Effect of Rapid Infusion on Venous Pressure

Abstract

The response of the heart to increased work is an indication of its reserve strength. This response is measured clinically in various exercise tests, with observation of pulse and respiratory rate changes. These tests operate, at least in part, by increasing the return of venous blood to the heart. A similar mechanism is brought into action by increasing the volume of the venous return to the heart by injecting fluids intravenously. If such fluids are injected rapidly and in large volume, an increased load is put on the right side of the heart.

Since the introduction and widespread use of simple methods of infusion, there has been much discussion of the proper rate of injection of such fluids. In the investigation of this problem, observation of the venous pressure before, during and after the infusion offers the most direct physiological evidence of the ability of the vascular system to accommodate the rapidly increased blood volume. The venous pressure measurements give a partial indication of the power of the heart to respond to increased load by increased work.

Venous pressures have been measured during infusions given in cases of diabetic acidosis and post-operative shock. Large volumes of fluid have been injected, up to 2,500 cc. of normal saline in one hour, without any alteration of the venous pressure from a normal level. (Table I.) In making these determinations a three-way stop-cock has been used connecting the needle in the vein with the infusion reservoir and the venous pressure apparatus (of Moritz and v. Tabora), and pressure readings have been taken at intervals of 2 to 5 minutes.

For extending this method in an attempt to develop an infusion test of cardiac function, the technique used has been to inject 1,500 cc. of normal saline solution into one of the arm veins in 30 minutes, with venous pressure values recorded at 2 minute intervals.