• A technique for accessing the epidural space in order to deliver medications. Epidurals are placed perioperatively for analgesia, surgical anesthesia, in laboring patients. Pain physicians also perform the procedure for diagnostic therapeutic purposes.
• Epidurally administered medications are delivered close to their intended site of action, as opposed to the intravenous route. This allows the anaesthetist to deliver smaller doses, with the benefit of reduced side effects. Furthermore, medications within the epidural space serve in an “extended release” capacity.

• Epidural kits: Accessing the epidural space requires the use of a hollow bore needle (varies in length, diameter, sharp edge). Single shots can be performed with a 19 G Crawford epidural needle; continuous catheters can be placed with a styletted Tuohy epidural needle that is usually 16–18 G 8–10 cm in length. Syringes are available in glass or plastic.
• Identification of the epidural space relies on tactile sensation. Unlike IVs where blood return confirms correct location or intrathecal/spinal blocks where CSF return confirms location, epidural placement relies on a slight change in resistance to injection.
  • Loss of resistance technique utilizes fluid or air; chronic pain physicians often utilize radiographic imaging to assist with correct placement. No difference in block success has been identified between air saline for localization of the epidural space. Air may be associated with a patchy block, or rarely pneumocephalus or subcutaneous emphysema.
• Indwelling catheters allow for medication delivery either as repeat boluses or continuous infusions. Stiff, plastic catheters facilitate easy insertion; however, paresthesias intravascular catheter insertion may be more frequent. Flexible wired catheters may result in a slightly more difficult insertion, but may reduce the likelihood of puncturing intravascular or intrathecal spaces. Patient-controlled epidural analgesia (PCEA) allows for continuous infusion with patient-initiated bolus dosing has been associated with overall lower drug usage higher patient satisfaction.
• Depth of insertion 4 cm may increase the risk of catheter dislodgement by patient movement whereas insertion >6 cm increases the risk of migration into the subdural or intrathecal space or knot development.
• Medications commonly used include local anesthetics, opioids, vasopressors (epinephrine, phenylephrine), clonidine. All medications need to be preservative-free to avoid undesired effects (i.e., transient neurologic symptoms).
• Local anesthetics produce differential blockade; nerve fibers have different sensitivities due to their location in the spinal cord, diameter, the presence or absence of myelin. Sympathetic nerve fibers are blocked first, are usually followed by pain, touch, motor blockade. Large, myelinated nerve fibers are more sensitive to local anesthetic blockade compared to smaller, unmyelinated fibers.
  • Concentration: Affects block density
  • Volume: Influences spread the number of segments blocked (taller patients require larger volumes).
  • Dermatomal distribution: Approximately 1–2 mL of local anesthetic is required to block each anatomic segment. Generally half of the volume spreads cranially half spreads caudally; however, spread may be greater cranially.
• Opioids: Effective as a sole or adjuvant analgesic agent when administered epidurally. They do not generally cause hypotension. Choice is often based upon availability, institution, pharmacokinetics (lipid solubility, duration of action, onset, safety profile).
  • Lipid solubility: Lipophilic opioids (fentanyl, sufentanil) have effects at the spinal cord systemically (secondary to vascular absorption). Hydrophilic opioids (morphine) have effects primarily at the spinal cord.
  • Onset duration of action: Lipophilic opioids provide rapid onset of analgesia reduced respiratory depression due to rapid clearance from CSF. Hydrophilic opioids produce a delayed but longer duration of analgesia along with a higher incidence of side effects due to cephalic or supraspinal spread.
• Vasoconstrictors: Epinephrine enhances anesthetic depth duration by decreasing the rate of vascular absorption of local anesthetic. It is also an indicator of inadvertent intravascular injection. Phenylephrine is not as effective as epinephrine.
• Bicarbonate increases the pH of the local anesthetic solution the proportion of drug in its un-ionized form (capable of intraneuronal diffusion to access its site of action); thus it shorten the block onset time. Usual dose is 1 mL per 10 mL of local anesthetic.
• Clonidine: Prolongs intensifies epidural local anesthetic effects via agonism of alpha-2 receptors on primary afferents, interneurons, descending noradrenergic pathways found in the spinal dorsal horn. Side effects include sedation, dry mouth, dose-dependent hypotension bradycardia.
• Dexmedetomidine: Analgesic effect via alpha-2 receptor agonism at the spinal cord. Rapid diffusion into CSF with epidural effects seen in 5–20 minutes.
• Ketamine: Safety in epidural space is not established. Racemic mixtures are associated with neurotoxicity, but the preservative-free S(+) enantiomer may be safe.
• Steroids: The optimal dose, site of injection, concurrent use of local anesthetics have not been established in romized controlled trials. Epidural steroid injections appear to benefit patients with radicular pain disc herniation, but only on a short-term basis.
• Dermatomes: Catheter incision-congruent epidural analgesia is associated with superior analgesia, decreased morbidity, minimal side effects such as lower extremity motor block urinary retention.
• Pressure changes in the pleural cavity are transmitted to the paravertebral space, then to the epidural space. Deep inspiration will increase the negative epidural pressure, while coughing will produce positive pressure.

