The role of halothane and fentanyl in the production of balanced anaesthesia.

Abstract

The aim of the study was to quantitate the degree of respiratory depression when tolerance of superficial nociception and of an endotracheal tube was achieved by supplementing N2O + O2 anaesthesia either with halothane alone or with halothane in combination with fentanyl. Eighty-four patients, matched into seven groups, were studied after induction of anaesthesia with thiopental (4 mg/kg) and suxamethonium (3 mg/kg) using the following supplementation: 0.8, 0.6, 0.4% halothane alone or 0.4, 0.2, 0% halothane with 0.5-2 micrograms/kg fentanyl. After 10 min administration of the anaesthetic mixture using manual intermittent positive pressure ventilation (IPPV) (end-tidal CO2 c. 5.5%), IPPV was discontinued and spontaneous respiration allowed to return. When the end-tidal CO2 had stabilized, samples for blood gas analysis were taken and superficial antinociception was tested by pinching an inguinal skin fold. Supplementation of an N2O + O2 mixture with 0.8% halothane without fentanyl or with 0.4% halothane with 0.5 microgram/kg fentanyl seemed to come closest to the optimum in producing tolerance of an endotracheal tube and of superficial nociception (in about 85% of cases with an increase in PCO2 to only 7 kPa.