An Open-label, Exploratory Trial to Assess Gastric Acid Control in Critically Ill Subjects Receiving Nexium

Inclusion Criteria: * Critically ill male or female subjects 18 years or older who have a baseline gastric aspirate pH less then or equal to 4 * Subjects admitted to an ICU requiring mechanically ventilated * Subjects will have at least one additional stress ulcer risk factor Exclusion Criteria: * Anticipated use of pre-pyloric enteral feeding after screening until the end of study * Physician estimated survival of less then 96 hours * Anticipation of major surgery within 96 hours of study enrollment