Nerve blocks and dehorning- By: Dr. Najmu Saaqib Reegoo DVM

Dehorning
The cornual nerve block is one of the most common techniques
used for dehorning cattle.
Innervation:
The horn and skin around the base of the horn are innervated
by the cornual branch of the lacrimal or zygomaticotemporal
nerve, which is part of the ophthalmic division of the trigeminal
nerve.
The cornual nerve passes through the periorbital tissues
dorsally and runs along the frontal crest to the base of the
horns.
Approximately 5–10 ml of local anaesthetic is administered subcutaneously and relatively superficially
midway between the lateral canthus of the eye and the base of the horn along the zygomatic process.
Complete anaesthesia occurs within 10 minutes following the administration of local anaesthetic.
C a t t l e
Cornual Block
By: Najmu Saaqib Reegoo DVM (2015-19) 2

The horn base in goats is also heavily innervated by the cornual branches of the infratrochlear nerve
which exits the orbit at or in close proximity to the medial canthus. Because of the widespread
branching, the nerve is best blocked using a line block midway between the medial canthus of the eye
and the medial horn base.
Alternatively, a ring block around the base of the horn may also be used for anaesthesia for dehorning.
Because of anatomical differences, the cornual nerve block in
goats requires at least two injection sites per horn versus the
aforementioned one site in cattle.
In goats, the cornual nerve is a branch of the
zygomaticotemporal nerve and lies halfway between the
lateral canthus of the eye and the lateral base of the horn.
G o a t s
Line Block
By: Najmu Saaqib Reegoo DVM (2015-19)
Dehorning
Cornual Block
3

Traditionally, dental blocks have involved blocking the infraorbital, mental, and mandibular foramina.
Recent work suggests that blocking the infraorbital and mental foramina is sufficient to provide
analgesia extending from the canines to the molars in both the maxilla and the mandible.
Indications:
• To provide intra- and postoperative analgesia for maxillary canine, molar, and premolar extractions.
• The same technique also provides analgesia to the area around the upper lips and nares.
Area and nerves blocked:
• The infraorbital nerves supply the caudal, medial, and rostral superior alveolar nerves with multiple
nerve branches innervating the upper lip, buccal, and nasal areas.
Landmarks:
• The infraorbital foramen ipislateral to the tooth to be extracted is located just below the zygomatic arch.
• The lateral bone margin of the infraorbital foramen is easily palpated immediately dorsal to the root of
the maxillary third premolar.
• The foramen is triangular and is easily palpated in medium and large dogs both intraorally and
extraorally.
D e n t a l
I n f ra o r b i t a l B l o c k
Dental

Drugs and Equipment:
• A combination of 0.5 ml 2% lidocaine and 0.5 ml 0.5% bupivacaine, dosed at
0.15ml/4.5 kg (10 lb), is administered.
• This combination takes advantage of the fast onset of action of lidocaine
(3–5minutes) and the longer duration of action (6–8 hours) of bupivacaine.
• A 22–25 gauge, 1–1.5 inch needle should be used.
• Lidocaine with epinephrine (1:100,000) may be used to prolong the duration
of the effect.
Indications:
• To provide analgesia and muscle relaxation for the forelimb, from shoulder to the toes, to facilitate orthopedic or
soft tissue surgeries.
• If an amputation is going to be performed, injecting local anaesthetic around the brachial plexus nerves is thought
to prevent limb pain (neuropathic).
Brachial plexus nerves derived from the ventral branch of spinal nerves exiting from C6–T1, branches into the
suprascapular nerve, musculocutaneous nerve, axillary nerve, radial nerve, median nerve, ulnar nerve, and
thoracodorsal nerve, which innervate the forelimb
Limbs
Brachial plexus block :
L i m b s
5

Landmarks:
• Tip of the greater tubercle of the humerus.
• During forelimb amputation, the nerves of the brachial plexus are directly exposed.
• Lidocaine or bupivacaine alone or mixed together.
• Mepivacaine can also be used.
• Dose: 1–2 mg/kg of 0.5% bupivacaine.
• A 22-gauge, 1.5–2.5 inch spinal needle is suitable for most dogs and cats.
• An insulated catheter needle (240) can also be used, together with a low-current
nerve stimulator to locate the nerves.
Indications:
• Intra and postoperative analgesia when performing feline forelimb declawing or removal of tumors.
• This technique can also be applied to hindlimb declawing or similar growth removal.
Ring and Point block for feline forelimb:
Limbs

