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Carbon monoxide generation in carbon dioxide absorbents
J Baum1, G Sachs, C vd Driesch
1Abteilung für Anästhesie und Intensivmedizin, Krankenhaus St. Elisabeth-Stift, Damme, Germany.
Anesthesia and Analgesia
|July 1, 1995
Summary
Low-flow anesthesia techniques are safe and do not increase carboxyhemoglobin (COHb) levels during general anesthesia. This study found no dangerously high COHb in patients, suggesting low-flow anesthesia protects against carbon monoxide generation by preserving absorbent moisture.
Area of Science:
- Anesthesiology
- Biochemistry
- Environmental Health
Background:
- Unexpected high carboxyhemoglobin (COHb) levels have been reported in patients under general anesthesia.
- Traditional recommendations to avoid carbon monoxide (CO) intoxication include high fresh gas flows and frequent absorbent changes.
- Low-flow anesthesia offers economic and ecological benefits, necessitating reevaluation of CO risk.
Purpose of the Study:
- To investigate the risk of COHb formation in patients undergoing low-flow anesthesia.
- To determine if absorbent duration impacts COHb levels.
- To assess the safety of enflurane or isoflurane anesthesia with low fresh gas flows.
Main Methods:
- 1001 patients undergoing enflurane or isoflurane anesthesia were studied.
- Blood samples were analyzed for COHb 30 minutes after reducing fresh gas flow to 0.5 L/min.
- Absorbent canisters (soda lime) were used for multiple days, and COHb levels were analyzed irrespective of absorbent age.
Main Results:
- The mean COHb level was 1.17% +/- 0.97%, with a range of 0%-7.6%.
- No statistically significant difference in COHb levels was observed based on the duration of absorbent canister use.
- No dangerously high COHb levels were detected in any patient.
Conclusions:
- Low-flow anesthesia, utilizing enflurane or isoflurane, does not lead to significant COHb elevation.
- Preserving absorbent moisture, a characteristic of low-flow techniques, appears to prevent carbon monoxide generation.
- Low-flow anesthesia is a safe method regarding COHb risk, contrary to previous concerns.