B-type Natriuretic Peptide (BNP)-Guided Diagnostic Strategy in Intensive Care Unit (ICU) Patients With Respiratory Failure

Background: Respiratory failure is not only the most important reason for admission of patients to a medical intensive care unit (ICU), but also a common reason for the deterioration of patients already treated in the ICU. It is a very serious condition associated with significant mortality. Heart failure is a common reason for respiratory failure in both circumstances. Unfortunately, the rapid and accurate differentiation of heart failure from other causes of respiratory failure in the ICU remains a clinical challenge. After evaluation of symptoms, physical examination, arterial blood gases, ECG, and chest x-ray, the clinician is often left with a considerable diagnostic uncertainty that results in misdiagnosis and delay in the initiation of appropriate therapy. In addition, misdiagnosis of heart failure causes morbidity, and increases total treatment time and treatment cost, because treatments for heart failure may be hazardous to patients with other conditions such as chronic obstructive pulmonary disease, and vice verse.

B-type natriuretic peptide (BNP) is a 32-amino acid polypeptide secreted from the cardiac ventricles in response to ventricular volume expansion and pressure overload. BNP levels are significantly higher in patients with congestive heart failure as compared to patients with respiratory failure due to other causes. Therefore, rapid measurement of BNP might be very helpful in establishing or excluding the diagnosis of heart failure in patients with respiratory failure in the ICU.

Aim: The aim is to test the hypothesis that a BNP guided diagnostic strategy would improve the evaluation and management of patients presenting with primary (on admission) or secondary (while in the ICU) respiratory failure in the ICU and thereby reduce total treatment time and total cost of treatment.

Endpoints: Primary endpoints: Time to discharge and total cost of treatment. Secondary endpoints: ICU length of stay, ICU cost, In-hospital mortality, 30-day mortality, cost-effectiveness, 6 and 12 month mortality, 6 and 12 month dyspnea score.

Patients and Methods: The trial is designed to enroll 286 patients presenting with primary (on admission) or secondary (while in the ICU) respiratory failure in the ICU. Patients will be randomly divided 1:1 into a clinical group using evaluation of patients according to local standards without the use of BNP (or other natriuretic peptides) and to a BNP group with early testing for BNP.

Expected results: The researchers hypothesize that a BNP guided diagnostic strategy will improve the evaluation and management of patients presenting with respiratory failure to the ICU and thereby reduce time to discharge and total cost of treatment.

Significance: If in fact, BNP testing could be shown to improve the evaluation and management of patients with respiratory failure in the ICU, this would represent a major advance in the clinical care of seriously ill patients, and as well, highlight the potential for considerable cost-saving. Accordingly, if this study would have a positive result and in fact demonstrate that a BNP guided diagnostic strategy reduces total treatment time and total cost of treatment, it would be the first randomized controlled trial demonstrating that a new diagnostic test improves the evaluation and management of ICU patients. Given the enormous expenses associated with intensive care, such a study seems overdue.

Inclusion criteria

• Patients presenting with primary or secondary respiratory failure in the ICU

Exclusion criteria

• Age <18 years
• Obvious traumatic cause
• Renal dysfunction (serum creatinine >250umol/l)
• Sepsis
• Cardiopulmonary reanimation within the last 12 hours
• Shock
• Respiratory insufficiency triggered during bronchoscopy