The blog Depressed Metabolism examines the technical side of cryonics, the indefinite low-temperature storage of the recently deceased. Cryonic suspension aims to preserve the fine structure of the brain, so as to allow plausible future medical technologies to repair and revive the suspendees. As Depressed Metabolism puts it:
Cryonics involves placing critically ill patients that cannot be treated with contemporary medical technologies in a state of long-term low temperature care to preserve the person until a time when treatments might be available.
Like all things medical these days, cryopreservation is more easily described than accomplished. A great deal of specialist knowledge, research, investment and experience goes into the present standard for the process, and into the organizations that provide cryosuspension services. For example:
One argument that is often raised in favor of “field vitrification” (or vehicle based vitrification) is that it will reduce the time of (cold) ischemia and eliminate the harmful effects of remote blood washout and transport of a patient on water ice to a cryonics facility. A related argument is that field vitrification will eliminate stabilization.
In fact, field vitrification will not eliminate the need for stabilization because patients need to be protected from warm ischemic injury after cardiac arrest until a location to carry out cryoprotectant perfusion has been secured and surgical access to the patient’s vessels has been established (a procedure that, in cryonics, takes at least fifteen minutes under the best of circumstances). During that period the patient will still require prompt cardiopulmonary support, induction of hypothermia, and administration of anticoagulants and neuroprotective agents. As a consequence, stabilization times should not differ between field vitrification or remote blood washout. In light of the possibility that field vitrification will likely require more demanding and time-consuming surgery, field vitrification might even necessitate longer stabilization times.
The critical period in cryonics is the time taken to safely lower temperature in the brain to a point at which injury is prevented. The faster the better, but as the material above indicates, it's not a straightforward process - just as for any major medical intervention. You can find out more about the technical aspects of cryonics at the Alcor website: