Regional vascular effects of rHb1.1, a hemoglobin-based oxygen carrier

The goals of this study were to determine the effects of recombinant human hemoglobin (rHb1.1, 1 g/kg i.v.) on systemic hemodynamics, regional blood flows, and regional vascular resistances in rats. Cardiac output (CO) and regional blood flow in 13 tissues were determined by using the radiolabeled-microsphere method during halothane anesthesia. Microspheres were injected at three time points: before (control, t = 0), t = 30 [10 min after a 20-min infusion of vehicle (diluent) or rHb1.1], and at t = 120 min. Infusion of diluent did not alter CO, heart rate (HR), mean arterial pressure (MAP), or systemic vascular resistance (SVR) and had minimal effects on regional blood flows. Infusion of rHb1.1 did not alter CO or HR but did increase MAP and SVR compared with diluent. Infusion of rHb1.1 increased blood flow to the heart and decreased blood flow to the gastrointestinal tract (GIT) and liver. Compared with the corresponding values in the diluent-treated rats, resistance was increased after rHb1.1 in spleen, kidney, and hepatic artery. In conclusion, rHb1.1 administration increased MAP and SVR. The vasoconstriction was heterogeneous and was associated with increased coronary blood flow and with increased regional resistance in kidney, spleen, and hepatic artery, compared with diluent-infused controls.