Spinal anaesthesia. An anaesthetist positions a cannula in a patient's spine in preparation for a spinal anaesthetic. The anaesthetic is injected into the subarachnoid space (the space between the inner-most and middle membranes of the three membranes that surround the spinal cord). Spinal anaesthesia is commonly used both alone and in combination with either sedation or general anaesthesia, for surgical procedures below the waist. The spinal anaesthetic will provide longer-lasting pain-relief after the surgery than just a general anaesthetic alone. See clip K004 6228.