Effect of Hip/Shoulder Width Ratio on the Spread of Spinal Anaesthesia in Term Parturients: A Cross-sectional Study

Introduction: There is increased cephalad spread of spinal anaesthesia with similar dose of hyperbaric bupivacaine in parturients with greater hip width and shorter shoulder width.

Aim: To determine the effect of Hip and Shoulder width Ratio (HSR) on the spread of spinal anaesthesia in term parturients.

Materials and Methods: The present study was a prospective cross-sectional study conducted in the Department of Anaesthesiology, Regional Institute of Medical Sciences, a tertiary care centre, at Imphal, Manipur, India, from October 2019 to September 2021. A total of 92 parturients aged 18-40 years of age, American Society of Anaesthesiologists (ASA) I and II, undergoing elective caesarean section under subarachnoid block were enrolled. With the parturient in lateral position, a 25G spinal needle was inserted in the L4-L5 interspace. A 2 mL of 0.5% hyperbaric bupivacaine was injected intrathecal in 10 seconds. Age, height, weight, Body Mass Index (BMI), HSR and Vertebral Column Length (VCL) were recorded. Spinal anaesthesia spread was assessed at 0,5,10,15,20,25,30 minutes after the procedure with pin prick test starting from the anaesthetised area and continued cephalad till the sensation changed from the dullness to sharp pain in both the mid-clavicular lines. Statistical analysis of the data obtained was done using Windows based Statistical Package for Social Sciences (SPSS) version 21.0.

Results: The mean age, weight, height and BMI were 28.82±6.2 years, 62.36±5.8 kilograms, 158.63±4 centimetre, and 24.77±2 Kg/m2, respectively. HSR and shoulder width had a significant correlation with the cephalad spread of spinal anaesthesia with r=-0.672 and p-value <0.001 and r=0.369 and p-value <0.001, respectively.

Conclusion: The HSR and shoulder width has a significant correlation with spread of spinal anaesthesia with a given dose of 0.5% hyperbaric bupivacaine in parturients. The study should expect more cephalad spread of anaesthesia in parturient population when the HSR >1.