Preventing pain during injection of propofol: the optimal dose of lidocaine.

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.