Jenny I Shen

Stanford University, Palo Alto, California, United States

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Publications (7)26.11 Total impact

  • American Journal of Kidney Diseases 05/2014; 63(5):741-4. · 5.29 Impact Factor
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    ABSTRACT: 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. 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. 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. 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. Copyright © 2014 John Wiley & Sons, Ltd.
    Pharmacoepidemiology and Drug Safety 02/2014; · 2.90 Impact Factor
  • American Journal of Kidney Diseases 01/2014; 63(5):741–744. · 5.29 Impact Factor
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    ABSTRACT: Background Although heparin is used to anticoagulate the extracorporeal circuit for most patients on maintenance hemodialysis (HD), some patients undergo heparin-free HD. We describe the determinants of heparin-free HD and its association with adverse outcomes using data from a national dialysis provider merged with Medicare claims.Methods We identified patients aged ≥67 years with no recent history of warfarin use who initiated maintenance HD from 2007 to 2008. We applied the Cox regression to a propensity score-matched cohort to estimate the hazards of all-cause mortality, bleeding (gastrointestinal hemorrhage, hemorrhagic stroke, other hemorrhage), atherothrombosis (ischemic stroke, myocardial infarction) and venous thromboembolism (VTE) (deep vein thrombosis, pulmonary embolism).ResultsAmong 12 468 patients, 836 (6.7%) were dialyzed heparin-free. In multivariable-adjusted analyses, a history of gastrointestinal bleeding, hemorrhagic stroke and lower hemoglobin and platelet counts were associated with higher odds of heparin-free HD. Heparin-free HD use also varied as much as 4-fold by facility region. We found no significant association of heparin-free HD with all-cause mortality [hazard ratio (HR) 1.08; 95% confidence interval (CI): 0.94-1.26], bleeding (HR 1.15; 95% CI: 0.83-1.60), atherothrombosis (HR 1.09, 95% CI: 0.90-1.31) or VTE (HR 1.23, 95% CI: 0.93-1.64) compared with HD with heparin.Conclusions Patient markers of increased risk of bleeding and facility region associated with heparin-free HD use. Despite the potential benefits of avoiding heparin use, heparin-free HD was not significantly associated with decreased hazards of death, bleeding or thrombosis, suggesting that it may be no safer than HD with heparin.
    Nephrology Dialysis Transplantation 04/2013; · 3.37 Impact Factor
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    ABSTRACT: Atrial fibrillation is common among patients with end-stage renal disease undergoing hemodialysis. Although oral anticoagulation is recommended for stroke prevention in most patients with atrial fibrillation, limited evidence is available to guide treatment in hemodialysis patients with this arrhythmia. We summarize the available evidence on the epidemiology of atrial fibrillation in dialysis patients and review the data on the effectiveness of oral anticoagulation in this population. Atrial fibrillation is increasingly common in patients undergoing chronic hemodialysis, especially among older patients wherein one in six patients is diagnosed with this arrhythmia. Patients with atrial fibrillation experience double the mortality of otherwise similar patients without it. Few hemodialysis patients with atrial fibrillation receive oral anticoagulation, which is consistently associated with excess risks of hemorrhagic stroke. Observational studies did not detect a beneficial association of oral anticoagulation with the risk of ischemic stroke, with some studies describing higher risks of ischemic stroke among warfarin users. New therapeutic options including one oral direct thrombin inhibitor and two oral factor Xa inhibitors have become available, but were not tested in patients with advanced kidney disease. Atrial fibrillation is increasingly common in patients undergoing hemodialysis, yet little is known about the optimal management of these patients. The current evidence does not support net benefits from oral anticoagulation in the dialysis population.
    Current opinion in nephrology and hypertension 11/2012; 21(6):600-6. · 3.96 Impact Factor
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    ABSTRACT: OBJECTIVES: Switching from peritoneal dialysis (PD) to hemodialysis (HD) is undesirable, because of complications from temporary vascular access, disruption of daily routine, and higher costs. Little is known about the role that social factors play in technique failure. Design, Setting, Participants, Measurements: We followed for 3 years a nationally representative cohort of US patients who initiated PD in 1996 - 1997. Technique failure was defined as any switch from PD to HD for 30 days or more. We used Cox regression to examine associations between technique failure and demographic, medical, social, and pre-dialysis factors. We estimated hazard ratios (HRs) with 95% confidence intervals (CIs). RESULTS: We identified an inception cohort of 1587 patients undergoing PD. In multivariate analysis, female sex (HR: 0.78; 95% CI: 0.64 to 0.95) was associated with lower rates of technique failure, and black race [compared with white race (HR: 1.48; 95% CI: 1.20 to 1.82)] and receiving Medicaid (HR: 1.48; 95% CI: 1.17 to 1.86) were associated with higher rates. Compared with patients who worked full-time, those who were retired (HR: 1.49; 95% CI: 1.07 to 2.08) or disabled (HR: 1.38; 95% CI: 1.01 to 1.88) had higher rates of failure. Patients with a systolic blood pressure of 140 - 160 mmHg had a higher rate of failure than did those with a pressure of 120 - 140 mmHg (HR: 1.24; 95% CI: 1.00 to 1.52). Earlier referral to a nephrologist (>3 months before dialysis initiation) and the primary decision-maker for the dialysis modality (physician vs patient vs shared) were not associated with technique failure. CONCLUSIONS: This study confirms that several socio-demographic factors are associated with technique failure, emphasizing the potential importance of social and financial support in maintaining PD.
    Peritoneal dialysis international : journal of the International Society for Peritoneal Dialysis. 10/2012;
  • Jenny I Shen, Wolfgang C Winkelmayer
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    ABSTRACT: Anticoagulation is essential to hemodialysis, and unfractionated heparin (UFH) is the most commonly used anticoagulant in the United States. However, there is no universally accepted standard for its administration in long-term hemodialysis. Dosage schedules vary and include weight-based protocols and low-dose protocols for those at high risk of bleeding, as well as regional anticoagulation with heparin and heparin-coated dialyzers. Adjustments are based largely on clinical signs of under- and overanticoagulation. Risks of UFH use include bleeding, heparin-induced thrombocytopenia, hypertriglyceridemia, anaphylaxis, and possibly bone mineral disease, hyperkalemia, and catheter-associated sepsis. Alternative anticoagulants include low-molecular-weight heparin, direct thrombin inhibitors, heparinoids, and citrate. Anticoagulant-free hemodialysis and peritoneal dialysis also are potential substitutes. However, some of these alternative treatments are not as available as or are more costly than UFH, are dependent on country and health care system, and present dosing challenges. When properly monitored, UFH is a relatively safe and economical choice for anticoagulation in long-term hemodialysis for most patients.
    American Journal of Kidney Diseases 05/2012; 60(3):473-86. · 5.29 Impact Factor