The hemodynamic effects of cell-free hemoglobin during general and epidural anesthesia

Although hemoglobin-based oxygen carriers (HBOC) are now being investigated, the effects of HBOC solutions during regional anesthesia have never been analyzed. Therefore, we investigated the hemodynamic changes after HBOC infusion during general anesthesia and thoracic epidural anesthesia. Sheep were assigned to three different groups: a) a control group with six unanesthetized sheep; b) six sheep with a halothane anesthesia (2.0 vol. % in oxygen); and c) six awake sheep with a thoracic epidural anesthesia with bupivacaine. After a period of stabilization, all 18 animals received 100 mg/kg of the HBOC pyridoxalated hemoglobin polyoxyethylene conjugate. The infusion of the HBOC caused a significant increase in mean arterial pressure and pulmonary artery pressure in both the control and epidural anesthesia groups. Anesthesia with halothane reduced the effects of the HBOC-solution on mean arterial pressure but did not abolish the increase in pulmonary artery pressure. Our results demonstrate that vasoconstriction caused by HBOC solutions is not abolished by epidural anesthesia, but halothane anesthesia may alter the hemodynamic effects of HBOC solutions. Implications: We evaluated the effects of epidural anesthesia and halothane anesthesia on the vasoconstrictive properties of a cell-free hemoglobin solution. The vasoconstriction caused by a cell-free hemoglobin solution was similar in unanesthetized sheep and sheep with thoracic epidural anesthesia and was reduced in sheep with halothane anesthesia.