Beyond the vascular triage, the metabolic slowdown induced by hypothermia may have been protective in ways that are not fully understood.

Cells require oxygen.

At normal temperature, a cell that is deprived of oxygen for more than a few minutes begins to die — irreversibly.

But at low temperatures, the metabolic demand for oxygen drops dramatically, and cells can survive much longer periods of reduced oxygen delivery without sustaining permanent damage.

This is the same principle that makes it possible to conduct cardiac surgery with the heart stopped and the blood cooled — the brain, which is the organ most vulnerable to oxygen deprivation, can tolerate the surgery because the cold has reduced its oxygen requirement to a fraction of its normal level.

In Jean Hilliard, the cold that was threatening to kill her was simultaneously protecting her most critical organs from the consequences of her reduced circulation.