Cerebral oxygen delivery by liposome-encapsulated hemoglobin: a positron-

Cerebral oxygen delivery by liposome-encapsulated hemoglo-bin: a positron-emission tomographic evaluation in a rat model of hemorrhagic shock. J Appl Physiol 103: 28–38, 2007; doi:10.1152/japplphysiol.00136.2006.—Liposome-encapsulated Hb (LEH) is being developed as an artificially assembled, low-toxicity, and spatially isolated Hb-based oxygen carrier (HBOC). Standard methods of evaluating oxygen carriers are based on surrogate indica-tors of physiology in animal models of shock. Assessment of actual delivery of oxygen by HBOCs and resultant improvement in oxygen metabolism at the tissue level has been a technical challenge. In this work, we report our findings from 15O-positron emission tomographic (15O-PET) evaluation of LEH in a rat model of 40 % hypovolemic shock. In vitro studies showed that PEGylated LEH formulation containing 7.5 % Hb and consisting of neutral lipids (distearoylphos-phatidylcholine:cholesterol:-tocopherol, 51.4:46.4:2.2) efficientl