When administering an epidural analgesic, the doctor or specially trained nurse injects or infuses medication into the epidural space, which lies just outside the subarachnoid space where cerebrospinal fluid (CSF) flows. The drug diffuses slowly into the subarachnoid space of the spinal canal and then into the CSF, which carries it directly into the spinal area, bypassing the blood-brain barrier. In some cases, medication is injected directly into the subarachnoid space. (See Understanding intrathecal injections.)

Epidural analgesia helps manage acute or chronic pain, including moderate to severe postoperative pain. It’s especially useful in patients with cancer or degenerative joint disease. This procedure works well because opioid receptors are located along the entire spinal cord. Opioid drugs act directly on the receptors of the dorsal horn to produce localized analgesia without motor blockage. Opioids, such as preservative-free morphine, fentanyl, and hydromorphone, are administered as a bolus dose or by continuous infusion, either alone or in combination with a local anesthetic. Infusion through an epidural catheter is preferred because it allows a smaller drug dosage to be given continuously. The epidural catheter, inserted into the epidural space, eliminates the risks of multiple IM injections, minimizes adverse cerebral and systemic effects, and eliminates the analgesic peaks and valleys that usually occur with intermittent IM injections. (See Placement of an epidural catheter.)¹

Typically, epidural catheter insertion is performed by an anesthesiologist using sterile technique. Once the catheter has been inserted, the nurse is responsible for monitoring the infusion and assessing the patient.¹

Epidural analgesia is contraindicated in patients who have local or systemic infection, neurologic disease, coagulopathy, spinal arthritis or deformity, hypotension, marked hypertension, or an allergy to the prescribed drug as well as in those who are undergoing anticoagulant therapy.