LOW-DOSE DOPEXAMINES EFFECT ON LUNG AND GUT FUNCTION AFTER CPB IN A SHEEP MODEL

Objective. The lung injury regularly associated with cardiopulmonary b ypass (CPB) may be linked to gut mucosal dysfunction occurring as the result of mucosal ischemia associated with nonpulsatile CPB. To examin e this possibility we postulated that the weak-beta 2 agonist dopexami ne would improve gut mucosal blood how, thereby decreasing gut and lun g dysfunction seen after CPB in sheep. Methods. Anesthetized sheep had 2 h of hypothermic (24 degrees C), nonpulsatile CPB, and 60 min of co ld, blood cardioplegic arrest. After warming they were separated from CPB for 2 h of reperfusion. Before and during CPB, dopexamine at 2 mu g/kg/min (n = 7) or saline (n = 7) were infused in a blinded fashion. Hemodynamic parameters were measured. Biatrial thromboxane Bz levels w ere obtained. Mesenteric arterial how (Q(SMA)), mucosal flow (Q(muc)), FD-4 clearance (ClFD-4), and tonometric pill were measured at baselin e and 30-min intervals on, and after, CPB. Results. After CPB, similar reductions in MAP were seen (P < 0.05 vs. baseline), but heart rate a nd the mean pulmonary vascular resistance were significantly increased in the dopexamine animals (P < 0.05 vs. placebo). Plasma thromboxane was similarly increased in both groups after CPB (P < 0.05 vs. baselin e), returning to baseline 1 h after CPB. The Q(sma) was not altered, b ut a statistically significant decrease in Q(muc) and pH(i) occurred i n both groups (P < 0.05 vs. baseline). In both groups FD-4 clearance r eached a peak 30 min after CPB (P < 0.05; dopexamine vs, baseline). Af ter 2 h neither of these changes returned to control levels. Conclusio ns. In this ovine model, gut mucosal ischemia and increased permeabili ty occur with hypothermic CPB, but dopexamine administration during CP B, compared to placebo, neither ameliorates these intestinal derangeme nts nor reduces post-CPB lung pathophysiology. (C) 1998 Academic Press .