anaesthesia is not in itself therapeutic, and it should not add to the risks faced by patients, even if they are unwell in the first place. There is, therefore, considerable room for improvement.
In developing countries, the situation is much worse. The risk of avoidable mortality associated with anaesthesia in some rural areas of the world may be as much as 1,000 times higher than in cities that can afford to invest in well-trained anaesthetists, expensive drugs and modern technology. Illustrative estimates vary from 1:3,000 in Zimbabwe to 1:150 in Togo. This high risk reflects a failure to invest in anaesthesia as part of the provision of surgical services. Surgery without safe anaesthesia cannot be safe, but it can be marketable. Countries may claim to provide "essential surgical services" when, in fact, the net effect of these services may be to the detriment of public health, because of inadequate infrastructure including the necessities for safe anaesthesia (trained anaesthetists being the foremost requirement, but oxygen, equipment and drugs are also essential).
In the developed world, the level of training for anaesthesia providers is comparable similar to that provided to surgeons. In the UK, Australia and New Zealand, anaesthetists (called anaesthesiologists in the US) must be medically qualified and require seven years of training after qualifying as a doctor. In the US, Scandanavia and certain other countries, many anaesthetics are provided by nurses, but these providers must satisfy high standards of training and examination, and typically work in teams that include medically qualified anaesthesiologists. In some countries, on the other hand, anaesthetics are given by people with no medical or nursing background, and with little if any specific training: in fact, it is not uncommon for the surgeon to take responsibility for the anaesthetic as well as the surgery. This might possibly be workable if the surgeon were also an adequately trained anaesthetist, but that is often not the case. Under these circumstances, poor anaesthesia technique, lack of monitoring and lack of expertise have been identified as factors contributing to the high death rate. In addition to lack of training and expertise, anaesthesia providers in these circumstances usually face a shortage of the most basic facilities, equipment and drugs, particularly in rural areas. A recent study from Uganda, where there are few medically qualified anaesthesia providers (13 anaesthesiologists for 27 million vs. 12,000 for 64 million in the UK), identified deficiencies in running water, electricity and the availability of oxygen for example. Even sterile gloves were in short supply.
The goal of the American Society of Anaesthesiologists is "no harm from anaesthesia". Even in developed countries we are a long way from achieving this. The most obvious problems today involve avoidable errors, particularly in the assessment of patients before administering their anaesthetics, and in the processes of administering anaesthetics. For example, it has been shown that a wrong drug is given once every 150 anaesthetics. Often, this is without serious consequence, but occasionally the results are catastrophic. For countries that can afford it, technological advances will build on the gains already made and lead to continued if gradual improvements in safety. These will include the use of bar coding (or other technologies, such as radio frequency identification devices or RFIDs) to improve the safety of drug administration, computerised systems for facilitating the pre-operative assessment of patients, and further improvements in the drugs available for anaesthesia. Adjunctive agents designed to mitigate the cardiac and renal effects of anaesthesia and surgery will be as important as anaesthetic agents, and research will increase our understanding of how to mitigate the stress response of the human body to the assault of surgery. Improvements in surgery (the greater use of endoscopic "keyhole" techniques) and lesser need for major radical and mutilating procedures will also help. The holy grail of a synthetic, effective and safe substitute for blood will be another important advance if it is ever achieved. The high standards of training in anaesthesia will need to be maintained, and in fact, extended. Increased expertise in diagnostic imaging (notably echocardiography) will enable anaesthetists to improve their pre-operative assessment and their intra-operative management of patients. In addition, there is considerable evidence of over treatment in relation to a number of surgical procedures. An important part of reducing the risk of anaesthesia is to limit surgery to those operations that are truly indicated and genuinely likely to improve the quality of the patient's life. It seems likely that this insight will gain traction over the next few decades and anaesthetists, as perioperative physicians, will have a greater role in ensuring the appropriateness of surgery.