Silent myocardial ischemia is known to occur in the general medical intensive care unit
population immediately following tracheal extubation. We believe these patients are at risk
for primary cardiac events in the 4 hours immediately following extubation. Metoprolol is a
selective beta-1 antagonist, with little to no beta-2 activity at low and moderate doses.
The cardioprotective effects of beta blockade have been well documented in randomized
controlled trials. In patients undergoing extubation, prophylactic use of intravenous
metoprolol may reduce post-extubation ischemia events as well as precursors of cardiogenic
pulmonary edema (atrial and ventricular wall tension). Our primary hypothesis is that
prophylactic metoprolol (titrated to reduce resting heart rate by at least 10%) prior to
tracheal extubation will reduce the rate of ischemia as judged by ST segment analysis.
- Adult medical or cardiac intensive care unit patients on mechanical ventilation who
have known coronary artery disease or have at least 2 of the following risk factors
for coronary artery disease:
- Cigarette smoking
- Hypertension (BP 140/90 or antihypertensive medication)
- Low HDL-cholesterol (HDL-C) (<40 mg/dL [1.03 mmol/L])
- Family history of premature CHD (in male first degree relatives <55 years, in
female first degree relative <65 years)
- Age (men 45 years, women 55 years)
- Diabetes mellitus
- Symptomatic carotid artery disease
- Peripheral arterial disease
- Abdominal aortic aneurysm
- Arterial hypotension, defined as mean arterial pressure < 60 mmHg or requiring any
intravenous vasoactive medication.
- The presence of known reactive airway disease.
- Resting heart rate of <60 in the period prior to tracheal extubation..
- The presence of decompensated congestive heart failure, defined as requiring
continuous infusion of an inotropic agent.
- Known hypersensitivity to beta-blockers or any other contraindication to their use.
- Subjects younger than 18 years of age.
- Inability to obtain consent from the subject or the subjects authorized
- Digoxin therapy
- Current therapy with a beta-blocker