Area and nerves blocked :
Fore limbs: The radial nerve, palmar and dorsal branches of the ulnar nerve, and the palmer median nerve are
blocked at the level of the carpus.
Hind limbs: The superficial peroneal nerve on the dorsal side of the limb and the tibial nerve on the plantar side at
the level of tarsus are blocked.
If using a ring block, these nerves are blocked at the level of the carpus.
Landmarks :
Ring block: a circular block is performed immediately above the metacarpal pad of the forelimb and immediately
below the tarsal joint of the hind limb.
2% lidocaine and 0.5% of bupivacaine combined without epinephrine as it can potentiate an ischemic response by
constricting blood vessels.
0.6 ml of 2% lidocaine and 0.6 ml of 0.5% bupivacaine are drawn up in the same syringe and administered at 0.2 ml
per site.
A 22-gauge needle is used to administer the block.
Limbs

Approach :
Two approaches can be used: a ring block or a three-point block.
The block is usually performed immediately prior to surgery (i.e. soon after the animal has been anesthetized).
The injection site is prepared as for a sterile procedure.
A ring block is performed by inserting a 22gauge needle subcutaneously at the level above the metacarpal pad
(forelimb) or immediately below the tarsal joint (hind limb) and injecting in a circular pattern.
The area is seen to bulge post injection as the local anaesthetic infiltrates the tissues around the limb.
A two-point injection involves infiltration of 0.2–0.3 ml of local anaesthetic at both the radial and ulna branches
Indications :
To provide intra- and postoperative analgesia for lateral thoracotomy in dogs and cats.
The internal surface of the thoracic wall is covered by costal parietal pleura.
The internal intercostal muscle fascicles run between the ribs together with the intercostal nerve.
The artery and vein run along the caudal border of each rib.
The intercostal nerve block desensitizes the intercostal nerves innervating the intercostal spaces on the ipsilateral side of the
thorax as the surgery.
Intercostal Nerve Blocks
Thorax
T h o r a c i c
8

Landmarks :
Depending on the size of the animal, the injection should be made
approximately 5–10 cm (2–4 in) from the ventral portion of the paravertebral
area of the pleura.
Drugs and Equipment :
Bupivacaine 0.5% with or without epinephrine (0.3–0.5 ml per site). •
Alternatively, 0.25 ml of lidocaine 2% incombination with 0.25 ml of
0.5%bupivacaine can be used (administer 0.5 ml per site).
A tuberculin syringe with a 22-gauge needle is usually used.
Approach :
The procedure is performed aseptically either at the beginning of the
thoracotomy or at the conclusion prior to closure of the pleural layer of the
thorax.
Three injections are administered :(1) Dorsal to the surgical incision site in the ventral portion of the pleura;
(2) Intercostal cranial nerve; and (3) Intercostal nerve caudal to the incision site.
Some practitioners use five injection sites as shown in 247, with two injection sites cranial to the incision and two caudal
Thorax

Indications:
• Intra- and postoperative analgesia for hind quarter surgeries in dogs and
cats (e.g.tail amputation, anal–rectal surgeries, tibial–femoral fractures,
total hip replace ment, cruciate ligament repair), exploratory laparotomy,
cesarean section, and surgical procedures caudal to the region of the
twelfth or thirteenth ribs.
• Pelvic plexus nerves.
Landmarks :
• Lumbosacral junction.
• Morphine: It an be given with or without a preservative (preferred). Dose
is 0.1 mg/kg.
Onset of action is 20–60 minutes.
Duration of action is 6–8 hours
• Oxymorphone or hydromorphone
Dose of 0.1 mg/kg.
Duration of action is 2–3 hours in dogs.
Fentanyl
Dose is 5–10 mcg/kg.
Short duration of action (less than 1 hour) due to high lipid
solubility makes it of minimal benefit when administered
epidurally
EpiduralLumbosacral epidural blocks

