Minimum alveolar concentration of desflurane in patients older than 65 yr.
BACKGROUND
The minimum alveolar concentration (MAC) of desflurane/oxygen is 7.25% in the 18-30-yr age group, and 6.0% in the 31-65-yr age group. The addition of 60% N2O reduces MAC to 4.0 and 2.83%, respectively. Because MAC of other inhaled anesthetics is less than that for younger adults, we determined MAC of desflurane in adults aged 65 yr and older.


METHODS
Thirty-nine patients, 21 of whom received 60% N2O/O2/desflurane, and 18 of whom received desflurane/oxygen, scheduled for surgery, were enrolled. They received no premedication, intravenous induction agent, opioid, or neuromuscular blocking agent for intubation. After 10 min or more at a steady end-tidal desflurane concentration, the incision was made. In both groups, six crossover pairs of patients responses (movement-no movement) provided a mean end-tidal concentration. Minimum alveolar concentration was defined as the average of the six crossover midpoints in each subgroup.


RESULTS
MAC was 5.17 +/ 0.6% (mean +/- SD) in the desflurane/oxygen group. It was 1.67 +/- 0.4% in the desflurane/nitrous oxide/oxygen group.


CONCLUSIONS
In the geriatric patient, MAC of desflurane, with or without nitrous oxide, is less than that reported in patients aged 18-65 yr. This is in agreement with results with all other inhalation agents.
Gold
M I
MI
University of Miami School of Medicine, Department of Anesthesiology, Florida 33125.
Abello
D
D
Herrington
C
C
D000280:Administration, Inhalation; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D000777:Anesthetics / Q000032:analysis / Q000493:pharmacokinetics* / Q000494:pharmacology; D000077335:Desflurane; D006801:Humans; D007530:Isoflurane / Q000031:analogs & derivatives* / Q000032:analysis / Q000493:pharmacokinetics / Q000494:pharmacology; D008875:Middle Aged; D009609:Nitrous Oxide / Q000008:administration & dosage / Q000494:pharmacology*; D010100:Oxygen / Q000008:administration & dosage / Q000494:pharmacology*; D011650:Pulmonary Alveoli / Q000737:chemistry* / Q000378:metabolism
D000777:Anesthetics; D000077335:Desflurane; D007530:Isoflurane; D009609:Nitrous Oxide; D010100:Oxygen