Splanchnic ischemia, leading to intestinal mucosal damage, is thought to be common in patients after severe trauma. The adequacy of mucosal oxygenation can indirectly be determined by gastric intramucosal pH (pHi) measurement. We prospectively examined the posttraumatic gastric pHi values in 15 multiple trauma patients. In all patients gastric pHi was measured using a tonometer via the nasogastric route. A pHi value < or = 7.32 was used to differentiate between normal and low gastric pHi. Six hours after the injury four patients showed abnormally low pHi levels. Four other patients with normal initial pHi values exhibited low pHi values during one or more of the next measuring periods. Three of these eight patients developed major complications (two, ARDS) and two of them subsequently died. The seven remaining patients never had abnormal pHi levels and all patients had an uncomplicated recovery. Although intestinal ischemia was expected to be a common condition in multiple trauma patients, no consistent pattern of abnormal pHi measurements in the direct posttraumatic course could be discovered. No correlation was found between initial pHi values (at 6 hours) and ISS, shock, and lactic acidosis or APACHE II scores on admission. It is concluded that monitoring gastric pHi is useful in severely injured patients admitted to the ICU.