The effect of isoflurane, halothane, sevoflurane, and thiopental/nitrous oxide on respiratory system resistance after tracheal intubation.
BACKGROUND
After tracheal intubation, lung resistance and therefore respiratory system resistance (R[rs]) routinely increase, sometimes to the point of clinical bronchospasm. Volatile anesthetics generally have been considered to be effective bronchodilators, although there are few human data comparing the efficacy of available agents. This study compared the bronchodilating efficacy of four anesthetic maintenance regimens: 1.1 minimum alveolar concentration (MAC) end-tidal sevoflurane, isoflurane or halothane, and thiopental/nitrous oxide.


METHODS
Sixty-six patients underwent tracheal intubation after administration of 2 microg/kg fentanyl, 5 mg/kg thiopental, and 1 mg/kg succinylcholine. Vecuronium or pancuronium (0.1 mg/kg) was then given to ensure paralysis during the rest of the study. Postintubation R(rs) was measured using the isovolume technique. Maintenance anesthesia was then randomized to thiopental 0.25 mg x kg(-1) x min(-1) plus 50% nitrous oxide, or 1.1 MAC end-tidal isoflurane, halothane, or sevoflurane. The R(rs) was measured after 5 and 10 min of maintenance anesthesia. Data were expressed as means +/- SD.


RESULTS
Maintenance with thiopental/nitrous oxide failed to decrease R(rs), whereas all three volatile anesthetics significantly decreased R(rs) at 5 min with little further improvement at 10 min. Sevoflurane decreased R(rs) more than either halothane or isoflurane (P < 0.05; 58 +/- 14% of the postintubation R(rs) vs. 69 +/- 20% and 75 +/- 13%, respectively).


CONCLUSIONS
After tracheal intubation in persons without asthma, sevoflurane decreased R(rs) as much or more than isoflurane or halothane did during a 10-min exposure at 1.1 MAC.
Rooke
G A
GA
Veterans Affairs Puget Sound Health Care System and the University of Washington, Seattle 98108, USA. rooke@u.washington.edu
Choi
J H
JH
Bishop
M J
MJ
D000328:Adult; D000368:Aged; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D016084:Bronchoconstriction / Q000187:drug effects*; D001993:Bronchodilator Agents / Q000494:pharmacology*; D004987:Ethers / Q000494:pharmacology; D005260:Female; D006221:Halothane / Q000494:pharmacology; D006801:Humans; D007442:Intubation, Intratracheal / Q000009:adverse effects*; D007530:Isoflurane / Q000494:pharmacology; D008297:Male; D008738:Methyl Ethers; D008875:Middle Aged; D009609:Nitrous Oxide / Q000494:pharmacology; D012143:Respiratory Physiological Phenomena; D012137:Respiratory System / Q000187:drug effects*; D000077149:Sevoflurane; D013874:Thiopental / Q000494:pharmacology
D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D001993:Bronchodilator Agents; D004987:Ethers; D008738:Methyl Ethers; D000077149:Sevoflurane; D007530:Isoflurane; D013874:Thiopental; D009609:Nitrous Oxide; D006221:Halothane