◊ 2-Regional analgesia ◊
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II-Regional Analgesia...
Regional analgesia can be achieved by preventing conduction of nerve impulse through sensory nerve that finally retains certain area analgesic. The technique has been widely used in cattle as general anesthesia is not suitable for that species, and it can be used alone or in conjunction with sedation, on the contrary it is of low value in pets as the general anesthesia in that species is superior to other analgesic methods.
Advantages: -
1-The technique requires no expensive equipments
2-Consumes lesser amount of drug
3-It has lower expense than local analgesia
4-It has lower possibility of toxicity than local analgesia
5-Disadvantages of local analgesia like; changes in anatomical features at seat of injection, delayed healing, and possibility of transmission of infection by needle can be avoided.
6-The analgesic area is large enough and there is no need to increase the size of analgesic field during surgery like with local analgesia.
7-It is suitable for operations that should be performed on standing animals either with or without sedation.
Disadvantage: -
1-Technicaly it is more complicated than local analgesia
2-It has risk of toxicity especially when the nerve is associated with blood vessels
3-General complications of epidural including fracture, infection of neural canal, etc….
I-Perineural Analgesia
The method comprises the injection of local analgesic into the connective tissue around the nerve trunk. Absorption of the agent by the nerve resulting in block of its function.
A-Regional Analgesia Of The Head…
1-The Horse.
1-Infra-orbital nerve block: -
Anatomy:
It is the continuation of the maxillary division of trigeminal nerve (V cranial nerve) and as it passes the infra-orbital canal to innervates;
1-The 3rd premolar
2-The 3 molar teeth
While during it passes through the infra-orbital canal and 2.5 cm before it exit the canal it sends fibers that pass through maxilla and premaxilla to innervate;
| 1-The upper 1st and 2nd premolar teeth 2-The canine 3-The incisors | and their alveoli and gum |
Then after, it exits through the infra-orbital foramen partially covered with levator nasolabialis muscle to innervate;
1-Skin of the upper lip
2-Skin of the cheek
3- Skin of the nostril
Indications: -
1-Suturing of a wound at the lip or nostril
2-Trephining the facial sinus
3-Tooth extraction (but preferred to be removed under general anesthesia)
Dose: -
5 ml Lidocaine HCl 2%
Seat of injection, technique of injection and desensitized areas: -
a-After the nerve emerges from the canal: -
The lip of the infra orbital foramen can be felt as bony ridge lying beneath the edge of the flat levator nasolabialis muscle, at a point 5 cm forward and downward from the anterior end of facial crest. The needle is introduced until its point can be felt beneath the bony lip of the foramen then after the analgesic drug can be injected.
Desensitized areas are:
1-Skin of the upper lip
2-Skin of the cheek
3-Skin of the nostril
4-Skin of face up to the level of the foramen
b-Within the canal: -
The technique of injection is the same as mentioned in site (a) but the needle should be advanced 2.5 cm up the canal.
Desensitized areas are:
| 1-The incisors 2-The canine 3-The upper 1st and 2nd premolar | and their alveoli and gum |
4-The skin of the face up to the level of the medial canthus of the eye
c-Within the pterygopalatine fossa: -
With this technique of injection the needle should be inserted at a point on the side of the face opposite to the lateral canthus, inferior to the facial crest, and above transverse facial vessels.
The needle is advanced medially, slightly anteriorly to process and drop into the pterygopalatine fossa just posterior to maxillary tuberosity. The needle should be pushed until it strikes the perpendicular portion of palatine bone in the region of maxillary foramen at a depth of 7 cm but generally it is a dangerous procedure and not recommended to be used.
Desensitized areas are:
1-All the previously mentioned regions
2-The molar teeth up to the 6th
2-Mental nerve block: -
Anatomy: -
It is the alveolar branch of the mandibular division of the trigeminal nerve (V cranial nerve) that enters the mandibular foramen on the medial aspect of the vertical ramus of the mandible under the medial pterygoid muscle. It traverses the mandibular canal and giving off dental and alveolar branches then it emerges from the mental foramen and called mental nerve. The innervation of the incisors and canines arises from the trunk nerve 3-5 cm before it emerges from the mental foramen.
Indications: -
Suturing of wounds of the lower lip
Technique: -
The mental foramen, through which the mental nerve emerges, lies on the lateral aspect of the ramus in the middle of the inter-dental space and covered with the tendon of depressor labii inferioris muscle. Injection of the nerve at this point desensitizes the lower lip only, while advancing the needle 3-5 cm into the canal will desensitize the incisors and canine too.
Dose: -
5 ml of Lidocaine HCl 2%
3-Mandibualr nerve block: -
Indications: -
If the mandibular nerve is injected at its point of entry into the mandibular canal at the mandibular foramen, practically the whole of the lower jaw and all the teeth and alveoli on that side will become desensitized.
Technique: -
The mandibular nerve is injected at its point of entry into the mandibular canal at the mandibular foramen. The mandibular foramen lies opposite to the point of intersection of a line passes vertically downwards from the lateral canthus and a line extending backwards from tables of mandibular molar teeth. This nerve can be blocked by two methods.
1-Method I: -
The needle is inserted into a point 3 cm below the temporomandibular joint between the wing of the atlas and base of ear. Then the needle is advanced towards the point of intersection of the mentioned lines, medial to the medial surface of the mandible.
2-Method II: -
The needle is inserted directly in front of the angle of the mandible, medial to the medial surface of the mandible, towards the mentioned point. The needle should be inserted 12 cm forwards at least.
Dose: -
5 ml Lidocaine HCl 2%
4-Supra-orbital (frontal) nerve block: -
Anatomy: -
Supra-orbital or frontal nerve is a branch of ophthalmic division of trigeminal nerve (V cranial nerve), emerges from the orbit through the supra-orbital foramen in the supra-orbital process. It innervates the upper eyelid and skin of the fore head.
Indications: -
Operations of the upper eyelid or suturing of wounds
Technique: -
The upper and lower borders of the supra-orbital process, close to its junction to the frontal bone, are palpated, and the foramen is detected midway between the two borders, then the needle is inserted into the foramen and the nerve is blocked.
