Alkalinisation of local anaesthetics prescribed for pain relief after surgical decompression of carpal tunnel syndrome.

PURPOSE To compare the duration of analgesia achieved following administration of buffered prilocaine versus plain prilocaine to patients undergoing surgical decompression of the median nerve. METHODS 40 (32 female and 8 male; mean age, 50.5 years) patients who underwent surgical decompression of carpal tunnel syndrome were recruited. Patients were randomly allocated to 2 groups: the alkalinised group was given 10 ml of prilocaine hydrochloride 2% buffered with 1 ml of sodium bicarbonate 8.4%, whereas the non-alkalinised group received 10 ml of plain prilocaine hydrochloride 2% solution. Patients were asked to rate their comfort level at the operation site in the first 6 hours following surgery and after discharge from hospital using a visual analogue scale (VAS). The duration of analgesic effect was evaluated every 3 hours. Additional oral analgesia in the form of paracetamol 500 mg tablets was available to patients if required for break-through pain. RESULTS Significantly lower VAS scores were reported by the alkalinised group during the first postoperative 12 hours. The change of VAS scores over time was significantly higher in the non-alkalinised group. The mean analgesic requirement for paracetamol tablets in the alkalinised and non-alkalinised groups was 4 and 34, respectively. CONCLUSION Buffered prilocaine provided a longer postoperative pain-free period for patients undergoing surgical decompression of the median nerve. It is easy, safe, and cost-effective.