[Assessment of left ventricular contractility during intravenous induction of anesthesia by echocardiographic...

A recently developed echocardiographic imaging system provides real-time automated border detection (ABD), which enables the measurement of cyclic changes in cavity area, and thus the calculation of changes in intracavity volumes. Eight patients (ASA 1-2) for non-cardiac surgery received thiopental (6 mg.kg-1) and succinylcholine (1 mg.kg-1) intravenously, and the trachea was intubated. The transthoracic echocardiography (TTE) was performed before induction. after induction, and after orotracheal intubation. Left ventricular end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV) and ejection fraction (EF) were measured with ABD in apical four-chamber view. Mean arterial pressure (MAP) was measured simultaneously. MAP/ESV and MAP/SV were calculated as parameters of left ventricular contractility and left ventricular afterload, respectively. EF decreased significantly (P < 0.05) after induction (50.3 +/- 8.6%) compared with the value before induction (57.9 +/- 8.7%), and decreased further after intubation (41.7 +/- 10.6%). MAP/ESV also decreased significantly (P < 0.05) after induction (2.75 +/- 1.12 mmHg.ml-1) compared with the pre-induction value (3.81 +/- 1.73 mmHg.ml-1), and then returned to the pre-induction level after intubation (3.25 +/- 1.22 mmHg.ml-1). MAP/ SV showed no significant change during induction, and increased significantly (P < 0.05) after intubation (4.60 +/- 1.66 mmHg.ml-1) compared with pre-induction value (2.60 +/- 0.46 mmHg.ml-1). These findings suggest that the significant reduction in EF after induction of anesthesia was due to depression of cardiac contractility by thiopental, and that the further decrease after intubation was due to increase in afterload caused by the stimuli during intubation.