The correlation between mean arterial blood pressure and tissue oxygenation after uncontrolled hemorrhagic shock

Abstract

We hypothesized that spontaneous elevation in blood pressure following cessation of bleeding after uncontrolled hemorrhage is associated with improved tissue oxygenation. Twenty-five anesthetized swine (35 ± 3 kg) underwent carotid line placement, celiotomy, and splenectomy. Tissue oxygenation (StO 2) was measured utilizing infrared spectroscopy. A Grade V liver injury was made and animals were allowed to bleed without resuscitation for 30 min. Means were compared using a paired t-test and correlations were measured using Pearson’s Correlation Coefficient. Mean blood loss was 642 ± 108 ml. Changes in blood pressure and tissue oxygenation are shown in the figure. There was excellent overall correlation between MAP and StO 2 ( r = 0.90, P < 0.01). Celiotomy was associated with a significant reduction in StO 2 that was not reflected by the blood pressure (−5 min until injury, P < 0.01). Correlations between MAP and StO 2 during the periods after injury and bleeding cessation and from bleeding cessation to the end of the study were significant ( r = 0.96, P < 0.01 and r = 0.84, P < 0.01). Celiotomy results in diminished tissue oxygenation that is not reflected by blood pressure. There is excellent correlation between blood pressure and tissue oxygenation after hemorrhagic shock. Elevation in blood pressure following cessation of hemorrhage is associated with improved tissue oxygenation.