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

The objective of the present study was to assess the accuracy of an air tonometry device in vivo within a wide range of regional carbon dioxide tension (PrCO2) values by using saline tonometry as the standard and to investigate the possibilities to monitor perfusion of the intestine by tonometry in the intraperitoneal cavity.

Piglets were anesthetized and mechanically ventilated. A pair of tonometry catheters was placed in the sigmoid colon, while another pair was placed intraperitoneally in the right lower quadrant of the abdomen. Air tonometric regional PCO2 (aPrCO2) was measured every 15 min intraperitoneally and every 20 min in the sigmoid colon. Saline tonometric measurements were made every 30 min and steady-state values (ssPrCO2) were derived. Hypoperfusion shock was induced by graded constriction of the aorta. Endotoxin shock was induced by administration of lipopolysaccharide (LPS).

The obtained average PrCO2 (=matched (aPrCO2+ ssPrCO2)/2) values ranged from 5.1 kPa to 14.7 kPa. Regional air PCO2 (aPrCO2) and steady-state saline PCO2 (ssPrCO2) exhibited a strong positive linear relationship (r=0.959). The 95% confidence interval of the mean of dPrCO2 (=aPrCO2-ssPrCO2) 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.

The regional air PCO2 (aPrCO2) showed good agreement with the steady-state saline regional PCO2 (ssPrCO2). Intraperitoneal measurements may be an alternative method of monitoring intestinal perfusion after abdominal surgery.