The spread of spinal anesthesia in term parturient: effect of hip/shoulder width ratio and vertebral column length
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Objective: This study aims to determine the effect of age, height, weight, BMI, hip/shoulder width ratio, and vertebral column length on the spread of spinal anesthesia in term parturient. In pregnant patients with a larger hip width and a relative narrow shoulder width, more cephalad spread of spinal anesthesia is observed with a fixed dose of hyperbaric bupivacaine. We hypothesized that the increase in cephalad spread of spinal anesthesia may be correlated with the increased hip/shoulder width ratio. Methods: Age, weight, height, body mass index, hip width, shoulder width, hip/shoulder width ratio, and vertebral column length were recorded for 75 term parturient. The L4-L5 interspace was introduced and 2 ml 0.5% hyperbaric bupivacaine was injected subarachnoid in 10 seconds without barbotage. Pearson and Sperman's Rho Correlation Tests were used for the analysis of correlation between patient characteristics and the cephalad spread of spinal anesthesia. Results: Hip/shoulder width ratio had a positive correlation with the cephalad spread of spinal anesthesia (P=0.037). Other patient variables in the present study did not have correlation with the cephalad spread of spinal anesthesia (P>0.05). Vertebral column length had correlation with patient height (P=0.01). Conclusions: The cephalad spread of spinal anesthesia is correlated with hip/shoulder width ratio in term parturient patients. Vertebral column length has no correlation with the spinal anesthesia spread but correlates with the height of the parturient. The hip/ shoulder width ratio may be more important than either patient height or vertebral column length in predicting the cephalad spread of spinal anesthesia for each parturient.