Medicine is like war – it causes collateral damage. Often the damage is all the more shocking because it is so unexpected. Take oxygen. Every child knows it is essential for life – so how can it make babies blind? If given in too high a concentration to premature babies, oxygen causes a condition called retrolental fibroplasia (overgrowth of the capillaries in the retina), which destroys their sight. In the 1950s, babies in intensive care units were blinded while under the best, most skilled care available, until the cause was found.
Decades after I learnt of this discovery, the shock of it still lingers. What could be wrong with giving premature babies, whose lungs are underdeveloped, extra oxygen? Oxygen seemed such an unlikely villain.
It was an early lesson that one should never make assumptions in medicine, and never think that "it's common sense" is any kind of argument. Even the most seemingly benign treatments can cause serious harm.
Last week, history repeated itself. We learnt that premature babies are being made deaf by something almost as ubiquitous as oxygen in hospitals – antibiotics. Antibiotics are life-saving in the way oxygen is life-giving. Who would have thought that a common class of antibiotics, called aminoglycosides, used for decades on some 20,000 premature babies a year, could have such a devastating side-effect?
It was known the drugs could cause deafness, but it was thought to be extremely rare and linked with the dose. Now, it has emerged that doctors were in effect engaged in a game of Russian roulette; one in 500 babies has a genetic susceptibility that means the drugs can condemn them to a life of silence. Though unusual, one in 500 is not extremely rare. It means one child a week is going permanently, profoundly deaf. This could be avoided if pregnant women were screened for the mutation.
How was the problem missed? Because deafness in a premature baby was thought more likely to be due to its prematurity – just as, half a century ago, blindness was. Perhaps the fact that antibiotics are such effective, important and long-used drugs put them above suspicion.
Doctors use all weapons at their disposal to defend the body against invaders. As in wars, there is an inevitable cost. But what is acceptable? Eight-year-old Laila MacDougall, whose picture appeared in this newspaper last week, was saved by antibiotics from infections that threatened her life while she was being treated for leukaemia. What has she got to complain about? Unfortunately, you cannot put the question to her directly. She would not hear you.