[Gastrointestinal mucosal ischemia in hemorrhagic shock--measurement with a tonometer]

Splanchnic ischemia produces the most rapid progression of mucosal injury. A reliable method for monitoring the adequacy of tissue oxygenation in the mucosal layer would be clinically valuable. In this study, we investigated the potential value of tonometric intestinal intramucosal pH (pHi) monitoring during hemorrhagic shock in twelve anesthetized dogs. The tonometer consists of a sampling tube with a silicone balloon attached to the tip that is freely permeable to CO2. Intestinal pHi was calculated by the Henderson-Hasselbalch equation and measurements of the PCO2 of the normal saline within the balloon and arterial bicarbonate. The tonometer was placed in the midpart of the small intestine through a small enterotomy. Arterial blood was removed into a heparinized bag to achieve a mean arterial blood pressure of 50-60 mmHg for two hours. Baseline pHi level was 7.28 +/- 0.02 (mean +/- SE). Following hemorrhage, pHi continued to decrease significantly during the experiments down to 6.94 +/- 0.05 at one hour and 6.82 +/- 0.12 at two hours. By treatment with an intravenous infusion of dopamine at a rate of 3 micrograms.kg-1.min-1 started at one hour after hemorrhage, pHi did not returned to baseline levels. Monitoring pHi in the small intestine using tonometer could be a useful technique to provide early detection of insufficient mucosal blood flow.