Spinal anaesthesia (or spinal anesthesia), also called spinal block, subarachnoid block, intradural block and intrathecal block, is a form of neuraxial regional anaesthesia involving the injection of a local anaesthetic with or without an opioid into the subarachnoid space. Usually a single-shot dose is administrered through a fine needle, alternatively continuous spinal anaesthesia through a intrathecal catheter can be performed. It is a safe and effective form of anesthesia usually performed by anesthesiologists that can be used as an alternative to general anesthesia commonly in surgeries involving the lower extremities and surgeries below the umbilicus. The local anesthetic with or without an opioid injected into the cerebrospinal fluid provides locoregional anaesthesia: true anaesthesia, motor, sensory and autonomic (sympathetic) blockade. Administering analgesics (opioid, alpha2-adrenoreceptor agonist) in the cerebrospinal fluid without a local anaesthetic produces locoregional analgesia: markedly reduced pain sensation (incomplete analgesia), some autonomic blockade (parasympathetic plexi), but no sensory or motor block. Locoregional analgesia, due to mainly the absence of motor and sympathetic block may be preferred over locoregional anaesthesia in some postoperative care settings. The tip of the spinal needle has a point or small bevel. Recently, pencil point needles have been made available (Whitacre, Sprotte, Gertie Marx and others).
Indications Spinal anaesthesia is a commonly used technique, either on its own or in combination with sedation or general anaesthesia. It is most commonly used for surgeries below the umbilicus, however recently its uses have extended to some surgeries above the umbilicus as well as for postoperative analgesia. Procedures which use spinal anesthesia include:
Orthopaedic surgery on the pelvis, hip, femur, knee, tibia, and ankle, including arthroplasty and joint replacement Vascular surgery on the legs Endovascular aortic aneurysm repair Hernia (inguinal or epigastric) Haemorrhoidectomy Nephrectomy and cystectomy in combination with general anaesthesia Transurethral resection of the prostate and transurethral resection of bladder tumours Hysterectomy in different techniques used Caesarean sections Pain management during vaginal birth and delivery Urology cases Examinations under anaesthesia Spinal anaesthesia is the technique of choice for Caesarean section as it avoids a general anaesthetic and the risk of failed intubation (which is probably a lot lower than the widely quoted 1 in 250 in pregnant women). It also means the mother is conscious and the partner is able to be present at the birth of the child. The post operative analgesia from intrathecal opioids in addition to non-steroidal anti-inflammatory drugs is also good. Spinal anesthesia may be favored when the surgical site is amenable to spinal blockade for patients with severe respiratory disease such as COPD as it avoids the potential respiratory consequences of intubation and ventilation. It may also be useful in patients where anatomical abnormalities may make tracheal intubation relatively difficult. In pediatric patients, spinal anesthesia is particularly useful in children with difficult airways and those who are poor candidates for endotracheal anesthesia such as increased respiratory risks or presence of full stomach. This can also be used to effectively treat and prevent pain following surgery, particularly thoracic, abdominal pelvic, and lower extremity orthopedic procedures.
Contraindications Prior to receiving spinal anesthesia, it is important to provide a thorough medical evaluation to ensure there are no absolute contraindications and to minimize risks and complications. Although contraindications are rare, below are some of them:
Patient refusal Local infection or sepsis at the site of injection Bleeding disorders, thrombocytopaenia, or systemic anticoagulation (secondary to an increased risk of a spinal epidural hematoma) Severe aortic stenosis Increased intracranial pressure Space occupying lesions of the brain Anatomical disorders of the spine such as scoliosis (although where pulmonary function is also impaired, spinal anaesthesia may be favored) Hypovolaemia e.g. following massive haemorrhage, including in obstetric patients Allergy Relative contraindication:
Ehlers–Danlos syndrome, or other disorders causing resistance to local anesthesia
Risks and complications Complications of spinal anesthesia can result from the physiologic effects on the nervous system and can also be related to placement technique. Most of the common side effects are minor and are self-resolving or easily treatable while major complications can result in more serious and permanent neurological damage and rarely death. These symptoms can occur immediately after administration of the anesthetic or be delayed. Common and minor complications include:
Mild hypotension Bradycardia Nausea and vomiting Transient neurological symptoms (lower back pain with pain in the legs) Post-dural-puncture headache or post-spinal headache – Associated with the size and type of spinal needle used. A 2020 meta analysis recommended use of the 26G atraumatic spinal needle to lower the risk of PDPH – specifically, the Braun Atraucan 26G needle. Serious and permanent complications are rare but are usually related to physiologic effects on the cardiovascular system and neurological system or when the injection has been unintentionally at the wrong site. The following are some major complications:
Nerve injuries: Cauda equina syndrome, radiculopathy Cardiac arrest Severe hypotension Spinal epidural hematoma, with or without subsequent neurological sequelae due to compression of the spinal nerves. Epidural abscess Infection (e.g. meningitis)
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