The effects of drugs used in anaesthesia on platelet membrane receptors and on platelet function.

Platelet dysfunctions are known origins of perioperative bleeding disorders which are a major concern in the management of surgical patients. Among multiple factors, interactions of drugs used in anaesthesia with platelets have been implicated to aggravate the risk of haemorrhagic complications. This paper reviews in vitro and in vivo studies which have examined the effects of inhalational, intravenous, and local anaesthetics, opioids, and muscle relaxants on platelets. A brief summary of platelet physiology, function tests, and flow cytometric assessment of membrane receptors is included. Although the results of many studies have been conflicting, it appears that halothane, sevoflurane, and propofol inhibit platelet function in a reversible and dose-related manner at concentrations used clinically. Ilalothane affects the intracellular activating second messenger inositol triphosphate, platelet calcium homeostasis, thromboxane A2 formation, and the inhibiting signal transduction pathway including cyclic adenosine monophosphate. The proposed platelet inhibiting mechanism of sevoflurane involves the suppression of thromboxane A2 formation. Propofol appears to cause platelet dysfunctions by inhibiting calcium mobilisation upon agonist stimulation. Nitrous oxide causes a modest suppression of calcium mobilisation. An interaction of local anaesthetics with components in the platelet membrane appears to account for their inhibiting effect, but only at concentrations far higher than that found during clinical use. A clinically relevant antithrombotic effect of regional anaesthesia has been observed, though. Isoflurane, enflurane, desflurane, barbiturates, etomidate, opioids, and muscle relaxants seem to have negligible effects on platelets at therapeutic concentrations. Anaesthetists should be aware of the potential impairment of the coagulation profile by anaesthetic agents.