Epidural

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The term epidural is often short for epidural anesthesia, a form of regional anesthesia involving injection of drugs through a catheter placed into the epidural space. The injection can cause both a loss of sensation (anaesthesia) and a loss of pain (analgesia), by blocking the transmission of pain signals through nerves in or near the spinal cord.

The epidural space (sometimes called the extradural space or peridural space) is a part of the human spine inside the spinal canal separated from the spinal cord and its surrounding cerebrospinal fluid by the dura mater.

Epidural anesthesia

Indications

Injecting medication into the epidural space is primarily performed for analgesia. This may be performed using a number of different techniques and for a variety of reasons. Additionally, some of the side-effects of epidural analgesia may be beneficial in some circumstances (e.g. vasodilation may be beneficial if the patient has peripheral vascular disease). When a catheter is placed into the epidural space (see below), the effects of the analgesia may be prolonged for several days, if required. Epidurals may be used:

For analgesia alone, where surgery is not contemplated. An epidural for pain relief (e.g. in childbirth) is unlikely to cause loss of muscle power, but is not usually sufficient for surgery.

As an adjunct to general anaesthesia. The anaesthetist may use epidural analgesia in addition to general anaesthesia. This may reduce the patient's requirement for opioid analgesics. This is suitable for a wide variety of surgery, for example gynaecological surgery (e.g. hysterectomy), orthopaedic surgery (e.g. hip replacement), general surgery (e.g. laparotomy) and vascular surgery (e.g. open aortic aneurysm repair). See also caudal epidural, below.

As a sole technique for surgical anaesthesia. Some operations, most frequently Caesarean section, may be performed using an epidural anaesthetic as the sole technique. Typically the patient would remain awake during the operation. The dose required for anaesthesia is much higher than that required for analgesia.

For post-operative analgesia, in either of the two situations above. Analgesics are given into the epidural space for a few days after surgery, provided a catheter has been inserted. Through the use of a patient-controlled analgesia (PCA) infusion pump, a patient may be given the ability to control post-surgical pain medications administered through the epidural.

For the treatment of back pain. Injection of analgesics and steroids into the epidural space may improve some forms of back pain. See below.

For the treatment of chronic pain or palliation of symptoms in terminal care, usually in the short or medium term.

A patient getting a modern epidural for pain relief generally receives a combination of local anesthetics and opioids. Common local anesthetics include lidocaine, bupivicaine, ropivicaine, and chloroprocaine. Common opioids are morphine (or hydromorphone), fentanyl, sufentanil, and pethidine (known as meperidine in the U.S.). These are then injected in relatively small doses. Occasionally other agents may be used, such as clonidine or ketamine.

Because of the nature of epidurals, they are most suitable for analgesia for the abdomen, pelvis or legs. They are much less suitable for analgesia for the chest, neck, or arms and are not possible for the head.

http://en.wikipedia.org/wiki/Epidural

A local anesthetic is a drug that reversibly inhibits the propagation of signals along nerves. When it is used on specific nerve pathways, effects such as analgesia (loss of pain sensation) and paralysis (loss of muscle power) can be achieved.

Clinical local anesthetics belong to one of two classes: aminoamide and aminoester local anesthetics. synthetic local anesthetics are structurally related to cocaine. They differ from cocaine mainly in that they have no abuse potential and do not act on the sympathoadrenergic system, i.e. they do not produce hypertension or local vasoconstriction.

An opioid is a chemical substance that has a morphine-like action in the body. The main use is for pain relief. These agents work by binding to opioid receptors, which are found principally in the central nervous system and the gastrointestinal tract. The receptors in these two organ systems mediate both the beneficial effects, and the undesirable side effects. There are four broad classes of opioids:

endogenous opioid peptides (opioids produced naturally in the body);

opium alkaloids, such as morphine (the first alkaloid isolated from opium) and codeine;

semi-synthetic opioids, such as heroin and oxycodone; and

fully synthetic opioids, such as pethidine and methadone.

Although the term opiate is often used as a synonym for opioid, it is more properly limited to the natural opium alkaloids and the semi-synthetics derived from them.

http://en.wikipedia.org/wiki/Opioid

For more information look up the use, side effects and complications of the individual drugs used in epidurals:

Common local anesthetics include lidocaine, bupivicaine, ropivicaine, and chloroprocaine. Common opioids are morphine (or hydromorphone), fentanyl, sufentanil, and pethidine (known as meperidine in the U.S.).