Sodium bicarbonate--an alternative to hyaluronidase in ocular anaesthesia for cataract surgery.

PURPOSE: To evaluate and compare the safety, efficacy and cost-effectiveness of 7.5% sodium bicarbonate buffered lidocaine (pH 7.2) with hyaluronidase mixed lidocaine (pH 4.6) for local anaesthesia in cataract surgery.

METHODS: This prospective study comprised two parts. Part I: We evaluated the ocular and systematic anaesthetic safety and efficacy of 7.5% sodium bicarbonate buffered lidocaine on 112 consecutive patients undergoing cataract extraction with intraocular lens (IOL) implantation. At 12-week postoperative follow up final visual acuity and detailed fundus examination was done. Part II: It was conducted as a double blind, randomized comparative clinical trial involving 120 patients undergoing cataract surgery under retrobulbar anaesthesia. Patients were randomly assigned to one of the two groups: 60 eyes received 2 ml of 2% lidocaine with 1:200,000 epinephrine and 1 ml of 7.5% sodium bicarbonate, (0.299 mmol/ml); the remaining 60 eyes received 2 ml of 2% lidocaine with 1:200,000 epinephrine and 450 units of hyaluronidase (15 U/ml). In the event of incomplete akinesia, retrobulbar blocks were supplemented at 10 minutes. Onset and duration of anaesthesia and akinesia were assessed and compared in both groups.

RESULTS: The pH-adjusted lidocaine group did not show any demonstrable variation in blood pressure (BP) or other systemic reaction. No anaesthesia-related adverse ocular effects were observed either during or after surgery. Thirty-one eyes (51.6%) achieved complete anaesthesia and akinesia within 5 minutes compared to 13 eyes (21.6%) in the hyaluronidase group. However, the overall mean onset time of anaesthesia and akinesia, repeat block rate and the duration of the anaesthesia were comparable in both the groups--p: 0.14). Twelve weeks postoperatively 88.39% of patients showed a best corrected visual acuity of 6/18 or better (73.21%-6/12 or better).

CONCLUSION: In this study, sodium bicarbonate buffered 2% lidocaine was found to be a safe and effective local anaesthetic, with reduced time of onset, and improved quality of both anaesthesia and akinesia. Sodium bicarbonate (7.5%) may be used as an alternative to hyaluronidase in ocular anaesthesia. It is readily available and is cost effective.