Effect of abdominal girth and vertebral column length on predicting the dose of isobaric plain bupivacaine for spinal anesthesia

Objective Some study shows that abdominal girth and vertebral column length could predict the suitable intrathecal bupivacaine dose for T₁₀ block level to a great extent, but the clinical evidence is lack. This study is to evaluate the accuracy of regression equation between abdominal girth, vertebral column length and the dose of 0. 5% plain bupivacaine for T₁₀ block level. Methods Two hundred ASA physical statusⅠ-Ⅲ patients, aged 19-65 years, scheduled for lower limbs surgery undergoing spinal anesthesia were enrolled. The patients were placed in the supine position, and at the level of the umbilicus, the abdominal girth was measured at the end of expiration, and the vertebral column length was measured from the C₇ vertebra to the sacral hiatus, with the patient placed supine on the operation table. After abdominal girth and vertebral column length obtained, the L_3/4 interspace was entered, 0. 5% plain bupivacaine with room temperature was injected intrathecally at a speed of approximately 2 ml in 10 s when free flow of the cerebrospinal fluid was obtained. The dose of bupivacaine was based on the regression equation expounded in reference. Block level was measured 30 min after spinal anesthesia. The upper block level for loss of pinprick discrimination, age, height, weight, abdominal girth and vertebral column length were recorded. Results A total of 198 patients were enrolled in this study finally. Two patients were excluded from this study because of unsuccessful puncture at L_3/4 intervertebral space. The average dose of 0. 5% plain bupivacaine was (3. 2 ±0. 4) ml. One hundred and fifty-nine cases of patients were with the block level T₁₀, accounted for 80. 3% of all patients. The upper block level was T₈, and the lowest block level was T₁₂. Conclusion The regression equation between abdominal girth, vertebral column length and the dose of 0. 5% plain bupivacaine for T₁₀ block level during spinal anesthesia can apply for clinic accurately.