Changes in ejection fraction during induction of anesthesia with two different i.v. techniques.

Two intravenous induction techniques were compared with respect to changes in ejection fraction (EF) and central hemodynamics in 30 patients scheduled for coronary artery surgery. Left ventricular EF was measured with a collimated single crystal probe linked to a microcomputer, after injection of 200 MBq Tc 99 m HSA. Stroke volume index (SI) determined by thermodilution and EF were used to calculate left ventricular volume in end-systole and end-diastole. In 20 patients (Group I), anesthesia was induced with diazepam (94 micrograms x kg-1), thiopentone (3 mg x kg-1) and fentanyl (3 micrograms x kg-1). In 10 patients (Group II), fentanyl (30 micrograms x kg-1) was used for induction. In Group I, EF decreased from 0.43 to 0.26 at intubation, while systemic vascular resistance index (SVRI) showed an increase. Left ventricular volume decreased during induction of anesthesia except during intubation. In Group II, EF and left ventricular volume remained unchanged during the study period. SVRI showed no increase at intubation. No change in contractility was indicated from the relation between the end-systolic pressure and volume, in any of the groups.