Dose: -
5 ml Lidocaine HCl 2%
5-Retrobulbar nerve block: -
It is a technique used for blocking of nerves behind the eye ball including;
| 1-Abducens 2-Trochlear 3-Oculomotor 4-Ophthalmic division of trigeminal |
that innervate ocular muscles |
| that innervates the conjunctiva, globe, 3rd eyelid, and lower eyelid |
Oculomotor nerve is the motor to the dorsal, ventral and medial rectus muscles the inferior oblique muscle, the levator palpebra muscle, and the papillary sphincter muscle, trochlear nerve is the motor to the superior oblique muscle, trigeminal nerve is the sensory to the eye and ocular adnexae, and abducens nerve is a motor to the lateral rectus and retractor bulbi muscles
Indications: -
Induction of analgesia and akinesia of periocular muscles for enucleation of the eyeball. The large amount of injected drugs creates state of exophthalmos to facilitate enucleation.
Technique: -
1-Method I (Four-point block): -
The needle is inserted into the orbit at 12:00, 3:00, 7:00 and 9:00 positions (6:00 should be avoided to minimize the chance of damaging the optic nerve). A slight ‘pop’ is felt as the orbital septum is penetrated; if the needle does not penetrate the septum, anesthetic may migrate subconjunctivally. Deposit 5–10 ml of anesthetic at each site.
2-Method II (Peterson-type block): -
This is a modification of the Peterson deep orbital block used in cattle. A slightly curved 18-gauge 10 cm needle is inserted 1 cm temporal to the temporal canthus and directed inferonasally towards the opposite nasal canthus.
3-Method III ( Infiltration anesthesia of the eye): -
It refers to injection of local anesthetic agent into tissue without regard for the course of nerves supplying the area of interest. Motor and sensory innervations of the infiltrated area will be affected, with the sensory component usually affected to a greater extent than the motor component.
This technique generally requires larger volumes of anesthetic agent, and can affect tissue architecture if applied overzealously. The needle is inserted 1.5 cm behind the middle of the supra-orbital process and pushed towards the upper molar teeth of the opposite side. Generally it can be used for enucleation of the eye ball.
Dose: -
20-30 ml Lidocaine HCl 2%
Potential complications of deep orbital blocks: -
Retrobulbar hemorrhage, inadvertent penetration of the globe, and laceration of the optic nerve among the most common complications of that technique. Sudden death has been reported following deep orbital blocks in cows, presumably due to injection of anesthetic into the subarachnoid space of the optic nerve which is contiguous with the subarachnoid space of the brain.
Field block (line block) anesthesia of the eye: -
Deposition of a line of local anesthetic along the superior and/or inferior orbital rims will effectively block all motor and sensory innervation to the eyelid(s), greatly facilitating surgical procedures and subpalpebral lavage apparatus placement.
6-Auriculopalpebral nerve block: -
Anatomy: -
It is one of terminal branches of facial nerve that carry motor innervation to the orbicularis oculi muscle of the upper eyelid, so its blocking produce paralysis of the upper eyelid without abolishing sensation and it is called akinesia.
Indications: -
1-Examination of the eye
2-Reliefe of blepharospasm
3-To facilitate sub-conjunctival injection
4-Removal of foreign bodies from the cornea or conjunctive in conjunction with topical analgesia
Technique: -
The nerve can be injected at the highest point of zygomatic arch rostoral to the base of ear (depression on the temporal aspect of zygomatic arch)
Dose: -
5 ml Lidocaine HCl 2%
2-The Ox .
1-Auriculopalpebral nerve block: -
Anatomy:
It is one of terminal branches of facial nerve. It is a motor nerve supply of the orbicularis oculi muscle of the upper eyelid.
Technique: -
The needle is inserted in front of the base of the ear at the end of the zygomatic arch. The nerve can be felt in a depression or notch on the dorsal border of zygomatic arch. The block can be performed by subcutaneous injection of the analgesic drug at that notch.
Indications and dose: -
As in horse
2-Cornual nerve block: -
Anatomy: -
The horn corium and the skin around the horn base in cattle are innervated by the cornual branch of the zygomaticotemporal (lacrimal) nerve. It is a branch of the ophthalmic division of the trigeminal nerve. It emerges from the orbit and ascends behind the lateral ridge of the frontal bone and it lies superficially in the upper 3rd of the ridge.
Indications: -
1-Surgical intervention for fractured or separated horn
2-Dehorning
3-Disbudding in young calves
Technique: -
The site for injection is the upper third of the temporal ridge, about 2.5 cm below the base of the horn. The needle is inserted immediately behind the ridge. The needle must not be inserted too deeply, otherwise injection will be made beneath the aponeurosis of the temporal muscle and the method will fail.
In large animals with well developed horns, a second injection should be made about 1 cm behind the first to block the posterior division of the nerve. This nerve block has been widely used for the dehorning of adult cattle but the block is not always complete. Variability in the curvature of the lateral ridge of the frontal bone makes exact determination of the site of the nerve difficult. In a struggling animal, it may be difficult to ensure that the point of the needle is at the correct depth. A third injection may be required in adult cattle with well developed horns; it is made caudal to the horn base to block the cutaneous branches of cervical nerves.
Dose: -
5 ml Lidocaine HCl 2%
3-Retrobulbar nerve block: -
Anatomy and indications: -
As equine
Technique: -
1-Method I: -
The circumference of the eye is considered as watch and classified into 12 hours then the needle is inserted into 4 sites at 3, 6, 9, and 12 O'clock.
2-Method II: -
Modified Peterson's technique can be performed by inserting needle in the notch formed by supra-orbital process cranially, zygomatic arch ventrally and coronoid process of the mandible posteriorly. The needle is advanced towards orbitorotundum foramen and the analgesic drug is injected to produce block of oculomotor, abducens, trochlear, ophthalmic, maxillary, and mandibular nerves as they exit the thus it produce analgesia of the eyeball and large area of the head.
Dose: -
20-30 ml Lidocaine HCl 2%
3-The Goat .
