Assessment of Graded Intestinal Hypoperfusion and Reperfusion Using Continuous Saline Tonometry in a Porcine Model

Abstract

Objective. To evaluate effects of graded intestinal hypoperfusion and reperfusion on intestinal metabolic parameters as assessed by a modified continuous saline tonometry technique.Materials. Twelve barbiturate-anaesthetized female pigs.Methods. Measurements were performed prior to and during three predefined levels of superior mesenteric mean arterial blood pressure (PSMA 70, 50 and 30 mmHg, respectively, each 80 min long), obtained by an adjustable clamp around the origin of the superior mesenteric artery, and during reperfusion. We continuously measured jejunal mucosal perfusion (laser Doppler flowmetry), jejunal tissue oxygen tension (PO2TISSUE; microoximetry) and intramucosal PCO2 (continuous saline tonometry) and calculated net intestinal lactate production, mesenteric oxygenation, PCO2 gap (jejunal mucosal PCO2−arterial PCO2) and pHi.Results. At PSMA 70 and 50 mmHg mesenteric oxygen uptake and net lactate production remained unaltered, in spite of decreased oxygen delivery. At these PSMA levels PCO2 gap increased, while pHi and PO2TISSUE decreased. At PSMA 30 mmHg pronounced increases in PCO2 gap and mesenteric net lactate production as well as marked decreases in PO2TISSUE and pHi were demonstrated. Data indicate absence of anaerobic conditions at an intestinal perfusion pressure (IPP)⩾41 mmHg, a pHi⩾7.22 or PCO2 gap⩽15.8 mmHg.Conclusions. Continuous saline tonometry detected intestinal ischemia as induced by graded reductions in IPP. A threshold could be defined above which intestinal ischemia does not occur.