Hypothermia can cause many problems:
increased SVR
hypertension
mediastinal bleeding
increased myocardial O2 demand
increased filling pressures masking hypovolaemia
increased risk of arrhythmias and VF
shivering causing increased O2 consumption and CO2
production
coagulopathy from decreased platelet function and
impairment of clotting cascade
prolonged time to extubation