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Carbon monoxide re-breathing during low-flow anaesthesia in infants and children

V Nasr1, J Emmanuel, N Deutsch

  • 1Division of Anesthesiology and Pain Medicine, Children's National Medical Center, The George Washington University School of Medicine and Health Sciences, 111 Michigan Ave., NW, Washington, DC 20010, USA.

British Journal of Anaesthesia
|October 16, 2010
PubMed

Insights

Low-flow anaesthesia (LFA) in children increases re-breathing of carbon monoxide (CO), particularly in infants under two years old. This CO re-breathing leads to elevated carboxyhaemoglobin (COHb%) levels, posing a potential risk.

Area of Science:

  • Anesthesiology
  • Respiratory Physiology
  • Environmental Health

Background:

  • Carbon monoxide (CO) is detected in anesthesia breathing systems.
  • Endogenous CO from exhalation is a potential source.
  • Re-breathing of CO during low-flow anesthesia (LFA) in pediatric patients was hypothesized.

Purpose of the Study:

  • To investigate the hypothesis that CO is re-breathed during LFA in infants and children.
  • To quantify exhaled and inspired CO levels during LFA and high-flow anesthesia (HFA).
  • To assess changes in carboxyhaemoglobin (COHb%) during different anesthesia flow rates.

Main Methods:

  • Prospective observational study of 20 children (2 months-7 years) undergoing general anesthesia.
  • Measurement of exhaled and inspired CO every 5 minutes during 60 minutes of LFA, followed by 60 minutes of HFA.
  • Measurement of COHb% at baseline, 60 minutes (post-LFA), and 120 minutes (post-HFA).

Main Results:

  • CO concentrations increased during LFA, with inspired CO peaking at 14 ppm.
  • Exhaled CO levels remained constant during HFA, while inspired CO decreased significantly.
  • COHb% significantly increased in children under 2 years old after LFA and remained elevated.

Conclusions:

  • LFA increases exhaled and inspired CO, leading to CO re-breathing and elevated COHb% in young children.
  • Re-breathing exhaled gas during LFA poses a risk for acute CO exposure, especially in vulnerable patients.
  • Matching or exceeding minute ventilation with fresh gas flow can limit CO re-breathing during anesthesia.
Abstract

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