Useulness of B Natriuretic Peptides and Procalcitonin in Emergency Medicine

Abstract

Congestive heart failure (CHF) is the main cause of acute dyspnea in patients presented to an emergency department (ED), and it is associated with high morbidity and mortality. B-type natriuretic peptide (BNP) is a polypeptide, released by ventricular myocytes directly proportional to wall tension, for lowering renin-angiotensin-aldosterone activation. For diagnosing CHF, both BNP and the biologically inactive NT-proBNP have similar accuracy. Threshold values are higher in elderly population, and in patients with renal dysfunction. They might have also a prognostic value. Studies demonstrated that the use of BNP or NT-proBNP in dyspneic patients early in the ED reduced the time to discharge, total treatment cost. BNP and NT-proBNP should be available in every ED 24 hours a day, because literature strongly suggests the beneficial impact of an early appropriate diagnosis and treatment in dyspneic patients.Etiologic diagnosis of febrile patients who present to an ED is complex and sometimes difficult. However, new evidence showed that there are interventions (including early appropriate antibiotics), which could reduce mortality rate in patients with sepsis. For diagnosing sepsis, procalcitonin (PCT) is more accurate than C-reactive protein. Thus, because of its excellent specificity and positive predictive value, an elevated PCT concentration (higher than 0.5 ng/mL) indicates ongoing and potentially severe systemic infection, which needs early antibiotics (e.g. meningitis). In lower respiratory tract infections, CAP or COPD exacerbation, PCT guidance reduced total antibiotic exposure and/or antibiotic treatment duration.

Figure 1

Effects of an appropriate (black bars) or inappropriate (white bars) initial diagnosis in the emergency department on prognosis (used with permission from Ray et al. 2006a).

Figure 2

Physiologic actions of BNP.

Figure 3

Figure 4

Diagnostic strategy based on B natriuretic peptide levels in elderly patients admitted for ARF in the emergency department. ¹In the grey zone (BNP between 100 and 500 pg/mL) which represents less than a quarter of patients, further investigations are needed, and ER physicians should consider massive PE, severe exacerbation of COPD or severe pneumonia as possible diagnoses… ²Emergency physicians should be keep in mind that half of elderly patients with ARF has more than one, i.e. a BNP greater than 500 pg/ml strongly suggests CHF, but other diagnosis could have precipitated CHF. ³For NT-proBNP, the cut-off values are 500 and 2,000 pg/mL. Abbreviation: CXR: chest x- ray; EKG: Electrocardiogram; ABG: arterial blood gas analysis; CHF: congestive heart failure; ACS: acute coronary syndrome, CT: computed tomography; IV: intra-venous; NIV: non invasive ventilation including continuous positive airway pressure; ACEi: angiotensin converting enzyme inhibitor; EC: echocardiography.

Figure 5

Kaplan-Meier curves showing survival according to NT-proBNP (from Chenevier-Gobeaux with permission (Chenevier-Gobeaux et al. 2007)).

Figure 6

Suggested diagnostic strategy based on PCT levels in EDs. ¹Systolic Blood Pressure less than 90 mmHg, mottling, oliguria, lactate >2 mmol/L or other signs of septic shock or trouble CSF after lumbar puncture, obvious clinical presentation of community-acquired pneumoniae (thoracic symptoms, fever, and consolidation on chest x-ray).