Blood volume and cardiac index in rats after exchange transfusion with hemoglobin-based oxygen carriers

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Abstract
Migita, Russell, Armando Gonzales, Maria L. Gonzales, Kim D. Vandegriff, and Robert M. Winslow. Blood volume and cardiac index in rats after exchange transfusion with hemoglobin-based oxygen carriers. J. Appl. Physiol. 82(6): 1995–2002, 1997.—We have measured plasma volume and cardiac index in rats after 50% isovolemic exchange transfusion with human hemoglobin cross-linked between the α-chains with bis(3,5-dibromosalicyl)fumarate (ααHb) and with bovine hemoglobin modified with polyethylene glycol (PEGHb). ααHb and PEGHb differ in colloid osmotic pressure (23.4 and 118.0 Torr, respectively), oxygen affinity (oxygen half-saturation pressure of hemoglobin = 30.0 and 10.2 Torr, respectively), viscosity (1.00 and 3.39 cP, respectively), and molecular weight (64,400 and 105,000, respectively). Plasma volume was measured by Evans blue dye dilution modified for interference by plasma hemoglobin. Blood volumes in PEGHb-treated animals were significantly elevated (74.0 ± 3.5 ml/kg) compared with animals treated with ααHb (49.0 ± 1.2 ml/kg) or Ringer lactate (48.0 ± 2.0 ml/kg) or with controls (58.2 ± 1.9 ml/kg). Heart rate reduction after ααHb exchange is opposite to that expected with blood volume contraction, suggesting that ααHb may have a direct myocardial depressant action. The apparently slow elimination of PEGHb during the 2 h after its injection is a consequence of plasma volume expansion: when absolute hemoglobin (concentration × plasma volume) is compared for PEGHb and ααHb, no difference in their elimination rates is found. These studies emphasize the need to understand blood volume regulation when the effects of cell-free hemoglobin on hemodynamic measurements are evaluated.