• Bupivacaine and morphine combinations
The most common combination is bupivacaine at 0.2 mg/kg with preservative-free morphine at 0.1 mg/kg
(final injection volume dosed at 1ml/4.5kg [10 lb] in dogs and cats).
Duration of analgesia is approximately 8hours
Approach:
• This procedure is performed aseptically under general anesthesia or profound sedation. The animal can be in
lateral or sternal recumbency. The hanging drop technique can be applied to animals in sternal recumbency.
Indications :
To provide intra- and postoperative analgesia for fore- or hindlimb soft tissue
surgeries.
Area and nerves blocked :
The nerves that innervate the distal portion of the limb below the elbow or stifle.
Landmarks :
The cephalic vein of the forelimb and the saphenous vein of the hindlimb.
Regional
Bier blocks (Intravenous regional block)
Regional

Drugs and equipments:
2% lidocaine without epinephrine is administered IV at 5 mg/kg.
A lidocaine (3 mg/kg) and bupivacaine mixture (1mg/kg) may also
be used.
• Rubber tubing is used as a tourniquet.
• A blood pressure cuff can also be used to block local circulation.
Approach:
• The limb must be exsanguinated prior to application/inflation of
the tourniquet. This is accomplished by wrapping a bandage
tightly around the limb proximal to the needle placement site.
• Alternatively, the limb can be elevated for 30 seconds prior to
application of the tourniquet.
• If using a blood pressure cuff for a tourniquet, the cuff is inflated
to a pressure 50 mmHg higher than the animal’s systolic blood
pressure (261, 262).
• Adequate inflation has been achieved when the distal pulse
disappears.
• Surgery should last no more than 60minutes to prevent ischemia
of the extremity with the tourniquet
Regional

• Anesthesia of the eyelid is accomplished by performing a line block of the eyelid or by blocking the
auriculopalpebral branch of the facial nerve.
Line block:
• It is performed by using a 20- or 22-gauge, 2.5-cm needle to inject 10 ml of local anaesthetic at multiple sites 0.5
cm apart on a line approximately 0.5 cm from the margin of the eyelid.
Auriculopalpebral nerve block:
• It is performed by using an 18- or 20-gauge, 2.5-cm needle placed subcutaneously approximately 5–7.5 cm
lateral to the zygomatic arch. 5–10 ml of local anaesthetic is then injected.
• It only blocks the lower eyelid, therefore desensitization of the upper eyelid with a line block is also required if
the surgical procedure involves upper eyelid.
Anesthesia of the eye and orbit and immobilization of the globe necessary for procedures like enucleation may be
accomplished by performing;
1. Retrobulbar eye block.
2. Peterson eye block.
Opthalmic
Eye
Eye and orbit

It is used for enucleation of the eye or for surgery of the cornea and when
properly performed, causes analgesia of the cornea, mydriasis, and
proptosis.
Adequate restraint of the head is necessary when performing this
procedure.
Sites for needle placement:
• The medial and lateral canthus or the upper and lower eyelids (Figure 7.3).
An 18-gauge, 15-cm needle is used and may be bent slightly to facilitate
passage around the globe once it has been introduced through the eyelid
or canthus at the orbital rim. The surgeon’s finger is used to deflect the globe to protect it from the point of the
needle. Approximately 15 ml of local anaesthetic is injected in small increments as the needle is advanced slowly
toward the back of the orbit.
Adverse effects:
• Penetration of the globe,
• Orbital hemorrhage,
• Damage to the optic nerve,
• Cardiac dysrhythmias caused by initiation of the oculocardiac reflex, and injection of the local anaesthetic into the
optic nerve meninges.
1. Retrobulbar eye block
Opthalmic

.
It requires significantly more skill to perform than the retrobulbar eye block but is considered safer and more
effective if performed correctly.
• There is less edema and inflammation associated with the Peterson eye block than with infiltration of local
anaesthetics into the eyelids and orbit.
• Desensitisation: Oculomotor, Trochlear, Abducent, and Trigeminal nerves responsible for sensory and motor
function of all structures of the eye except the eyelid.
• Landmark: The notch created by the supraorbital process cranially, zygomatic arch ventrally and the coronoid
process of the mandible caudally.
• Injection: 5 ml of local anaesthetic is injected subcutaneously at this site using a 22-gauge, 2.5-cm needle.
A 14-gauge, 2.5-cm needle serves as a cannula and is placed through the anesthetized area as far anterior and
ventral as possible in the notch.
A straight or slightly curved 18-gauge, 10- to 12-cm needle is inserted into the cannula and directed horizontally
and slightly caudally until it comes into contact with the coronoid process of the mandible at approximately 2.5 cm
below the skin.
The needle is then gently manipulated rostrally until its point passes medially around the coronoid process. It is
then advanced to the pterygopalatine fossa rostral to the solid bony plate that is in close proximity to the orbital
foramen at a depth of 7.5–10 cm (Figure 7.1E).
2. Petersons eye block:
Opthalmic