1-Nerve block for dehorning: -
Anatomy:
The cornual branches of the lacrimal and infratrochlear nerves provide sensory innervation to the horns.The cornual branch of the lacrimal (zygomatico-temporal) nerve emerges from the orbit behind the root of the supra-orbital process covered by thin layer of frontalis muscle and innervates the caudolateral aspect of the horn. The infra-trochlear nerve emerges from the orbit dorsomedially and divided into dorsal corneal branch that innervates thedorsomedial aspect of the horn, and medial frontal branch that innervates the caudomedial aspect of the horn.
Both nerves are covered with orbicularis muscle at the lower part and with frontalis muscle at the dorsal part.
Indications: -
As cattle
Technique: -
The cornual branch of lacrimal nerve is injected close to caudal ridge of the root of the supra-orbital process to a depth of 1.0–1.5 cm in adult goats. The syringe plunger should be withdrawn before injection to check that the tip of the needle has not penetrated the large blood vessel located at this site.
The corneal branch of the infra-trochlear nerve is injected at the dorsomedial margin of the orbit, 0.5 cm deep.
Dose: -
3 ml Lidocaine HCl 2% for each nerve
2-Retrobulbar nerve block: -
As cattle
4-The Dog.
This technique of dental nerve block is no longer be used in dogs as a result of the development of technique of general anesthesia in this species, and when it is used, it is combined with sedatives.
1-Infra-orbital nerve block: -
Anatomy: -
The maxillary nerve derived from the trigeminal nerve that emerges from the cranium through foramen rotundum, passes forwards in the pterygopalatine fossa, and continued in the infra-orbital canal as infra-orbital nerve. The incisors, canines and molar teeth are innervated in the following manner;
| The 1st and 2nd molar teeth | innervated by small branches derived from the main trunk before it inters the canal. |
| The 4 premolars and their alveoli and gum | innervated by filaments derived from the nerve as it passes through the canal |
| The canines and incisors | innervated by branches derived from the nerve as it pass the canal and passes forwards in the maxillary and premaxillary bones |
Technique: -
a-In the pterygopalatine fossa: -
At this point the nerve is blocked at its point of entry to the canal so the whole teeth in the upper jaw in that side will be desensitized. A point 4 cm below the lateral canthus in the space between the posterior border of malar bone and anterior border of coronoid process of the mandible is detected. The needle is inserted in this area and advanced in the soft tissue until its point passes the edge of malar bone then after it is redirected forwards towards the maxillary foramen 3 cm far from the point of insertion. The technique is difficult and risky.
b-In the lower part of the infra-orbital canal: -
It can be preformed through infra-orbital foramen for desensitization of incisors, canines, and first two premolars. This technique is made through the gum over the 3rd premolar tooth at line of reflection of mucous membrane of cheek under which the lip of the infra-orbital foramen can be detected. The needle should be advanced 1 cm in the canal. The technique is easy but the area of desensitization is small.
Dose: -
1-2 ml Lidocaine HCl 2% 2 ml
2-Mandibular nerve block: -
Anatomy: -
It is derived from trigeminal nerve, passes downwards deep to the medial pterygoid muscle and inters the mandibular canal at the mandibular foramen on the medial aspect of the ramus.
| The canines and incisors | innervated by branch derived from the main trunk that passes forwards within the ramus |
| The Molar and premolar teeth | innervated by fibers derived from the main trunk while it stills inside the canal. |
Technique: -
1-Technique I: -
The needle is inserted into the medial aspect of the ramus at the mandibular foramen, and this will desensitize all teeth of the lower jaw on that side. The needle is inserted at the middle of the depression on the posterior part of the ventral border of the ramus, in a right angle to the ventral border of the jaw, close to the medial aspect of the bone, and advanced for 2 cm to reach the mandibular foramen. Generally the technique is difficult to be performed.
2-Technique II: -
The needle is inserted into the anterior part of the mandibular canal through the mental foramen and this will desensitize the lower incisors, canines, and first two premolars on that side.
The mental foramen is injected through the gum immediately beneath the anterior root of the 2nd premolar tooth, and the needle should be advanced 0.7 cm in the canal. Despite the technique is easy but the desensitized area is small.
Dose:
1-2 ml Lidocaine HCl 2% 2 ml
3-Auriculpalpebral nerve block: -
Anatomy: -
The nerve runs caudal to mandibular joint at the base of the ear, gives the anterior auricular nerve and then proceeds as temporal branch along the upper border of zygomatic arch towards the orbit, and finally near the orbit it divides into medial and lateral branches to innervate the orbicularis oculi muscle.
Indications: -
The nerve is a motor nerve runs behind the mandibular joint at the base of the ear and after giving off the anterior auricular branch, it proceeds as the temporal branch along the upper border of zygomatic arch towards the orbit,
Technique: -
The needle should be inserted at the midpoint of posterior 3rd of zygomatic arch, just where the arch can be felt sharply inwards.
Dose: -
2 ml Lidocaine HCl 2%
Indications: -
1-Facilitating eye examination
2-Surgery of the eye
3-Prevention of blinking and squeezing of the eye after intra-ocular surgery
B-Regional Analgesia Of The Limbs…
1-The Horse..
Perineural analgesia of the limb in the horse is used for many purposes either diagnostic or therapeutic.
1-Diagnosis of lameness
2-Surgery of the limb
3-Treatment of certain foot affections like laminitis
Generally speaking, during diagnosis of lameness, perinural analgesia should be applied in systemic manner starting at the lowest branch and the level of analgesia should proceed gradually proximally over the limb till reaching definite diagnosis.
Anatomy:
The medial high volar nerve (palmar/ planter nerve) passes with the vein and artery (VAN) in the groove between the suspensory ligament and digital flexor tendons. At the middle of the cannon bone, the medial high volar (palmar/ planter nerve) sends small branch to the lateral high volar (palmar/ planter nerve) that passes behind the flexor tendons and join the lateral branch at the level of the button of splint bone.
At the fetlock region, every volar nerve (palmar/ planter nerve) divides into three branches named low volar nerves (palmar/ planter digital nerve)) and pass in the same relation to the artery and vein (VAN) but the artery sinks slightly.
