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
Give an example of a GA in the field for a castration including drugs and maintenance of anaesthesia?
