Study objective: To define the optimal dose of lidocaine to be added to propofol to reduce the incidence of pain during its injection.
Design: Double-blind, randomized, placebo-controlled study.
Setting: Medical center operating rooms.
Patients: 135 ASA I and II female patients undergoing minor outpatient surgery.
Interventions: Patients were randomly allocated to one of five groups: Group A (control), no lidocaine: Group B, lidocaine 10 mg: Group C, lidocaine 20 mg; Group D, lidocaine 30 mg; Group F, lidocaine 40 mg. For each patient, pain during injection of the propofol solution was graded as none, mild, moderate, or severe.
Measurements and main results: The incidence of pain in the control group was 85%. All treatment groups receiving lidocaine had a significantly lower incidence of pain compared with the control group (P < 0.001). The lidocaine 30 mg and 40 mg groups both had a 7% incidence of pain, which was significantly less than a 33% incidence in the lidocaine 10 mg group (P < 0.05).
Conclusions: Within this dose range and in this patient population, 30 mg of lidocaine is optimal for reducing the pain during injection of propofol.