[Biological rhythms for anaesthesia and intensive care]

Knowledge of biological rhythms has led to better understanding of the time-of-day dependent effects of anaesthetic drugs. These chronopharmacological effects are currently explained by the biological rhythms modulating the pharmacokinetic, toxic and pharmacodynamic parameters of these substances. Such effect has been described for general anesthetics, local anaesthetics, analgesics as well as for antibiotics. But recent data also highlight that general anaesthetics, probably part of their brain effects, also alter the regulation of biological rhythms, including the sleep-wake or the endogenous circadian temperature rhythms. This desynchronization of biological rhythms can led to disturbance of the circadian secretion of many substances, including hormones. Finally, biological rhythms have been also described with regard to physiology of pain and cardiovascular physiopathology. The concept of biological rhythm should be present in mind not only for the clinical management of patients but also for setting studies in the field of anaesthesia, pain and intensive care.