Sciatic Nerve Blocks With or Without Femoral Block Versus Spinal Anaesthesia in Patients Undergoing Diabetic Foot Surgery

Background: Dysautonomia refers to the abnormal function of the autonomic nervous system including sympathetic and parasympathetic nervous system. Diabetes mellitus causes secondary dysautonomias (1). The Survey of Autonomic Symptoms (SAS) is a simple and validated tool to assess the presence and severity of autonomic symptoms (2). Diabetic patients also suffer from chronic neuropathic pain. After amputation surgeries, up to 78% of these patients may develop post surgical neuropathic pain (3). The self-report version of the Leeds Assessment of Neuropathic Symptoms and Signs pain scale (S-LANSS) is validated as a diagnostic tool to assess patients with neuropathic pain (4). This scale will be used to assess if there is any changes in the pain experienced after diabetic foot surgery. Currently, both spinal anaesthesia (SAB) and ultrasound guided femoral and sciatic peripheral nerve blocks (FSNB) are acceptable anaesthesia for dysautonomic diabetic patients with diabetic foot ulcer going for wound debridement, Ray\'s amputation and below knee amputation (5) Many studies have compared multiple perioperative parameters of patients undergoing lower limb surgery under peripheral nerve blocks versus spinal anaesthesia. These parameters include preparation time, anaesthetic complications (e.g. hypotension, nausea and vomiting, post-dural puncture headache, urinary retention), patient satisfaction and postoperative pain control (6,7,8). The investigators want to study if patients with dysautonomia have a different haemodynamic response to spinal anaesthesia or peripheral nerve blockade changes compared to patients with normal autonomic function. Secondarily, the investigators would also study if there is a difference in post operative pain control as well as incidence in chronic pain in patients who receive spinal anaesthesia versus peripheral nerve blockade.