Comparison of minimum alveolar concentration between intravenous isoflurane lipid emulsion and inhaled isoflurane in dogs.
BACKGROUND
As in inhaled isoflurane anesthesia, when isoflurane lipid emulsion (ILE; 8%, vol/vol) is intravenously administered, the primary elimination route is through the lungs. This study was designed to determine the minimum alveolar concentration (MAC) and the time course of washout of isoflurane for intravenously infused ILE by monitoring end-tidal isoflurane concentration.


METHODS
Twelve healthy adult mongrel dogs were assigned randomly to an intravenous anesthesia group with 8% ILE or to an inhalation anesthesia group with isoflurane vapor. An up-and-down method and stimulation of tail clamping were used to determine MAC of 8% ILE by intravenous injection in the intravenous anesthesia group and MAC by the inhaled approach in the inhalation anesthesia group, respectively. Isoflurane concentration and partial pressure in end-tidal gas, femoral arterial blood, and jugular venous blood were measured simultaneously just before each tail clamping and during washout.


RESULTS
The induction time in the intravenous anesthesia group (105 +/- 24 s) was shorter than that in the inhalation anesthesia group (378 +/- 102 s; P < 0.01). MAC of 8% ILE by intravenous injection (1.12 +/- 0.18%) was significantly less than MAC by the inhaled approach (1.38 +/- 0.16%; P < 0.05). No significant difference was found between the two groups in the time course of washout of isoflurane.


CONCLUSIONS
The MAC of intravenous anesthesia with 8% ILE was less than that of inhalation anesthesia with isoflurane vapor in dogs.
Yang
Xiao-Lin
XL
Department of Anesthesiology, West China Hospital, Sichuan University, China.
Ma
Han-Xiang
HX
Yang
Zong-Bin
ZB
Liu
Ai-Jie
AJ
Luo
Nan-Fu
NF
Zhang
Wen-Sheng
WS
Wang
Li
L
Jiang
Xue-Hua
XH
Li
Jie
J
Liu
Jin
J
D000280:Administration, Inhalation; D018685:Anesthetics, Inhalation / Q000008:administration & dosage*; D000818:Animals; D004285:Dogs; D005217:Fat Emulsions, Intravenous / Q000008:administration & dosage*; D007530:Isoflurane / Q000008:administration & dosage* / Q000493:pharmacokinetics / Q000494:pharmacology; D011650:Pulmonary Alveoli / Q000378:metabolism*
D018685:Anesthetics, Inhalation; D005217:Fat Emulsions, Intravenous; D007530:Isoflurane