Correlation of anthropometric measurements with the epidural distance

Aim: Epidural anesthesia is a world wide used regional anesthetic However, this method requires a technical skill and to feel the region accurately where the epidural needle is applicated. Otherwise, there can be neurological complications and insufficient anesthsia. To predict the epidural space accurately, distance from skin to epidural space must be known. The aim of this study is, to determine the distance from the skin to epidural and spinal spaces, to research the correlation with anthropometric measurements (femur and vertebra) and to develop mathematical model to calculate the distance.Methods: After obtaining approval from the Instutional Ethics Committee, epidural anesthesia was performed using a portex spinal/epidural set, in the sitting position, at L3-4 interspace with the loss of resistance method. Using the procedure the skin epidural to distance and skin to spinal distance was measured. Anthropometric parameters were recorded prospectively: age, gender, weight, height, BMI, shoe size, L3 spinosus procesus length, L3 vertebrae length, L3 vertebrae width, intervertebral disk space, interpedinculer distance, pelvis width, femur diameter, femur neck shaft axis. Correlation test, t test and stepwise regression test were used for statistical analyses.Results: This study enrolled 100 patients. Mean values ± standart deviations for weight, length, BMI and age were 77.8 ±13.5kg, 167.6±8.3cm, 27.3±3.8 kg/m2 and 50±14.1 years, respectively. The only significant parameter which is correlated between the anthropometric measurements and the distance from skin to both of spaces was weight (p<0.001). Using the correlation between weight, for prediction of the distance from skin to epidural space (SED) SED: 24.732 + [0.355XWeight(kg)] and the ditance from skin to spinal space (SSD) SSD: 37.390 + [0.287XWeight(kg)] formulas were obtained.Conclusion: To predict the distance from skin to epidural and spinal spaces, age, gender, height, BMI, shoe size, L3 spinosus procesus length, L3 vertebrae length, L3 vertebrae width, intervertebral disk space, interpedinculer distance, pelvis width, femur diameter, femur neck shaft axis were not statistically significant. Weight seems to be the most important parameter. By using the formula that contains this parameter, distance from skin to epidural space can be predicted with 30% probability and distance from skin to spinal space can be predicted with 25% probability.Key Words: Epidural space, Spinal space, Anthropomeri, Correlation, Weight