title: Tubular proteinuria and enzymuria following open heart surgery.
abstract: OBJECTIVE
  We investigated the effect of cardiac surgery on a marker of tubular damage, an enzyme called neutral endopeptidase (NEP), and on a marker of tubular function, retinol binding protein (RBP). Markers of tubular damage or function are useful in the early detection of acute renal failure and help identify the risk factors for this disease. We also examined if colloid interfered with NEP measurement.
  
  
  METHODS
  A controlled prospective cohort study.
  
  
  METHODS
  A teaching cardio-thoracic unit in London, England.
  
  
  METHODS
  Thirty-four patients underwent cardiac surgery. Eight patients waiting for cardiac surgery acted as controls.
  
  
  METHODS
  Twenty-five patients had coronary artery bypass graft, four patients had valve replacements, one patient had a coronary artery bypass graft with a valve replacement and one patient had a left ventricular aneurysm repair.
  
  
  RESULTS
  Neutral endopeptidase was measured in all the patients and controls. In separate subgroups RBP ( n=5) and Gelofusine use ( n=12) were recorded. Urine samples were collected pre-operatively, 3 h, 1 and 4 days post-operatively. NEP rose significantly ( p<0.05) after cardiac surgery compared with the control population. RBP also rose significantly ( p<0.05) after cardiac surgery. NEP correlated with RBP 3 h post-operatively ( p<0.05, r(2)=0.97). There was no correlation between the amount of Gelofusine given and NEP excretion.
  
  
  CONCLUSIONS
  Excretion of NEP and RBP were both increased after cardiac surgery. Colloid did not affect the excretion of NEP, although in other studies it has affected the excretion of RBP. This may make NEP excretion a better index of acute and impending renal damage following cardiac surgery.
authors.affiliation: Department of Physiology, University College London, Crower Street, WCIE 6XA, London, UK. jblaikley@yahoo.co.uk
authors.forename: John
authors.initials: J
authors.lastname: Blaikley
authors.forename: Peter
authors.initials: P
authors.lastname: Sutton
authors.forename: Mary
authors.initials: M
authors.lastname: Walter
authors.forename: Martha
authors.initials: M
authors.lastname: Lapsley
authors.forename: Anthony
authors.initials: A
authors.lastname: Norden
authors.forename: Wilf
authors.initials: W
authors.lastname: Pugsley
authors.forename: Robert
authors.initials: R
authors.lastname: Unwin
mesh_terms: D058186:Acute Kidney Injury / Q000175:diagnosis; D015331:Cohort Studies; D006801:Humans; D015260:Neprilysin / Q000652:urine*; D011182:Postoperative Care; D011446:Prospective Studies; D011507:Proteinuria / Q000209:etiology* / Q000652:urine; D012177:Retinol-Binding Proteins / Q000652:urine; D019616:Thoracic Surgical Procedures
chemical_list: D012177:Retinol-Binding Proteins; D015260:Neprilysin