• Penetration of the nasopharynx and turbinates should be avoided.
Aspiration ensures that the ventral maxillary artery has not been
penetrated.
• Approximately 15 ml of local anaesthetic is then injected.
• Both the retrobulbar block and the Peterson eye block prevent
blinking for several hours.
• The cornea must be kept moist if these blocks are used for
procedures other than enucleation.
• Caution must also be used with animals that are transported
immediately following these procedures.
• A lubricating eye ointment can be applied to the cornea, or the
eyelids may be sutured together until motor function of the eyelids
returns.
These techniques include;
1. Proximal paravertebral nerve block,
2. Distal paravertebral nerve block,
3. Inverted-L block,
4. Infusion of the incision or line block.
Indications: Abomasopexy, Omentopexy , Rumenotomy,
Volvulus, Cesarean section, Ovariectomy,
Liver and Kidney biopsy.
Laparotomy
Laparotomy

• It desensitizes the dorsal and ventral nerve roots of the last thoracic (T13) and first and second lumbar (L1 and L2)
spinal nerves as they emerge from the intervertebral foramina.
Desensitisation:
To desensitize T13, the cannula needle is placed through
the skin at the anterior edge of the transverse process of
L1 at approximately 4–5 cm lateral to the dorsal midline.
The 18-gauge, 10- to 15-cm spinal needle is passed
ventrally until it contacts the transverse process of L1. The
needle is then walked off of the cranial edge of the
transverse process of L1 and advanced approximately
1 cm to pass slightly ventral to the process and into the
intertransverse ligament. A total of 6–8 ml of local
anaesthetic is injected with little resistance to desensitize
the ventral branch of T13. The needle is then withdrawn
1–2.5 cm above the fascia or just dorsal to the transverse
process, and 6–8 ml of local anaesthetic is infused to
desensitize the dorsal branch of the nerve.
Laparotomy
1. Proximal Paravertebral nerve block:
17

• To desensitize L1 and L2, the needle is inserted just caudal to the transverse processes of L1 and L2. The
needle is walked off of the caudal edges of the transverse processes of L1 and L2, at a depth similar to the
injection site for T13, and advanced approximately 1 cm to pass slightly ventral to the process and into the
intertransverse ligament. A total of 6–8 ml of local anaesthetic is injected with little resistance to desensitize
the ventral branches of the nerves. The needle is then withdrawn 1–2.5 cm above the fascia or just dorsal to
the transverse processes, and 6–8 ml of local anaesthetic is infused to desensitize the dorsal branch of the
nerves.
Evidence of a successful proximal paravertebral nerve block
1. It includes increased temperature of the skin;
2. Analgesia of the skin, muscles, and peritoneum of the abdominal wall of the paralumbar fossa; and
3. Scoliosis of the spine toward the desensitized side.
Advantages:
• Small doses of anaesthetic, wide and uniform area of analgesia and muscle relaxation, decreased intra-
abdominal pressure, and absence of the local anaesthetic at the margins of the surgical site.
Disadvantages:
• Scoliosis of the spine, which may make closure of the incision more difficult; difficulty in identifying
landmarks in obese and heavily muscled animals; and more skill or practice required for consistent results.
Laparotomy

• The distal paravertebral nerve block desensitizes the
dorsal and ventral rami of the spinal nerves T13, L1, and
L2 at the distal ends of the transverse processes of L1, L2,
and L4, respectively.
• An 18-gauge, 3.5- to 5.5-cm needle is inserted ventral to
the transverse process, and 10 ml of local anaesthetic is
infused in a fan-shaped pattern.
• The needle can then be removed completely and
reinserted or redirected dorsal to the transverse process,
in a caudal direction, where 10 ml of local anaesthetic is
again infused in a fan-shaped pattern.
• Advantages of the distal paravertebral nerve block
compared with the proximal paravertebral nerve block
include lack of scoliosis, it is easier to perform, and it
offers more consistent results.
• Disadvantages of the distal paravertebral nerve block compared with the proximal paravertebral nerve block
include larger doses of local anaesthetic required and variations in efficiency caused by variation in anatomical
pathways of the nerves
Laparotomy
2. Distal Paravertebral nerve block:
19