1-The anterior branch innervates coronary cushion
2-The middle branch innervates coronary cushion and sensitive laminae
3-The posterior digital branch innervates sensitive laminae and os pedis.
Palmar nerves in the forelimb are continuation of the median and ulnar nerves that fuse at the carpus then separate to form medial and lateral palmar nerves at metacarpal region and downward, while in the hind limb, planter nerves are the continuation of posterior tibial nerve. They have the same anatomical position like the forelimb, but their clinical significance is lower than that of the forelimb, because the digit is innervated by branches from the anterior tibial nerve (deep peroneal) and saphenous nerve.
1-Low volar (posterior digital, palmar/plantar digital) nerve block: -
Technique: -
The needle is inserted at the midway between fetlock and coronet in the groove between the 1st phalanx and the flexor tendon with an angle of 15° with the vertical line and directed downward and inward.
Structures Anesthetized: -
1-Navicular bone
2-Navicular bursa
3-Distal sesamoidean ligaments
4-Deep Digital Flexor tendon and sheath
5-Digital cushion
6-Corium of frog
7-Palmar pastern and coffin joints
8-Palmar distal phalanx / wings of coffin bone
9-Palmar Skin
Indications: -
Sensation remains in the anterior and lateral parts of the foot, so it is used mainly for diagnosis of navicular disease.
Dose: -
2-5 ml Lidocaine HCl 2%
2-Abaxial (basisesamoid) nerve block: -
Definition: -
It is a process through which the medial and lateral high volar nerves (palmar/plantar nerves) are blocked as they pass the abaxial aspects of sesamoid bone, accordingly all the three branches of low volar are anesthetized and all of the structures below the fetlock joint are anaesthetized except for the anterior aspect of the fetlock.
Structures Anaesthetized: -
1-Three phalanges
2-Coffin and Pastern joints
3-Entire corium
4-Entire sole
5-Dorsal branches of suspensory ligament
6-Digital extensor tendon
7-Distal sesamoidean ligaments
Indications: -
1-Diagnosis of laminitis
2-Diagnosis of ring bone
3-Diagnosis of injuries to the soft tissue of pastern
4-Neurectomy of low volar nerve
5-Repair of skin lacerations over anesthetized areas
3-High volar (palmar/planter) nerve block: -
1-Technique I: -
The site of injection is determined 5 cm above the fetlock at the level of the distal enlargements of the 2nd and 4th metacarpal or metatarsal bones, in the groove between suspensory ligament and flexor tendons. The needle is inserted with an angle of 15° with the vertical line and directed downward and inward then the drug is injected. The technique should be used for blocking of both the medial and lateral branches.
Anesthetized area: -
The same as the previous technique
Indications: -
Desensitization of the limb from the fetlock and downward, including pastern and coffen joints for;
1-Diagnosis of lameness of affected limb and opposite one
2-Relieve of pain
3-Performing operative procedures like neurectomy or operative procedures at the foot.
2-Technique II: -
This technique involves two steps
a-Low palmar/planter (low 4-point) nerve block: -
1-The medial and lateral palmar/planter nerves are blocked at the space between flexor tendon and suspensory ligament at the level of distal enlargement of small metacarpal (metatarsal).
2-The medial and lateral palmar metacarpal/planter metatarsal nerves are blocked at the space between suspensory ligament and splint bone at the level of distal enlargement of small metacarpal (metatarsal) where they emerge.
Structures Anaesthetized: -
1-Navicular structures
2-Soft tissue structures of pastern and foot
3-Sole Laminae
4-Three phalanges
5-Distal Digital tendon Sheath
6-Coffin and Pastern
7-Fetlock joint (may be not anesthetized and requires ring block proximal to the fetlock)
b-High palmar/planter (high 4-point) nerve block: -
1-The medial and lateral palmar/planter nerves are blocked at the space between flexor tendon and suspensory ligament below the carpus. It doesn't anesthetise deep structures of metacarpus.
2-The medial and lateral palmar metacarpal/planter metatarsal nerves are blocked at the space between 3rd metacarpal bone and suspensory ligament, and the 2nd and 4th metacarpal bones at the same level of first injection (below the carpus).
As these nerves innervate the interosseous ligaments of 2nd and 4th metacarpal bones, interosseous lateralis and medials muscle, and suspensory ligament, all the deep structures of the metacarpus except for the proximal portion of the metacarpal bone are desensitized.
4-Regional analgesia of distal forelimb: -
For complete desensitization of the limb below the carpus, three nerves should be blocked. Theses three nerves are the median, ulnar, and musculocutaneous nerves. This technique of three nerves block can be used for performing of any surgical interference below the carpus.
Dose: -
10 ml Lidocaine HCl 2% for each nerve
a-Median Nerve Block: -
Anatomy: -
The nerve lies 5 cm below the elbow joint in the groove between the posterior border of the radius and the flexor carpi radialis, hand fist above the chest nut.
Technique: -
The needle is inserted in the mentioned site, and advanced inward and upward with an angle 20° with the vertical line
Indications: -
Indications for median nerve block alone are limited as the desensitized area is little more than that obtained by medial high volar block, however it can be used for median nerve neurectomy.
b-Ulnar nerve: -
Anatomy: -
Ulnar nerve can be located at the center of posterior aspect of the limb about 7 cm above the carpus or accessory carpal bone in the groove between the ulnaris lateralis and flexor carpi ulnaris. It innervates dorsolateral aspect of metacarpus.
c-Musculocutaneous nerve: -
Anatomy: -
Musculocutaneous nerve lies at the medial aspect of the limb on the surface of the radius half way between the elbow and the carpus in front of cephalic vein.
5- Regional analgesia of distal hindlimb (Posterior tibial, peroneal, and Saphenous nerves block): -
Tibial nerve
The tibial nerve lies 15 cm above the point of the hock in the space between Achilles tendon and long digital flexor on the medial aspect of the limb. The nerve becomes palpable closer to the Achilles tendon as the limb is flexed and vice verse. It innervates planter structures of metatarsus and most of the foot.
Tibial block is used for desensitization of the posterior aspect of metatarsus, the medial and lateral aspects of the fetlock, and the whole digit. For complete analgesia down the hock the saphenous, and superficial and deep peroneal nerves should be blocked.
