Maternal and neonatal responses related to the volatile agent used to maintain anaesthesia at caesarean section

A standardized technique of general anaesthesia, with one randomly selected variable, was provided for 237 patients undergoing elective and 540 undergoing emergency Caesarean section. The variable was the volatile agent used to maintain anaesthesia, the choice resting between trichloroethylene (0.2 or 0.3 vol.%) and halothane (0.2, 0.3, 0.4 or 0.5 vol.%). No association was found between the type of agent and the duration of anaesthesia, or the duration of either the I-D or the U-D interval. A smaller total dose of suxamethonium was administered in conjunction with the higher concentrations of volatile agent. A statistically significant but clinically unimportant increase in the time elapsing from the cessation of anaesthesia to maternal achievement of a "safe level of consciousness" was found with the higher concentrations. The incidence of maternal awareness plus unpleasant dreams was unacceptably high when the lower concentrations were used, and it is recommended that either trichloroethylene 0.3 vol.% or halothane 0.4 or 0.5 vol.% be used. Neither agent, at these concentrations, was associated with neonatal depression in group A elective sections in which the fetus presented by the vertex, and although there was a possible tendency for their use in cases of fetal compromise to be associated with an increase in the incidence of neonatal respiratory depression, the degree of depression was of little consequence to neonatal well-being. It was confirmed that breech presentation and prolongation of the U-D interval are important determinants of depression and birth asphyxia among infants delivered by Caesarean section under general anaesthesia.