Hypothermic circulatory arrest and Intelligence Outcomes

Here's an interesting study.  In some cardiac surgery cases, the patient is cooled profoundly and their circulation stopped for a critical portion of their cardiac surgery.  To prove that this was a risk to brain development, they compared the minutes of arrest time to the difference in IQ between patients and their siblings.  So, not every sibling has the same IQ as their sibling, but as an average across many siblings, they showed a decrease in IQ with every minute of circulatory arrest.
In this article,

Duration of circulatory arrest does influence the psychological development of children after cardiac operation in early life.

"...A decrease of 0.53 point per minute of arrest time was estimated for the entire group of 31 patients; that is, in the 19 patients with siblings, for each minute increase in circulatory arrest time, the patients dropped 0.69 IQ point below their siblings. "

And also in this article

The relationship between intelligence and duration of circulatory arrest with deep hypothermia.

".. indicating a decrease of 3 to 4 intelligence quotient points for each extra 10 minutes of arrest time. ."