Using BNP Levels to Triage Patients Presenting With Acute Dyspnea

Measurement of BNP helps to make the diagnosis of heart failure in the ED and may also assist in triage decisions, such as in identifying those patients who should be admitted directly vs those who might be treated and then discharged. In The Rapid Emergency Department Heart Failure Outpatient Trial (20) in 464 patients presenting to the ED with complaints ofdifficulty breathing, BNP measurements were performed on arrival, and then every 3 h in the ED, at the time of hospital admission, and at discharge. Physicians were informed only whether the initial BNP level was greater or less than 100 pg/mL and were blinded to subsequent BNP results. Notably, patients discharged from the ED had a higher median concentration of BNP than those admitted to the hospital (976 vs 766 pg/mL). Approximately 90% of all patients were admitted to the hospital. Of those admitted, 11% had BNP levels <200 pg/mL, indicative of less severe heart failure. Mortality for these patients was 0% at 30 d and only 2% at 90 d. Of the patients discharged from the ED, 78% had BNP levels >400 pg/mL. At 90 d, the mortality in this group was 9%. There were no

Fig. 5. (A) Frequency distribution of pretest assessment of heart failure by emergency physicians in patients presenting with dyspnea and enrolled in Breathing Not Properly Multinational Study; (B) accuracy of physician's diagnosis using all available tools except BNP, BNP alone, or the two combined; (C) rate of indecision based on clinical evaluation alone or using BNP. (Data from ref. 19.)

Fig. 5. (A) Frequency distribution of pretest assessment of heart failure by emergency physicians in patients presenting with dyspnea and enrolled in Breathing Not Properly Multinational Study; (B) accuracy of physician's diagnosis using all available tools except BNP, BNP alone, or the two combined; (C) rate of indecision based on clinical evaluation alone or using BNP. (Data from ref. 19.)

deaths through 90 d in patients discharged with a BNP <400 pg/mL. The results of this study demonstrated discordance between the perceived severity of heart failure by ED physicians and severity as determined by BNP. Thus, BNP testing in this setting may assist physicians in triaging patients, and making decisions regarding initial treatment.

The BASAL Study (21) evaluated the cost-effectiveness of BNP testing for guiding both the ED evaluation and in-patient management of patients with heart failure. Investigators randomly assigned patients presenting to the ED with dyspnea to undergo either a single measurement of BNP or no such measurement. Participating clinicians were advised that a level of BNP <100 pg/mL made the diagnosis of heart failure unlikely, whereas a level >500 pg/mL made it highly likely. For intermediate levels, the use of clinical judgment and adjunctive testing was encouraged. In this single-blind trial of 452 patients, rapid measurement of BNP in the ED was associated with a 10% decrease in the rate of hospital admission, a reduction in the median length of stay by 3 d, and a reduction in the mean total cost of treatment by approx $1800 (26% decrease), with no adverse effect on the risk of death or subsequent hospitalization. Because the study was performed in Switzerland, the data regarding length of hospitalization and costs might not be directly applicable to the United States. Nevertheless, this carefully performed trial suggests that the use of BNP in the emergency evaluation of acute dyspnea can improve both the efficiency and the quality of care by reducing the use of hospital resources and associated costs by eliminating the need for other, more expensive tests, or by establishing an alternative diagnosis that does not require hospitalization.

Table 2

Other Conditions Influencing Interpretation of BNP

Renal insufficiency

• BNP is increased in patients with chronic renal insufficiency (eGFR < 60); however it is still useful for the diagnosis of heart failure using a higher cut point, especially when baseline BNP levels are known. The relationship between NT-proBNP levels is less clear, although patients with renal insufficiency often have high levels of NT-proBNP.

Pulmonary disease

• Lung disease that results in pulmonary hypertension and right ventricular pressure or volume overload can lead to elevated BNP levels (usually in the range of 100-500 pg/mL).

• A high BNP level is associated with worse prognosis in several of these settings.

• BNP may be a useful screening test for patients with lung disease and associated cardiac risk factors, because many of these patients have underlying cardiac disease. A low BNP in this setting effectively rules out cardiac dysfunction.

Obesity

• Because patients with heart failure and obesity may have lower levels of BNP for any given NYHA functional class, low levels of BNP should be interpreted with caution.

• An obese patient with established heart failure can be followed for decompensation if baseline BNP levels are known.

Was this article helpful?

0 0

Post a comment