Euthanasia is a peaceful and virtually pain-free process but it is important to understand what will occur and how your pet's body may react. Knowing these things may make the process less traumatic for everyone involved.
To perform the euthanasia, the veterinarian will insert a catheter or needle into a vein of your pet's front or back leg. If your pet has been very sick or has had many intravenous injections, it may take a little time to find the best location.
Some veterinarians may then inject a drug into the vein to place your pet in a state of relaxation. The actual drug used to perform the euthanasia is a concentrated solution of pentobarbital which causes the pet's heart to stop beating. In most cases, it works very rapidly (5 seconds) but in some instances, the time between the injection and the death of the pet may be slightly longer. This is especially true if the pet has poor circulation.
In some instances, the pet's muscles may relax or contract after the pet has died. This can be very disconcerting if you are not aware of this possibility ahead of time. The muscles of the urinary bladder and the anus may relax and your pet may void urine and stool. Involuntary contractions of muscles may result in the pet appearing to gasp or move a leg. Again, remember your pet is not aware of these things happening since they happen after death. In almost all cases, the pet's eyes will not close upon death.
Knowing what happens during euthanasia may help you and other family members decide if they want to be present.