title: Atrial Natriuretic Peptide and Acute Changes in Central Blood Volume by Hyperthermia in Healthy Humans.
abstract: BACKGROUND
  Hyperthermia induces vasodilatation that reduces central blood volume (CBV), central venous pressure (CVP) and mean arterial pressure (MAP). Inhibition of atrial natriuretic peptide (ANP) could be a relevant homeostatic defense mechanism during hyperthermia with a decrease in CBV. The present study evaluated how changes in plasma ANP reflect the changes in CBV during hyperthermia.
  
  
  METHODS
  Ten healthy subjects provided with a water perfused body suit increased body core temperature 1 °C. In situ labeled autologous red blood cells were used to measure the CBV with a gamma camera. Regions of interest were traced manually on the images of the whole body blood pool scans. Two measures of CBV were used: Heart/whole body ratio and thorax/whole body ratio. CVP and MAP were recorded. Arterial (ANPart) and venous plasma ANP were determined by radioimmunoassay.
  
  
  RESULTS
  The ratio thorax/whole body and heart/whole body decreased 7 % and 11 %, respectively (p<0.001). MAP and CVP decreased during hyperthermia by 6.8 and 5.0 mmHg, respectively (p<0.05; p<0.001). Changes in both thorax/whole body (R=0.80; p<0.01) and heart/whole body ratios (R=0.78; p<0.01) were correlated with changes in ANPart. However, there was no correlation between venous ANP and changes in CBV, nor between ANPartand MAP or CVP.
  
  
  CONCLUSIONS
  Arterial but not venous plasma concentration of ANP, is correlated to changes in CBV, but not to pressures. We suggest that plasma ANPartmay be used as a surrogate marker of acute CBV changes.
authors.affiliation: Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Denmark ; Cluster for Molecular Imaging, University of Copenhagen, Denmark.
authors.forename: Thomas Wiis
authors.initials: TW
authors.lastname: Vogelsang
authors.affiliation: Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Denmark.
authors.forename: Jens
authors.initials: J
authors.lastname: Marving
authors.affiliation: Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Dallas, TX, USA ; Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA.
authors.forename: Craig G
authors.initials: CG
authors.lastname: Crandall
authors.affiliation: Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Dallas, TX, USA ; Department of Medicine, Pennsylvania State College of Medicine, Hershey, Pennsylvania, USA.
authors.forename: Chad
authors.initials: C
authors.lastname: Wilson
authors.affiliation: Department of Anesthesia, Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Denmark.
authors.forename: Chie C
authors.initials: CC
authors.lastname: Yoshiga
authors.affiliation: Department of Anesthesia, Copenhagen Muscle Research Center, Rigshospitalet, University of Copenhagen, Denmark.
authors.forename: Niels H
authors.initials: NH
authors.lastname: Secher
authors.affiliation: Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Denmark.
authors.forename: Birger
authors.initials: B
authors.lastname: Hesse
authors.affiliation: Department of Clinical Physiology, Nuclear Medicine & PET, Rigshospitalet, Denmark ; Cluster for Molecular Imaging, University of Copenhagen, Denmark.
authors.forename: Andreas
authors.initials: A
authors.lastname: Kjær
keywords: ANP; blood pool imaging; central blood volume; heating; natriuretic peptides; nuclear medicine