Effects of lidocaine on the anesthetic requirements for nitrous oxide and halothane

Abstract

The effects of various plasma concentrations of lidocaine on nitrous oxide anesthesia in man and halothane requirements in the dog were studied. The response to incision of the skin was observed in 20 patients who were anesthetized with nitrous oxide, 70 per cent inspired, and oxygen, 30 per cent, plus various plasma levels of lidocaine. In addition, changes in the MAC of halothane in dogs were observed at various levels of lidocaine. In both circumstances lidocaine concentrations of 3 to 6 μg/ml decreased anesthetic requirements approximately 10 to 28 per cent. At clinically common concentrations of lidocaine, significant decreases in anesthetic requirements should be anticipated.