Quantifying and communicating peri‐operative risk

摘要

Shallow men believe in luck. Strong men believe in cause and effect Risk is the potential that a chosen action or activity (including the choice of inaction) will lead to a specific outcome, and implies that the choice has an influence on the outcome. Most definitions are synonymous with the possibility of an adverse event but, of course, a risk can also be taken in the hope of a favourable outcome, particularly with investment. There is also a personal perspective on risk. A fatalist personality may be very accepting and unconcerned about risk whereas more pragmatic individuals know that there can be modifiable factors involved. This can apply to healthcare; for example, even though surgery may be necessary in a patient, there may be pharmaceutical interventions that could reduce morbidity. Almost any human endeavour carries some risk. Staying in hospital is far riskier than travelling by aeroplane. A recent study showed that a one-night stay in hospital carries a 11.1% risk of nosocomial infection, a 3.4% risk of an adverse drug reaction related to human error or allergy, and a 0.4% risk of pressure ulcer due to immobilisation 1. In 2007 in the USA, there were 1.31 fatal crashes per 100 000 flight hours for non-commercial flights and 0.016 per 100 000 for major airlines 2. Despite efforts to the contrary, healthcare is an intrinsically hazardous business. Anaesthesia is a medical specialty very much focused on risk management and patient safety and, consequently, the mortality risk attributable to anaesthesia itself has dropped dramatically over the years, from about one death in 1000 anaesthetic procedures in the 1940s to one in 100 000 in the early 2000s 3. However, although anaesthesia is relatively safe, surgery can be very dangerous. In 2000, the 30-day mortality risk in the UK was one death in 34 emergency operations (2.9%) and 1:177 after elective surgery (0.6%) 4. The European Surgical Outcomes Study was an observational study in which data were collected on 46 539 patients aged ≥ 16 years undergoing non-cardiac surgery, over a seven-day period, in 498 hospitals across 28 European nations 5. There was considerable variability from country to country but median death rates were 3% for elective and 10% for emergency surgery. Anaesthesia has an excellent track record for patient safety and has been described as the leading medical specialty in addressing such issues 6, yet it is apparent that the peri-operative process still has great potential for hazard from a host of factors, of which anaesthesia is but one. Ronald A. Howard, a pioneer of decision analysis, wanted to develop a scale that would more clearly confer risk rather than percentages. He coined the term ‘microprobability’ to refer to an event with a chance of one in a million. From this concept, a ‘micro-mort’ (from ‘micro’ and ‘mortality’) is then a one in a million chance of death 7. We face risk simply by being alive and this may be exacerbated by indulging in various activities. A mobile app is now available for illustrating how many micromorts are involved in our daily activities (see https://play.google.com/store/apps/details?id=com.zanzibartech.micromorts). The use of micromorts then allows us actually to quantify risk and translate it into whole numbers. A micromort denotes a one in a million chance of death from one-time dangerous events, a concept that can be easily understood and compared. A one in a million chance is, of course, rare but also an everyday occurrence. For example, the chance of a particular individual's winning the weekly lottery is less than 1 in 32 million people, but conversely this jackpot gets won almost every week by somebody. Micromorts are an expression of acute risks, such that once that event has been completed the risk has gone. The risk of surgical anaesthesia is in the range of various day-to-day activities. Audits of the risk of death from a general anaesthetic alone vary considerably geographically, but may be around