Not anywhere as cold as that (only 10 degrees F or so from normal body temp), but we keep them down for a good 24 hours. Indeed, cryonics refers to the medical / preservation application of croyogenics in particular.

Even in -50 ambient the core body temp would be pretty slow to drop so the person likely wouldn't freeze solid, but that Tahiti survival is still pretty amazing. I never heard if he had any more meaningful neurologic recovery though.

One of the original pilot / safety studies outlines a typical protocol:

Hypothermia After Cardiac Arrest: Feasibility and Safety of an External Cooling Protocol -- Felberg et al. 104 (15): 1799 -- Circulation