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

Abstract

To compare tissue pH in the stomach, bowel, and abdominal wall muscle during hemorrhagic shock and recovery using tissue electrodes; also, to compare tissue electrode pH measurements to gastric intramucosal pH (pHi), gastric luminal PCO2, and PCO2 gap (gastric luminal CO2--arterial CO2) measured with an air-equilibrated tonometer. Prospective animal study. University animal research laboratory. Eight anesthetized, mechanically ventilated Yorkshire swine. Hemorrhagic shock was initiated by withdrawing blood over a 15-min period to lower systolic blood pressure to 45 mm Hg. Shock was maintained 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 monitored for 60 mins. pH was measured with electrodes in the submucosa of the stomach, the submucosa of the small bowel, and the abdominal wall muscle. Gastric luminal PCO2 was measured with an air-equilibrated tonometer and pHi and PCO2 gap were calculated. Each organ showed a different sensitivity to shock and resuscitation. The bowel pH responded most rapidly to the onset of hemorrhagic shock and had the largest change in tissue pH. The bowel also showed the most rapid recovery during resuscitation. The submucosal pH of the stomach responded more slowly than the bowel, but faster than the abdominal wall muscle pH, gastric PCO2 gap, or pHi. The smallest changes in organ pH as a result of hemorrhagic shock were seen in the abdominal wall muscle and the stomach as assessed by gastric tonometry. Direct measurement of tissue pH indicates that intra-abdominal organ pH varies during hemorrhagic shock. The small bowel pH changes the most in magnitude and rapidity compared with stomach pH or abdominal wall muscle pH. Tonometrically derived parameters were not as sensitive in the detection of tissue acidosis during shock and resuscitation as pH measured directly in the submucosa of the stomach or small bowel.