[Effects of concentration and dosage of lidocaine on preventing the pain on injection of propofol].

Although it is well-known that 2% lidocaine has an effective action for preventing propofol-induced pain, it has been unclear whether or not lidocaine of the concentration below 2% has the effective action similar to 2% lidocaine. One-hundred and thirty-two patients were randomly assigned to one of the six groups according to concentration and dosage of lidocaine administered at the time of the initiation of propofol infusion. Groups I and II received 1 ml and 2 ml of 1% lidocaine, respectively; Groups III and IV were given 1 ml and 2 ml of 0.5% lidocaine, respectively; Group V received 2 ml of 2% lidocaine; Group VI was administered 1 ml of normal saline as a control. There were no significant differences in patients' profiles and alterations of hemodynamics during anesthetic induction among the six groups. Number of patients complaining of a pain during induction was more in Group VI with significance (P < 0.0001) and number of patients complaining of uncomfortableness was also more with significance (P < 0.0001). Incidence of propofol-induced pain and degree of satisfaction with anesthetic induction were similar among the groups receiving lidocaine. Even 0.5% lidocaine may have the same effective action as 2% lidocaine for preventing the pain on injection of propofol.