• The anterior border of the epidural space is comprised of the posterior aspect of the vertebral body that is covered by the posterior longitudinal ligament. The posterior border is formed by the ligamentum flavum.
• Epidural space communicates freely with paravertebral spaces root sleeves; it contains blood vessels, anterior posterior spinal nerve roots, lymphatics, fat, the filum terminale. Epidural fat is loose allows injected fluid to diffuse through it. Unilateral blocks can result from segmentation by tissue.
• When performing a lumbar epidural, the needle passes through skin, subcutaneous fat, supraspinous ligament, interspinous ligament, ligamentum flavum. Thoracic epidural placement via paramedian approach bypasses the supraspinous interspinous ligaments.

• Epidural hematomas may be secondary to traumatic neuraxial block, anticoagulants, or spontaneous bleeding from a spinal arteriovenous malformation. Patients present with sudden, severe back pain with a radicular component. Neurologic deficits may progress over hours to days.
• Epidural abscess is an infection with inflammatory granular tissue or pus in the epidural space; there is a potential for rapid neurologic impairment due to spinal cord compression.
• Nerve damage: Permanent neurologic injury is rare. Techniques to avoid nerve injury include minimal sedation during placement, discontinuing advancement if a paresthesia is encountered, insertion below the spinal cord when possible (L1 in adults, L3 in infants children).
• Postdural puncture headache is likely from a low-pressure CSF leak that is worsened by sting or straining, but relieved by lying supine. It develops in approximately 50–70% of patients after accidental dural puncture with an epidural needle. The sitting position increases CSF hydrostatic pressure may increase inadvertent dural puncture.
• Medication issues: Local anesthetics can cause hypotension bradycardia, motor block, nausea vomiting, toxicity, urinary retention. Opioids can cause nausea, vomiting, pruritus, constipation, systemic absorption, delayed respiratory depression requiring frequent monitoring or continuous pulse oximetry, urinary retention with potential delayed discharge.
• Total spinal: Inadvertent introduction of local anesthetics into the intracranial subarachnoid space may result from unintentional dural puncture during placement, catheter migration, or subdural spread.
• Adhesive arachnoiditis is associated with 2-chloroprocaine.
• Epidural catheter breakage can occur intrathecally, intravascularly, or subcutaneously.
• Failed epidural or placement of nonfunctioning epidural catheter ranges from 6% to 25%. Unilateral block is more common when catheter insertion is >5 cm into the epidural space or when the epidural needle is aimed towards a unilateral nerve root during insertion.

• Indications: Intraoperative postoperative pain relief for lower limb, pelvic, lower/upper abdominal, thoracic surgery as well as nonsurgical pain
• Contraindications (absolute): Patient refusal, bleeding diathesis/coagulopathy, infection at the insertion site, proven local anesthetic allergy
• Contraindications (relative): Bacteremia, increased intracranial pressure, hypovolemic shock, pre-existing neurologic injury or disease, severe valvular cardiac disease, previous back surgery at the site of blockade, certain thromboprophylaxis regimens
• Surgical anesthesia: Epidural anesthesia may also be utilized as a primary anesthetic with or without MAC. With any epidural placement, preparation for airway management a difficult airway is necessary due to potential complications such as failed epidural, high or total spinal, or local anesthetic systemic toxicity. Blockade to the mid-thoracic level does not significantly change tidal volume, vital capacity, minute ventilation in patients with adequate lung function. Patients with severe chronic lung disease who are dependent on accessory muscle function may be at higher risk of respiratory distress.
  • In contrast to spinal analgesia, epidural analgesia requires a longer onset, has a longer duration of action after single bolus injections, increased medication dose is utilized compared to spinals. Appropriate level of insertion is more important as compared to spinal medications where the level of anesthesia may be adjusted significantly using the effect of gravity.
• Postoperative analgesia: Catheters may be placed preoperatively or postoperatively. Preoperative placement can allow for easier positioning improved pain control on emergence. Benefits of epidural analgesia include decreased postoperative pulmonary complications, lower incidence of deep venous thrombosis, attenuation of stress response to surgery, reduced intraoperative blood loss, reduced mortality, facilitation of earlier return of GI motility via attenuation of spinal reflex inhibition of the GI tract.
• T4–8 catheter insertion: Thoracotomy, video-assisted thoracic surgery (VATS), radical mastectomy, thymectomy, post-traumatic rib fractures. Results in improved ventilation with consequent decreases in postoperative pulmonary complications (hypoxia/atelectasis, infection).
• T6–8 catheter insertion: Whipple procedure, gastrectomy, duodenectomy, esophagectomy, hepatic resection
• T7–10 catheter insertion: General abdominal surgery, cystoprostatectomy, nephrectomy
• T8–11 catheter insertion: Abdominal aneurysm repair, colorectal surgery, radical prostatectomy, total abdominal hysterectomy
• L1–L4 catheter insertion: Femoral-popliteal bypass, knee surgery, other lower extremity surgery
• Epidural blood patch is effective in 50–70% of patients with postdural puncture headaches. After accessing the epidural space, approximately 20 mL of freshly drawn blood is slowly injected into the epidural space after obtaining the blood using sterile technique.
• Blockade of cardiac sympathetic fibers by thoracic epidural anesthesia leads to dilation of normal stenotic coronary arteries.

Pregnancy Considerations

Pediatric Considerations

Pediatric Considerations

• Total Spinal
• Combined Spinal Epidural
• Epidural Hematoma
• Epidural Abscess

Sharon L. Lin , MD

Jane C. Ahn , MD