Reduction in post-intubation respiratory resistance by isoflurane and albuterol.
OBJECTIVE
This study examined the bronchodilating effects of 0.6 MAC and 1.1 MAC isoflurane (ISF) on respiratory system resistance (Rrs) following tracheal intubation and determined whether albuterol supplements that effect.


METHODS
Sixty-seven adult patients were anaesthetized with 2 micrograms.kg-1 fentanyl and 5 mg.kg-1 thiopentone and their tracheas intubated following administration of 1 mg.kg-1 succinylcholine. Respiratory system resistance was measured following intubation and the patients then randomized to receive either 1.1 MAC ISF in oxygen or 0.6 MAC ISF in 50% nitrous oxide and oxygen. Ten minutes later, Rrs was again measured. Patients were then further randomized to receive albuterol or a placebo using incremental doses of 2, 5, and 10 puffs (albuterol puff = 90 micrograms) delivered via a metered dose inhaler at ten minute intervals.


RESULTS
Isoflurane at 1.1 MAC decreased post-intubation Rrs by 23 +/- 5% (mean +/- sem) whereas the decrease was only 7 +/- 5% for 0.6 MAC ISF (P < 0.01). Two puffs of albuterol resulted in a further decrease of 12 +/- 3% (mean +/- sem) in Rrs compared with a 2 +/- 4% decrease in the placebo groups (P < 0.05). Additional puffs of albuterol resulted in no further changes in Rrs.


CONCLUSIONS
We conclude that following tracheal intubation the reduction in Rrs produced by ISF is highly concentration dependent. Albuterol results in a small further reduction in Rrs.
Choi
J H
JH
Department of Anesthesiology, University of Washington School of Medicine, Seattle, USA.
Rooke
G A
GA
Wu
S C
SC
Bishop
M J
MJ
D000318:Adrenergic beta-Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D000403:Airway Resistance / Q000187:drug effects*; D000420:Albuterol / Q000008:administration & dosage / Q000494:pharmacology*; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000494:pharmacology*; D016084:Bronchoconstriction / Q000187:drug effects; D001993:Bronchodilator Agents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D007442:Intubation, Intratracheal; D007530:Isoflurane / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged
D000318:Adrenergic beta-Agonists; D018685:Anesthetics, Inhalation; D001993:Bronchodilator Agents; D007530:Isoflurane; D000420:Albuterol