title: B-type natriuretic peptide secretion without change in intra-cardiac pressure.
abstract: OBJECTIVE
  In clinical cardiology, B-type natriuretic peptide (BNP) is used as a non-invasive surrogate marker for intra-cardiac filling pressures, particularly in patients with heart failure. It is unknown whether and to what extent increase in intravascular volume and/or sympathetic tone while maintaining constant intra-cardiac pressures leads to an increase in levels of BNP in vivo.
  
  
  METHODS
  We aimed to test this hypothesis in an experimental in vivo model of patients directly after off-pump coronary artery bypass grafting admitted to the intensive care unit. These patients require high volumes of intravenous fluids titrated to keep intra-cardiac filling pressures and arterial blood pressure in the normal range while awakening from deep general anesthesia. In 27 consecutive patients, intra-cardiac filling pressures (using a pulmonary artery catheter) and levels of BNP were measured simultaneously every 6h.
  
  
  RESULTS
  At 0, 6, 12, and 18h, the pulmonary capillary wedge pressure remained constant (12±4, 13±3, 12±3, and 13±3mmHg, respectively; p=0.351). Similarly, right heart filling pressures did not change during the study period. In contrast, BNP levels increased significantly during the study period: Median levels were 82 [IQR 37-162] pg/ml at 0h, 153 [92-246] pg/ml at 6h, 274 [156-392] pg/ml at 12h, and 320 [200-528] pg/ml at 18h (p<0.001). No significant correlation between BNP levels and pulmonary capillary wedge pressures was found (r=0.052; p=0.604).
  
  
  CONCLUSIONS
  After cardiac surgery, BNP cannot be considered a reliable non-invasive surrogate for PCWP. In vivo, substantial BNP secretion occurs independently of PCWP in a setting of increasing intravascular volume and consciousness/sympathetic tone.
authors.affiliation: Department of Cardiology & Cardiovascular Research Institute Basel, University Hospital, Basel, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Puelacher
authors.affiliation: Department of Cardiology & Cardiovascular Research Institute Basel, University Hospital, Basel, Switzerland.
authors.forename: Jasna
authors.initials: J
authors.lastname: Rudez
authors.affiliation: Department of Cardiology & Cardiovascular Research Institute Basel, University Hospital, Basel, Switzerland.
authors.forename: Raphael
authors.initials: R
authors.lastname: Twerenbold
authors.affiliation: Department of Cardiology & Cardiovascular Research Institute Basel, University Hospital, Basel, Switzerland.
authors.forename: Zoraida
authors.initials: Z
authors.lastname: Moreno Weidmann
authors.affiliation: Department of Cardiology & Cardiovascular Research Institute Basel, University Hospital, Basel, Switzerland.
authors.forename: Stefan
authors.initials: S
authors.lastname: Osswald
authors.affiliation: Division of Cardio-Thoracic Surgery, University Hospital, Basel, Switzerland.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Eckstein
authors.affiliation: Department of Anesthesia, Division of Operative Critical Care, University Hospital, Basel, Switzerland.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Lurati-Buse
authors.affiliation: Department of Anesthesia, Division of Operative Critical Care, University Hospital, Basel, Switzerland.
authors.forename: Hans
authors.initials: H
authors.lastname: Pargger
authors.affiliation: Department of Cardiology & Cardiovascular Research Institute Basel, University Hospital, Basel, Switzerland. Electronic address: christian.mueller@usb.ch.
authors.forename: Christian
authors.initials: C
authors.lastname: Mueller
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D001026:Coronary Artery Bypass / Q000639:trends; D005260:Female; D006439:Hemodynamics / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D020097:Natriuretic Peptide, Brain / Q000097:blood* / Q000378:metabolism*; D011446:Prospective Studies; D011669:Pulmonary Wedge Pressure / Q000502:physiology*
chemical_list: D015415:Biomarkers; D020097:Natriuretic Peptide, Brain
keywords: BNP; Cardiac surgery; Endocrinology; Intra-cardiac pressure; Volume