Modified hemoglobin solution as a resuscitation fluid

Hemoglobin solution, as a potential oxygen-carrying resuscitation fluid in blood volume replacement therapy, has two limitations: higher oxygen affinity (P50 approximately 12-16 mm Hg) and shorter vascular retention time (plasma half-disappearance time approximately 2-4 h) of free hemoglobin as compared to hemoglobin in the red cells. To overcome these two limitations, several investigators have used a variety of reactions and procedures for the modification of the hemoglobin molecule. This article presents a review of the modifications of the hemoglobin, including reactions with different agents for the intra- or intermolecular cross-linking of hemoglobin, reactions with pyridoxal phosphate with or without subsequent polymerization, and manipulations for the encapsulation of hemoglobin to obtain artificial cells. The P50 and the vascular retention time of the products obtained are indicated whenever they have been reported in the literature. The oxygen transport characteristics of a resuscitation fluid, in general, and of modified hemoglobin solution, in particular, have been correlated to the oxygen dissociation curve and to the hemoglobin concentration.