EFFECT OF HEMORRHAGE ON SUPERIOR MESENTERIC-ARTERY FLOW DURING INCREASED INTRAABDOMINAL PRESSURES

Background: Elevations in intra-abdominal pressure (IAP) adversely aff ect organ function. Prior hemorrhage and resuscitation exacerbates the cardiac and pulmonary effects of IAP. We have recently shown that sup erior mesenteric artery flow (SMAF) is reduced with increasing IAP, Th is study was designed to determine whether and how hemorrhage and resu scitation affects SMAF with increasing IAP, Methods: Ten pigs were div ided into two groups after placement of a Doppler now probe around the proximal SMA and insertion of a pulmonary artery (PA) catheter, Group 1 underwent intraperitoneal infusion of fluid to increase IAP to 10, 20, 30, and 40 mm Hg followed by a 20-minute equilibration period at e ach IAP, Group 2 was hemorrhaged 20% of circulating volume followed by standard resuscitation. After equilibration, this group had IAP incre ased in the same manner as group 1, Cardiac output (CO), PA pressures, and SMAF were recorded 1 hour after laparotomy and after equilibratio n at each IAP, Comparisons were made using repeated measures of analys is of variance, Student's t test, and linear regression analysis, Resu lts: In group 2, a reduction in SMAF was noted at 30 and 40 mm Hg of I AP when compared with baseline (p = 0.009). This reduction was not see n in group 1, There was also a significant(p = 0.001) reduction in CO between baseline and all levels of increased IAP in group 2, This decr ease was again not seen in group 1, The correlation between CO and SMA F in group 2 was p = 0.74, r(2) = 0.55, p = 0.0001. There was no signi ficant correlation between CO and SMAF in group 1, Conclusion: SMAF an d CO are reduced with increasing IAP to a greater degree when preceded by hemorrhage and resuscitation, Although there is a strong correlati on between the reductions in CO and SMAF, the reduction in SMAF is gre ater than the reduction in CO. This finding suggests that optimizing c ardiac function alone during periods of even moderate levels of increa sed IAP may be inadequate to normalize SMAF, This lends further suppor t for early abdominal decompression in the treatment of trauma patient s with increased IAP.