Control of postoperative pain after awake craniotomy with local intradermal analgesia and metamizol

Background: Pain following brain surgery is a significant problem. Infiltration of the scalp with local intradermal anesthetics was suggested for postoperative pain control but was assessed only in the first hour postoperatively. Objectives: To evaluate wound infiltration with a single dose of metamizol (dipyrone) for postoperative pain control in patients undergoing awake craniotomy. Methods: This open, prospective, non-randomized observational study, conducted in anesthesiology and neurosurgical departments of a teaching hospital, included 40 patients undergoing awake craniotomy for the removal of brain tumor. Intraoperative anesthesia included wound infiltration with lidocaine and bupivacaine, conscious sedation using remifentanil and propofol, and a single dose of metamizol (dipyrone) for postoperative pain control. Outcome was assessed by the Numerical Pain Scale on arrival at the postoperative care unit, and 2, 4 and 12 hours after the end of surgery. Results: On arrival at the postoperative care unit, patients reported NPS scores of 1.2 +/- 1.1 in a scale of 0-10 (mean +/- SD) (median = 1, range 0-4). The scores were 0.8 +/- 0.9, 0.9 +/- 0.9 and 1 +/- 0.9 at 2 hours, 4 hours and 12 hours after the end of surgery, respectively. Based on patients' complaints and NPS lower than 3, 27 patients did not require any supplementary analgesia during the first 12 postoperative hours, 11 patients required a single dose of oral metamizol or intramuscular diclofenac, one patient was given 2 mg of intravenous morphine, and one patient required two separate doses of metamizol. Conclusions: Although the clinical setup prevents the use of placebo local analgesia as a control group, the results suggest the possible role of local intradermal infiltration of the scalp combined with a single dose of metamizol to control postoperative pain in patients undergoing craniotomy.