Anaesthesia Flashcards
Approx tidal volume for adult cattle, small ruminants & pigs
Cattle- 8-12ml/kg
Small ruminants - 5-7ml/kg
Pigs 10-20ml/kg
Location & technique for the Peterson block
What nerves are desensitised?
Needle inserted in the gap formed caudal to the orbit between it and the coronoid process of the mandible.
Use 18g 3.5” needle advanced into the pterygopalatine fossa toward the foramen orbitorotundum to a depth of 7 -10 cm, depositing 15ml of 2% lidocaine
Desensitises oculomotor, trochlear, and abducens nerves and the trigeminal nerve (ophthalmic, maxillary) (shouldn’t block mandibular but some conflicting text)
Safer than RB block & should rx in desentitisation of all occular structures except eyelid motor func (req auriculopalpabral block CN VII).
Can inadvertently desensitise optic nn
Decr risk of hemorrhage, penetration of the globe, damage to the optic nerve, or injection into the meninges vs retrobulbar block
Techniques of retrobular blockade
4 point - needle inserted medial & lateral canthus, & dorsal & ventral orbital rims w 3.5” curved 18g spinal needle. Will desensitise all EOM & optic nn. 15ml between 4 sites
Care re inadvertent possible damage to the globe, intraneural or meningeal injection, retrobulbar haemorrhage, or damage to the optic nerve
Supra-orbital fossa - not mentioned but presumably can do same as in horses
Purpose for & site for auriculopalpaebral block
Site: rostral to the base of the ear over the zygomatic arch. Should be palpable here. Suggest 10-15ml (1-2 in horses…?)
Desensitises the AP nn - branch of CN VII which provides motor function to the upper lid
Local anaesthesia techniques for abdominal sx in ruminants
1) Line block - along proposed incision
2) Inverted L - parallel to last rib & horizontally under transverse processes
3) Proximal paravertebral -
4) Distal paravertebral
Technique for proximal paravertebral block
Aims to desensitise spinal nerves T13, L1 & L2 which supply skin, mm peritoneum in the flank.
- Palpate L5, just cranial to tuber coxa
- Count forward to L1
- Bleb local skin/sq w 1” needle at injection sites
- 20g 10cm needle used 3-5cm off midline perpendicular to the transverse process.
- Needle ‘walked off’ the cranial edge of L1 & advanced approx 0.75cm through the intertransverse ligament (felt as a pop). 10ml lido placed here &5ml dorsal to lifgament on the way out. This desensitises dorsal & larger ventral branches of T13
- Process repeated off cranial edge of L2 for L1 nn & L3 for L2nn
Will see vasodialtion & temporary deviation of the spine dt mm relaxation.
Care re further caudal - L4 site of nn root exit for HL
Technique for distal paravertebral block
Desensitises T13, L1 & L2 at the proximal & distal portions of TP of L1, L2 & L4 (since the nerves run caudally).
18g needle inserted under each TP - 10ml local instilled, then additional local fanned cranial & caudal. Then withdraw & direct dorsal to TP to desensitise dorsal branch.
Upto 25ml per site used in cattle (2% lido)
Care re sheep - don’t exceed 6mg/kg. 2mg/kg recommended
(Image from techniques in LA sx)
Location for epidural
CRANIAL - lumbosacral
CAUDAL: Sacrococcygeal or 1st intercoccygeal space. Spinal cord not present at this site
Methods of teat desensitisation
Ring block: An elastic band (tourniquet) may be placed around the base of the teat. 25g needle, 5-6 mL lido infiltrated around the teat. Gentle massage will facilitate diffusion into deeper tissues
Cistern Infusion: For procedures affecting the mucous membrane lining of the teat, such as polyp removals or opening of spider teats, an infusion into the teat cistern of approximately 10mL of local w a teat cannula is usually sufficient to provide anaesthesia. A tourniquet needs to be applied to the base of the teat to prevent any milk diluting the local anaesthetic solution
IV regional anaesthesia: After a tourniquet is placed at the base of the teat, any superficial vein can be catheterised and infused with approx 5-7mL lido; will anaesthetise entire teat distal to the tourniquet.
