The effect of solution temperature on the pain of peribulbar anesthesia

Background: Peribulbar anesthesia is the preferred technique of local anesthesia of the majority of cataract surgeons. Local anesthetic injections at other sites in the body have been shown to be less painful if the solution is warmed to body temperature before injection. To determine whether this is of advantage with peribulbar anesthesia, the authors performed a prospective, randomized, single, blind trial comparing local anesthetic injections that have been warmed to room temperature. Methods: Forty consecutive patients undergoing routine cataract surgery were randomized into two groups of 20 patients and received local anesthetic at 20 degrees C or 37 degrees C. The peribulbar injection contained a solution of 5 ml 2% Lignocaine, 5 ml 0.5% bupivicaine (Marcaine), and 1550 IU hyaluronidase (Hylase) in a 10-ml syringe on a 25-mm, 25-gauge needle. Seven milliliters of the final solution was injected transcutaneously at the junction of the lateral and medial thirds of the lower lid. The patients graded the pain of the injection using a visual analogue scale. Results: The pain sensation of local anesthesia is less when the solution is warmed to body temperature compared with room temperature (P = 0.026, using an unpaired Student's t test). Conclusion: Warming the local anesthetic used in peribulbar anesthesia to body temperature before injection reduces this iatrogenic pain significantly.