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Wednesday, May 27, 2015

Congestive Heart Failure, what I needed to learn

So if we all know the basic management of CHF, diagnosed clinically based on history and exam supported by some labs like BNP and echocardiogram and managed mainly with diuresis. Beyond the basic management, these were the aspects of CHF diagnosis and management that I wasn't clear about and decided to research them.

Does Obesity affect BNP interpretations? What are the things to consider when interpreting BNP?

What are natriuretic peptides? So in summary, we have BNP (brain Natriuretic Peptide), which is derived from the cleavage of pro-BNP (released primarily by the heart, but initially found in the brain), resulting in production of BNP the active form and the N-terminal-Pro-BNP (NT-BNP) which is inactive. There is also Atrial Natriuretic Peptide. Both are released in heart failure in response to increased ventricular filling pressure. Both ANP and BNP have diuretic, natriuretic, and hypotensive effects. They also inhibit the renin-angiotensin system, endothelin secretion, and systemic and renal sympathetic activity.
Things to consider when interpreting levels:
  • In a normal healthy person: both BNP and NT pro BNP levels are the same.
  • In heart failure: NT pro BNP> BNP, as per uptodate, NT pro BNP 900~100BNP
  • Both levels lower in obese patients, so a normal or low BNP does NOT exclude heart failure in obese patients.
  • Both levels are higher in patients with renal disease and it is not recommended to use it as a diagnostic tools in such patients.
  • NT pro BNP levels higher in women and elderly.
  • Value may also be elevated in coronary heart disease, valvular heart disease, pulmonary hypertension, and sepsis.
  • Diastolic vs systolic: number will go up in both, but cannot differentiate one from another based on BNP.
  • Should NOT be measured during Niseritide therapy.
  • As per AHA recommendations, BNP is used when diagnosis is not clear and should not be used solely to include or exclude the diagnosis of heart failure.

How do you decide what dose of Lasix to give? What factors to consider before or during treatment with Lasix?
  • No single dose has been recommended, varies from patient to patient. But consider the following factors:
  • In acute exacerbation, always start with IV Lasix because there may be impaired absorption orally because of intestinal edema.
  • Instead of increasing frequency, increase the dose of Lasix as response is threshold based.
  • If diuresis does not increase after a certain dose, then increasing the dose further won’t make a difference, consider adding eplerenone or spironolactone to Lasix (aldosterone antagonists).
  • If creatinine goes up or BP goes down, do NOT stop diuresis, just lower the dose to slow the rate of fluid removal. 
  • Goal is to achieve dry weight and then find the right oral dose to maintain dry weight.
(to be continued)

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