A patient who has had an MI is taking a beta blocker.

What is the main benefit of beta blocker therapy for this patient?

Choice A rationale

Simply informing the patient of the delay does not address the immediate physiological need. Lispro (Humalog) is a rapid-acting insulin with an onset of action of 15 to 30 minutes, a peak of 0.5 to 2.5 hours, and a duration of 3 to 6 hours. Waiting 45 minutes for the tray puts the patient at significant risk for hypoglycemia.

Choice B rationale

While checking the blood glucose level is good practice, it is not the most urgent action. The priority is to prevent hypoglycemia, which is an immediate and potentially life-threatening complication of giving rapid-acting insulin without a meal. The patient is already at risk given the time elapsed.

Choice C rationale

Lispro (Humalog) has a rapid onset of action, so the patient must eat within 15 to 30 minutes of administration to prevent hypoglycemia. Providing a fast-acting carbohydrate source like juice, followed by a protein and complex carbohydrate source like cereal and skim milk, will raise blood glucose levels and prevent a hypoglycemic event until the breakfast tray arrives.

Choice D rationale

While calling dietary to expedite the tray is a reasonable action, it may not be fast enough to prevent a hypoglycemic event. The most immediate and critical action is to provide the patient with food to counteract the rapid action of the lispro insulin. This directly addresses the patient's safety.

Choice A rationale

Beta-blockers reduce the workload on the heart by blocking the effects of catecholamines (epinephrine and norepinephrine) on beta-adrenergic receptors. This action leads to a decrease in heart rate, a reduction in the force of myocardial contraction (contractility), and a decrease in blood pressure. These effects collectively lower the heart's oxygen demand, which is crucial in preventing further damage after a myocardial infarction.

Choice B rationale

Beta-blockers do the opposite of this. They reduce heart rate and contractility by inhibiting the sympathetic nervous system's effect on the heart. This action is beneficial because it reduces the heart's workload and oxygen demand, helping to prevent further ischemic damage. Increasing heart rate and contractility would be detrimental to a post-MI patient as it would increase myocardial oxygen demand.

Choice C rationale

While beta-blockers do not directly cause coronary artery vasodilation, they improve overall coronary blood flow by reducing heart rate and increasing diastolic time. This allows more time for blood to flow through the coronary arteries to the myocardium. Calcium channel blockers or nitrates are the medications primarily used for direct vasodilation of the coronary arteries.

Choice D rationale

Beta-blockers do not prevent the formation of blood clots. This is the primary function of antiplatelet agents (like aspirin or clopidogrel) and anticoagulants (like heparin or warfarin). These medications work by inhibiting different parts of the coagulation cascade or platelet aggregation to prevent thrombosis in the coronary arteries.