Epidural Anaesthesia

Epidural anaesthesia is a commonly used regional anaesthetic technique in veterinary obstetrics, especially in large animals like cows, buffaloes, and mares.

In ruminants epidural anaesthesia is ideal for obstetrical purpose. It is form a multiple spinal nerve block in which, by means of a single injection of local anaesthetic solution into the epidural space, the coccygeal and posterior sacral nerves are affected, thus producing anaesthesia of the anus, perineum, vulva and vagina.

Advantages of Epidural Anaesthesia

Painless birth is possible, and straining is prevented. Thus, intravaginal manipulations are facilitated, retropulsion is made easier, fetal fluid supplements are retained, and defecation is suspended.

The patient stands more quietly, and if recumbent initially, often gets up when relieved of painful pelvic sensations; this again makes the obstetrician’s task easier and cleaner.

This form of anaesthesia is useful whenever straining is troublesome, as in prolapse of the uterus, vagina, rectum, or bladder.

It is also indicated for episiotomy and for suturing the vulva or perineum.

Epidural anaesthesia does not affect uterine contractions; the main force of labour is not antagonized, and the third stage of labour as well as uterine involution are not affected.

Agent Used & Site

The local anaesthetic usually employed is 2% lignocaine, with or without
adrenaline as a epidural anesthesia.

The sacrococcygeal space or first intercoccygeal space is the site of administration.

Types

1. Anterior epidural or high or cranial epidural: 0.5 to 1 ml per 10 pound body weight.
2. Posterior epidural or low epidural or caudal epidural: 0.5 to 1 ml per pound body weight.

The posterior epidural is commonly used in bovine obstetrics.

Epidural Anaesthesia in Cattle & Buffaloes

The site of injection is located by raising the tail in a “pump-handle” fashion. After properly shaving and disinfecting the site, the needle (16–18 gauge and 5 cm long) is inserted in the cow between the first and second coccygeal vertebrae or between the first coccygeal and last sacral vertebrae.

The needle is introduced at a 10-degree angle caudally from the perpendicular and strikes the floor of the vertebral canal of the last sacral vertebra. Between the first and second coccygeal vertebrae, the needle may pass entirely through the spinal nerves and joint.

When the needle point reaches the proper location, the anaesthetic solution flows easily from the syringe into the epidural space. If the needle is not correctly placed, the solution is injected with difficulty.

Within 2 minutes of the injection, the tail becomes flaccid.

In order to produce obstetrical anaesthesia, heifers and small cows require a volume of 5-7 ml of 2% lignocaine solution and large cows will need 7-10 ml.

Epidural Anaesthesia in Mares

The technique of epidural injection in the mare is the same; however, because the root of the tail is well covered by muscle and fat, the spines of the coccygeal vertebrae are not as easy to locate. Owing to the thickness of the tail, a longer needle must be used and inserted to a depth of 4–8 cm.

The dose of local anaesthetic for mares should not exceed 15 ml.

Epidural Anaesthesia in Sheep and Goats

Epidural injection is occasionally useful in ovine and caprine obstetrics. The method of injection is the same as in the cow, using a 4 cm long, 18-gauge needle and 2–4 ml of local anaesthetic.

Epidural Anaesthesia in Swine

Epidural anaesthesia in swine is rarely required for obstetrical purposes but may be induced by injecting 5 ml of local anaesthetic solution into the lumbosacral space.

The wings of the ilia are joined by an imaginary transverse line, and where this crosses the mid-dorsal line, a 10 cm needle is inserted perpendicularly until it strikes the floor of the vertebral canal. The needle is then withdrawn slightly, and the injection is made.

Epidural Anaesthesia in Bitches

The technique is similar to that used in swine. In bitches, epidural anaesthesia should be preceded by a sedative or narcotic; about 1 ml of local anaesthetic solution per 2.25 kg of body weight is required.