Sodium bicarbonate versus sodium hyaluronidase in ocular regional anaesthesia--a comparative study

It has been reported that alkalinisation of an anaesthetic medication enhances the rate of onset of regional anaesthesia. The purpose of this study therefore was to find out whether alkalinisation really hastened peribulbar anaesthesia as given prior to routine cataract surgery. Two hundred and forty otherwise healthy patients with bilateral cataracts were selected for this study irrespective of their demographic attributes. The first eye (group FE) received a routine peribulbar block with a standard solution of 6 ml of 2% lignocaine mixed with 15 IU/l units of sodium hyaluronidase at a pH of 4.6. The second eye (group SE) was taken up for surgery after one week and received a peribulbar block with 6 ml lignocaine 2% mixed with 7.5% sodium bicarbonate at a pH 7.4. The time taken for onset of akinesia in both the situations was measured to the last minute with the aid of a stop watch by an independent observer. Thirty-five per cent of patients in group FE had complete akinesia at the end of 5 minutes, another 60% at the end of 7 minutes and remaining 6% at 10 minutes. Sixty-eight per cent of patients in group SE had complete akinesia at the end of 5 minutes and 100% at the end of 7 minutes. No anaesthesia related ocular or systemic complications were seen in any group. Sodium bicarbonate buffered peribulbar block is faster than routine hyaluronidase augmented block with a reduced time of onset of akinesia.