PURPOSE: Plasma B-type natriuretic peptide and N-terminal proB-type natriuretic peptide (NT-proBNP) assays have become widely available to diagnose and manage congestive heart failure(CHF). NT-proBNP is easily measured, unaffected by vascular endotheliases, and only excreted via urine. These peptides are used to guide therapy in CHF patients. We hypothesize that since mechanical ventilation (MV) affects the intra-thoracic pressure, it may also affect ProBNP level.
METHODS: We prospectively screened patients who are expected to undergo MV and did not have history of CHF or renal failure. Baseline pro-BNP level was obtained before intubation and daily for the first 72 hours and after extubation for 72 hours. The mean levels of Pro-BNP before, during and after MV were analyzed utilizing one-way ANOVA test and by the nonparametric Kruskal-Wallis test.
RESULTS: Data was collected in 32 consecutive patients admitted to intensive care unit, who were MV for non-cardiac reasons during the period of January 2006 to March 2007. A total of 23 patients completed the study. Nine patients were excluded because they failed extubation and required long term MV or because the patient died before extubation. The most common admitting diagnosis was hypercapnic respiratory failure, aspiration pneumonia, sepsis and status epilepticus. The mean age of patients was 70.5 years. The average duration of MV was 5.4 days. The mean baseline Pro-BNP level was 2363 (pg/ml). The mean Pro-BNP was 7317(pg/ml) obtained on day 1 s/p intubation; 5619(pg/ml) on day 2 and 1863(pg/ml) on day 3. The average post-extubation level was 2318 on day 1, decreasing to 1419(pg/ml) on day 3(graph 1). The analysis of the ranked means shows significance (p<0.05). A similar graph was obtained after excluding the patients with abnormal echocardiographic findings (graph 2).
CONCLUSION: Pro-BNP level is affected with dynamic change in the intrathoracic pressure with mechanical ventilation. The Pro-BNP level increases significantly on the day after intubation and gradually decreases. It also increases after extubation and then gradually decreases.
CLINICAL IMPLICATIONS: When evaluating Pro-BNP levels, the effect of mechanical ventilation should be taken into consideration.
DISCLOSURE: Ayman Bishay, No Financial Disclosure Information; No Product/Research Disclosure Information