**7.4.1 Epidural anesthesia in cattle**

For caudal and epidural anesthesia the injection site used is between coccygeal C1 and C2. For a 500 kg bovine 5-10 ml 2% lidocaine will give caudal anesthesia without causing hind limb ataxia or paralysis.

Onset of paralysis of the tail should occur in 1-2 minutes. The block will last 1-2 hours. Larger doses will produce increasingly anterior effects.

By the time 100-150 ml 2% lidocaine is injected, the block will be sufficiently anterior to allow surgery of the hindlimbs, mammary tissue, flanks and abdominal wall. However, the bovine will be recumbent. Injection of local anesthetics can be carried out at the lumbosacral junction in order to produce an anterior block with less anesthetic.

There is a danger of accidental subarachnoid injection. Segmental epidural anesthesia, where the anesthetic is injected into the epidural space at the region required can be used for analgesia of any 'segment' with less overall side effects. It is more difficult to perform; penetration of the meninges is likely, but in skilled hands it is a very useful technique.

Local Anesthesia for Husbandry Procedures and Experimental Purposes in Farm Animals 241

inadequate tourniquet, inadequate time, and lack of exsanguination). e) Collapse when tourniquet is removed (this is because of anoxic waste products re-entering circulation); it is

This term is used where specific nerves to the area concerned are blocked. Examples include specific nerve blocks to the limbs; paravertebral blocks; cornual block (for dehorning) and

Paravertebral anesthesia refers to the perineural injection of local anesthesia about the spinal

The technique may theoretically be carried out in any species, and at any level of the spinal cord but in practice, its main use is to provide anesthesia of the lumbar region in ruminants. Its advantage is that it provides analgesia and muscle relaxation of the whole area covered

The method described whereby the needle is inserted ventral to the transverse processes of the spine has the disadvantage that the dorsal branches of the segmental nerves are not

Paravertebral anesthesia is easy to carry out, and almost always effective, except in the very

Indicated for standing laparotomy surgery such as C-section, rumenotomy, cecotomy,

The dorsal aspect of the transverse processes of the last thoracic (T-13) and first and second

The dorsal and ventral nerve roots of the last thoracic (T-13) and 1st and 2nd lumbar spinal nerves emerging from the intervertebral foramina are desensitized. 10-20 ml of 2% lidocaine is injected to each site and onset of anelgesia occurs usually within 10 minutes after injection Increased skin temperature due to vasodilation (paralysis of cutaneous vasomotor nerves)

The dorsal and ventral rami of the spinal nerves T13, L1 and L2 are desensitized at the distal ends of L-1, L-2 and L-4. A 7.5-cm, 18-gauge needle is inserted ventral to the tips of the

large beef breeds where it may be very difficult to locate the necessary landmarks.

correction of gastrointestinal displacement, intestinal obstruction and volvulus.

indicates effective block. Duration of analgesia is approximately 90 minutes.

**7.6.3 Distal paravertebral block (Magda, Cakala, or Cornell technique)** 

lumbar (L-1 and L-2) vertebrae is the site for needle placement.

Indication is the same as the proximal paravertebral block.

**7.6.2 Proximal paravertebral block (Farquharson, Hall or Cambridge Technique)** 

nerves as they emerge from the vertebral canal through the intervertebral foraminae.

Several different methods of achieving paravertebral anesthesia have been described.

All methods approaching from the dorsal surface are equally effective.

preferable if the animal is recumbent at this time.

**7.6 Regional anesthesia** 

**7.6.1 Paravertebral anesthesia** 

by the segmental nerves blocked.

blocked, thus some skin sensitivity remains.

many others.

Fig. 1. For caudal and epidural anesthesia in cattle the injection site used is between coxygeal C1 and C2 (Modified from Thurmon *et al,* 1996)

#### **7.4.2 Epidural anesthesia in the sheep and goat**

In both sheep and goats, anterior epidural anesthesia, induced by injection at the lumbosacral junction is easily performed and provides excellent analgesia and muscle relaxation for abdominal surgery.

Recumbency may occur but is not a problem in these small animals. As in cattle, there is a risk of subarachnoid injection.

#### **7.4.3 Epidural anesthesia in the horse**

Hind limb ataxia is a serious problem, so only caudal epidural techniques are used. These are useful for various obstetrical manipulations and surgery on the rectum, vagina and tail.

The technique is less reliable than in cattle. Site of injection is usually sacrococcygeal junction but can be between C1 and C2. For a 500 kg horse, a mixture of 50 mg of xylazine and 6 ml of 2% mepivacaine (may be repeated for another dose) may prove very effective.

#### **7.5 Intravenous regional local anesthesia**

In this technique, a limb vein is catheterized. The limb is then exsanguinated (Esmarchs bandage), and a tourniquet placed around the limb, at a pressure adequate to prevent arterial circulation (> 150 mmHg).

Local anesthetic (preferably without epinephrine) is then injected into the vein. After a period of 15 minutes the area distal to the tourniquet is anesthetized until the tourniquet is removed.

Potential problems are: a) Difficulty in finding the vein once the limb is exsanguinated (this is why it is best to have a catheter in place first). c) Cardiac arrhythmias or even arrest (this is due to an inadequate tourniquet). d) Failure to take effect. (common reasons are inadequate tourniquet, inadequate time, and lack of exsanguination). e) Collapse when tourniquet is removed (this is because of anoxic waste products re-entering circulation); it is preferable if the animal is recumbent at this time.
