The purpose of this study is to determine whether continuing or discontinuing furosemide (a diuretic) on the day of elective noncardiac surgery for those who take furosemide on a chronic basis, causes more intraoperative hypotension (low blood pressure) during surgery. Our hypothesis is that the usual practice of continuing furosemide on the day of surgery would contribute to more hypotension during surgery than discontinuing furosemide.

A significant proportion of patients who undergo surgery take medications on a chronic basis. Little is known about the effects of these medications on the successful conduct of anesthesia and surgery. Diuretics like furosemide may contribute to low blood pressure during surgery, an outcome associated with cardiovascular complications. However, many patients are recommended to take their diuretics on the day of surgery. We wished to determine if preoperative administration of furosemide contributes to intraoperative hypotension compared to placebo.

Comparison: We conducted a randomized, double blind placebo controlled trial to compare the effect of furosemide with that of placebo on intraoperative hypotension using intraoperative blood pressure recordings in patients who take furosemide chronically and were undergoing noncardiac surgery.

Inclusion Criteria:

• All adults referred to preoperative assessment clinics by surgeons for elective non-cardiac surgery who routinely take furosemide.
• Participants must also be able to give informed consent

Exclusion Criteria:

• Less than 18 years of age
• Have comorbid conditions with which brief periods of hypotension may be particularly harmful such as: 1) pregnancy; 2) baseline hypotension (systolic <100 mmHg at the preoperative assessment clinic); 3) autonomic dysfunction; 4) severe aortic stenosis.
• Patients who take furosemide only on an 'as needed basis' rather than 'regularly'.
• Those patients who take less than 10 mg of furosemide daily
• Those patients who are undergoing local anesthetic only surgical procedures
• Patients who are unwilling or unable to give informed consent.