Correlation of skin epidural distance and posterior epidural space depth with age, weight, height, BMI, abdominal girth and position of the patient: A prospective randomised study

Lumbar epidural block is a commonly used procedure for providing anaesthesia, post-operative analgesia in all groups of patients irrespective of age, sex, weight and height of the patients. The knowledge of posterior space is important in view of the fact that this is the space where drugs for epidural anaesthesia/ analgesia are used. The knowledge of variability of this space with physical parameters of the patient, help us in reducing the incidence of total spinal anaesthesia. Two hundred adult patients in the age group of 20-60 years requiring subarachnoid block were chosen for the study. Using 22G Quincke spinal needle, epidural space was identified and skin epidural distance was measured. Proceeding the spinal needle further, causes needle to lie in subarachnoid space. The skin subarachnoid distance was measured. The difference between skin-subarachnoid distance and skin epidural distance denoted the posterior epidural space width. Its correlation with physical parameters was studied. Mean skin epidural distance was 4.30 ±0.57 in lateral position and 4.05 ± 0.57 in sitting position, the difference being statistically significant. (P= 0.002). There was positive correlation between skin epidural distance with weight, BMI and abdominal girth of the patient. Mean posterior epidural space depth was 0.468+14 cm in lateral position and 0.459+0.14 cm in sitting position, the difference being statistically insignificant. There was a positive correlation between posterior epidural space depth and height of the patient. The skin epidural distance varies with weight, BMI, abdominal girth and position of the patient. The posterior epidural space depth varies with the height of the patients.