Cardiovascular signs of acute hypoxaemia and hypercarbia during enflurane and halothane anaesthesia in man.

We investigated the impact of enflurane and halothane (1.1 MAC) on heart rate and blood pressure responses to experimental hypoxaemia (PETo2 6.0 kPa [45 torr]) and small increments in PCO2 (1.3--1.6 KPa [10--12 torr]). The results reaffirm that circulatory signs of mild hypercarbia are vitually abolished by these anaesthetics. The important new observation is that signs of acute moderate hypoxaemia are also markedly depressed. Although potential modifying factors such as surgical stimulation were not evaluated, this study indicates that human subjects anaesthetized with enflurane or halothane lack reliable cardiovascular signs of acute hypoxaemia.