Double blind, double dummy trial of the use of IV acetaminophen versus oral acetaminophen for the prevention of delirium after cardiac surgery. The underlying hypothesis is that better pain control and less use of narcotics will lead to a lower incidence of delirium from day 1 to 7 following cardiac surgery. Other important secondary outcomes are the total use of narcotics, ICU and hospital stay, improved cognitive function at 6 months and 1 year post surgery, NSAID use at each centre and associated NSAID complications.