Hemoglobin solutions - Not just red blood cell substitutes

Objective: To review current knowledge about cell-free hemoglobin solutions . Data Sources: All studies involving cell-free hemoglobin were retrieved fro m a computerized MEDLINE search from 1980 to 1998. We also reviewed the ref erence lists of all available review articles and primary studies to identi fy references not found in the computerized search. Study Selection: Clinical and experimental studies in which cell-free hemog lobin solutions were studied. Data Extraction: From the selected studies, information was obtained regard ing the experimental model or the study population in which cell-free hemog lobin solutions were investigated, the type of cell-free hemoglobin solutio n, their deleterious or beneficial effects, and their possible indications. Data Synthesis: In many studies, hemoglobin solutions were considered as ef ficient resuscitative agents and good alternatives to red blood cell transf usion, because of their marked vasopressor effect coupled with their capaci ty to improve the microcirculation and quickly restore metabolic parameters . Nevertheless, potential problems include an increased susceptibility to i nfection, immunosuppression, oxidative damage, excessive pulmonary and syst emic vasoconstriction, and platelet activation. Conclusions: Hemoglobin solutions are more than mere blood substitutes. Pro mising effects on oxygen transport and the microcirculation need to be conf irmed, and the results of continuing research are eagerly awaited.