Increasing the duration of isoflurane anesthesia decreases the minimum alveolar anesthetic concentration in 7-day-old but not in 60-day-old rats.
Anesth Analg
; 109(3): 801-6, 2009 Sep.
Article
in En
| MEDLINE
| ID: mdl-19690249
ABSTRACT
BACKGROUND:
While studying neurotoxicity in rats, we observed that the anesthetic minimum alveolar anesthetic concentration (MAC) of isoflurane decreases with increasing duration of anesthesia in 7-day-old but not in 60-day-old rats. After 15 min of anesthesia in 7-day-old rats, MAC was 3.5% compared with 1.3% at 4 h. We investigated whether kinetic or dynamic factors mediated this decrease.METHODS:
In 7-day-old rats, we measured inspired and cerebral partial pressures of isoflurane at MAC as a function of duration of anesthesia. In 60-day-old rats, we measured inspired partial pressures of isoflurane at MAC as a function of duration of anesthesia. Finally, we determined the effect of administering 1 mg/kg naloxone and of delaying the initiation of the MAC determination (pinching the tail) on MAC in 7-day-old rats.RESULTS:
In 7-day-old rats, both inspired and cerebral measures of MAC decreased from 1 to 4 h. The inspired MAC decreased 56%, whereas the cerebral MAC decreased 33%. At 4 h, the inspired MAC approximated the cerebral MAC (i.e., the partial pressures did not differ appreciably). Neither administration of 1 mg/kg naloxone nor delaying tail clamping until 3 h reversed the decrease in MAC. In 60-day-old rats, inspired MAC of isoflurane was stable from 1 to 4 h of anesthesia.CONCLUSIONS:
MAC of isoflurane decreases over 1-4 h of anesthesia in 7-day-old but not in 60-day-old rats. Both pharmacodynamic and a pharmacokinetic components contribute to the decrease in MAC in 7-day-old rats. Neither endorphins nor sensory desensitization mediate the pharmacodynamic component.
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Pulmonary Alveoli
/
Anesthetics, Inhalation
/
Isoflurane
/
Anesthesia
Limits:
Animals
Language:
En
Journal:
Anesth Analg
Year:
2009
Document type:
Article
Affiliation country:
United States