Splanchnic metabolism during gut ischemia and short-term endotoxin and hemorrhagic shock as evaluated by intravasal microdialysis

The splanchnic area is of considerable interest in different types of shock. To characterize the metabolic changes in the splanchnic region in response to different types of shock we used a model where shock-induced metabolic changes in the splanchnic region were studied by the use of intravasal microdialysis. 23 anesthetized domestic pigs were randomized into four groups: Group I, serving as controls (n = 5); Group II, mesenteric ischemia for 180 followed by 120 min of reperfusion (n = 5); Group III, endotoxin shock for 5 h (n = 5); and Group IV, hemorrhagic shock for 180 min followed by re-transfusion of shed blood (n = 8). Microdialysis catheters were placed in the left femoral artery, portal vein and a small ileal mesenteric vein. Samples of the perfusate were continuously collected in micro-vials and analyzed for glucose, lactate, pyruvate and glycerol. In gut ischemia and endotoxin shock the outflow-pattern of lactate, lactate/pyruvate ratio and glucose in the mesenteric vein differed significantly from controls and hemorrhage whereas an increase in glycerol was only noted in the ischemic group. The most prominent differences were detected in lactate/pyruvate ratio, a marker of tissue ischemia with the most pronounced changes during mesenteric ischemia/reperfusion. During endotoxin shock increases in microdialysate metabolites were only noted in the splanchnic region suggesting a specific vulnerability in the region. Studying the lactate/pyruvate ratio may provide additional information when interpreting increased blood lactate levels. In addition glycerol may prove to be a useful marker of splanchnic ischemia. Intravasal microdialysis represents a potentially useful method for monitoring regional metabolic events.