Spinal anesthesia is a method of regional anesthesia, by injecting an appropriate amount of anesthetic into the subarachnoid space. Usually this anesthetic has a high concentration, when the anesthetic is mixed with the cerebrospinal fluid, it will act on the nerve roots, causing loss of sensation and motor paralysis. The purpose of this technique is to help numb or reduce pain for surgeries in the lower abdomen (below the navel) and lower limbs (legs). To avoid damaging the spinal cord, people often puncture the lumbar region from the third lumbar region down.