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Epidural analgesia: Complications

Complications of epidural analgesia can be broken down into three main categories: complications related to drug toxicity, complications related to needle/catheter placement, and exaggerated effects of appropriately injected drug.

Complications related to drug toxicity primarily consists of local anesthetic systemic toxicity (LAST). LAST rarely occurs from epidural blockade when appropriate doses of local anesthetic are used. Inadvertent intravascular injection is the most likely cause of systemic local anesthetic toxicity.

Complications related to needle/catheter placement can vary significantly in incidence and morbidity. One of the most common and benign complications of epidural placement is backache. Accidental dural puncture during placement can lead to postdural puncture headache, diplopia, and/or tinnitus. Trauma from needle or catheter placement can result in nerve root or spinal cord injury. Injury to epidural blood vessels during catheter placement could result in epidural hematoma with resulting compression of neural structures. Most cases of clinically significant epidural hematoma occur in patients with abnormal coagulation secondary to disease or medication. Though rare, epidural hematoma is an emergency and requires prompt recognition and treatment. Catheter misplacement can result in no or inadequate analgesic effect, inadvertent intravascular injection, or inadvertent subarachnoid injection. Catheter shearing or retention during placement or removal is typically the result of attempting to withdrawal the catheter through the needle or excessive tension during catheter removal. Infections including meningitis or epidural abscess are an uncommon, but severe complication of epidural catheter placement. Infections may result from contamination of equipment or injected solutions, or microorganisms tracked in from the skin.

Complications associated with exaggerated responses to appropriately placed drugs include high neural blockade and urinary retention. High neural blockade with exaggerated dermatomal spread can occur as the result of administration of an excessive dose, failure to reduce standard doses in susceptible patient groups, or abnormal sensitivity/spread of local anesthetic. Urinary retention can result from the blockade of S2-4 nerve root fibers, which results in decreased bladder tone and inhibition of voiding reflexes. These effects can be potentiated by epidural opioid administration.