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 (CaO2) falls. Oxygent® is a perfluorocarbon (PFC) emulsion that has a high capacity to dissolve oxygen and can thus increase CaO2 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 CaO2 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 CaO2 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 PaO2 (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.