Hemodynamic responses during induction of anesthesia with halothane-nitrous oxide in children with or without atropine premedication

Forty three children ranged from 1yr. to 6yr. were randomly assigned to non-atropinized group (n = 20; A(–)) and atropinized group (0.015mg·kg^–1 i.m., n = 23; A(+)). Control hemodynamics were measured under 0.5% halothane and 67% nitrous oxide and 33% oxygen for three minutes, and then halothane was increased to 2.5% and maintained for 15min. In the A(–) group, stroke volume (SV) decreased to 64%, heart rate (HR) increased from 100/min to 111/min, and blood pressure (BP) decreased from 65mmHg to 62mmHg. Skin blood flow (SBF) concomitantly measured by a laser doppler flowmeter decreased to 48% and total peripheral resistance (TPR) increased to 128%. In the A(+) group, HR increased from 117/min to 132/min (P 0.05, vs. A(–) group), BP decreased from 67mmHg to 66mmHg. SV decreased to 71% (P 0.05, vs. A(–) group). Changes in SBF and TPR were 68% and 128% respectively. End-expired halothane concentration in the A(+) group increased slower than in the A(–) group but not significantly. The results indicate increased sympathetic tone would work as a compensating mechanism for decreased SV and CO. Atropine premedication attenuated cardiovascular depression by maintaing HR and possibly by delaying induction speed of anesthesia. In conclusion, halotane-nitrous oxide anesthesia decreased SV without a marked decrease in heart rate and blood pressure in children. This decrease in SV and BP was attenuated by atropine premedication.(Kawana S, Namiki A, Morita Y, et al.: Hemodynamic responses during induction on anesthesia with halothane-nitrous oxide in children with or without atropine premedication. J Anesth 6: 63–68, 1992)