title: Activated charcoal effectively removes inhaled anesthetics from modern anesthesia machines.
abstract: BACKGROUND
  If a malignant hyperthermia-susceptible patient is to receive an anesthetic, an anesthesia machine that has been used previously to deliver volatile anesthetics should be flushed with a high fresh gas flow. Conflicting results from previous studies recommend flush times that vary from 10 to 104 minutes. In a previously proposed alternative decontamination technique, other investigators placed an activated charcoal filter in the inspired limb of the breathing circuit.
  
  
  METHODS
  We placed activated charcoal filters on both the inspired and expired limbs of several contaminated anesthesia machines and measured the time needed to flush the machine so that the delivered concentrations of isoflurane, sevoflurane, and desflurane would be <5 parts per million (ppm). We next simulated the case for which malignant hyperthermia is diagnosed 90 minutes after induction of anesthesia and measured how well activated charcoal filters limit further exposure.
  
  
  RESULTS
  Activated charcoal filters decrease the concentration of volatile anesthetic delivered by a contaminated machine to an acceptable level in <2 minutes. The concentrations remained well below 5 ppm for at least 60 minutes. When malignant hyperthermia is diagnosed after induction of anesthesia, we found that with charcoal filters in place, the current anesthesia machine may be used for at least 67 minutes before the inspired concentration exceeds 5 ppm.
  
  
  CONCLUSIONS
  Activated charcoal filters provide an alternative approach to the 10 to 104 minutes of flushing that are normally required to prepare a machine that has been used previously to deliver a volatile anesthetic.
authors.affiliation: University of Utah, Salt Lake City, UT 84132, USA. nathaniel.birgenheier@hsc.utah.edu
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Birgenheier
authors.forename: Robert
authors.initials: R
authors.lastname: Stoker
authors.forename: Dwayne
authors.initials: D
authors.lastname: Westenskow
authors.forename: Joseph
authors.initials: J
authors.lastname: Orr
mesh_terms: D000769:Anesthesia, Inhalation / Q000295:instrumentation* / Q000379:methods; D018685:Anesthetics, Inhalation / Q000008:administration & dosage*; D002606:Charcoal / Q000494:pharmacology*; D000077335:Desflurane; D004867:Equipment Design; D005334:Fever; D005374:Filtration / Q000295:instrumentation; D005740:Gases; D006801:Humans; D007530:Isoflurane / Q000008:administration & dosage / Q000031:analogs & derivatives; D008305:Malignant Hyperthermia / Q000517:prevention & control; D008422:Materials Testing; D008738:Methyl Ethers / Q000008:administration & dosage; D000077149:Sevoflurane; D013997:Time Factors
chemical_list: D018685:Anesthetics, Inhalation; D005740:Gases; D008738:Methyl Ethers; D002606:Charcoal; D000077149:Sevoflurane; D000077335:Desflurane; D007530:Isoflurane