Peroneal (fibular) nerve
The superficial and deep branches of this nerve are best blocked simultaneously in the groove between the tendons of the long and lateral digital extensors about 10 cm proximal to the lateral malleolus of the tibia. First a needle is introduced subcutaneously and 5 ml of the local analgesic solution injected through it to block the superficial nerve. The needle must then be inserted another 2–3 cm to penetrate the deep fascia and about 5 ml of local analgesic solution injected around the deep branch.
Desensitizing the superficial and deep peroneal nerve provides analgesia to the anterolateral tarsal and metatarsal regions and the joint capsule of the tarsus.
Saphenous nerve
Saphenous nerve runs along the saphenous vein on the medial aspect of the limb and it only innervates skin of craniomedial aspect of the thigh to the fetlock joint.
Blocking of tibial, saphenous, and peroneal (superficial and deep branches) nerves will desensitize the dorsal stifle, structures distal the tarsus, and skin of craniomedial aspect of the thigh to the fetlock joint.
Technique: -
The needle is inserted in the mentioned sites
Dose: -
20 ml Lidocaine HCl 2% for tibial
10 ml Lidocaine HCl 2% for saphenous
10 ml Lidocaine HCl 2% for peroneal
2-The Ox..
1-Nerve block in the forelimb: -
Nerve supply of the digits of the ox is much more complex than the horse and for complete analgesia of the digits, 5 points (1, 2, 3, 4 & 5) should be blocked. For analgesia of the medial digit, points (1, 4 & 5) should be injected with analgesic. While for complete analgesia of the lateral digit points (1, 2, 3 & 4) should be blocked.
1-Medial branch of the median nerve can be injected in the grove between suspensory ligament and flexor tendon on the medial aspect.
2-Volar branch of ulnar nerve about 5 cm above the fetlock, and caudal to the suspensory ligament at the same level of dorsal ulnar nerve.
3-Dorsal branch of ulnar nerve about 5 cm above the fetlock on the lateral aspect in the groove between suspensory ligament and metacarpal bone.
4-Dorsal metacarpal (Radial) nerve at the middle of metacarpal bone medial to extensor tendon.
5-Lateral branch of the median nerve and small branch of the ulnar nerve can be injected at the midline just above the fetlock on the caudal aspect of the limb.
For blocking of the medial digit, 1, 4 and 5 points should be blocked, while blocking of the lateral digit requires injection of 2, 3, 4 and 5 points, however the technique is not easy and missing of one nerve block requires re-blocking of all the mentioned sites again, so it is preferred to make ring block rather than perineural injection for surgical interference at the digits.
2-Nerve block in the hind limb: -
A-The tibial and external popliteal (common peroneal) nerve block: -
Advantages: -
1-Only two injections are necessary
2-Injection to soft tissue and at convenient level permits easy application with thin needle, during standing with minimal restraint
3-The nerves can be located by clear landmarks
4-There is moderate interference with the motor function of the limb
5-It avoids complications of injection at the diseased tissue of the digit
6-Most of the lower limb rendered analgesic
Technique: -
1-The external popliteal nerve (common peroneal or fibular) can be blocked behind the posterior edge of the lateral condoyle of the tibia, over the fibula (before it dips down between the extensor pedis and flexor metatarsi muscles for giving off superficial and deep peroneal nerves). Analgesia and motor paralysis of extensor muscles of the digit develope after 5-20 mins.
2-The tibial nerve can be blocked 10 cm above the summit of os calcis on the medial aspect of the limb anterior to Achilles tendon.
Blocking of both nerves induces analgesia from fetlock joint and downward.
Dose: -
20 ml Lidocaine HCl 2% for each nerve
B-Peroneal and plantar metatarsal nerve block: -
Technique: -
1-The superficial peroneal can be blocked, subcutaneously, over the dorsal aspect of the upper 3rd of metatarsus.
2-The deep peroneal nerve can be located in a groove covered with extensor tendons, halfway down the dorsal aspect of metatarsus.
3-The two planter metatarsus nerves can be blocked on both sides like high volar in horse.
Dose: -
5 ml Lidocaine HCl 2% for each nerve of the mentioned 4 nerves
3-The Dog .
1-Brachial plexus block: -
It is a simple method for induction of analgesia of the forelimb, and it causes analgesia and relaxation from the elbow joint and downwards.
Technique: -
With the animal standing, the depression at the center of the triangular area (bounded by the anterior border of supraspinatus muscle, the chest wall, and the dorsal border of brachiocephalicus muscle) is detected. The head is held away, and the 7.5 cm long needle is inserted into of that depression after locating the 1st rib. The needle is guided backwards lateral to the chest wall and medial to subscapularis muscle until its point is judged to be at the level of scapular spine.
Dose: -
2 ml Lidocaine HCl 2%
Complications: -
1-Hematoma
2-Acedintal intravenous injection of the drug
3-Infection of the axilla
4-Damage and neuritis of the plexus
5-Penetration of the thorax
2-Infiltration of digital nerves: -
These nerves are injected subcutaneously, medial and lateral to the 1st phalanx of each digit, with 2 ml Lidocaine HCl 2%.
C-Regional analgesia about the trunk...
1-The Horse..
1-Analgesia for castration: -
Local infiltration of the scrotum and direct injection of up to 20 ml Lidocaine HCl 2% into the testicle itself
2-The Ox..
1-Paravertibral nerve block: -
It is a perineural injection of spinal nerves as they emerge from the vertebral canal through the inter-vertebral foramina. This technique is commonly used to provide analgesia for laparotomy (rumenotomy or caesarian).
