If we translate these figures into the chance in a million of dying, or micromorts, this becomes a risk of 10 micromorts – equivalent to travelling around 60 miles on a motorbike, or a bit more than a parachute jump. Around half of that risk, 5 micromorts, arises from errors made in administering the anaesthetic, which is nice to know. Risks for day-cases are lower, and higher if you are older or it’s an emergency operation.
OK, so you survive the anaesthetic, but what about the operation itself? One of the most commonly performed procedures is a coronary artery bypass graft (known as CABG, and pronounced like the green vegetable), which relieves symptoms of angina by improving the bloodstream to the heart using a piece of artery or vein removed from elsewhere in the body. The risks have been carefully studied. This type of operation started in 1960, and mortality in the US was down to 3.9% in 1990 and to 3.0% in 1999. The UK now reports a ‘98.4% survival rate’, based on 21,248 operations in 2008.
Note the different framing of this information: The UK figures describe survival rather than mortality. In the US, people die from surgery while in the UK they do not survive. This change of framing is a neat device that tends to make performance look better and obscure differences: the difference between two hospitals with 98% and 96% survival, as we would describe it in the UK, looks negligible, while the same comparison expressed as it would be in the US as 2% versus 4% mortality is a doubling and looks far more serious. The sort of figures that news outlets are more likely to pick up on, for instance.
Whichever way we choose to frame it, the fact that some states in the US mandate mortality reporting mean we can explore the risks of the procedure in further detail. For instance, all hospitals in New York State that perform cardiac surgery must file details of their cases with the State Department of Health. In 2008 there were 10,707 CABG operations in 40 hospitals, and 194 patients died either in hospital or within 30 days – a mortality rate of 1.8%. Or, as they would say in the UK, a survival rate of 98.2%.
Surgery on heart valves was a higher risk: of 21,445 operations in New York State between 2006 and 2008, 1,120 patients died, a mortality rate of 5.2%, or more than 1 in 20. That’s an average of 52,000 micromorts per operation, equivalent to around 10,000 scuba dives or two RAF bombing missions in World War II.
As stark as the risk might seem, presumably the risk without an operation is higher. So you may want to go under the knife like you’d want a hole in the head. But at least thank your lucky stars that the days of actually receiving a hole in the head in the name of medicine are long gone.