Subarachnoid block /spinal anaesthesia is one of the most important anaesthetic techniques in the 21st century even though it was first introduced 100 years ago by August bier in 1861. It is the anaesthetic technique of choice for most lower limb orthopedic cases, urological cases, lower abdominal surgeries, and caesarian sections as it is technically easy to perform and economically feasible. Also, the incidence of complications are reduced and the associated difficulties of general anaestheisa like difficult airway management, intraoperative awareness, extubation, polypharmacy, postoperative nausea and vomiting are avoided.