Discussion
peripheral nerve block, sciatic nerve tract, connective and adipose
CYTOTOXICITY
In the present study, we demonstrated that warming ropivacaine 0.5% to 30℃ shortened the onset time of sensory and motor blockade in the ultrasound-guided subgluteal sciatic nerve block. The duration of sensory and motor blockade showed no significant difference between the studied groups. No evident clinical neural symptoms were detected and the proportion of the patient satisfaction with the anesthetic effect was equal in both groups.The sciatic nerve is the largest peripheral nerve in the body whoes anatomical structure determines the prolonged latency of sciatic nerve block. The sciatic nerve tract is surrounded by a variety of non-neural tissues, primarily composed of abundant connective and adipose tissues, which serve as a physical barrier to slow down the diffusion of local anesthetics [The basic mechanism that warming local anesthetics accelerate the onset of sensory and motor blockade still remains uncertain. The hypothetical explanation is that with temperature increasing, a lower pKa value of local anesthetic solutions leads to an increased proportion of non-ionized molecules which have greater lipophilicity to enhance the diffusion capacity of local anesthetics across tissues and nerve membranes [Similarly, in theory, the alkalinization of local anesthetics can also accelerate the onset time of nerve block by increasing the proportion of non-ionized molecules. However, the use of the alkalinization technique is limited in clinical practice for its uncertain efficacy, because the precipitation generated by alkalization of local anesthetic solutions may reduce drug bioavailability [Makharita et al. [Apart from peripheral nerve block, several studies have investigated the effect of warming local anesthetics on neuraxial block. Liu et al. [In an animal study, Nikolaos et al. [We recognize several limitations in our study. First, we just warmed the ropivacaine to 30℃, which was different from previous studies where the target temperature was set at 37℃. Since the storage temperature of ropivacaine should be strictly controlled below 30℃ as specified, the off-label use was not permitted by the ethics committee for safety reasons. Currently, the effect of warming temperature beyond 30℃ on the ingredients, properties and potential cytotoxicity [