Gastrointestinal monitoring using measurement of intramucosal PCO2

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.

Tonometry of partial carbon dioxide tension in gastric mucosa: use of saline, buffer solutions, gastric juice or air

Tonometry of gastric mucosal partial carbon dioxide tension (PCO2) has been forwarded as a clinically applicable tool to monitor regional perfusion adequacy during circulatory failure. The technique is still not used widely, partly because of methodological problems. Current measurement principles are reviewed, with help of the report on PCO2 measurements in gastric juice and tonometer in this issue.

Splanchnic perfusion during controlled hypotension with haemodilution under isoflurane anaesthesia in elderly patients

We investigated the effects of controlled hypotension with haemodilution under isoflurane anaesthesia on splanchnic perfusion in elderly patients. We determined the intramucosal pH using gastric tonometry in 28 patients scheduled for hip surgery. Patients without cardiac disease were assigned to two groups according to age. Group A (adult patients, n = 14) included patients aged less than 60 years (range 29-58 years, 47 +/- 11 years, mean +/- SD) and group B (elderly patients, n = 14) more than 65 years (68-78 years, 72 +/- 5 years). Anaesthesia was maintained with N2O-O2-isoflurane. After induction of anaesthesia, haemodilution was produced by drawing 800-1000 mL of blood and replacing it with the same amount of hydroxyethyl starch. Final haematocrit values were 23-24% in all groups. Controlled hypotension was induced with prostaglandin E1 (PGE1) and mean blood pressure was maintained at approximately 60 mmHg for approximately 80 min. Measurements, including gastric intramucosal pH (pHi), arterial blood pH (pHa) and serum lactate were measured before haemodilution (T0), after haemodilution (T1), 80 min after starting hypotension (T2), 60 min after recovery from hypotension (T3) and on the 1st post-operative day (T4). The values of pHa and lactate showed no change in the groups throughout the time course. The gastric pHi values showed significant decreases from 7.418 +/- 0.035 to 7.334 +/- 0.024 (P < 0.05) in group A and from 7.428 +/- 0.029 to 7.320 +/- 0.039 (P < 0.05) in group B after haemodilution, while no further decreases were found at 80 min after starting the hypotension (7.329 +/- 0.038 in group A and 7.322 +/- 0.031 in group B) and 60 min after recovery from hypotension (7.331 +/- 0.029 in group A and 7.328 +/- 0.034 in group B). It can be concluded that moderate haemodilution under isoflurane anaesthesia might impair splanchnic perfusion in adult and elderly patients. The addition of controlled hypotension with PGE1 or an increase in age did not further impair splanchnic perfusion nor the splanchnic oxygen supply.