The effect of temperature on the discomfort caused by topical local anaesthesia.

The warming of local anaesthetic solutions to reduce the pain felt on injection is common practice in a number of medical sub-specialties. A study was undertaken to assess the effect of temperature on the discomfort caused by local anaesthetic eye drops. Tropical anaesthetics amethocaine 1%, oxybuprocaine 0.4% and lignocaine 4% were studied, and after the application of strict exclusion criteria 60 patients were selected, 20 patients for each anaesthetic. Each patient group received a topical anaesthetic at 42 degrees C in one eye and at room temperature in the other. A 10 point visual analogue scale was used to assess the discomfort experienced. No statistically significant difference was found between the discomfort caused by drops at each temperature for any of the three anaesthetics studied. There appears no benefit in warming topical anaesthetic agents prior to their use.