Advantages: -
1-Short post-surgical convalescence period
2-Lower amount of local analgesia can be used
3-Complete and uniform desensitization of the abdominal wall and peritoneum
4-Relaxation of the abdominal muscles with reduction of intra-abdominal pressure
5-It over comes the disadvantages of inverted-L block and linear infiltration
Anatomical and physiological consideration
The area of the flank bounded cranially by the last rib, caudally by the angle of the ilium and dorsally by the lumbar transverse processes, is innervated by the thirteenth thoracic and first and second lumbar nerves. In addition, the third lumbar nerve, although it does not supply the flank, gives off a cutaneous branch which passes obliquely backwards in front of the ilium. Operations involving the ventral aspect of the abdominal wall will require additional desensitization of the dorsal nerves cranial to the thirteenth thoracic. The last thoracic and first lumbar intervertebral foramina in cattle are occasionally double. The last thoracic foramen lies immediately caudal to the head of the last rib and on a level with the base of the transverse process of the first lumbar vertebra. The lumbar foramina are large and are situated between the base of the transverse processes and approximately on the same level. The spinal nerves, after emerging from the foramina, immediately divide into a smaller dorsal and a larger ventral branch. The dorsal branch supplies chiefly the skin and muscles of the loins, but some of its cutaneous branches pass a considerable distance down the flank. The ventral branch passes obliquely ventrally and caudally between the muscles and comprises the main nerve supply to the skin, muscles, and peritoneum of the flank. The ventral branch is also connected with the sympathetic system by a ramus communicans. Paralysis of the nerves at their points of emergence from the intervertebral foramina will provoke desensitization of the whole depth of the flank wall and complete muscular relaxation. Block of the rami communicantes will result in splanchnic vasodilatation and potential for hypotension.
The number of nerves to be blocked will depend on the site and extent of the proposed incision. For rumenotomy, using an incision parallel with and about 7 cm caudal to the last rib, analgesia of the thirteenth thoracic and first and second lumbar nerves is required. While for a more caudal incisions the first three lumbar nerves should be blocked as in caesarian section in the flank region.
Technique: -
I-Proximal Paravertebral analgesia
The more accurate location of the nerves might be obtained by directing the needle towards the cranial border of the transverse process of the vertebra behind the nerve to be blocked. For example, to block the 1st lumbar nerve the needle should be directed to strike the cranial border of the 2nd lumbar vertebra about 5–6 cm from the animal’s midline.
To block the thirteenth thoracic and first, second and third lumbar nerves skin weals should be raised in line with the most obvious parts of the transverse processes of the second, third and fourth lumbar vertebrae, 5–6 cm from, the midline of the body. Location of the transverse process of the first lumbar vertebra is usually difficult (particularly in well-muscled or obese animals) so in most cases the site for infiltration around the thirteenth thoracic nerve is found by simple measurement. The distance between the skin weals over the second and third lumbar transverse processes is measured and another skin weal is produced at a distance equal to this, cranial to the anterior weal, to mark the site where the needle is to be introduced to strike the cranial border of the first lumbar transverse process.
A long needle (10cm long, 2 mm bore) is inserted through each skin weal and the underlying longissimus dorsi muscle, and advanced to strike the anterior border of the transverse process. Each needle is then redirected cranially over the edge of the transverse process and advanced until it is felt to penetrate the intertransverse ligament. Injection of 15 ml of local analgesic solution is made immediately below the ligament and a further 5 ml is injected as the needle is withdrawn to just above the ligament. During final withdrawal of the needle the skin is pressed downwards to prevent separation of the connective tissue and aspiration of air through the needle.
Successful infiltration around the nerves is indicated first by the development of a belt of hyperaemia which causes a distinct and appreciable rise in skin temperature. Full analgesia develops in about ten minutes. When a unilateral block is fully developed it produces a curvature of the spine, the convexity of which is towards the analgesic side.
II-Distal Paravertebral analgesia
The needle is inserted ventral to the tips of the respective transverse process. 20 ml of local analgesic solution is injected in a fan-shaped infiltration pattern. The needle is then completely withdrawn and reinserted dorsal to the transverse process, in a slightly caudal direction, where approximately 5ml of the analgesic solution is injected
Disadvantage of Paravertebral nerve block
a- failure or at least partial failure may be due to:
The nerve trunk is situated at a depth of 5-7cm from the surface of the body.
The nerves pass obliquely and in some animals the nerve roots are double emerging from double foramina.
Penetration of the muscular mass of the back tends to cause spasmodic contraction of the muscles with consequent modification of the needle direction.
b- Slightly difficult to perform.
c- Paralysis of back muscles.
Complications:
Potential for penetration of the aorta.
Potential for penetration of the thoracic longitudinal vein or vena cava.
2-Pudic or internal pudendal nerve block: -
This nerve is blocked for induction of protrusion of the penis by a method other than epidural analgesia to avoid the disadvantages of epidural in large or heavy bulls.
Technique: -
After location of the nerve per rectum, in the sacrosciatic foramen, the needle is introduced via the ischiorectal fossa medial to the sacroisciatic ligament, and is directed forwards and downwards for 7 cm.
Dose: -
30-40 ml Lidocaine HCl 2% (20-25 at the mentioned site and 10-15 slightly behind)
Disadvantages: -
1-The success rate of this technique is 66%.
2-The onset can be delayed as late as 30-45 minutes.
3-Some bulls may show protrusion of the penis as long as 24 hours post injection.
3-Local analgesia for castration: -
A-Surgical castration: -
The site of the proposed incision in the scrotum may be rendered analgesic by local or subcutaneous infiltration, however this will not block the nerve fibers in the spermatic cord. Accordingly, these fibers can be rendered analgesic by one of the following;
1-Direct injection of 10 ml Lidocaine HCl 2% into each cord at the neck of the scrotum
2-Direct injection of 5-25 ml Lidocaine HCl 2% into the testicle itself. Accordingly the drug will pass through the lymph, diffuses, and blocks the fibers in the spermatic cord.
B-Bloodless castration: -
For induction of bloodless castration by Burdizzo, both local infiltration at the skin of scrotal neck and direct injection into the spermatic cord should be performed.
3-The Small Ruminants .
1-Paravertibral nerve block: -
It can be performed as with cattle, and each nerve is blocked by 7 ml Lidocaine HCl 1% (5 ml below the inter-transverse ligament and 2 ml above it).
2-Pudendal nerve block: -
Anatomy: -
The anterior tuberosity of tuber ischii is used as fixed point, and the length of sacro-tuberous ligament is used as a radius. This distance is used to establish a site on a line parallel to the midline in front of the fixed point. A finger is introduced through the rectum for detection of the lesser sciatic foramen, and the needle is inserted at the previously mentioned point. The penis will protrude 5 minutes post injection.
