HEMODYNAMIC CHANGES DURING THIOPENTAL ANESTHESIA IN HUMANS: CARDIAC OUTPUT, STROKE VOLUME, TOTAL PERIPHERAL RESISTANCE, AND INTRATHORACIC BLOOD VOLUME 12

Abstract

Cardiac output (modified dye dilution technique) and related hemodynamic changes were studied in 14 subjects during thiopental anesthesia prior to surgery. Anesthesia levels were classified according to eeg patterns. Mean cardiac index during the resting state was 3.37 [plus or minus] 0.20 L/minute/[image]2. During the very light level of anesthesia (hypnosis) there was no significant change in cardiac index. During surgical levels of anesthesia, the following changes were found: (a) a 25% reduction in cardiac index (P< 0.001), (b) a 23% decrease in intrathoracic blood volume (P < 0.00l), and (c) a 35% reduction in stroke volume (P< 0.001). A positive correlation was found to exist between the cardiac index and the intrathoracic blood volume index (r = + 0.703), between the cardiac output and the stroke volume (r = + 0.858), and between the intrathoracic blood volume (r = + 0.765). Reduction in the intrathoracic blood volume during surgical anesthesia seems to indicate a reduction in the central blood pool, and a redistribution and pooling of blood in the periphery. This may cause a diminished venous return to the heart and a reduction in cardiac output.