Clinical significance of mean circulatory filling pressure and cardiac preload under anesthesia.

The circulatory effects of a rapid infusion of plasma substitute with intravenous administration of nitroglycerine (TNG) were investigated in low pressure systems of anesthetized patients by measuring various hemodynamic parameters. Measurements were made when the systolic blood pressure reached 70-80% of the control value after intravenous administration of TNG at 1-2 microg/kg/min and a 3.5% modified gelatin solution (Haemaccel) at a rate of 0.5 ml/kg/min. After the TNG was administered, the mean circulatory filling pressure (Pms) decreased, and the venous to arterial capacitance ratio (CV/CA) increased; however, they returned to control values after a rapid Haemaccel infusion. Changes in the pressure gradient between the X and Y valley of the right atrial pressure wave decreased to 70 +/- 14% of the control value when TNG was given and recovered to 106 +/- 22% by infusion. Pulmonary vascular resistance (PVR) decreased to 70 +/- 24% of the control value when TNG was administered and was restored to 96 +/- 40% by a rapid infusion. In the left ventricle, the mean velocity of myocardial circumferential fiber shortening (VCF) decreased in all cases when TNG was given and it recovered by a rapid infusion. In the right ventricle, VGF did not always decrease, and in a few case increased, but all cases recovered by a Haemaccel rapid infusion. We conclude that the augmentation of the right ventricular preload reserve is achieved by administration of TNG and infusion of a plasma substitute.