Postmastectomy analgesia with subcutaneous infiltration of ketamine with lidocaine in surgical wound.

Background: Ketamine is an analgesic adjuvant useful in acute pain preventive treatment. However, there are few studies evaluating its efficacy in local administration for postoperative pain management. Objective: To compare ketamine´s efficacy plus 2% lidocaine versus placebo plus 2% lidocaine infiltrated into surgical wound as postoperative analgesia in patients undergoing mastectomy. Material and methods: An experimental, randomized, single-blind study was carried out in 18 patients older than 18 years scheduled for mastectomy under general anesthetic technique. The surgical wound was infiltrated before to its closure with 0.5 mg/kg of ketamine plus 10 mL of simple 2% lidocaine volumetric to 20 mL with saline solution (group 1) or 10 mL saline solution + 10 mL of simple 2% lidocaine (group 2). Each patient was randomly assigned to one of the two intervention groups by draw (from which a piece of paper was drawn indicating the group to which they would belong). The pain intensity was assessed by Analog Numerical Scale (ANS) at 2, 8 and 12 hours after surgery and the need for analgesic rescue doses. Results: The scores on the ANS scale in both groups were similar at leaving (p 0.26) and 2 hours later (p 0.05). The ENA value was lower with 2% ketamine/lidocaine infiltration at 8 hours (ketamine 2.5 [2-3]; placebo 4 [3-7], p 0.01) and 12 hours (ketamine 3 [1-5]; placebo 5 [4-6], p < 0.001). Conclusions: Ketamine infiltrated into the surgical wound provides superior analgesia and improves ENA scores in the post-surgical period.