Background: Various factors including anthropometric measurements are known to affect the skin to subarachnoid distance. Out of these, certain anthropometric values such as BMI, weight and height can be easily measured and are helpful in predicting the depth of spinal needle to be inserted.

Aim: The Aim of our study is to evaluate the correlation between skin to subarachnoid distance and BMI.

Setting and Design: This Prospective observational study will be conducted at Deen Dayal Upadhyay Hospital, New Delhi after obtaining approval from the Scientific Research committee, Institutional Ethics Committee and written informed consent of participating patients.

Material and Methods: Thirty-Seven patients fulfilling the inclusion criteria undergoing infraumbilical surgeries under spinal anaesthesia will be enrolled in the study. Preoperatively, patient will be explained in detail about the procedure to be performed and anthropometric measurements of the patient like height, weight and BMI which are required for the study will be taken. Using a 25G Quincke’s needle, 3 ml of 0.5 % hyperbaric bupivacaine will be administered intrathecally to the patient in a sitting position at L3-L4 interspace. After giving the intrathecal injection, the spinal needle will be marked using a sterile skin-marking pen then grasped firmly between the thumb and the index finger abutting the patient’s back and removed. The depth of spinal needle insertion will be measured using a vernier caliper.

Statistical Analysis:  Spearman/Pearson correlation will be used to determine the statistical significance between skin to subarachnoid distance and BMI. For all statistical tests, a p value less than 0.05 will be taken to indicate a significant difference

Conclusion: This study will be helpful in Correlating relation between Skin to Subarachnoid space during lumbar puncture and the BMI of the patient.