The Evaluation of the Efficacy of Oxygent® as an Oxygen-Carrying Substitute on Cerebral Blood Flow

Cerebral blood flow (CBF) is tightly regulated to meet metabolic demands, and it increases during hemodilution as arterial oxygen content (CaO 2 ) falls. Oxygent is a perfluorocarbon (PFC) emulsion that has a high capacity to dissolve oxygen and can thus increase CaO 2 in patients breathing supplemental oxygen. PFCs have shown excellent oxygen therapeutic value in both phase II and phase III clinical trials. However, the effects of Oxygent on CBF in hemodilution are unknown. We performed this study to investigate how Oxygent alters CBF in rats undergoing stepwise isovolumetric hemodilution under isoflurane anesthesia with 100% oxygen ventilation. In vivo Laser Doppler Flow (LDF) probes measured CBF as blood was gradually replaced with equal volumes of either 5%Albumin (controls) or (1:1) PFC and Albumin. Hematocrit and blood gases were measured and CaO 2 calculated after each dilution. Target values were to achieve a hematocrit value of 10% and fluorocrit between 7.5-10%. We compared CBF in the Oxygent vs. control group at decreasing levels of hematocrit and CaO 2 with repeated t-tests. At hematocrits less than 15%, CBF rate approached baseline in the Oxygent group, and was lower than the control group (p = 0.004). At maximal hemodilution, Oxygent treated rats also showed higher PaO 2 (p < 0.001) and required lower phenylephrine infusion rates to maintain blood pressure (p = 0.002). These data support that administration of Oxygent improves tissue oxygenation during hemodilution.