Left Ventricular Performance Monitored by Radionuclide Cardiography during Induction of Anesthesia

Abstract

Radionuclide cardiography with 99mTc-labeled erythrocytes was carried out in 3 different studies comprising 20 female patients without heart or lung diseases. Left ventricular ejection fraction (LVFF) and other hemodynamic variables were measured immediately before and during induction of anesthesia (thiopental, N2O/O2, succinylcholine, laryngoscopy + oral intubation, halothane). Serial measurements of LVEF, left ventricular volume, and derived variables were obtained by gamma camera in 7 patients using 3-min sampling periods. LVEF was monitored serially in 7 and 6 patients, respectively, by a portable, nonimaging probe (nuclear stethoscope) at .ltoreq. 1-min intervals. The induction period was prolonged to last 24 min in studies 1 and 2, against 9 min in study 3. In studies 1 and 2, there was an increase in blood pressure and heart rate after thiopental and after laryngoscopy and intubation. In study 3, a similar increase was observed after intubation. In the gamma camera study LVEF decreased from 0.72 to 0.53 after thiopental, with no further decrease during intubation. This decrease was accompanied by an increase in end-systolic volume and a decrease in the ratio: systolic cuff pressure/end systolic volume; end-diastolic volume and cardiac index remained unchanged. In the nuclear stethoscope studies, LVEF decreased both after thiopental and after intubation: in study 2, from 0.68 to 0.38 and from 0.53 to 0.41, respectively; in study 3, from 0.69 to 0.53 and from 0.57 to 0.44, respectively. Observations in healthy, female individuals, provide an impetus for further noninvasive radionuclide studies during anesthesia, in patients with cardiovascular disease.