Dose: -
7 ml Lidocaine HCl 2%
3-Local analgesia for castration: -
1-Direct injection of 2-10 ml Lidocaine HCl 1% into the testicle itself, followed by local subcutaneous infiltration at the line of incision.
2-Other methods mentioned in cattle.
4-The Dog..
1-Paravertibral Block: -
The last three thoracic and the 1st four lumbar nerves should be blocked to produce analgesia and relaxation of abdominal muscles; accordingly it can be used with light general anesthesia. This technique can be used bilaterally to induce complete relaxation of abdominal muscles, however, disadvantage of this technique is time consuming, and its advantage is there is no need for muscle relaxant and artificial ventilation.
Dose: -
Lignocaine HCl 1 % 2 ml
II-Spinal Analgesia.
Spinal analgesia is a special type of regional block comprising the injection into some part of the spinal canal of a local analgesic solution. By coming into contact with the spinal nerves the drug temporarily paralyses them and gives rise to loss of sensation in those parts of the body from which the sensory portion of the nerves carries impulses and, when more concentrated solutions are used, paralysis of those parts supplied by the motor fibers. It is divided into two distinct types:
- Epi- (extra-) dural injection: in which the needle enters the spinal canal but does not penetrate the meninges, and the injected solution permeates along the spinal canal outside the dura mater.
- Subarachnoid injection: in which the needle penetrates the dura mater and the arachnoid mater so that the analgesic solution is introduced directly into the cerebrospinal fluid.
Anatomical consideration
The spinal cord lies within the spinal canal and is covered by three membranes, the dense dura mater, the arachnoid mater and the delicate pia mater. The wall of the spinal canal is formed by the vertebral arches and bodies, the intervertebral discs and the intervertebral ligaments. The tubelike canal is somewhat flat in the lumbar region. The spinal cord and dura mater end at the lumbar enlargement and the canal itself tapers off caudal to this enlargement to end in the 4th or 5th coccygeal vertebra. In each vertebral segment the canal has lateral openings between the vertebral arches, the ‘intervertebral foraminae’, through which pass blood vessels and the spinal nerves. In the cranial cavity the dura mater is arranged in two layers, the ‘periosteal’ and ‘investing’ layers. The outer layer forms the periosteum of the inner surface of the cranial bones and in the spine acts as the periosteum lining the vertebral canal. The investing layer is continued from the cranium into the spinal canal but at the foramen magnum is firmly adherent to the margins of the foramen where it blends with the outer or periosteal layer. Between the two layers in the spinal canal is the ‘extra-’ or ‘epidural’ (perhaps more strictly the ‘interdural’) potential space.
1- Epidural analgesia
It is now customary to classify epidural spinal blocks as caudal and lumber epidural, according to the site of injection.
A-Caudal Epidural: -
1-The Ox..
It is a process through which the analgesic solution is injected between the two layers of dura matter and affects the terminal nerves or cauda equina thus producing analgesia of the posterior part of the animal. The term anterior and posterior epidural analgesia is related to the dose of injected analgesic solution and not to the site of injection.
1-Posterior epidural: -
It is characterized by no affection of the motor function of the hind limbs, but analgesia or loss of sensation can be observed over the tail, croup as far as the mid-sacral region, the anus, vulva, perineum, and posterior aspect of the thighs. Paralysis of motor fibers predisposes to relaxation of anal sphincter and ballooning of posterior part of the rectum. Defecation will be suspended and stretching of the vulva provokes no response. The vagina will dilate and straining, during parturition, ceases without affecting uterine contraction.
2-Anterior epidural: -
It shows some degree of interference with motor function of the hind limbs. This will vary from partial paralysis of stifle flexors, and flexors and extensors of hocks and digital joints, to complete paralysis. In coordination may predispose to injury to the animal or the workers. Loss of sensation spreads forwards, according to the dose; over the croup; between hind limbs till the inguinal region, scrotum, and prepuce; over the hind limbs; mammary gland; and finally flanks and abdominal wall till the umbilicus.
As the drug blocks the sympathetic outflow of the thoracic and lumbar segments, hypotension will occur and the normal compensatory mechanism (tachycardia) will be affected as the cardiac accelerator nerves will be blocked so the heart rate will not be increased to compensate the hypotension.
This hypotension has the advantage of lowering the chance of bleeding during surgery but on the other hand, minimal loss of blood threatens the animal life.
Seat of injection: -
Seat of injection is the first intercoccygeal space between the 1st and 2nd coccygeal vertebra. The dimensions of the opening in the dorsal wall of the neural canal are 2 cm transversely, 2.5 cm anterior-posteriorly, and 0.5 cm deep. The canal is 2-4 cm deep from the skin surface.
Technique: -
The needle is inserted with 15° degrees with the vertical. When the needle reaches the accurate site, there will be no resistance for injection, and suction of the drug from the hub of the needle can be seen.
1-The tail is gripped 15 cm from its base and raised in pump-handle fashion. Seat of injection is the 1st obvious articulation behind the sacrum.
2-Standing on one side of the animal and observing the line of the croup, the prominence of the sacrum is seen. Moving the eye back towards the tail, the next prominence to be observed is the spine of the first coccygeal bone. The site is the depression immediately behind it.
3-The caudal prominence of the tuberosity of the ischium is palpated and the point selected 10–11 cm in front of it. A line drawn directly over the back from this point passes, in a medium-sized animal, through the depression between the first and second coccygeal spines.
