Background: Preoperative oral gabapentin has been shown to reduce postoperative pain. However, the effects of gabapentin as an adjunct to regional anesthesia is unclear and its effects on chronic pain remains unknown. In patients undergoing thyroidectomy, we investigated the effects on early and late (at 6 mo) postoperative pain of preoperative oral gabapentin as an adjunct to superficial cervical plexus block (SCPB).
Method: Fifty consecutive consenting patients were randomized to receive either 1200 mg of gabapentin (Group G) or placebo (Group P) 2 h preoperatively. Preoperative anxiety was assessed on a numeric scale from 0 to 6. A SCPB was performed after a standardized induction of anesthesia. The primary outcome, analgesic drug consumption, was assessed during the procedure and postoperatively in the postanesthesia care unit and after discharge to the ward. Over the first 24 h, pain levels at rest and during swallowing were measured on a numeric scale from 0 to 10. If the pain level was more than 4/10 at rest, patients received 1 g/6 h of IV paracetamol and/or 50 mg/6 h of IV tramadol as a rescue analgesic treatment in the interval. The day before operation and 6 mo after thyroidectomy, included patients were asked to answer a neuropathic pain diagnostic questionnaire.
Results: Population characteristics, preoperative anxiety, intraoperative drug consumption, procedure duration, and postoperative care unit stay were comparable in both groups. Analgesic consumption during the first 24 postoperative hours was similar in both groups (G: 3 [0-5] doses/24 h; P: 3 [1-5] doses/24 h; P = NS), as well as pain at rest (G: 2,2 [0.2-3.7]; P: 2 [0-6.3]; P = NS), and during swallowing (G: 2.8 [0.4-8.9]; P: 3 [1.4-6.3]; P = NS]). Eight patients had a diagnostic questionnaire score more than 3, 6 mo after operation versus 2 in preoperative period (P = 0.04). Such delayed neuropathic pain complaints were reported in seven patients receiving SCPB alone and only in one patient receiving both SCPB and preoperative adjunctive oral gabapentin. (P = 0.01).
Conclusion: Oral preoperative administration of gabapentin did not modify immediate pain management in thyroidectomy patients receiving SCPB, but prevented delayed neuropathic pain at 6 mo.