Definition:
Spinal anaesthesia, also known as spinal block or subarachnoid block, is a form of neuraxial anaesthesia involving the injection of a local anaesthetic or other agent into the subarachnoid space, typically in the lumbar region of the spinal canal. This results in a reversible loss of sensation and motor function in the lower part of the body, commonly used for surgical procedures below the umbilicus.
Overview:
Spinal anaesthesia is widely employed in clinical practice for procedures such as caesarean sections, orthopaedic surgeries of the lower extremities, urological operations, and certain types of abdominal surgery. It is administered by inserting a thin needle into the intrathecal space between the lumbar vertebrae, usually at the L3–L4 or L4–L5 interspace, avoiding damage to the spinal cord by targeting below the termination of the cord (conus medullaris), which typically ends at L1–L2 in adults. The technique provides rapid onset of anaesthesia with high reliability and is often preferred over general anaesthesia in selected patients due to reduced systemic effects, lower risk of airway complications, and improved postoperative outcomes such as less nausea and faster recovery.
Etymology/Origin:
The term "spinal" derives from the Latin spina, meaning "spine" or "backbone", referring to the anatomical location of the intervention. "Anaesthesia" originates from the Greek anaisthēsia, meaning "insensibility", combining an- (without) and aisthēsis (sensation). The procedure was first described in 1898 by German surgeon August Bier, who conducted the first successful spinal anaesthesia using cocaine, marking a milestone in regional anaesthetic techniques.
Characteristics:
- Administration: Performed under aseptic conditions with the patient positioned either in the lateral decubitus or sitting position.
- Onset and Duration: Rapid onset (within 5–10 minutes), with duration dependent on the agent used and presence of adjuvants (e.g., opioids, epinephrine).
- Level of Block: Determined by the spread of the anaesthetic agent in the cerebrospinal fluid; influenced by patient position, baricity of the solution, and dose.
- Effects: Produces sensory, motor, and sympathetic blockade, leading to numbness, muscle relaxation, and vasodilation (potentially causing hypotension).
- Complications: May include post-dural puncture headache, hypotension, urinary retention, nerve injury (rare), and infection (very rare with standard precautions).
- Contraindications: Include patient refusal, infection at the injection site, coagulopathy, increased intracranial pressure, and severe aortic or mitral stenosis.
Related Topics:
- Epidural anaesthesia
- Combined spinal-epidural anaesthesia (CSE)
- Local anaesthetics (e.g., bupivacaine, lidocaine)
- Neuraxial blockade
- Cerebrospinal fluid dynamics
- Perioperative medicine
- Obstetric anaesthesia
Sources: Widely documented in medical literature, including anaesthesia textbooks such as "Miller’s Anaesthesia" and clinical guidelines from organizations like the American Society of Anesthesiologists (ASA).