Effects of intrabdominal hypertension on superior mesenteric artery (SMA) flow and lactatemia

Introduction: Intrabdominal hypertension (IAH) may complicate or cause mesenteric ischemia for which hyperlactatemia may be an early marker. We investigated the relationship between IAH, gastric and superior mesenteric vein (SMV) pCO2 and lactatemia in the pig. Methods: Six anesthetized pigs were instrumented. After laparotomy, a magnetic flowmeter was placed around the SMA to measure blood flow (SMAQ). Two catheters were inserted into the peritoneum to infuse normal saline and measure intrabdominal pressure (LAP). Saline infusion increased LAP to 30 mmHg and 50 mmHg. Results Increasing LAP decreased SMAQ out of proportion to the decreased cardiac output. Gastric and SMV PCO2 increased. However because arterial PCO2 also increased, the role of hypoperfusion in producing mesenteric hypercarbia is unclear. Arterial and SMV lactatemia decreased despite the SMAQ reduction. Conclusions These discrepencies between flow, PCO2 and lactate suggest that in this model, lactatemia may not be a good marker of hypoperfusion. Further studies are needed. Table 1. IAP IAP IAP Baseline 30mmHg 50 mmHg CO 3.96±0.37 3.24±0.79 2.86±1.2 SMAQ 458±59 217±103*131±44*A PCO2 36.2±5.5 48.7±3.8*57.0±4.7*SMV Lactate 2.0±0.7 1.5±0.7*1.8±0.5*SMV PCO2 43.6±4.2 58.4±4.6*63.2±4.9*A Lactate 2.1±0.6 1.5±0.4*1.4±0.3*MV Lactate 2.3±0.5 1.5±0.4*1.4±0.2*Mean±SD *p<0.05 vs baseline.