Purpose: To evaluate the incidence of pain on injection in children during anesthetic induction with a 3:1.2 volume admixture of 1% propofol and 2.5% thiopentone (P/T) compared to a 10:1 volume admixture of 1% propofol and 2% lidocaine (P/L).
Methods: After Ethics Committee approval and informed written parental consent, 127 children, aged one to ten years were studied and randomized into two groups; Group P/L received an induction with 5 mg x kg(-1) of 1% propofol and 1 mg x kg(-1) of lidocaine, Group P/T with 3 mg x kg(-1) of 1% propofol and 3 mg x kg(-1) of 2.5% thiopentone in a standardized fashion. A single, blinded observer scored pain behaviour defined as a motor response of the arm, a verbal complaint of pain, cry and/or one of three standardized facial expressions of pain.
Results: The incidence of pain was 14% in the P/T group, compared to 35% in the P/L group (chi(2)(1) = 7.5, P = 0.006). Motor response was the most frequent pain response in the P/L group (68%).
Conclusion: The P/T admixture is a practical and efficacious alternative to P/L for reducing pain on induction in children. Further work to evaluate the optimum proportions and possible adverse effects of this admixture should be done.