Correct me if I am wrong, but I wonder if vets over-think autotransfusions as something too complicated for use within their own practices.
Ghosal and Bos published a recent case report describing autotransfusion from a non-sterile suction pot. Think about this for a second. They literally took the blood out of the suction pot and infused it back into the patient! You do need to administer it back via a hemofilter, but this is a small, inexpensive filter. It filters the blood as you administer it back to the patient (see second photo) and needs changing every few syringes. I recommend every practice performing desexing or other abdominal surgical procedures stock these (or blood products - which is more tricky).
The patient in the case report had a massive bleed, which is defined as blood loss greater than total blood volume. Non-sterile blood autotransfused into this patient saved their life - it is better red than dead.
Now ideally, you want the blood to be as sterile as possible. A catheter tip syringe can be a great way to collect blood from the abdomen, then you can transfer this into a luer -tip syringe (see photo for these syringes). This can be a good way to collect blood if you have a post-spey bleed and are re-exploring the abdomen. Alternatively, you can collect the blood via abdominocentesis, and again, infuse directly back to the patient via a hemofilter.
Just a final rule of thumb from our lovely anaesthnetist Dr Kieren Maddern - for every 1ml of blood you have lost, give 3 mls of crysalloids IV to re-expand the volume and maintain blood pressure.
Hemonate Filter Systems can be obtained from Sound Veterinary (and no, this is not a paid ad).
Reference: "Successful management of catastrophic peripheral vascular hemorrhage using massive autotransfusion and damage control surgery in a dog" JVEEC 2019