Single vital capacity inhalational anaesthetic induction in adults--isoflurane vs sevoflurane.
OBJECTIVE
To evaluate whether isoflurane is as suitable as sevoflurane for the single vital capacity breath (VCB) method of inhalational induction in patients premedicated with midazolam.


METHODS
A randomised, controlled, double-blind study involving 67 ASA I-II patients aged between 18-50 yr undergoing elective surgery under general anaesthesia. All participants received premedication with 0.03 mg.kg-1 midazolam i.v. Using a primed circle absorber circuit, inhalational induction of anaesthesia was performed with the single VCB method using either isoflurane 3.5% or sevoflurane 7.5% in nitrous oxide 67% in oxygen, representing approximately equivalent MAC-multiples of 3.6 MAC. Isoflurane was compared with sevoflurane in terms of rapidity, efficacy, safety and acceptability of induction.


RESULTS
With the single VCB method, sevoflurane produced a faster (45 +/- 21 vs 71 +/- 22 sec, P < 0.01), more successful (100% vs 75.8%, P < 0.01) induction of anaesthesia, with fewer induction-related complications (11.8% vs 84.8%, P < 0.01) than did isoflurane. There was also greater patient acceptability of induction with sevoflurane (76.4% vs 42.4%, P < 0.05).


CONCLUSIONS
In adults given midazolam premedication, isoflurane is not as suitable as sevoflurane for single VCB inhalational anaesthetic induction technique as it is associated with slower, more complicated induction and less patient acceptability.
Ti
L K
LK
Department of Anaesthesia, National University Hospital, Singapore. anatilk@nus.edu.sg
Pua
H L
HL
Lee
T L
TL
D000293:Adolescent; D000328:Adult; D000764:Anesthesia, Closed-Circuit; D000769:Anesthesia, Inhalation / Q000379:methods; D018685:Anesthetics, Inhalation / Q000008:administration & dosage* / Q000009:adverse effects; D003371:Cough / Q000139:chemically induced; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D006993:Hypnotics and Sedatives / Q000627:therapeutic use; D007530:Isoflurane / Q000008:administration & dosage* / Q000009:adverse effects; D007826:Laryngismus / Q000139:chemically induced; D008297:Male; D008738:Methyl Ethers / Q000008:administration & dosage* / Q000009:adverse effects; D008874:Midazolam / Q000627:therapeutic use; D008875:Middle Aged; D009609:Nitrous Oxide / Q000008:administration & dosage; D010100:Oxygen / Q000008:administration & dosage; D017060:Patient Satisfaction; D011229:Preanesthetic Medication; D012449:Safety; D000077149:Sevoflurane; D013035:Spasm / Q000139:chemically induced; D013997:Time Factors; D014797:Vital Capacity
D018685:Anesthetics, Inhalation; D006993:Hypnotics and Sedatives; D008738:Methyl Ethers; D000077149:Sevoflurane; D007530:Isoflurane; D009609:Nitrous Oxide; D008874:Midazolam; D010100:Oxygen