Characteristics of unilateral spinal anesthesia at different speeds of intrathecal injection

Abstract

Unilateral spinal anesthesia is performed to provide restriction of sympathetic and motor block. The purpose of this study is to compare the effect of different speeds of intrathecal injection on unilateral spinal anesthesia. The patient cohort comprised 66 patients who were placed in the lateral position with the side to be operated on dependent. After dural puncture, the needle aperture was turned towards the dependent side, and hyperbaric 0.5% bupivacaine was injected at a rate of 1 ml/min in Group Slow patients (Group S, n = 33) or 0.5 ml/min in Group Extra Slow patients (Group ES, n = 33). The lateral position was maintained for 15 min. Skin temperature, loss of pinprick sensation, and degree of motor block were recorded. There were significant differences in the characteristics of the non-operative side between the groups when on the block. Sensorial block was unilateral in 25 (75.8%) patients in Group S and in 29 patients in Group ES (87.9%) 15 min post-injection. At the end of the operation (approximately 50 min after spinal anesthesia), strictly unilateral anesthesia was present in 31 patients in Group ES (93.9%) and in 22 patients in Group S (66.6%) (p < 0.05). Unilateral sensory and motor block were observed in both groups, and the incidence of strict unilateral block was significantly higher in group ES patients. The result of the study show that the extra-slow injection of hyperbaric bupivacaine provided strictly unilateral sensorial and sympathetic block in 93.9 and 87.9% of the patients, respectively, and that a slow injection of low doses of hyperbaric 0.5% bupivacaine 1 ml was sufficient to provide unilateral spinal anesthesia.