Effect of αα-cross-linked hemoglobin and pyridoxalated hemoglobin polyoxyethylene conjugate solutions on gastrointestinal regional perfusion in hemorrhagic shock

Background: Hemoglobin-based blood substitutes may cause vasoconstriction, which could limit organ perfusion during trauma resuscitation. We investigated the effect of two hemoglobin solutions on regional blood flow and mucosal perfusion in the gastrointestinal tract in a hemorrhagic shock model. Methods: Twenty-four swine were bled 30% of blood volume over 1 hour. Six additional animals were anesthetized and monitored but did not undergo hemorrhage. Bled animals were resuscitated with αα- hemoglobin (ααHb), pyridoxalated hemoglobin polyoxyethylene conjugate (PHP), shed blood, or lactated Ringer's solution. Regional blood flow was measured by radio-labeled microspheres. Gastric mucosal perfusion was estimated by measuring intramucosal pH (pHi) by tonometry. Results: PHP and shed blood restored small-bowel flows to sham values, whereas lactated Ringer's solution and ααHb did not. Shed blood and PHP, but not ααHb, restored cardiac index (CI) to baseline (p < 0.05). Mean pulmonary artery pressure was elevated over baseline with ααHb and PHP and remained elevated with ααHb (p < 0.05). pHi was significantly lower after resuscitation with PHP than with other fluids. Conclusion: PHP was efficacious in restoring CI and small-bowel flow, but the pHi remained low, indicating possible continued mucosal ischemia. ααHb led to limited recovery of CI and small-bowel blood flow but restored pHi close to baseline. Shed blood was efficacious in restoration of pHi, gastrointestinal blood flows, and systemic hemodynamics.