Increased oxygen uptake following phlebotomy and simultaneous fluid replacement in polycythemic patients.

To study the isolated effects of decreased hemoglobin concentration without volume loss, eight patients with the diagnosis of polycythemia were studied following acute phlebotomy and simultaneous volume replacement. These patients had been treated previously by repeated phlebotomy, without volume replacement, to a hemoglobin level of 14.8 +/- 0.5 gm%. Following hemodilution by additional phlebotomy and volume replacement, which further lowered the mean hemoglobin level to 11.4 +/- 0.4 gm%, cardiac index increased significantly from 2.8 +/- 0.3 to 3.5 +/- 0. 3 liter/min/m(2) (P<0.05), oxygen delivery did not change, but total body oxygen consumption increased significantly from 140 +/- 16 to 180 +/- 15 ml/min/m(2) (P<0.05). Mixed venous PO2, systemic and pulmonary vascular resistance decreased significantly (P<0.05). Vascular pressure, heart rate, intrapulmonary shunt, arterial pH and bicarbonate, limb blood flow, limb oxygen delivery and limb oxygen consumption did not change. Thus, with phlebotomy and fluid replacement, a reduction of hemoglobin concentration to a subnormal level increased oxygen consumption without lowering oxygen delivery.