Hypoxemic reperfusion after 120 mins of intestinal ischemia attenuates the histopathologic and inflammatory response

OBJECTIVE: It has been suggested that reactive oxygen species play a pivotal role in the initial organ-tissue injury during reperfusion, eliciting inflammatory reaction and multiple organ failure. It was investigated if hypoxemic reperfusion attenuates tissue injury and inflammatory response. DESIGN: Randomized animal study. SETTING: Medical school laboratory. SUBJECTS: Twenty-five male pigs weighing 25-28 kg. INTERVENTIONS: Pigs were subjected to 120 mins of intestinal ischemia by clamping the superior mesenteric artery. Upon declamping, the animals were randomly assigned to receive either hypoxemic reperfusion (HR group, n = 9) reperfused with a Pao2 = 30-35 or normoxemic reperfusion (control group, n = 16) reperfused with a Pao2 = 100 mm Hg for 120 mins. Fluids without inotropes were given to combat circulatory shock during reperfusion. MEASUREMENTS AND MAIN RESULTS: Portal blood and intestinal and lung biopsies were collected at baseline, end of ischemia, and end of reperfusion. Histopathologic changes were scored, and interleukin-1beta, qualitative Limulus amebocyte, lysate test, and Pao2/Fio2 were measured. Eight of 16 animals of the control group and seven of nine of the HR group survived (p = .22). At the end of reperfusion, the intestinal (p = .004) and lung (p = .028) pathologic scores were lower in the HR group compared with controls. The only significant difference in concentration of interleukin-1beta in the portal blood between the two animal groups occurred 120 mins after reperfusion (p = .006). The number of HR animals with a positive Limulus test was significantly smaller compared with controls at 60 (p = .041) and 120 (p = .07) mins of reperfusion. During the period of ischemia, the Pao2/Fio2 decreased similarly in the control and HR group, whereas after 120 mins of reperfusion the rate was significantly higher in the HR group. CONCLUSIONS: Hypoxemic reperfusion represents an intervention that may attenuate the triggering of multifactorial cascade and organ tissue injury.