title: Cystatin C: influence of perfusion and myocardial injury on early (<24 h) renal function after pediatric cardiac surgery.
abstract: BACKGROUND
  Cardiopulmonary bypass (CPB)-associated renal dysfunction following cardiac surgery is well recognized. In patients with renal disease, cystatin C has emerged as a new biomarker which in contrast to creatinine (Cr) is sensitive to minor changes in glomerular filtration rate (GFR).
  
  
  OBJECTIVE
  We utilized cystatin C to investigate the association of CPB perfusion parameters with acute renal injury after pediatric cardiac surgery.
  
  
  METHODS
  Twenty children, aged 4-58 months (AVSD, n = 7; VSD, n = 9; and ASD, n = 4), were prospectively studied. Glomerular filtration rate was quantified postoperatively by creatinine clearance (first and second 12-h periods; CrCl(0-12) and CrCl(12-24) ). Serum cystatin C and Cr were measured preoperatively and on days 0-3. Recorded CPB parameters included bypass duration (BP), perfusion pressure (PP), lowest pump flow (Q(min) ), lowest hematocrit, and corresponding lowest oxygen delivery (DO(2 min) ). Myocardial injury was determined by troponin-I.
  
  
  RESULTS
  Postoperatively, GFR remained unchanged (CrCl(0-12) 63.6 ± 37.0 vs CrCl(12-24) 65.1 ± 27.5; P = 0.51) and only correlated with cystatin C (CrCl(0-12) vs cystatin C(Day 0) [r = 0.58, P = 0.018] and Cr(Day 0) [r = 0.09, P = 0.735]). Cr and cystatin C increased postoperatively to peak on days 2 and 3, respectively (Cr(PreOp) 31 ± 6.9 vs Cr(Day 2) 36.9 ± 12.2, P = 0.03; cystatin C(Day 0) 0.83 ± 0.27 vs cystatin C(Day 3) 1.45 ± 0.53, P = 0.02). Increased cystatin C was significantly associated with BP (P = 0.001), mean PP (P = 0.029), Q(min) (P = 0.005), troponin-I (P < 0.001), and DO(2 min) <300 ml·min(-1) ·m(-2) (P = 0.007). Receiver-operator cutoff >1.044 mg·l(-1) for cystatin C exhibited 100% sensitivity and 67% specificity for detecting renal dysfunction, defined as GFR <55 ml·min(-1) ·1.73 m(-2).
  
  
  CONCLUSIONS
  Cystatin C is a sensitive marker of early renal dysfunction following pediatric heart surgery. Variations in bypass parameters, myocardial injury, and ultimately critical oxygen delivery are significantly associated with the degree of renal impairment.
authors.affiliation: Royal Hospital for Sick Children, Yorkhill Division, Glasgow, UK.
authors.forename: Antony
authors.initials: A
authors.lastname: Vassalos
authors.forename: David
authors.initials: D
authors.lastname: Young
authors.forename: Kenneth
authors.initials: K
authors.lastname: MacArthur
authors.forename: James
authors.initials: J
authors.lastname: Pollock
authors.forename: Fiona
authors.initials: F
authors.lastname: Lyall
authors.forename: Mark H D
authors.initials: MH
authors.lastname: Danton
mesh_terms: D015415:Biomarkers / Q000097:blood; D002315:Cardiopulmonary Bypass / Q000009:adverse effects*; D002675:Child, Preschool; D003404:Creatinine / Q000097:blood; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006331:Heart Diseases / Q000097:blood* / Q000150:complications; D006801:Humans; D007223:Infant; D007677:Kidney Function Tests; D008297:Male; D011183:Postoperative Complications / Q000097:blood*; D011446:Prospective Studies; D012372:ROC Curve; D051437:Renal Insufficiency / Q000097:blood* / Q000150:complications; D012680:Sensitivity and Specificity; D019210:Troponin I / Q000097:blood
chemical_list: D015415:Biomarkers; D055316:Cystatin C; D019210:Troponin I; D003404:Creatinine