Having to have your animal put to sleep can be distressing and may be performed for a variety of reasons including severe disease or trauma. In chelonians there are a number of peculiarities that need to be understood as the procedure is slightly different from other species and make take considerably longer. Thus your veterinarian may be unable to allocate a suitable timeslot in the consulting room for you. In many cases the chelonian will be admitted for the procedure.
Some chelonians can be aggressive or difficult to obtain a blood vessel to inject into. In these cases the chelonian will require sedation by injecting drugs into a muscle. The chelonians should then be placed somewhere warm while the sedative takes effect. This may take 20 – 30 minutes. Typically high doses of ketamine or alfaxalone are used.
After the sedation has taken effect then venous access is possible and many sites can be used. These include the dorsal tail vein, jugular veins or the subcarapacial vein. In severely collapsed individuals it will still be difficult to find a vein and an intracardiac injection may be used. In this case a needle is inserted between the head and front leg.
The drugs used firstly anaesthetise the animal and then, in overdose, stop both the heart and respiratory function. However chelonians are designed to survive without oxygen (for example red eared terrapins can survive in nitrogen for 27 hours) and the brain may continue to function. This means nervous sensation can continue and the animal may still be in pain.
This means the brain must be destroyed. This is typically performed away from the owners. This is known as pithing. This can be performed via the choana in the mouth using a dental probe or a large gauge needle. This is also possible via the back of the head. In most cases this is performed after the heart has stopped beating. If the brain is required for post mortem examination then formalin injection can be used to preserve the tissues.
Confirming death in a chelonian can be difficult. This technically is the point when the brain is no longer functioning and the animal is unable to feel pain. The heart for example can still beat after death and can still be beating after the rest of the tortoise is in rigor mortis. Thus a heart beat does not equate to the tortoise still being alive.
A practical approach is to monitor the heart beat with a Doppler probe or an ECG. If the heart is not beating or is very slow then it is likely the chelonian is beyond help. In these cases it may be best to euthanase the chelonian to make sure, with pithing being performed after the heart has stopped.
The tortoise can be kept warm overnight and rigor mortis, with no heart beat, confirmed the following day. Some veterinarians may freeze a chelonian after lethal injection and pithing.
Methods such as freezing have been shown to be painful and inhumane and should not be used.