Dose: -
1-posterior block: -
| a-Procaine HCl 15-20 ml 1%. 10-15 ml 2%. 5-10 ml 3-5%. | b- Lidocaine HCl 5-10 ml 2% |
2-Anterior block: -
| a-Procaine HCl 40 ml 3% (mastectomy) 170 ml 1% or 120 ml 1.5% (digit amputation) 45 ml 2% (caesarean) | b-Lidocaine HCL 60-100 ml 2% (difficult obstetrical interferences)
120 ml 2% (caesarean) |
Onset and duration: -
a-posterior block: -
Paralysis of the tail can be observed after 1-2 minutes, the maximal effect appears after 10-20 minutes, and lasts for 60 minutes, and the animal becomes normal again by the end of 120 minutes.
b-Anterior block: -
Paralysis of the tail can be observed after 1-2 minutes, the maximal effect appears after 10-20 minutes, and the animal will be unable to rise for 120 minutes, and in coordination may persist for up to 3-4 hours
Indications: -
1-posterior block: -
a-Obstetrics: -
1-To overcome straining for correction of mal-presentation, or for simpler embryotomy
2-Operative treatment of parturient injuries
3-Reduction of prolapsed uterus or vagina
b-General: -
1-Surgical operations of the tail
2-Surgical correction of tears of vulva or perineum
3-Examination of the vagina or external cervical os
4-Protrusion of the penis
2-Anterior block: -
a-Obstetrics: -
1-To overcome straining during extensive embryotomy
2-Amputation of gangrenous prolapsed uterus
3-Caesarian section
b-General: -
1-Surgery of penis
2-Cutting operations about the prepuce or inguinal region
3-Amputation of the udder
4-Castration
5-Surgery of hind limb like amputation of digit
Disadvantages: -
1-Fracture of the animal pelvis, and injury to workers, or veterinarian (anterior block)
2-Infection of the nervous system
3-Hypovolumic shock due to involvement of vasomotor nerve fibers and pooling of blood in the venous side with absence of compensatory tachycardia (anterior block)
4-Asphyxia due to paralysis of phrenic nerve
5-Twisting of the tail few days or even permanent paralysis after injection due to injury of nerve fibers innervate the tail
2-The Buffaloes..
The needle is inserted downwards and forwards in the sacrococcygeal with an angle 45º with the vertical.
3-The Horse..
The technique is not common in equine as in bovine because the indications for such technique in equine are not frequent and the detection of site of injection is more difficult.
Seat of injection: -
Seat of injection is 1st inter-coccygeal space in horse and 2nd inter-coccygeal space in donkey. The depth of the canal is 4-8 cm.
Technique: -
The needle is inserted forwards and downwards with a right angle with the contour of the croup (30° degrees with the vertical) and this technique (A) is easier than the other technique (B) where the needle is inserted at the posterior part of intercoccygeal space with an angle of 60° with the vertical to permit gliding of the needle along the floor of the neural canal. The intercoccygeal space can be detected by;
1-A line drawn connecting the hip joints and intersects the midline at the level of the sacrococcygeal joint caudal to which the dorsal spine of the 1st coccygeal bone can be felt. The needle inserted into the depression directly caudal to this point.
2-The space is opposite the caudal fold formed on each side of the tail when raised.
Indications: -
1-posterior block: -
a-Obstetrics: -
1-To overcome straining during manipulative correction of simpler forms of mal-presentation
2-Partial embryotomy
b-General: -
1-Amputation of the tail
2-Operations about the anus, perineum, or vulva
3-Operation for rectal prolapse
4-Caslick operation for wind sucking
2-Anterior block: -
Because of the great risk of injury during recovery, there is no place for this technique in the horse. Anterior block to the level of costal arch requires 100-150 ml lignocaine 2%. With this large amount of drug, any signs of hypotension require rapid transfusion of fluid and administration of vasopressors. Accordingly general anesthesia is superior to anterior epidural in this species.
a-Obstetrics: -
Obstetrical difficult manipulative repositions and extensive embryotomy
b-General: -
Scrotal hernia and cryptorchidism
Dose: -
1-posterior block: -
| a-Procaine HCl 2% 5-15 ml (amputation of the tail) 10-25 ml (perineal and vulvar operation) 15-30 ml (obstetric manipulation) | b- Lidocaine HCl 2% 10 ml |
2-Anterior block: -
| a-Procaine HCl 50-120 ml 1% (severe obstetrical interferences) 30-80 ml 2% (cutting operation) | b- Lidocaine HCl 2% 100 -150 ml (analgesia of hind limbs to the costal arch) |
4-The Sheep..
Seat of injection: -
Sacrococcygeal space
Dose: -
3-4 ml 2% lignocaine HCl (intravaginal obstetrical procedures)
1 ml 2% lignocaine HCl (docking of lambs)
Indications: -
1-Intravaginal obstetrical procedures
2-Relief of painful conditions of vagina and rectum that provoke severe straining
5-The Dog..
Seat of injection: -
Sacrococcygeal or 1st intercoccygeal space
Dose: -
1 ml 2% lignocaine HCl
Indications: -
Docking of tail
B-Lumbar epidural analgesia: -
1-The Ox..
Injection of analgesic solution into the epidural space in the caudal region (caudal epidural) affords very save method of inducing epidural analgesia, but sometimes it is not easy to produce satisfactory anterior block via this site. The lumbar epidural analgesia through the anterior lumbar region or lumbosacral spaces, affords a belt of analgesia around the trunk of the animal without affecting the motor function of the hind limbs.
Seat of injection: -
Seat of injection is just to the right of the lumbar spinous process of the 2nd lumbar vertebra, 1.5 cm caudal to the anterior edge of the second lumbar transverse process.
Dose: -
10 ml Procaine HCL 4% (15 ml weakens the hind limbs- 20 ml the animal lie down)
10 ml Lidocaine 2%
Indications: -
This technique is used for induction of flank analgesia for rumenotomy or caesarian.
2-The Sheep..
Seat of injection: -
Lumbosacral space to avoid puncturing of the meninges. It is located just behind the spinous process of last lumbar vertebra that lies at a point of intersection between line drawn to connect the anterior borders of the two illiums and midline.
Technique: -
The needle is inserted in the mentioned space with an angle 10° anterior and 15° lateral with the vertical.
Dose: -
8-15 ml Lidocaine 1%
Indication: -
Intra-abdominal, pelvic, or hind limb surgery
3-The Dog..
Seat and technique: -
Lumbosacral space as sheep
Dose: -
0.5 ml/Kg Lidocaine 1%
Indications: -
1-Posterior abdominal (hysterectomy, or cystotomy) or inguinal surgery
2-Treatment of hind limb fracture