Directly measured tissue pH is an earlier indicator of splanchnic acidosisthan tonometric parameters during hemorrhagic shock in swine

Objective: To compare tissue pH in the stomach, bowel, and abdominal wall m uscle during hemorrhagic shock and recovery using tissue electrodes; also, to compare tissue electrode pH measurements to gastric intramucosal pH (pH, ), gastric luminal Pco(2), and Pco(2) gap (gastric luminal CO2 - arterial C O2) measured with an air-equilibrated tonometer. Design: Prospective animal study. Setting: University animal research laboratory. Subjects: Eight anesthetized, mechanically ventilated Yorkshire swine. Interventions: Hemorrhagic shock was initiated by withdrawing blood over a 15-min period to lower systolic blood pressure to 45 mm Hg. Shock was maint ained for 45 mins and was followed by a 5-min resuscitation to normal blood pressure with a blood/lactated Ringer's (1:2) mixture, Recovery was monito red for 60 mins, Measurements and Main Results: ph was measured with electrodes in the submu cosa of the stomach, the submucosa of the small bowel, and the abdominal wa ll muscle. Gastric luminal Pco(2) was measured with an air-equilibrated ton ometer and pH(i) and Pco(2) gap were calculated. Each organ showed a differ ent sensitivity to shock and resuscitation. The bowel pH responded most rap idly to the onset of hemorrhagic shock and had the largest change in tissue pH, The bowel also showed the most rapid recovery during resuscitation. Th e submucosal pH of the stomach responded more slowly than the bowel, but fa ster than the abdominal wall muscle pH, gastric Pco(2) gap, or pH(i). The s mallest changes in organ pH as a result of hemorrhagic shock were seen in t he abdominal wall muscle and the stomach as assessed by gastric tonometry, Conclusions: Direct measurement of tissue pH indicates that intra-abdominal organ pH varies during hemorrhagic shock. The small bowel pH changes the m ost in magnitude and rapidity compared with stomach pH or abdominal wall mu scle pH. Tonometrically derived parameters were not as sensitive in the det ection of tissue acidosis during shock and resuscitation as pH measured dir ectly in the submucosa of the stomach or small bower.