Euthanasia

Pentobarbital protocol

• There are a number of authorised formulations of pentobarbital sodium for use in the horse.
• These formulations are generally highly concentrated, which limits the quantity of injection required.
• Always check the required volume of the chosen formulation.
• Sedation is recommended prior to pentobarbital administration.
• Pentobarbital is a schedule 3 drug, so specific drug recording is not required.
• Standard safe custody requirements should be followed.
• Given the viscosity of these products, some clinicians choose to place them (capped) in warm water before injection.
• Although this not an authorised method of use, some clinicians consider that it may facilitate administration.
• Co-administration of muscle relaxants (such as midazolam) may improve the quality of induction.
• Other unauthorised muscle relaxants have been used by some but are not recommended. 
• If there is a need to present a peaceful process to onlookers, a reliably smooth and rapid effect can be achieved using ketamine to induce anaesthesia, followed by euthanasia using any of the protocols listed below (euthanasia of the anaesthetised horse).

This is an effective and safe method of euthanasia under the following protocol, but it is observed that horses tend to move backwards during euthanasia:

1. Place and secure an intravenous catheter into the jugular vein
2. Add a long extension tube (50-100cm) so that injection can continue as the horse moves away from you/backwards during euthanasia
3. Sedate the horse as for anaesthesia (20ug/kg of detomidine ie 1 ml for a 500kg horse)
4. Draw up the multiple syringes required for the horse. Overestimate the volume!
5. Once the horse is sedated and in a safe location administer the full dose required as quickly as is safely possible – continue injecting as the animal begins to be anaesthetised
6. If necessary, continue to administer further pentobarbital solution until the horse dies.

Euthanasia of horses that are already anaesthetised or that are anaesthetised via other means can be undertaken using Pentobarbital (as above) or using a concentrated solution of potassium chloride (if other methods are unavailable and if considered appropriate under the prescribing cascade).

Potassium chloride protocol

Potassium chloride must never be used in the conscious horse.

• Sterile solutions are not required
• Potassium Chloride powder/crystals can be dissolved in water (until the solution is fully saturated)
• 100ml saturated solution is usually enough for a 500kg horse
• Ensure safety of those around the horse; legs/muscles will move spontaneously due to muscle cell depolarisation - this can be dangerous and distressing to clients (who must be warned)
• Administer by rapid IV injection until the heart stops