Increased Vascular Resistance with Hemoglobin-Based Oxygen Carriers

Abstract

PURPOSE: To compare the effects of resuscitation with hemoglobin-based oxygen-carriers and conventional resuscitation fluids on hemodynamics, oxygen transport, and oxygen consumption in an animal model of the use of these fluids in the treatment of hemorrhagic shock. PROTOCOL: Twenty-eight immature swine were surgically prepared, allowed to recover five days, water deprived for 48 hours, hemorrhaged of 25 ml/kg over one hour, resuscitated promptly with 1) Ringer's lactate, 75 ml/kg, 2) 7% albumin in Ringer's acetate, 25 ml/kg, 3) 9% unmodified hemoglobin in Ringer's acetate, 25 ml/kg, or 4) 9% alpha alpha-crosslinked hemoglobin in Ringer's acetate, 25 ml/kg, and observed with three hours of hemodynamic and oxygen transport measurements. RESULTS: Systemic and pulmonary vascular resistance were increased in hemoglobin-treated animals to more than twice the levels seen in crystalloid- or colloid-treated controls. Oxygen consumption and the rate of correction of lactic acidosis were not increased in hemoglobin-treated animals. CONCLUSIONS: Increased vascular resistance limits the oxygen transport benefit of cell-free-hemoglobin-based oxygen carriers. Cell-free-hemoglobin-induced increases in vascular resistance may place animals' hearts on an unfavorable portion of the Frank-Starling curve as well as complicate further medical treatment by reducing the animals' tolerance to increases in blood viscosity.