Blood clotting is not caused by red blood cells but by platelets. They do get caught up by the clot spreading around them and then act as parts of the barrier, but removing them too fast would actually increase ischemia because they're what carry the oxygen.
(By the way, I hope that the cryoprotectant solutions contain high concentrations of dissolved oxygen. Not nearly as good as having the actual RBCs, but you can increase the amount (supersaturation) by keeping it under pressure.)
Anyways, given that perfusion is already taking place (and this is removing all of the components of the blood including the platelets), the other option is to disable the blood clotting cascade, for example by administration of anticoagulants such as warfarin. I don't know if this is already done. You would also have access to more "extreme" types of anticoagulation, chemicals (or higher doses) that aren't on the medical market because the effects are normally too strong.
I suppose another option would be to suggest that the patient to start taking anticoagulants before death. I'm not sure whether that would have legal implications though.
Blood clotting is not caused by red blood cells but by platelets.
I thought ischemic tissue caused RBCs to form Rouleaux complexes. Even without RBC's, ischemia causes plenty of changes that have effects functionally equivalent to clotting: Swelling of myocytes and the endothelium, subsarcolemmal and endothelial blebs, et cetera.
I suppose another option would be to suggest that the patient to start taking anticoagulants before death. I'm not sure whether that would have legal implications though.
This is certainly helpful and doesn't seem to have been...
I just read this article (which is well worth reading for anyone interested in cryonics). One of the important things that the article points out is that, while it takes some time for the memory structures of the brain to degrade due to ischemia, one of the more rapid effects is blood clotting in the fine capillaries of the brain after fairly brief ischemia. This reduces the flow of cryoprotectant, and causes large swathes of neural tissue to be frozen, instead of vitrified, which would be catastrophic for personal identity. While this is not a problem for best-case 'standby' cryonics, it is a problem for those who cannot afford a standby team, or are simply hit by cars.
Being an engineer, my first thought is that this is ridiculous, and there has to be a better solution to the problem. It may be possible to build a device, maybe the size of a shoe box, which can be deployed in the field by a minimally-trained amateur (like a defibrillator), and perfuses the brain with cold saline and anti-coagulants -- or even a synthetic oxygen carrier). I'm picturing a cylinder of fluid, large needles with sterilizing caps for tapping the jugular and carotid arteries, and a gas cylinder to provide pressure. You'd simply break a chemical cold pack, put a plastic neck brace in place and insert the needles, and press a button.
Such a device could even be useful to non-cryonicists, as a way to prevent ischemic injury in people found medically dead at the scene of an accident, during transport to the hospital.
Does anyone with more of a medical background know if such a machine would be at all feasible? I can't imagine it would be expensive to construct.