title: Carbon monoxide production from desflurane, enflurane, halothane, isoflurane, and sevoflurane with dry soda lime.
abstract: BACKGROUND
  Previous studies in which volatile anesthetics were exposed to small amounts of dry soda lime, generally controlled at or close to ambient temperatures, have demonstrated a large carbon monoxide (CO) production from desflurane and enflurane, less from isoflurane, and none from halothane and sevoflurane. However, there is a report of increased CO hemoglobin in children who had been induced with sevoflurane that had passed through dry soda lime. Because this clinical report appears to be inconsistent with existing laboratory work, the authors investigated CO production from volatile anesthetics more realistically simulating conditions in clinical absorbers.
  
  
  METHODS
  Each agent, 2.5 or 5% in 2 l/min oxygen, were passed for 2 h through a Dräger absorber canister (bottom to top) filled with dried soda lime (Drägersorb 800). CO concentrations were continuously measured at the absorber outlet. CO production was calculated. Experiments were performed in ambient air (19-20 degrees C). The absorbent temperature was not controlled.
  
  
  RESULTS
  Carbon monoxide production peaked initially and was highest with desflurane (507 +/- 70, 656 +/- 59 ml CO), followed by enflurane (460 +/- 41, 475 +/- 99 ml CO), isoflurane (176 +/- 2.8, 227 +/- 21 ml CO), sevoflurane (34 +/- 1, 104 +/- 4 ml CO), and halothane (22 +/- 3, 20 +/- 1 ml CO) (mean +/- SD at 2.5 and 5%, respectively).
  
  
  CONCLUSIONS
  The absorbent temperature increased with all anesthetics but was highest for sevoflurane. The reported magnitude of CO formation from desflurane, enflurane, and isoflurane was confirmed. In contrast, a smaller but significant CO formation from sevoflurane was found, which may account for the CO hemoglobin concentrations reported in infants. With all agents, CO formation appears to be self-limited.
authors.affiliation: Clinic of Anesthesiology, Intensive Care and Pain Therapy, University Hospital Frankfurt, Germany. wissing@em.uni-frankfurt.de
authors.forename: H
authors.initials: H
authors.lastname: Wissing
authors.forename: I
authors.initials: I
authors.lastname: Kuhn
authors.forename: U
authors.initials: U
authors.lastname: Warnken
authors.forename: R
authors.initials: R
authors.lastname: Dudziak
mesh_terms: D018685:Anesthetics, Inhalation / Q000737:chemistry*; D017610:Calcium Compounds / Q000737:chemistry*; D002248:Carbon Monoxide / Q000138:chemical synthesis*; D000077335:Desflurane; D004737:Enflurane / Q000737:chemistry; D006221:Halothane / Q000737:chemistry; D007530:Isoflurane / Q000031:analogs & derivatives / Q000737:chemistry; D008738:Methyl Ethers / Q000737:chemistry; D010087:Oxides / Q000737:chemistry*; D000077149:Sevoflurane; D012972:Sodium Hydroxide / Q000737:chemistry*
chemical_list: D018685:Anesthetics, Inhalation; D017610:Calcium Compounds; D008738:Methyl Ethers; D010087:Oxides; D000077149:Sevoflurane; C004569:soda lime; D012972:Sodium Hydroxide; D002248:Carbon Monoxide; D004737:Enflurane; D000077335:Desflurane; D007530:Isoflurane; D006221:Halothane