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

Markus Weiss1, Achim Schmitz, Bettina Salgo

  • 1Department of Anaesthesia, University Children's Hospital, Steinwiesstrasse 75, CH-8032, Zurich, Switzerland.

Journal of Anesthesia
|August 10, 2006
PubMed

Insights

Rectal partial pressure of carbon dioxide (Pr(CO2)) does not accurately reflect gastric Pr(CO2) in children. Rectal measurements are influenced by enteral gas production, especially when feces are present.

Area of Science:

  • Pediatric Anesthesiology
  • Gastrointestinal Physiology
  • Medical Device Technology

Background:

  • Accurate monitoring of physiological parameters is crucial in pediatric anesthesia.
  • Partial pressure of carbon dioxide (Pr(CO2)) is a key indicator of tissue perfusion and metabolism.
  • Non-invasive methods for monitoring luminal Pr(CO2) are desirable.

Purpose of the Study:

  • To compare rectal luminal Pr(CO2) with gastric luminal Pr(CO2) in children undergoing elective surgery.
  • To evaluate the reliability of rectal Pr(CO2) measurements as a surrogate for gastric Pr(CO2).

Main Methods:

  • Automated air tonometry was used to measure rectal and gastric luminal Pr(CO2) at 10-minute intervals.
  • The study included 20 children aged 6-16 years undergoing general anesthesia.
  • Paired measurements were obtained in 15 children, with rectal measurement failures in 5 patients.

Main Results:

  • A bias of -1.79 kPa and precision of 2.89 kPa were observed between gastric and rectal Pr(CO2) measurements.
  • Measurements in patients with feces in the rectum showed a greater bias (-2.7 kPa) and precision (2.6 kPa) compared to those with empty rectums (-0.75 kPa bias, 1.42 kPa precision).
  • Statistical analysis indicated a significant difference (P < 0.001) based on rectal contents.

Conclusions:

  • Rectal luminal Pr(CO2) measurements, using automated air tonometry, do not reliably reflect gastric luminal Pr(CO2) in pediatric patients.
  • Enteral luminal gas production within rectal feces significantly impacts rectal Pr(CO2) readings, leading to discrepancies.
  • The presence of feces in the rectum is a major confounding factor for using rectal Pr(CO2) as a surrogate for gastric Pr(CO2).

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