The temperature of bupivacaine 0.5% affects the sensory level of spinal anesthesia

Three milliliters of plain bupivacaine 0.5% was injected intrathecally in two groups of 20 patients. Group 1 received a solution that had been equilibrated to 37 degrees C, group 2 received a solution that had been equilibrated to 4 degrees C. Patients were kept sitting for 3 minutes after injection. All observations were observer-blind. The differences between segmental levels of sensory loss between groups 1 and 2 (T4 and T9, respectively) and of temperature loss (T3 and T8, respectively) 10 and 20 minutes after injection of bupivacaine were statistically significant. It is concluded that the time needed for thermal equilibration in the cerebrospinal fluid and hence temperature of the injected solution plays an important role in the sensory spread of plain bupivacaine 0.5%.