CENTRAL AND REGIONAL HEMODYNAMICS DURING ACUTE HYPOVOLEMIA AND VOLUMESUBSTITUTION IN VOLUNTEERS

Objectives: To study the central and regional hemodynamics and oxygen consumption during acute hypovolemia and volume replacement with cryst alloid and colloid solutions. Design: Prospective, randomized, laborat ory investigation. Setting: Clinical physiology department at a univer sity hospital. Subjects: Eighteen healthy male volunteers, between 21 and 35 yrs of age (mean 26). Interventions: Catheters were inserted in the cubital vein, brachial artery, pulmonary artery, thoracic aorta, right hepatic vein, and left renal vein for measurements of systemic a rterial and pulmonary arterial pressures, total and central blood volu mes, extravascular lung water, and the splanchnic (liver) and renal bl ood flow rates, The exchange of respiratory gases was measured, using the Douglas bag technique. Measurements were made before and after a v enesection of 900 mL and again after the subjects had been randomized and received volume replacement with either 900 mL of Ringer's acetate solution 900 mL of albumin 5%, or 900 plus 900 mL of Ringer's solutio n. Measurements and Main Results: Withdrawal of 900 mL of blood decrea sed cardiac output and the splanchnic and renal blood flow rates by be tween -16% and -20%, The oxygen uptake decreased by 13% in the whole b ody, while it remained unchanged in the liver and kidney. The systemic and pulmonary vascular resistances increased, while the extravascular lung water decreased. Autotransfusion of fluid from tissue to blood w as indicated by hemodilution, which was most apparent in subjects show ing only a minor change in peripheral resistance. Cardiac output, bloo d volume, and systemic vascular resistance were significantly more inc reased by infusion of 900 mL of albumin 5% than by 900 mL of Ringer's solution, However, infusion of 1800 mL of Ringer's solution increased the extravascular lung water and the pulmonary arterial pressures to s ignificantly above baseline, while no significant difference from base line was found after 900 mL of Ringer's acetate solution. Conclusions: Withdrawal of 900 mL of blood induces similar reductions in cardiac o utput as in the splanchnic and renal blood flow rates, A fluid shift f rom the extravascular to the intravascular fluid compartment might res tore up to 50% of the blood loss, Optimal volume substitution with Rin ger's solution can be effectuated by infusing between 100% and 200% of the amount of blood lost.