Correlation of skin to lumbar epidural depth with demographic and anthropometric factors: A hospital based cross-sectional study

Abstract

Background: Epidural catheter placement is difficult techniques to acquire, with a success rate <60% at first attempt, and an overall success rate of nearly 90%. Availability of advanced techniques at low resource, high load settings is seldom possible making it no less
than a blind technique. Hence thorough knowledge of influencing factors and ability to predict depth becomes an essential skill for an anesthetist. Objective: To study correlation of skin to lumbar epidural depth with demographic and anthropometric factors Methods:Hospital based cross-sectional study was carried among 40 cases posted for elective surgeries requiring lumbar epidural anesthesia. Age, sex, height, weight, Body mass index (BMI) were recorded. After ensuring correct position of needle by loss of resistance to air and hanging drop method, epidural catheter was threaded leaving nearly 6cm inside epidural space. Depth at which epidural space achieved was calculated by calculating length between skin and end of needle at hub and in turn subtracting it from 8cm.
Results:There was significant correlation between weight, BMI and epidural depth. Age, sex and height were not correlated.From multiple linear regression model it can be stated that sex and weight significantly predicted epidural depth. With increase in 1kg body weight, the epidural depth increased by 0.036cm. Males have on an average 0.361cm more depth compared to females.
Conclusion:Skin to epidural depth depends on weight and sex. Formula derived also helps to roughly determine depth and achieve successful placement of catheter in fewer attempts.