The outcome of coronary bypass surgery was analyzed in 25 patients who were on 
thyroxin replacement therapy for chronic thyroid disorders at the time of 
operation. It was hypothesized that if such patients were given only their 
routine dose of thyroxin on the day of surgery, hemodynamic and 
cardiorespiratory recovery may be poor. All the patients on thyroxin replacement 
therapy were given their routine dose of thyroxin orally or via a nasogastric 
tube in the perioperative period. No supplemental dose was used. Based on 
preoperative levels of thyroid stimulating hormone, 68% of these patients were 
biochemically hypothyroid prior to surgery. Analysis of a large number of 
variables showed no difference in outcome against a control group who had no 
previous thyroid problems. We conclude that routine thyroxin administration is 
all that is required for a satisfactory outcome in patients undergoing coronary 
bypass surgery while on thyroxin replacement therapy.