Does Warming of Anesthetic Solutions Improve Analgesia and Akinesia in Retrobulbar Anesthesia?

Purpose: The authors assess the effect of warming local anesthetic solutions on pain of injection and on bulbar akinesia and analgesia of retrobulbar anesthesia (RBA). Methods: Seventy patients undergoing RBA for cataract surgery were enrolled in a prospective, double-blind trial. They were allocated randomly to receive 5 ml either warm (37 °C) or cold (20 °C) anesthetic solution for RBA. Additionally, O'Brien's method was used to create an akinesia of the orbicularis oculi muscle. The following data were collected before and 20 minutes after retrobulbar injection: pain of injection, eye motility (Kestenbaum test), and corneal sensitivity (0: no sensitivity; 1: sensitivity remaining) at four different sites. The pain of injection was registered using an ordinal analogous scale before and immediately after the injection. Furthermore, data acquisition included any possible side effects and the bulbar length, measured with ultrasound. Results: The score for injection pain (4.5 ± 2.3 points), horizontal eye motility (0.2 ± 0.8 mm), vertical eye motility (0.9 ± 2.1 mm) all were lower for the warm group in comparison to the cold group (average pain score: 5.2 ± 2.6 points; horizontal eye motility: 0.7 ± 1.6 mm; vertical eye motility: 1.2 ± 2.0 mm). Two patients in the warm group and four patients in the cold group had remaining corneal sensitivity. None of the differences were significant. Conclusions: Data indicate no significant difference in bulbar analgesia and akinesia after RBA between injections of warm and cold anesthetic solutions.