"Cryoanalgesic preparation" before local anaesthetic injection for lid surgery

Lid surgery under local anaesthetic is commonplace in ophthalmic practise. The most distressing part of the surgery for the patient is often the injection of local anaesthetic into the sensitive lid skin. Various methods like pre-injection warming of the anaesthetic agent, buffering pH levels, varying agents used, and using thinner gauge needles have been tried to reduce pain levels. Cooling of tissue is known to have anaesthetic properties and has been proposed as a substitute to injection of local anaesthetic in certain surgical procedures. In this study we use the anaesthetic property of cooling, as a pre local anaesthetic injection procedure ("Cryo-preparation"). The anaesthetic injection induced discomfort with and without "cryo-preparation" was then assessed.

Thirty-nine patients aged 13-85 years (mean = 50, s.d. = 19) were randomly allocated and assessed. Twenty-two patients underwent local lid anaesthetic infiltration with "cryo-preparation," and 17 without. Pain monitoring was performed subjectively and objectively by scoring systems. Results were analysed using unpaired two tailed t-test on Microsoft Excel.

Significant reduction in injection pain with cryo-preparation (24.6% reduction in score) was achieved (statistically significant p = 0.039). Surgical anaesthesia was complete in all cases.

The study shows that "cryopreparation" by local ice application immediately prior to local anaesthetic injection reduces the sensitivity to the injection by a significant 24.6%. Thus while all the advantages of good analgesia are obtained from the injection, the distressing discomfort is reduced. This study serves as a pilot, in demonstrating a novel method of pain control for lid surgery.