**7.6.4 Local nerve blocks of the head**

Cornual nerve block - The cornual nerve block in cattle is indicated for dehorning and treating horn injury. Ophthalmic division of the fifth cranial nerve is desensitized by the injection of the anesthetic (3-5 ml of 2 % lidocaine) on the upper third of the temporal ridge, about 2.5 cm below the base of the horn. The nerve is relatively superficial, about 0.7-1 cm deep.

Onset of analgesia occurs 10-15 minutes following injection and duration of analgesia is approximately one hour.

In adult cattle with well-developed horns, a ring block around the base of the horn may be necessary.

Fig. 2. Needle placement site for cornual nerve block in cattle

The cornual nerve block in goats is indicated for dehorning, not as easy as in the cow as there are two branches of the nerve (lacrymal and infratrochlear branches).

It must not be used in kids, as tend to use a total overdose of local anesthetics in these very small animals.

Auriculopalpebral block in cattle and horses - Auriculopalpebral nerve supplies motor fiber to the orbicularis oculi muscle. It runs from the base of the ear along the facial crest, past and ventral of the eye, giving off its branches on the way.

respective transverse processes in cows where approximately 10-20 ml of a 2% lidocaine

The needle is completely withdrawn and reinserted dorsal to the transverse process, where

10-20 ml 2% lidocaine is used per site and onset and duration of analgesia are similar to the

Cornual nerve block - The cornual nerve block in cattle is indicated for dehorning and treating horn injury. Ophthalmic division of the fifth cranial nerve is desensitized by the injection of the anesthetic (3-5 ml of 2 % lidocaine) on the upper third of the temporal ridge, about 2.5 cm below the base of the horn. The nerve is relatively superficial, about 0.7-1 cm

Onset of analgesia occurs 10-15 minutes following injection and duration of analgesia is

In adult cattle with well-developed horns, a ring block around the base of the horn may be

The cornual nerve block in goats is indicated for dehorning, not as easy as in the cow as

It must not be used in kids, as tend to use a total overdose of local anesthetics in these very

Auriculopalpebral block in cattle and horses - Auriculopalpebral nerve supplies motor fiber to the orbicularis oculi muscle. It runs from the base of the ear along the facial crest, past and

the cutaneous branch of the dorsal rami is injected with about 5 ml of the analgesic. The procedure is repeated for the second and fourth lumbar transverse processes.

solution are injected in a fan-shaped infiltration pattern.

Fig. 2. Needle placement site for cornual nerve block in cattle

ventral of the eye, giving off its branches on the way.

there are two branches of the nerve (lacrymal and infratrochlear branches).

proximal technique.

approximately one hour.

deep.

necessary.

small animals.

**7.6.4 Local nerve blocks of the head** 

Fig. 3. Needle placement sites for cornual nerve block in the goat (Modified from Thurmon *et al,* 1996)

The needle is inserted in front of the base of the ear at the end of the zygomatic arch and is introduced until its point lies at the dorsal border of the arch. 10-15 ml of 2% lidocaine are injected.

Onset of analgesia occurs 10-15 minutes and duration of analgesia is approximately one hour. This block does not produce analgesia of the eye or the lids. In conjunction with topical analgesia (2% lidocaine), it is useful for the removal of foreign bodies from the cornea and conjunctival sac. Also used, but less frequently, in other species.

This block has no sensory effects but paralyses the muscles of the eyelid. It is used to keep the eye open, for example, as an adjunct in ophthalmic surgery.

This is one of the most commonly used techniques to block the motor function of the upper eye lid for ophthalmic surgery, preventing eyelid closure during examination of the eyeball.

Retrobulbar nerve block in cattle - Widely used in practice to enucleate the eye. May also be used in many other species.

Peterson's eye block in cattle - Requires more skill and specific anatomic knowledge than retrobulbar nerve block, but involves less risk in damaging surrounding anatomic structure around the eye globe, and less volume requirement reducing potential for systemic toxicity and expense.

The point of injection is the notch formed by the supraorbital process cranially, the zygomatic arch ventrally, and the coronoid process of the mandible caudally.

An one inch, 14 gauge needle is inserted through a desensitized skin as far anterior and ventral as possible in the notch.

A 4-5 inch, 18 gauge straight or slightly curved needle is inserted at the point of injection mentioned above in a horizontal and slightly posterior direction until it hits the coronoid process of the mandible.

Local Anesthesia for Husbandry Procedures and Experimental Purposes in Farm Animals 245

Cattle can be subjected to the following painful husbandry procedures: disbudding, dehorning, castration, branding and ear notching or tagging. In addition, some heifers may

Disbudding is used to mean the prevention of horn growth before it has become advanced, and dehorning means the amputation of horns at any stage after their growth has progressed beyond the early budding stage. Disbudding of calves at a very young age is

Cautery disbudding is preferable, but extreme escape behaviour of the calf shows that application of the hot iron is painful. This behaviour, and the often less obvious response that occurs with surgical disbudding, can both be eliminated using local anaesthetic

Removal of horns from mature cattle without anaesthetics is very painful. Dehorning

The behavioural response to the pain caused by the act of amputating the horn can be eliminated using local anaesthetic blockade of the corneal nerve or by a ring block around

Effective cornual nerve blockade using local anaesthetic eliminates the initial peak of the plasma cortisol response and cortisol concentrations remain at pre-treatment levels for about 2 hours. Thereafter the concentrations increase for about 6 hours before returning to

This is interpreted to indicate that effective corneal nerve blockade eliminates pain for about 2 hours, after which some pain is experienced. This delayed pain is probably dull and not as acutely sore as the initial pain of horn amputation. To eliminate the acute cortisol response for at least 12 hours the dehorned animal needs to be given a systemic analgesic along with the local anaesthetic; a combination of an NSAID (non-steroidal anti-inflammatory drug) with a local anaesthetic is effective in this regard (McMeekan *et al*., 1998b; Stafford *et al*.,

When local anaesthetic is given before dehorning, cautery of the wound to control haemorrhage also reduces the plasma cortisol response, and by inference the pain

Castration is a standard husbandry practice in most cattle production systems and it is painful. The cortisol response to clamp castration is less than the response to rubber-ring or

Local anaesthesia placed in the distal scrotum and testicles eliminates or reduces the painrelated behaviours seen at castration by these methods. It eliminates the plasma cortisol response to castration by rubber ring or band. This is because the tight ring or band stops blood and lymph perfusion of the testicles and scrotum so that the local anaesthetic remains in those tissues beyond the time required for anoxic death of the pain receptors and

Heifers are spayed to prevent mis-mating and to prevent mating of cull cows in extensive farming systems. The ovaries are removed either through the vagina in larger cows and

surgical castration, which suggests that the clamp is less painful (Stafford *et al*., 2002).

blockade of the corneal nerve or a ring block around the base of each horn bud.

mature animals may be more painful than most other procedures.

experienced by cattle, for at least 24 hours (Sutherland *et al*., 2002).

pre-treatment levels (McMeekan *et al*., 1998a).

2003; Milligan *et al*., 2004; Stewart *et al*., 2009).

be spayed, and dairy cattle may have their tails docked.

recommended.

the horn base.

associated nerves.

The needle must be gently manipulate anteriorly until its point passes medially around the coronoid process, then advanced to the pterygopalatine fossa rostral to the solid bony plate that is in close proximity of the orbitorotundum foramen. Following aspiration, 7–15 ml of local anesthetics are injected.

Oculomotor, trochlear, abducens, and three branches of the trigeminal nerve (ophthalmic, maxillary, and mandible) are desensitized in 10–15 minutes following injection.
