Optimal dose of thiamylal in combination with midazolam for induction of anaesthesia.
OBJECTIVE
The optimal dose range of thiamylal, combined with midazolam, in the induction of anaesthesia was evaluated using haemodynamic variables.


METHODS
The 200 patients, aged 30 to 70 yr, were randomly divided into five groups by midazolam dosage. Anaesthesia was induced with midazolam 0.05, 0.075, 0.10, 0.15, or 0.20 mg.kg-1. Two minutes later, 50 mg thiamylal was administered followed by 25 mg increments until verbal response and eyelash reflex disappeared and blood pressure decreased to a level less than that of preinduction. Tracheal intubation was performed with 0.15 mg.kg-1 vecuronium. Blood pressure and heart rate were monitored during induction. Optimal induction was defined as a systolic blood pressure one minute after intubation within +/- 20% of that before induction.


RESULTS
There were 164 patients whose systolic blood pressure were within these criteria. Blood pressure decreased two minutes after induction and 3 to 15 min after intubation in all groups. Heart rate increased one minute after intubation in 0.05 mg.kg-1, 0.075 mg.kg-1 and 0.10 mg.kg-1 midazolam groups. The optimal range of thiamylal was 4.0 +/- 1.1 (mean + SD), 3.1 +/- 1.2, 2.8 +/- 1.1, 2.3 +/- 1.2, and 1.7 +/- 1.0 mg.kg-1 in combination with midazolam 0.05, 0.075, 0.10, 0.15, and 0.20 mg.kg-1, respectively.


CONCLUSIONS
The optimal dose range, to maintain haemodynamic stability, for thiamylal induction of anaesthesia in combination with midazolam, 0.05-0.2 mg.kg-1 was found to range from 4.0 to 1.7 mg.kg-1.
Nishiyama
T
T
Department of Anesthesiology, Faculty of Medicine, University of Tokyo, Japan.
Hanaoka
K
K
D000328:Adult; D000368:Aged; D000758:Anesthesia; D018686:Anesthetics, Intravenous / Q000008:administration & dosage*; D001794:Blood Pressure / Q000187:drug effects; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008874:Midazolam / Q000008:administration & dosage*; D008875:Middle Aged; D013840:Thiamylal / Q000008:administration & dosage*
D018686:Anesthetics, Intravenous; D013840:Thiamylal; D008874:Midazolam