 Introduction Administration of intravenous lidocaine as an adjunct to placebo in postoperative pain is highly recommended. Its use has been proven safe and effective in mastectomy surgery.  Objective To determine the effectiveness of bolus administration of continuous intravenous lidocaine on pain intensity after mastectomy surgery at Haji Adam Malik General Hospital of Medan and North Sumatra University Hospital.  Method This research is a randomized controlled and double-blind clinical trial. It was conducted for 2 months in November-December 2019. The total sample obtained was 42 patients. This sample was divided into 2 groups: group A (lidocaine) and group B (placebo). Data was collected using the VAS questionnaire at hours 0 (T0), 2 (T1), 4 (T2) and 6 (T3) after surgery ended.  Results The results showed that the mean value of VAS-A in 72 patients was 4.14 ± 1.9. The mean MAP in the lidocaine group was 91.4 ± 6.8 mmHg while in the placebo group was slightly higher, which was 92.2 ± 5.2 mmHg (p = 0.541). The mean heart rate in the lidocaine group was 78.0 ± 6.06 times per minute while in the placebo group was slightly higher, which was 84.4 ± 7.3 times per minute (p = 0.003). In the lidocaine group, there was no correlation between MAP and postoperative VAS values (r = -0.106; p = 0.324) and a low negative correlation between heart rate and postoperative VAS values (r = -0.201; p = 0.524). VAS values in the lidocaine and placebo groups showed a significant difference in T0 observations (p = 0.039).  Conclusion VAS values in the lidocaine group were lower than those in the placebo group at T0 observations, but not significantly different in T1, T2, and T3 observations.

Keywords : Postoperative Pain, Lidocaine, Hemodynamics.