Ischemia of the intestinal mucosa during cardiopulmonary bypass.

Bacterial translocation is believed to occur during cardiopulmonary bypass (CPB) because serum endotoxin concentrations rise. Intestinal ischemia during CPB, however, has never been proven directly. The condition of the intestinal mucosa during CPB was studied by measuring serum diamine oxidase (DAO) activity, an index of intestinal ischemia. Serum DAO activity, blood lactate concentration, and the arterial ketone body ratio (AKBR) were measured intraoperatively in four successive patients who underwent aortic arch replacement by the open distal anastomosis method. DAO activity rose after restoration of blood flow to the lower half of the body, and continued to rise throughout CPB. The lactate concentration also rose, mirroring the change in DAO activity, and returned to nearly normal 12 h after the operation. The AKBR decreased during CPB, with a mean minimum vale of 0.16-0.07 immediately after the restoration of blood flow to the lower half of the body. The parallel rise in DAO activity and serum lactate concentration once blood flow to the lower half of the body was restored implies that ischemic injury to the mucosa of the small intestine occurs during CPB. The continued rise in these parameters throughout CPB is consistent with ongoing injury due to splanchnic hypoperfusion, as reflected in the decrease in the AKBR during the same period.