BACKGROUND: The aim of this study is to determine the effect of high dose fentanyl on the test dose containing 15microgram epinephrine during propofol anesthesia.

METHODS: One hundred patients with ASA physical status 1 were randomized to receive 2 mg/kg propofol with or without 10microgram/kg fentanyl at the induction of anesthesia (n = 50 each). Anesthesia was maintained with propofol 8 mg/kg/h and 67% nitrous oxide in oxygen. Each group of patients were further divided into a test dose group receiving 1.5% lidocaine 3 ml plus epinephrine 15microgram or a saline group receiving 3 ml of isotonic saline (n = 25 each). Heart rate (HR) and systolic blood pressure (SBP) were monitored for 4 min after intravenous injection of the study drugs.

RESULTS: In the propofol and the propofol-fentanyl group, the intravenous injection of the test dose produced a HR increase ≥ 20 bpm (conventional HR criterion) in 25 and 23 out of the total 25 patients, respectively. Therefore, in the propofol-fentanyl group, sensitivity, specificity, positive predictive value, and negative predictive value were 82%, 100%, 100%, and 92.6%. According to the modified HR criterion (HR increase ≥ 10 bpm), all the values were 100%. All patients receiving test dose developed SBP increase ≥ 15 mmHg.

CONCLUSIONS: Our results indicate that both HR increase ≥ 10 bpm or SBP increase ≥ 15 mmHg are clinically applicable during propofol-nitrous oxide anesthesia with 10microgram/kg fentanyl.