Haemodynamic and catecholamine changes during rapid sevoflurane induction with tidal volume breathing

Abstract

Purpose: To compare haemodynamic and plasma catecholamine changes with rapid (three minute) inhalational anaesthesia induction with tidal volume breathing of sevoflurane 7%, conventional (seven minute) slow inhalation induction with increasing sevoflurane concentration up to 5%, and induction with thiamylal i.v.

Methods: Twenty-four patients were randomly divided into three groups of eight. In Group A, anaesthesia was induced with tidal volume breathing of sevoflurane 7% (inspiratory concentration) and nitrous oxide 50% in oxygen (total flow; 6 l.min-1) for three minutes: Group B received conventional slow induction for seven minutes and increasing sevoflurane concentration by 0.5% every two or three breaths up to 5% with nitrous oxide 50% in oxygen: and Group C received 5 mg.kg-1 thiamylal with an inhalation of 100% oxygen. Blood pressure, heart rate, rate pressure product, and plasma concentrations of epinephrine and norepinephrine were measured.

Results: There were no changes in blood pressure before or after intubation in Group A (sevoflurane 7%) whereas both were increased in patients in Group C (thiamylal). Changes in heart rate and rate pressure product were not different for the two inhalation groups. Plasma epinephrine concentrations decreased in all the three groups. Norepinephrine concentrations were increased before intubation in both inhalation groups but not in the thiamylal group.

Conclusion: Rapid induction of anaesthesia with sevoflurane 7% and tidal volume breathing for three minutes induced less haemodynamic changes than the other methods studied and has no inhibitory effect on sympathetic activity.