Clinical: Farm Animal Local Blocks Flashcards
Indications for horn blocks:
- dehorning/disbudding
- horn injury
- inappropriate horn growth
Cornual n. block
- branch of lacrimal n. which is a branch of opthalmic division of trigeminal n.
Horn blocks in adults
- cornual branch of intratrochlear n., branch of trigeminal
- frontal n., branch of supraorbital n.
- nerves are close enough together than if one n. is blocked, the other is likely to be blocked
- Cutaneous branches of cervical n. –> SQ infiltration around the horn
Local anaesthetics for horn blocks?
2% lidocaine 5-10 mls (cascade)
Procaine + adrenaline (Adrenacaine)
Also give NSAID
Complications w/ horn block?
- block not 100% effective (variation in path of n., inaccurate assessment of depth, pass thru apneurosis of temporalis m. caudal to ridge –> no analgesia, misplacement of needle)
- pain on injection –> mvmt of animal –> misplacement of agent
Horn blocks in goats differ from cows by…
- wider n. supply to horn
- horn base is larger
Risk of doing horn block in neonate goat?
- immature resp & CV systems
- easily become hypothermic
- risk of hypoglycaemia
- sensitivity of alpha-2 agonists
Cornual branch of zygomaticotemporal block in goats
- laterally located behind caudal ridge of supraorbital process
- halfway btw lateral canthus & lateral edge of base of horn
- 2% lidocaine, 2-3 ml or adrenocaine 1-1.5 cm deep w/ 22-25 G needle
Cornual branch block of infratrochlear nerve in goats?
- medial, dorsomedial margin of orbit
- 2% lidocaine, 2-3 ml or adrenocaine 22-25G needle at 0.5 cm depth
Retrobulbar block indications
- enucleation sx
- corneal sx
Drugs for retrobulbar block?
- 10-15 ml 2% lidocaine (Cascade)
- Procaine (Adrenacaine) - Licensed
Retrobulbar block anaesthetises
cornea
lid (upper/lower)
Technique of Retrobulbar block
- 4-point (upper & lower lids 12/6 o’clock, lateral/medial canthus 3/9 o’clock)
- 1-point
Signs of satisfactory retrobulbar block
- corneal analgesia
- mydriasis
- proptosis
Complications of a retrobulbar block
- Penetration of the globe
- orbital haemorrhage
- damage to optic n.
- oculocardiac reflex
- inj into optic n. meninges
- inj into systemic circulation
Peterson block is used for
Anaesthesia of the eye in cattle
Peterson eye block desensitizes the nerves responsible for…
- sensory & motor fxn of all structures of the eye, except the eyelid
- Nerves: oculomotor, trochlear, abducent, trigeminal n.
Landmarks for Peterson eye block
- Cranially: supraorbital process
- ventrally: zygomatic arch
- Caudally: coronoid process of the mandible