page_title: Epidural administration
section_title: Anatomy and comparison to spinal anaesthesia
hierarchical_section_title: Epidural administration / Anatomy and comparison to spinal anaesthesia
caption_attribution_description: English: A needle may be inserted between the spinous processes into the epidural space and local anaesthetic agents may be introduced through this needle to provide anaesthesia or analgesia for labour or surgery.
context_page_description: Epidural administration is a medical route of administration in which a drug such as epidural analgesia and epidural anaesthesia or contrast agent is injected into the epidural space around the spinal cord. The epidural route is frequently employed by certain physicians and nurse anaesthetists to administer local anaesthetic agents, and occasionally to administer diagnostic and therapeutic chemical substances. Epidural techniques frequently involve injection of drugs through a catheter placed into the epidural space. The injection can result in a loss of sensation—including the sensation of pain—by blocking the transmission of signals through nerve fibres in or near the spinal cord.
  The technique of epidural anaesthesia was first developed in 1921 by Spanish military surgeon Fidel Pagés.
context_section_description: The epidural space is the space inside the bony spinal canal but just outside the dura mater ("dura"). In contact with the inner surface of the dura is another membrane called the arachnoid mater ("arachnoid"). The cerebrospinal fluid that surrounds the spinal cord is contained by the arachnoid mater. In adults, the spinal cord terminates around the level of the disc between L1 and L2 (in neonates it extends to L3 but can reach as low as L4), below which lies a bundle of nerves known as the cauda equina ("horse's tail"). Hence, lumbar epidural injections carry a low risk of injuring the spinal cord.
  Insertion of an epidural needle involves threading a needle between the bones, through the ligaments and into the epidural potential space taking great care to avoid puncturing the layer immediately below containing CSF under pressure.
  Spinal anaesthesia is a technique whereby a local anaesthetic drug is injected into the cerebrospinal fluid. This technique has some similarity to epidural anaesthesia, and lay people often confuse the two techniques. Important differences include:
  To achieve epidural analgesia or anaesthesia, a larger dose of drug is typically necessary than with spinal analgesia or anaesthesia.
  The onset of analgesia is slower with epidural analgesia or anaesthesia than with spinal analgesia or anaesthesia, which also confers a more gradual decrease in blood pressure.
  An epidural injection may be performed anywhere along the vertebral column (cervical, thoracic, lumbar, or sacral), while spinal injections are more often performed below the second lumbar vertebral body to avoid piercing and consequently damaging the spinal cord.
  It is easier to achieve segmental analgesia or anaesthesia using the epidural route than using the spinal route.
  An indwelling catheter is more commonly placed in the setting of epidural analgesia or anaesthesia than with spinal analgesia or anaesthesia.
  Epidural medication administration can be continued post-operatively (and re-dosed intraoperatively) via a catheter, while spinal anesthesia is generally a single shot injection.
caption: Simulation of the insertion of an epidural needle between the spinous processes of the lumbar vertebrae. A syringe is connected to the epidural needle and the epidural space is identified by a technique to assess loss of resistance
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