Continuous measurement of gut luminal pCO2 in an animal model � a sensitive index of reduced perfusion

Abstract

The sensitivity of gastric tonometry to fluctuations in mucosal perfusion is limited by long equilibration periods (minimum 30 min with saline). Delayed detection of splanchnic ischaemia may negate any benefit from subsequent improvements in splanchnic oxygen delivery. Continuous luminal pCO2 measurement for prompt detection and quantification of mucosal ischaemia could make gastric tonometry a more valid therapeutic end point. We tested the sensitivity of one continuous system to graded brief reductions in gut perfusion. Five Sprague-Dawley rats (430–r510 g) were anaesthetised with intraperitoneal sodium pentobarbitone and ventilated with 100% oxygen via tracheostomy to a paCO2 of 30–r50 mmHg. Distal aortic pressure was monitored invasively, and a Paratrend 7™ sensor inserted into the ileal lumen. Normal saline was infused at 3 ml/h, and isoflurane titrated to a mean aortic pressure of 80–r100 mmHg. Distal aortic pressure was reduced to predefined levels for 2 min intervals by digital elevation of an aortic silk sling above the coeliac artery, with intervening recovery periods to allow restabilisation of luminal PCO2. Measurements were downloaded every 2 s to a data acquisition system. Data are mean (SEM).