Intraoperative hypotension and postoperative organ injury: Pressure and perfusion from the population to the individual patient

Anaesthetists are often faced with a challenging problem: low intraoperative blood pressures (hypotension). It is not clear which intraoperative blood pressures are too low for the individual patient and whether intraoperative hypotension is related to postoperative organ injury. The results of our systematic review show that limited knowledge is available on the relation between intraoperative hypotension and cerebral outcomes. We performed three studies on cerebral outcomes: two studies on occurrence of delirium after cardiac procedures and one study on the effects of β-blockers on intraoperative hypotension and the need for a temporary shunt during carotid endarterectomy. There was no clear relation between intraoperative hypotension and these cerebral outcomes. Thereafter, our focus shifted to individual intraoperative blood pressure dynamics in the complex clinical context. Two new intraoperative hypotension analysis methods were developed and applied to data of a large cohort of patients who underwent noncardiac surgery. Short blood pressure dips were strongly related to postoperative myocardial injury and in-hospital mortality. In contrast, the relation between a steady intraoperative blood pressure course and both outcomes remains unclear. At last, the effects of blood pressure components in relation to hypotension mechanisms was studied. Intraoperative arterial waveform parts were decomposed and analysed in relation to mean blood pressure change after two blood pressure raising medicines. The relation between arterial waveform parameters and the mean blood pressure seems to be different between patients and vasopressors. Various waveform parameters and their relation with mean blood pressure are probably dependent on the underlying mechanism of intraoperative hypotension.