BACKGROUND: In this prospective, randomized, double-blind, controlled trial, our primary objective was to assess the effect of a 3 : 1 mixture of propofol and thiopental in reducing pain on injection in children. Our hypothesis was that a 3 : 1 mixture of propofol and thiopental (treatment) would reduce the incidence of pain on injection to 20% compared to the expected incidence of 40% in the control group of an 11 : 1 mixture of propofol and 2% lidocaine.

METHODS: Study subjects were patients 12-17 years old who were scheduled to undergo surgery and general anesthesia. Pain was assessed by a single-blinded observer present in the operating room. The major statistical method used in the analysis was multiple logistic regression.

RESULTS: Among the 164 children analyzed, 96 patients (58.5%) were male. The average age was 14.3 (sd = 1.65). The incidence of pain in the control group was 32.1% (26/81), compared to 25.3% (21/83) in the treatment group. The logistic regression analysis showed that there was not sufficient evidence that the treatment group was better than control group in reducing pain (P = 0.24). There were no significant differences in postoperative recovery time, nausea, vomiting, or blood pressure between the two groups (all P values >0.10).

CONCLUSION: There was not sufficient evidence to show that a 3 : 1 mixture of propofol and thiopental was better than an 11 : 1 volume admixture of propofol and lidocaine in reducing the incidence of pain on injection to 20%.