Bicarbonate-buffered ropivacaine-mepivacaine solution for medial caruncle anaesthesia

Abstract

Background: To compare self-reported pain during injection of plain versus alkalinised 0.75% ropivacaine-2% mepivacaine solution for anaesthesia performed at the medial caruncle site for eye surgery.

Methods: This prospective, monocentric, double blind, randomised, controlled trial involved 40 consecutive patients who received either a standard local anaesthetic solution (0.75% ropivacaine 5ml and 2% mepivacaine 5ml with a pH of 5.9), or an alkalinised solution composed with a pH-adjusted solution of 7.0 through adjunction of 0.15mEq sodium bicarbonate per 10ml of the same mixture. Before anaesthesia, patients received intravenous midazolam (0.03mg/kg) to ease potential anxiety. During injection performed at the medial caruncle site, patients were asked to grade a pain VRS (0 to 10) for the injection using a verbal analogue scale. The primary end point was to investigate pain during injection of local anaesthetics.

Results: Anxiety levels before anaesthesia were low and similar for both groups. The mean pain score for the alkalinised group was significantly reduced compared to the control group (6 [25-75%, IQR 4-9] versus 3 [25-75%, IQR 1-5]; P=0.02; 95% CI for the difference in median pain scores [1.9-3.3]).

Conclusion: Buffering local anaesthetics used in caruncular injection for eye surgery significantly reduces pain during injection. This simple strategy should be tested in routine clinical practice to improve patient satisfaction.

Keywords: Alkalinisation; Caruncle; Local anaesthetics; Pain.