Triple low, double low: it’s time to deal Achilles heel a single deadly blow

Since the report by Monk and colleagues¹ of an association between a cumulative duration of the bispectral index (BIS) <45 and postoperative mortality there has been debate regarding the plausibility that relatively excessive anaesthetic depth is deadly. It is not surprising that this premise has ignited a scientific controversy and that anaesthetists are both intellectually and emotionally vested in its resolution. If this hypothesis were indeed true, the concentration of (volatile) anaesthetic promoting death would be within what is currently considered the therapeutic window. Furthermore, if a minor increase in anaesthetic administration were truly fatally injurious, we would expect to see a marked increase in mortality with general compared with regional anaesthesia. Also, since some clinicians administer more anaesthesia than others, we would predict that these variations would manifest as differences in postoperative morbid and mortal outcomes. And yet, differences in major adverse outcomes, based on anaesthetic technique or individual anaesthetists, have not been apparent in several studies.^2–9

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