Can nitroglycerin be administered to patients following Coronary Artery Bypass Grafting (CABG)?

From the Guidelines

Nitroglycerin can be administered to patients following coronary artery bypass grafting (CABG), but its use should be carefully considered due to potential hypotensive effects and the need to monitor hemodynamic status closely. When used, nitroglycerin is typically given as an intravenous infusion, starting at a dose of 0.5-1 mcg/kg/min and titrated based on the patient's blood pressure and clinical response 1. The goal of nitroglycerin therapy in this setting is to prevent spasm of the bypass grafts and manage hypertension, while also reducing preload and afterload to decrease myocardial oxygen demand during the critical recovery period.

Key considerations for the use of nitroglycerin post-CABG include:

• Monitoring blood pressure closely to avoid hypotension, particularly in patients who may be hypovolemic or have altered vascular tone following surgery.
• Avoiding the use of nitroglycerin if systolic blood pressure is below 90 mmHg or if the patient shows signs of right ventricular infarction or significant aortic stenosis.
• Being aware that topical nitroglycerin may have uneven absorption, and when clinically indicated, it is reasonable to administer nitroglycerin intravenously to ensure consistent effects 1.
• Recognizing that the venodilating and arterial dilating effects of nitroglycerin can be mimicked by some anesthetic agents, potentially leading to significant hypotension and myocardial ischemia when combined 1.

The decision to use nitroglycerin post-CABG should be made on a case-by-case basis, taking into account the individual patient's risk factors, hemodynamic status, and clinical response to the medication. As noted in the guidelines, prophylactic nitroglycerin infusions have shown mixed results in reducing the incidence of myocardial ischemia or cardiac events in high-risk patients, including those undergoing CABG 1. Therefore, the use of nitroglycerin should be tailored to the specific needs of each patient, with careful monitoring and adjustment of the dose as necessary to balance the potential benefits and risks.

From the FDA Drug Label

The nitroglycerin concentration should not exceed 400 mcg/mL. Note: If the concentration is adjusted, it is imperative to flush or replace the infusion set before a new concentration is utilized If a peristaltic action infusion pump is used, an appropriate administration set should be selected with a drip chamber that delivers approximately 60 microdrops/mL When using a non-absorbing infusion set, the initial dosage should be 5 mcg/min delivered through an infusion pump capable of exact and constant delivery of the drug.

The FDA drug label does not answer the question.

From the Research

Administration of Nitroglycerin after CABG

• The administration of nitroglycerin to patients following coronary artery bypass grafting (CABG) has been studied in various research papers 2, 3, 4, 5.
• A study published in 1986 found that prophylactic infusion of nitroglycerin during CABG reduced the incidence of hypertension and hypotension, but had no significant effect on the incidence of ischemia 2.
• However, a study published in 1995 found that treatment with nitroglycerine was associated with a higher prevalence of ischemic episodes, suggesting that myocardial ischemia may be caused by extracorporeal circulation-induced alterations enhanced by the hypotensive effects of nitroglycerine 3.
• Another study published in 1999 found that nicardipine, but not nitroglycerin, significantly decreased the duration and number of myocardial ischemic episodes after CABG 4.
• A study published in 1990 found that infusion of nifedipine after CABG decreased the incidence of early postoperative myocardial ischemia, whereas the control group received nitroglycerin 5.
• It is worth noting that the current status and prospect of CABG, including the use of nitroglycerin, is still being researched and debated, with some studies suggesting that more prospective multi-center randomized trials are needed to provide more evidence for clinical questions 6.

Key Findings

• Nitroglycerin may reduce hypertension and hypotension after CABG, but its effect on ischemia is unclear 2.
• Nitroglycerin may actually increase the prevalence of ischemic episodes after CABG, possibly due to its hypotensive effects 3.
• Alternative medications, such as nicardipine and nifedipine, may be more effective in reducing myocardial ischemia after CABG 4, 5.

Considerations for Clinical Practice

• The use of nitroglycerin after CABG should be carefully considered, taking into account the potential benefits and risks, as well as the availability of alternative medications 2, 3, 4, 5.
• Further research is needed to fully understand the effects of nitroglycerin and other medications on patients after CABG, and to provide evidence-based guidance for clinical practice 6.