Correlation of subarachnoid space depth obtained from formula versus actual measurement at lumbar region to derive appropriate formula in patients undergoing spinal anaesthesia at a tertiary care centre- An observational study

Subarachnoid block is a commonly practiced anaesthesia technique for lower abdominal and limb surgeries, including cesarean sections.Performed using an anatomical landmark guided, blind approach, its sucess depends on factors like height weight BMI and BSA.In conditions such as obesity, pregnancy or edema  estimating subaracnoid space depth is crucial to minimize failed attempts and complications. Existing predictive formulas, largely derived from western population, require validation in indians hence this study aims to establish a reliable, population-specific model for accurate SSD estimation.

A prospective observational study will be conducted at hospitals attached to BMCRI form febrauary 2026 to april 2026  to determine skin to subarachnoid space depth in indian adults undergoing spinal anaesthesia and to assess the accuracy of anthropometric data (height, weight,BMI,BSA) will be  collected and actual SSD will be  measured during midline lumbar puncture. Predicted SSDs will be  calculated using existing and newly derived equations to validate populaton- specific accuracy and improve procedural precision and safety.