There has been one study that has reported moderately elevated BNP levels in patients with ARDS. BNP levels were correlated with pulmonary and systemic vascular resistance but not with PaO2 or the PaO2/fraction of inspired oxygen ratio. Another report has documented the normalization of very high BNP levels in a patient with severe ARDS following successful therapy.
In addition, the influence of catecholamine therapy has to be taken into account. The preferred vasopressor used to treat patients with septic shock is norepinephrine, which is a predominantly а-recep-tor agonist with systemic and pulmonary vasoconstrictor properties. However, in patients with septic shock norepinephrine has been shown even to enhance cardiac index due to its ^-adrenergic properties and thus might influence the echocardio-graphically assessed LVEF in sepsis patients, leading to an overestimation of the true left ventricular systolic function. In contrast, elevated pulmonary vascular resistance due to hypoxic vasoconstriction in patients with severe pulmonary disease might further increase due to norepinephrine infusion, thereby increasing right ventricular afterload. this
Renal Failure and BNP: Beyond heart failure, elevated BNP levels have been found in patients with end-stage renal failure, and thus patients with advanced renal failure have been excluded from most BNP studies. An analysis of the Breathing Not Properly Multinational Study found a weak inverse correlation between BNP level and the estimated creatinine clearance in patients presenting with acute dyspnea. In addition, a substudy of the B-type Natriuretic Peptide for Acute Shortness of Breath Evaluation trial revealed that patients with kidney disease (estimated creatinine clearance, < 60 mL/ min/1.73 m2; patients with a serum creatinine level of > 250 Mmol/L were excluded) had higher BNP levels than patients without, and that in patients with kidney disease BNP testing did not improve their management. This is a very important issue, since changes in renal function can occur very rapidly in patients with sepsis. However, data on the relationship between BNP level and renal function in ICU patients are sparse. McLean et al identified a weak correlation between BNP and serum creatinine levels. Unfortunately, the estimated levels for creatinine clearance have not been calculated, and thus this finding has only limited value.