A regional anesthetic is used when it is desirable that the patient remain conscious during the operation. Patients often have misconceptions about regional anesthesia that require detailed explanation of the safety of this technique. One disadvantage of regional anesthesia is the occasional failure to produce adequate anesthesia; another is hypotension due to sympathetic blockade. Regional anesthesia is used most often for surgery of the lower abdomen or lower extremities, since the effect of sympathetic blockade of these areas is minimal.

Spinal & epidural blocks. Spinal anesthesia is achieved by injecting a local anesthetic into the lumbar intrathecal space. This blocks the spinal nerve roots and dorsal root ganglia and probably also blocks the periphery of the spinal cord. Epidural anesthesia is accomplished by injecting a local anesthetic into the extradural (epidural) space. The epidural space is usually identified via the lumbar approach. The gastrointestinal tract is usually contracted with spinal and epidural anesthesia, facilitating exposure of the surgical site.

There are several complications of spinal anesthesia. Headache is the most common and is seen most frequently in young patients. The incidence is only 1% when a 25-gauge needle is used. For severe headache, а "blood-patch" epidural injection should be performed. This involves injecting 5~10 ml of the patient's blood into the epidural space at the site of the previous lumbar puncture. Pain relief is usually prompt, and headache usually does not recur. This technique is thought to plug the leak of cerebrospinal fluid, restoring pressure in the subarachnoid space to normal.

Because spinal anesthesia blocks innervation of the bladder, administration of large amounts of intravenous fluids may cause bladder distention, and a urethral catheter may be carried. This usually occurs with minor operations such as inguinal hernia repairs and can be avoided by keeping fluids to a minimum. Nausea and vomiting may occur when a spinal anesthetic is begun, especially if hypotension is present. If nausea and vomiting persist despite successful treatment of hypotension, diazepam of droperidol may be effective. Peripheral nerve damage is rare, occurring in one out of 10 000 cases.

Complications from epidural anesthesia are the same as those for spinal anesthesia, with the exception of headache.

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