Bicarbonate-buffered ropivacaine-mepivacaine solution for medial caruncle anaesthesia

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.

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.

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]).

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.