Abstract
Clinical and experimental studies have shown that trauma combined with hemorrhage shock (T/HS) is associated with myocardial contractile dysfunction. However, the initial events triggering the cardiac dysfunction are not fully elucidated. Thus we tested the hypothesis that factors carried in intestinal (mesenteric) lymph contribute to negative inotropic effects in rats subjected to a laparotomy (T) plus hemorrhagic shock (HS; mean arterial blood pressure of 30-40 Torr for 90 min) using a Langendorff isolated heart preparation. Left ventricular (LV) function was assessed 24 h after trauma plus sham shock (T/SS) or T/HS by recording the LV developed pressure (LVDP) and the maximal rate of LVDP rise and fall ( +/- dP/dt(max)) in five groups of rats: 1) naive noninstrumented rats, 2) rats subjected to T/SS, 3) rats subjected to T/HS, 4) rats subjected to T/SS with mesenteric lymph duct ligation (T/SS+LDL), or 5) rats subjected to T/HS+LDL. Cardiac function was comparable in hearts from naive, T/SS, and T/SS+LDL rats. Both LVDP and +/- dP/dt(max) were significantly depressed after T/HS. The T/HS hearts also manifested a blunted responsiveness to increases in coronary flow rates and Ca(2+), and this was prevented by LDL preceding T/HS. Although electrocardiograms were normal under physiological conditions, when the T/HS hearts were perfused with low Ca(2+) levels ( approximately 0.5 mM), prolonged P-R intervals and second-degree plus Wenckebach-type atrioventricular blocks were observed. No such changes occurred in the control or T/HS+LDL hearts. The effects of T/HS were similar to those of the Ca(2+) channel antagonist diltiazem, indicating that an impairment of cellular Ca(2+) handling contributes to T/HS-induced cardiac dysfunction. In conclusion, gut-derived factors carried in mesenteric lymph are responsible for acute T/HS-induced cardiac dysfunction.