Cardiovascular responses to tracheal intubation in small children. Effects of the induction of anaesthesia with halothane.

Cardiovascular changes in 27 children (mean age 1.5 yr) were studied during the induction of anaesthesia with 2.5% halothane and 70% nitrous oxide in oxygen. The eyelash reflex disappeared in a mean of 62 +/- 3.6 (SEM)s and tracheal intubation could be performed 4.9 +/- 0.2 min after the start of halothane anaesthesia. Intubating conditions were satisfactory in 85% of the children. Systolic arterial pressure increased by 10.8 +/- 1.9 mm Hg and diastolic pressures by 6.0 +/- 1.4 (SEM) mm Hg after intubation of the trachea. Heart rate decreased significantly after induction. No cardiac arrhythmias were noted. There were no significant changes in Q-T interval after induction, after intubation or during the later course of the anaesthetic.