The Effect of Lidocaine on Injection Pain of Different Propofol Concentrations in Patients Receiving Remifentanil

Objective: The effectivity of remifentanil and lidocaine combination on the injection pain with 1% propofol was reported previously. However, this finding has not been investigated with different propofol concentrations. In this prospective, randomized, double-blind trial, we aimed to compare the effect of lidocaine on the injection pain of 1% or 2% propofol in patients receiving remifentanil. Material and Methods: One hundred patients undergoing ear-nose-throat surgery were randomly assigned into four groups (n= 25 each). Following 0.5 mu g/kg/min remifentanil, patients in Group 1 and Group 2 received 1 mg.kg(-1) 1% or 2% propofol the mixed with 2 mL of saline, respectively. Patients in Group 3 and Group 4 received 1 mg.kg(-1) 1% or 2% propofol mixed with 2 mL of 2% lidocaine after 0.5 mu g kg(-1) min(-1) remifentanil. Pain during the injection of propofol was assessed on a four-point scale (0= none, 1= mild, 2= moderate, 3= severe) Results: The incidence of none-mild pain on injection of 1% propofol was significantly lower in Group 1 (56%) compared to Group 3 (100%) (p= 0.00017). This finding was also seen between Group 2 (36%) and Group 4 (72%) (p= 0.010). However, the number of patients suffering from the injection pain was significantly greater in Group 4 compared to Group 3 (p= 0.004). Conclusion: Lidocaine 2% 2 mL mixed with propofol completely abolished moderate-severe pain induced by 1% propofol in patients who were given 0.5 mu g/kg/min remifentanil. However, some patients still suffered from injection pain caused by 2% propofol in spite of the combined effect of lidocaine and remifentanil.