NITRIC-OXIDE MEDIATES FLUID ACCUMULATION DURING CARDIOPULMONARY BYPASS

Fluid accumulation during cardiopulmonary bypass may be related to the production of endogenous vasoactive substances. We investigated the r ole of nitric oxide in mediating fluid accumulation during cardiopulmo nary bypass. Normothermic cardiopulmonary bypass was carried out for 3 hours in male Sprague-Dawley rats with constant, nonpulsatile flow an d hemodilution. Fluid accumulation (rate of change of external reservo ir volume) was measured under three experimental conditions: saline so lution control (n = 8), L-arginine infusion (n = 6), and N-nitro-L-arg inine methyl ester infusion (n = 6). At the end of the experiments, bo dy weight and organ wet/dry ratios were examined. Percentage weight ga in was 77% greater in the N-nitro-L-arginine methyl ester group and 23 % less in the L-arginine group compared with control values. Fluid acc umulation was increased with N-nitro-L-arginine methyl ester after 30 minutes (p < 0.01) and reduced with L-arginine after 120 minutes (p < 0.01) compared with control animals. Water content was significantly d ecreased in the heart, lung, skin, muscle and peritoneum in rats recei ving L-arginine. These data suggest that endogenous nitric oxide plays an important role in minimizing fluid accumulation during cardiopulmo nary bypass.