Rectal luminal Pr(CO2), measured by automated air tonometry, does not reflect gastric luminal Pr(CO2) in children.

Rectal luminal regional P(CO2) (Pr(CO2)) was compared with gastric luminal Pr(CO2) measured by automated air tonometry at intervals of 10 min in 20 children aged 6-16 years scheduled for elective surgery under general anesthesia. In 5 patients, measurement of rectal Pr(CO2) failed because of catheter-related problems. In the remaining 15 children, aged 10.6 +/- 2.5 years, 19 +/- 7 paired rectal and gastric Pr(CO2) values (n total, 241) were measured. Bias and precision for gastric compared to rectal Pr(CO2) was -1.79 kPa and 2.89 kPa. In patients with obvious feces in the rectum, bias (precision) for gastric compared to rectal Pr(CO2) was -2.7 kPa (2.6 kPa) and in those with empty rectum, -0.75 kPa (1.42 kPa; t-test; P < 0.001). Based on our in vivo data, rectal luminal Pr(CO2), measured by automated air tonometry, does not reflect gastric luminal Pr(CO2) in children. Enteral luminal gas production within feces in the rectum seems to be a major source of this disagreement.