Anaesthesia for Colt Castration Flashcards
How do you make the decision for a standing or a GA castration:
- Small pony/shetland
- Mature large breed horse
- Donkey
- Large inguinal ring
- Testicle retained in inguinal canal
- Hisotyr of soft fluctuant swelling of testes
- Other structures palpable in scrotal region
- Horse persistently kicks despite sedation/ill behaved
- Facilities and cost?
- Small pony/Shetland
- Standing
- Mature large breed horse
- Standing
- Donkey
- Standing
- Large inguinal ring (fits > 3 fingers)
- Recumbent because you want to close the inguinal ring
- Testicle retained in inguinal canal
- Recumbent to reach the teste
- History of soft fluctuant swelling of testes
- Standing
- Other structures palpable in scrotal region
- Depends on what it is.
- Horse persistently kicks despite sedation/ ill behaved
- Recumbent
- Facilities & cost….
- Standing
What should we do as part of out pre-op evaluation for a castration?
- Perform a full clinical examination
- Check for any history of scrotal swelling
- Palpate carefully for any evidence of a scrotal hernia
- Palpate the size of the inguinal ring
- Talk to the owner re standing open technique vs a GA & closed technique
- The owner should make an informed decision
- The owner must sign a consent form
Name some alpha 2 agonists used in horses
xylazine, detomidine, romifidine
What sedation can be used for a standing surgical anaesthesia for a castration?
- Usually involves an alpha 2 agonist
- (xylazine, detomidine, romifidine) im or iv
- Can precede with acepromazine
- Licenced IV or gels for oral use
- Can also combine the alpha 2 agonist with an opioid (buprenorphine or butorphanol)
- Detomidine and butorphonal is preferred for sedation
- Using this combination
- Domeseden paste
- Can use moderate and profound sedation
- 0.5ml dom and 1ml torb for all horse >200kg
- Can adjust dom for size of the horse
- It is rare, but castration can be performed in colts with local infiltration and application of a twitch
What other drugs could be given at the time of sedation of the horse?
- NSAIDS
- Antibiotics
- Local anaesthesia
- Tetanus antitoxin 6000 -10,000 iu
In terms of sedation in horses for castration, what are some contraindications for drug combinations?
- ACP causes priapism that can result in paraphimosis
- ACP makes they sway
- Poor sedation: either asleep or awake
- No analgesia
- Don’t use alpha two and butorphonal in colic, heart or liver conditions, with sulphonamides
- Horses on alpha two agonists and butorphonal
- Makes them piss everywhere
- Deeper sedation.
- Use for profound sedation
- Increase dose increases duration and not the depth of sedation
never use TMPS IV and alpha 2 sedative
When injecting LA for a castration, where do we inject it?
- Testicle
- Cord
- Subcutaneously
What local anaesthetics are licensed in the horse?
- Mepivicain hydrochloride
- Lidocaine hydrochloride
- Procaine hydrochloride
- Adrenaline is in some preparations: quicker onset, some analgesia and longer duration analgesia
- Proceed to perform open castration once LA has taken effect
What are some common complications of a castration?
- nsufficient sedation
- Other post op complications
- Swollen scrotal tissue
- Ometum/vaginal tunic/intestinal protrusion
- Haemorrhage (during and post op)
How much bleeding do you tolerate in a castration?
- Not significant bleed if you can count the drops of blood.
- Haemorrhage should decrease and finish a few mins after surgery
How do you find a bleeding vessel?
- Need to determine where the blood is coming form: vaginal tunic or the scrotal vasculature. If the testicular artery is bleeding the blood comes from the tunic.
- Severe haemorrhage may also originate from branches of the external pudendal vein if these are inadvertently lacerated during castration.
- Pack the scortum with sterile gauze
- Isolate the stump of the spermatic cord
- Locate the edge of the vaginal tunic and then fixing it with two tissue forceps create a funnel into which a long pair of artery forceps or whelping forceps can be inserted.
