Mesenteric and renal oxygen transport during hemorrhage and reperfusion: Evaluation of optimal goals for resuscitation

Background. Changes in flow to the gut and the kidney during hemorrhage and resuscitation contribute to organ dysfunction and outcome. We evaluated regional and splanchnic oxygen (O-2) now distribution and calculated oxygen supply distribution during hemorrhage and reperfusion and compared them with global measures. Methods: Seven anesthetized pigs were instrumented to evaluate global hemodynamics, visceral blood now, and oxygen transport. Tonometric pH probes were positioned in the stomach and jejunum. Animals were bled to 45 mm Hg for I hour. Crystalloids and blood were infused during the following 2 hours to normalize blood pressure, heart rate, urine output, and hemoglobin. Results: During hemorrhage, mesenteric flow and O-2 consumption were significantly decreased, whereas systemic consumption remained normal. Renal flow was reduced, but renal O-2 consumption remained normal. After resuscitation, despite normal hemodynamics, neither systemic, mesenteric, nor renal O-2 delivery returned to baseline. Lactate remained significantly in-creased. Arterial pH, base excess, and gastric and jejunal pH were all decreased. Conclusion. During hemorrhage, the gut is more prone than other regions to O-2 consumption supply dependency. After resuscitation, standard clinical parameters do not detect residual O-2 debt. Lactate, arterial pH, base excess, and intramucosal gut pH are all markers of residual tissue hypoperfusion.