Achieving pH control in the critically ill patient: the role of continuous infusion of H2-receptor antagonists. Stress-related gastric mucosal damage is a common occurrence in intensive care unit (ICU) patients. Because of the significant morbidity and mortality associated with this mucosal damage, many ICU patients routinely receive prophylactic therapy, usually with histamine H2-receptor antagonists (H2RAs). Gastric acid secretion occurs in a circadian pattern, with late afternoon and evening surges. H2RAs by continuous infusion may control this uneven pattern of secretion more effectively than H2RAs given by bolus injection. More studies are needed to identify the target ICU population for prophylactic treatment. 