Advantages:
• The block is simple to perform, it does not interfere with ambulation, and deposition of the local
anaesthetic away from the incision site minimizes incisional edema and hematoma .
Disadvantages:
• Incomplete analgesia and muscle relaxation of the deeper layers of the abdominal wall
(particularly in obese animals), possible toxicity from the administration of larger doses of local
anaesthetic, and increased cost because of larger doses of local anaesthetic required.
• It is a nonspecific regional block that locally blocks the tissue
bordering the caudal aspect of the 13th rib and the ventral
aspect of the transverse processes of the lumbar vertebrae
• An 18-gauge, 3.8-cm needle is used to inject up to a total of
100 ml of local anaesthetic solution in multiple small injection
sites into the tissues bordering the dorsocaudal aspect of the
13th rib and ventrolateral aspect of the transverse processes
of the lumbar vertebrae (Figure 7.5). This creates an area of
anesthesia under the inverted-L block.
Laparotomy
3. Inverted-L block:
20

• Infusion of local anaesthetic into the incision site or a line
block may be used to desensitize a selected area of the
paralumbar fossa.
• An 18-gauge, 3.8-cm needle is used to infuse multiple, small
injections of 10 ml of local anaesthetic solution
subcutaneously and into the deep muscle layers and
peritoneum.
• Pain of successive injections may be alleviated by placing the
edge of the needle into the edge of the previously
desensitized area at an approximately 20°–30° angle [9].
In heavily muscled or overweight cattle, it may be necessary to use an 18-gauge, 7.5-cm needle to penetrate
through the large amount of subcutaneous fat to reach the deep muscle layers. The amount of local
anaesthetic needed to acquire adequate anaesthesia depends on the size of the area to be desensitized.
Adult cattle weighing 450 kg (990 lb) can safely tolerate 250 ml of a 2% lidocaine hydrochloride solution.
Delayed healing of the incision site is a possible complication of infiltration of local anaesthetic at the surgical
site
Laparotomy
4. Line block:
21

• The inverted-V block has been principally used for focal lesions
of the teat such as a teat laceration or wart. Using a 25-gauge,
1.5-cm needle, 5 ml of anaesthetic is injected into the skin and
musculature of the teat immediately dorsal to the surgical site
in an inverted-V pattern (Figure 7.13A) [8].
Ring block:
• The ring block has been commonly used to anesthetize the
teat for surgeries. A 25-gauge, 3.8-cm needle is used to inject 5
ml of local anaesthetic into the skin and musculature
circumscribing the base of the teat (Figure 7.13B) [8].
• Infusion of teat cistern: The teat cistern may be infused with
local anaesthetic for surgical procedures, such as removal of
polyps, which involve only the mucous membranes.
Prior to infusing the teat, the cistern should be stripped of milk and the orifice thoroughly cleaned with alcohol.
A tourniquet (rubber band) may then be placed at the base of the teat to prevent leakage of local anaesthetic
into the udder from the teat cistern.
A sterile teat cannula is then used to instil 10 ml of local anaesthetic into the teat (Figure 7.13C). It is important
to remember that the musculature and the skin are not desensitized using this technique. The teat cannula is
removed from the teat, and the remaining anaesthetic is milked out.
Once the surgery is performed, the tourniquet is removed.
Mammary
Teat anaesthesia
22

References
1. Rust, R., Thomson, D. and Loneragan, G. (2007) Effect of different castration
methods on growth performance and behavioral responses of postpubertal beef bulls.
The Bovine Practitioner, 41, 116–118.
2. Anderson, D. and Edmondson, M. (2013) Prevention and management of surgical
pain in cattle. Veterinary Clinics of North America: Food Animal Practice, 29, 157–184.
3. Broom, D. (2000) The evolution of pain. Vlaams Diergeneeskundig Tijdschrift, 69,
385–411.
4. Skarda, R. (2007) Local and regional anaesthetic techniques: ruminants and swine,
in Lumb and Jones’ Veterinary Anesthesia and Analgesia, 4th edn (eds W. Tranquilli, J.
Thurmon and K. Grimm), Blackwell Publishing, Oxford, pp. 731–746
5. Edwards, B. (2001) Regional anesthesia techniques in cattle. In Practice, 23, 142–
149

Nerve blocks and dehorning- By: Dr. Najmu Saaqib Reegoo DVM

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