title: Correlates and variance decomposition analysis of heparin dosing for maintenance hemodialysis in older US patients.
abstract: OBJECTIVE
  Heparin is commonly used to anticoagulate the hemodialysis (HD) circuit. Despite the bleeding risk, no American standards exist for its administration. We identified correlates and quantified sources of variance in heparin dosing for HD.
  
  
  METHODS
  We performed a cross-sectional study of patients aged 67 years or older who underwent HD with heparin on one of two randomly chosen days in 2008 at a national chain of dialysis facilities. Using a mixed effects model with random intercept for facility and fixed patient and facility characteristics, we examined heparin dosing at patient and facility levels.
  
  
  RESULTS
  The median heparin dose among the 17 722 patients treated in 1366 facilities was 4000 (25th-75th percentile: 2625-6000) units. In multivariable-adjusted analyses, higher weight, longer session duration, catheter use, and dialyzer reuse were significantly associated with higher heparin dose. Dose also varied considerably among census divisions. Of the overall variance in dose, 21% was due to between-facility differences, independent of facilities' case mix, geography, size, or rurality; 79% was due to differences at the patient level. The patient and facility characteristics in our model explained only 25% of the variance at the patient level.
  
  
  CONCLUSIONS
  Despite the lack of standards for heparin administration, we noted patterns of use, including weight-based and time-dependent dosing. Most of the variance was at the patient level; however, only a quarter of it could be explained. The high amount of unexplained variance suggests that factors other than clinical need are driving heparin dosing and that there is likely room for more judicious dosing of heparin.
authors.affiliation: Division of Nephrology, Department of Medicine, Stanford University School of Medicine, Palo Alto, CA, USA.
authors.forename: Jenny I
authors.initials: JI
authors.lastname: Shen
authors.forename: Maria E
authors.initials: ME
authors.lastname: Montez-Rath
authors.forename: Aya A
authors.initials: AA
authors.lastname: Mitani
authors.forename: Kevin F
authors.initials: KF
authors.lastname: Erickson
authors.forename: Wolfgang C
authors.initials: WC
authors.lastname: Winkelmayer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects; D003430:Cross-Sectional Studies; D004305:Dose-Response Relationship, Drug; D005260:Female; D006470:Hemorrhage / Q000139:chemically induced*; D006493:Heparin / Q000008:administration & dosage* / Q000009:adverse effects; D006801:Humans; D008297:Male; D006435:Renal Dialysis / Q000379:methods*; D013997:Time Factors; D014481:United States
chemical_list: D000925:Anticoagulants; D006493:Heparin
keywords: anticoagulation; facility; hemodialysis; heparin; pharmacoepidemiology