Clinical studies of induction agents. XVII. Relationship between dosage and side effects of intravenous barbiturates.

A retrospective analysis of the records of about 9,000 intravenous anaesthetics showed a striking relationship between dosage and induction complications. While the incidence of excitatory phenomena increased with dosage of thiobarbiturates, this effect was more marked with methylated barbiturates. The greater frequency of respiratory complications (cough, hiccough and laryngospasm) with high dosage was similar for both groups of drugs. Opiate premedications reduced the incidence of excitatory phenomena but had no effect on the respiratory complications. It is suggested that the "convulsive" element in the action of barbiturates predominates with higher dosage and the respiratory complications may be related to the action of the drugs on the parasympathetic nervous system.