Ice in Your Veins
In sports, to have ice in your veins is to be cold-blooded and clutch. In medicine, to have ice in your veins is a very serious medical condition associated with hypothermia and frost emboli.
There is very little information in the literature, especially The House of God, regarding the acquisition of ice in one's veins. It certainly couldn't have been preexisting or, if it did, would have melted due to our natural body temperature of 98.6 degrees Fahrenheit, which is more than adequate to melt ice. The expert consensus is that the ice was acquired later in life, with the most obvious source being intravenous injection, either as a form of street recreation (like the injection heroin) or an accidental order by a health care provider ("Please flush with 10 cc of ice cubes.")
Diagnosis is made on clinical grounds. 90% of patients with ice in their veins have the triad of hypothermia, frigid countenance, and palpable ice cubes in visible venous vessels.