Epidural anesthesia

Description:

Epidural anesthesia, it "peridural" — one of methods of regional anesthesia at which medicines are administered in an epidural space of a backbone through a catheter. The injection leads to loss of painful sensitivity (analgesia), loss of the general sensitivity (anesthesia) or to relaxation of muscles

The mechanism of effect of epidural anesthesia is connected, preferential, with penetration of drugs via dural couplings in a subarachnoid space and thereof, blockade of passing of nervous impulses (including painful) on radicular nerves and further in a spinal cord.

In a human body the backbone and nerve terminations located on a neck are shrouded in a special cover — a firm meninx. The epidural area surrounds this cover and passes along a backbone. Nerves cross epidural area in the direction of a neck, plechy and hands. The inflammation of these nerve terminations hurts in epidural area.

The inflammation can be caused by damage of vertebral disks or contact of nerves with bone structure of a backbone. The injection of anesthetic enters antiinflammatory medicine into the epidural area and causes an anesthesia and obtusion of pain.

Pain relief is done thanks to blocking of transfer of painful impulses on nerve terminations of a spinal cord. Respectively it is possible to mark out the following effects of epidural anesthesia:
analgesia (loss of painful sensitivity)
anesthesia (loss in general all sensitivity)
muscle relaxation (relaxation of muscles)
full mioplegiya (temporary paralysis of muscles)

Depending on a scope, execution of epidural anesthesia (analgesia) can be accompanied by big or smaller risk. The analgesia of a breast, stomach, inguinal area and legs is less risky, than an analgesia of a neck or hands. The head analgesia by means of epidural anesthesia is impossible because the touch innervation of the head is carried out through a craniocereberal nervous system. Epidural anesthesia can be applied:
For a local anesthesia. In case of lack of surgical intervention, for example, at childbirth.
As addition to the general anesthesia. Epidural anesthesia can reduce need of opioids for cases gynecologic (hysterectomy) and other operations (laparotomy).
As full anesthesia. Some operations (for example, Cesarean section) can be carried out under epidural anesthesia. Patients usually remain in consciousness, however the dose for such anesthesia is much higher, than for a local anesthesia.
For postoperative anesthesia. The drugs are administered within several days. The patient is given the chance to control amount of the administered drug for decrease in pain.
As treatment of a back. Injections of analgetics and steroids to the epidural area can remove some types of back pain.

For epidural anesthesia I am applied specially intended (especially cleared and not containing preservatives) solutions to Epi - and subdural introduction. Local anesthetics — lidocaine, bupivacaine and ропивакаин are most often applied.

For strengthening of effect of local anesthetics for epidural anesthesia quite often add opiates to solution, for example, morphine, fentanyl, Promedolum, buprenorphine. At the same time it is many times less dose of opiates, than at introduction to a vein or intramusculary, and quality of the provided analgesia and its duration is better. At epidural administration of opiates much more rare there are by-effects, characteristic of opiates — nausea, vomiting, respiratory depression, dizziness and so forth as at such way of introduction there comes the spinal, but not the central opiate analgesia. So, introduction of 5 mg of morphine to a vein is capable to provide adequate anesthesia at postoperative pains on 4-6 h, and introduction of only 1 mg of morphine to an epidural space provides permanent disappearance of pain on 18-24 h.

On the Pharmacopoeia accepted in the Russian Federation, any of opioid analgetics is not allowed for introduction to an epidural space.

Other components which are often added to solution for epidural anesthesia — a clonidine (clonidine), Ketaminum. At the same time much more smaller doses are required too, than at system introduction, and it is possible to avoid side effects (a lowering of arterial pressure in case of clonidine, hallucinations and alarm — in case of Ketaminum). Extremely seldom add physostigmine, drug whose analgetic activity is based on strengthening of carrying out "analgetic" (anti-nociceptive) impulses in cholinergic fibers, as opposed to the painful impulses which are transferred on sympathetic fibers to solution.

Earlier the list allowed for addition in solutions for epidural anesthesia included also the midazolam, a strong benzodiazepine tranquilizer capable to cause a surgical anesthesia at introduction to a vein and to give analgesic effect at epidural introduction. But recent researches showed that at epidural administration of midazolam small injuries (degenerative changes) of radicular nerves at laboratory zhivotnykhkh are sometimes observed. And though the person has no clinical observations of such phenomenon, and the clinical importance of these little changes at animals is not shown, nevertheless midazolam was withdrawn from the list of the drugs allowed for epidural introduction.