- The first forceps can be used to withdraw the stump of the cord to allow more accurate placement of a second pair of haemostats if the stump cannot effectively be ligated. Leave the forceps in for 24hrs.
Can you re-sedate the horse during a castration?
Re sedating the horse using alpha two agonists and opioids increases duration of sedation and not the depth.
What do you do if you cannot locate the bleeder?
- GA in indicated to enavble adequate exploration of the inguinal canal so that the stump of the spermatic cord can be located.
- Haemorrhage of unidentifiable origin usually occurs form the spermatic cord that has retracted through the inguinal canal.
What are the differences between field conditions and theatre - with a GA castration?
- Sterility: less sterile in the field
- Monitoring: less in the field
- Duration limitation (TIVA vs inhalant): duration of sedation affected by dose of sedation so limited duration. Not going to be able to have inhalants- issues with supply and scavenger.
- Support: less support in the field
- Recovery: cannot monitor recovery as well in the field
- Cost: cheaper in the field
How do we prepare for a GA castration?
- Pre-operative clinical examination
- Premedication
- Considerations similar to SSA
- Drugs, what do you want to use? See above for sedation
- IV catheterisation (position, direction, type)
- Positioning & padding
- How will you maintain anaesthesia?
- Equipment
- Surgical
- Anaesthesia
Give an example of a GA in the field for a castration including drugs and maintenance of anaesthesia?
What are some considerations for a donkey castration?
Is a sedation or GA easier?
- Timing, train donkey to walk in hand
- Conduct thorough pre op examination, consider doing haem & biochem (why?)
- FOC bloods at donkey sanctuary
- Tetanus status, ABs, NSAIDs
- Consider care of any companion donkey
- Sedate, place, IV catheter
- Difficult to do SSA in many
- GA easier
What can we use for IV access and premed in a donkey?
- More difficult to secure
- May need to sedate donkey first
- Acepromazine 0.03mg/kg
- Occasionally have to use veins in ears
- Weigh
How can we induce a donkey for a castration?
As for colt
Alpha 2 followed by ketamine
Top ups with ketamine (& alpha 2 if nec)
Donkey ‘triple drip’ also possible
Intubation, need selection of smaller ET tubes
In donkeys and NSAIDs - which ones require more frequent dosing?
More frequent dosing required of phenylbutazone, flunixin, ketoprofen
Which NSAID is metabolised slowed in donkeys than in horses?
Carprofen metabolised slower than in horses
How does the half life of meloxicam differ in donkeys compared to horses?
Meloxicam 1/10th half-life compared to horses
Which drug(s) are contraindicated in a stallion undergoing castration?
None
Some can cause the priaprism (ACP) - but if the stallion is going to be castrated, it doesn’t matter as its the end of its breeding life. Also, the chances of this happening with these drugs is about 1 in 10,000 - so its very rare!
Which drug would be suitable for induction of GA for castration?
- Xylazine and ketamine
- Guaiphenesin and Ketamine
- *Ketamin must be given with something else otherwise it will cause profound fasciculate and makes horse wild
Which protocol is suitable for maintaining field anaesthesia?
- Triple drip (xylazine, ketamine and Guaiphenesin)
- Ketamine
Which LA would you inject into the testicles prior to castration?
- Lidocaine and adrenaline
- Mepivicaine
- Procaine (also licensed but only under 5mls if givenm subcut can change colour of fur so people choose not to use it)
Where do you choose to inject the LA in the testicle?
- Subcutaneously
- Tunica dartos, body and spermatic cord
Which is the commonest used NSAID for equine castration?
Phenylbutazone
What are the differences in donkey airways when considering anaesthesia?
Donkeys tracheas are relatively smaller
Which NSAIDs is metabolised slower in the donkey?
Carprofen
Post op how much bleeding from scrotum would you tolerate before re-exploration?
Slow drip (drips can be counted)
