Gut mucosal ischemia has been associated with cardiopulmonary bypass (CPB) and may contribute to postoperative systemic inflammatory response and multiorgan dysfunction. Hypertonic saline/dextran (HSD) has been previously shown to selectively increase mucosal blood flow in circulatory shock. To determine whether adding HSD to the prime solution for CPB improves gut mucosal blood flow and oxygenation, we performed normothermic, non-cross-clamped CPB in pigs with 1 ml/kg of HSD (25% NaCl/24% dextran 70) (HSD group, n = 9) or lactated Ringer's solution (LRS group, n = 9) as control added to a standard prime. Animals were instrumented with ultrasonic flow probes on the superior mesenteric artery (SMA), laser Doppler mucosal flow probes in the ileum, and indwelling portal vein catheters and tonometers for mucosal hydrogen ion measurements and pH calculations in the stomach, ileum, and rectum. The total infused volume and net fluid balance was significantly lower in the HSD than in the LRS group (649 ± 171 ml vs 2075 ± 385 ml and 502 ± 182 ml vs 1891 ± 363 ml, respectively, P 0.01). SMA flow in the LRS group increased to 110-123% of baseline during CPB and was significantly higher than that in the HSD group which remained unchanged. Ileal mucosal blood flow decreased significantly to 70-50% of baseline in both groups with no difference between groups. Gut oxygen (O2) delivery decreased during CPB in both groups, but O2 consumption remained unchanged. Gastric ileal, and rectal mucosal pH decreased progressively, and portal venous blood pH also decreased in both groups, but there was no significant difference between groups. The HSD group had 34.5% less water content in the duodenum (P < 0.01), 28.2% less in jejunum, and 18.9% less in colon than the LRS group (P < 0.05). We conclude HSD added to the prime for CPB-reduced volume requirements and gut tissue water, but did not improve mucosal perfusion or prevent mucosal acidosis.
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