Changes in cardiac index and estimated systemic vascular resistance during induction of anaesthesia with thiopentone, methohexitone, propofol and etomidate.

Changes in cardiac index (CI) and estimated systemic vascular resistance (ESVR) were assessed non-invasively using pulsed Doppler ultrasound during induction of anaesthesia. Ninety-six ASA I patients were allocated randomly to one of four groups to receive alfentanil 8 micrograms kg-1 followed by a dose of thiopentone, methohexitone, propofol or etomidate sufficient to obtund the eyelash reflex. CI increased significantly by 8% 1 min after administration of both methohexitone (P < 0.05) and propofol (P < 0.05), returning to pre-induction values thereafter. CI increased after thiopentone but the increase was not statistically significant. There was a significant decrease in CI of 16% after induction with etomidate (P < 0.001). ESVR decreased significantly from pre-induction values by 18% after methohexitone (P < 0.001) and 23% after propofol (P < 0.001). ESVR in the thiopentone group decreased, but this was not statistically significant. ESVR increased significantly by 12% 1 min after induction of anaesthesia with etomidate (P < 0.05) and then decreased towards pre-induction values. The results suggest that the cardiostability of etomidate may not be as complete in all groups of patients as previous studies have suggested.