Intraperitoneal and sigmoid colon tonometry in porcine hypoperfusion and endotoxin shock models

Background: The objective of the present study was to assess the accuracy o f an air tonometry device in vivo within a wide range of regional carbon di oxide tension (PrCO2) values by using saline tonometry as the standard and to investigate the possibilities to monitor perfusion of the intestine by t onometry in the intraperitoneal cavity. Methods: Piglets were anesthetized and mechanically ventilated. A pair of t onometry catheters was placed in the sigmoid colon, while another pair was placed intraperitoneally in the right lower quadrant of the abdomen. Air to nometric regional PCO2 (aPrCO(2)) was measured every 15 min intraperitoneal ly and every 20 min in the sigmoid colon. Saline tonometric measurements we re made every 30 min and steady-state values (ssPrCO(2)) were derived. Hypo perfusion shock was induced by graded constriction of the aorta. Endotoxin shock was induced by administration of lipopolysaccharide (LPS). Results: The obtained average PrCO2 (=matched (aPrCO(2)+ ssPrCO(2))/2) valu es ranged from 5.1 kPa to 14.7 kPa. Regional air PCO2 (aPrCO(2)) and steady -state saline PCO2 (ssPrCO(2)) exhibited a strong positive linear relations hip (r=0.959). The 95% confidence interval of the mean of dPrCO(2) (=aPrCO( 2)-ssPrCO(2)) was 0.31-0.46 kPa. Intraperitoneal tonometric PrCO2 was lower than intraluminal PrCO2 in the sigmoid colon, and was also more sensitive to circulatory changes than sigmoid colon PrCO2. Conclusion: The regional air PCO2 (aPrCO(2)) showed good agreement with the steady-state saline regional PCO2 (ssPrCO(2)). Intraperitoneal measurement s may be an alternative method of monitoring intestinal perfusion after abd ominal surgery.