Flashcards in Equine anaesthesia Deck (80)
Does inhalation or IV anaesthesia carry the greatest risk of death?
inhalation because these are most often used for long duration anaesthesia which are the most risking.
What must be considered when anaesthetising a horse?
In Europe, horses are considered food animals.
What do you do if you want to do a procedure under sedation and LA but the horse is too excited?
Horse will not sedate well --> come back another day or use GA
Name 2 drugs that can be used to sedate a horse.
- PHENOTHIAZINES - Acepromazine
- ALPHA-2 AGONISTS - xylazine, detomidine and romifidine
Outline acepromzaine as a sedative - effects, ROA, combinations, side effects, CIs
- on own produces limited sedation
- calms horse and makes other procedures possible (clipping)
- ROA = IV, IM, oral and transmucosal
- COMBINE - opioids to give better sedation
- EFFECTS - hypotension
- CONTRAINDICATIONS - hypovolaemia, stallions (priapism risk), competition (abuse)
What is the effect of acepromzaine on volatile agent
considerably reduces dose and easier to maintain stable anaesthesia
What are the mainstay of equine sedation?
alpha 2 adrenoceptaor agonists (xylazine, detomidine and romifidine)
Outline alpha 2 agonists as a sedative - effects, side effects and ROA
- deep sedation is dose related to a maximum
- horse can still kick under deep sedation (adding a low dose opioid reduces this risk)
- SIDE EFFECTS (major) - bradycardia, decreased CO due to a biphasic BP change, hyperglycaemia, increased urine productine, gut atony, ecbolic (xylazine especially)
- ROA - IV or IM or sublingual gel (detomidine)
What are the differences between the alpha 2 agonists? 3
1.) extent of ataxia - romifidine the least
2.) duration of action - short xylazine, detomidine and romifidine (longest)
Is medetomidine licensed in horses?
NO - nevertheless it is used widely as an infusion during anaesthesia. Given on its own --> severe ataxia --> falling
Can all alpha 2 agonists be given with opioids in horses??
Yes (beware increased ataxia with romifine and) and/or to horses which have already received low doses of acepromazine (a phenothiazine).
T/F: opioids alone sedate horses
False (however a low dose of an opioid increases the depth of sedation of both phenothiazines and alpha 2 agonists), reduces touch response but can increase ataxia. This is not an analgesic dose.
T/F all sedation (except Mg) is banned in equine competition
What sedative can be used for horse box rest?
Out of competition, low dose acepromazine can be very effective without obvious sedation. In USA - a very long acting phenothiazine. Alpha-2 agonists tend to sedate too much. Reserpine used to be used, nasty side effects.
What should you consider when doing local anaesthesia of horse limbs?
consider if you want full weight on affected limb
Outline different analgesics in horses - 4
- local vs. epidural
- alpha 2 agonists
Outline NSAID use
excellent analgesia, especially as swelling often causes pain. High dose (flunixin) can mask surgical colic. BEWARE overdose toxicity is mainly colitis/chronic ulceration --> diarrhoea
Outline opioids use
- controversion - balance analgesia and excitement properties.
- BEWARE - gut effects can cause impacted colic, sedative reduce or prevent excitement effects
OUtline examples of opioids and ROA
- BUTORPHANOL - L, widely used, limited analgesia
- PETHIDINE (meperidine) L, antispasmodic for gut so useful in spasmodic colic,
- ROA = ONLY by IM injection - occasional dramatic anaphylactic reactions if given IV.
Outline alpha 2 agonist use
as for other species good analgesia but associated with sedation which may not be wanted, useful for anaesthesia and epidural protocols
Outline epidural analgesia
- easy to perform caudal analgesia - care (especially local and xylazine) --> ataxia, recumbency. For non-surgical a combination of detomidine and morphine is popular (detomidine works quickliy, morphine slow onset - several hours but long action. Morphine epidurally --> pruiritis..
How are longer surgeries maintained under anaesthesia?
volatile agents is most usual, although recently a few TIVA methods are becoming practicable.
How long does a horse need to be starved?
controversial - classically 8-12 hours - probably 2-4 hours sufficient.
Where should you place an IV catheter as a premed?
Outline preoperative preparation - 6-
- place IV catherter - jugular
- pre-op analgesia as relevant
- remove shoes
- AB/anti-tetanus (as relevant)
- wash out mouth
Name 3 potential IV accidents
- SC injection of irritant drugs
- intracarotid injection
- air embolism
- jugular thrombosis (esp guiaphenesin).
Outline a normal premed protocol
Acepromazine (long acting and reduces anaestheic death by half) followed LATER by (as part of induction combination) an alpha 2/ butorphanol PLUS further analgesia as required.
Name 3 ways a horse can be controlled during anaesthetic induction
- free fall
- padded gate
- tilting tables
What is the most common IV induction technique?
Ketamine based techniques