It is well established that surgical patients whose core body temperatures fall below 35 C (around 95 F) during surgery have much higher mortality rates than surgical patients whose core body temperatures remain above 35 C. Consequently, mortality rates could be significantly reduced during surgery if operating rooms were kept significantly warmer than they are presently kept under standard hospital guidelines, which call for temperatures of 20 C (around 68 F).

Which of the following, if true, argues most strongly against the view that surgical mortality rates could be reduced by raising operating room temperatures?