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Blood Products Advisory Committee June 14, 2002 Laurence Landow MD

Hetastarch Administration in Patients Undergoing Open Heart Surgery in Association with Cardiopulmonary Bypass (CPB). Blood Products Advisory Committee June 14, 2002 Laurence Landow MD. Questions for the Committee.

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Blood Products Advisory Committee June 14, 2002 Laurence Landow MD

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  1. Hetastarch Administration in Patients Undergoing Open Heart Surgery in Association with Cardiopulmonary Bypass (CPB) Blood Products Advisory Committee June 14, 2002 Laurence Landow MD

  2. Questions for the Committee • 1. Is the evidence for excessive bleeding in cardiac surgery patients who receive 6 % hetastarch strong enough to warrant a warning statement in the hetastarch labeling? • 2. If there is insufficient evidence for a labeling change, should a randomized controlled trial(s) be conducted to answer this question? • If a trial(s) is warranted, please comment on • Inclusion and exclusion criteria • What endpoints and differences are clinically meaningful • Major predictors of blood loss

  3. Venous tubing (from the right atrium) Arterial line microfilter Arterial tubing (to the aorta) Roller Pump

  4. FDA Background Package • 5 articles • 3 retrospective chart reviews • 1 case-control epidemiology study • 1 meta-analysis

  5. Canver and Nichols • Chart review • “Use of hetastarch in primary CPB circuitry is devoid of any added hemorrhagic risk after coronary bypass.” Chest 2000; 118:1616-1620

  6. Knutson et al • Chart review • “…use of hetastarch … may increase bleeding and transfusion requirements.” Anesth Analg 2000; 90:801-7

  7. Cope et al • Chart review • “Hetastarch infusion … produces a clinically important impairment in post-cardiac surgical hemostasis.” Ann Thorac Surg 1997; 63:78-83

  8. Herwaldt et al • Case-control study • “Patient age and hetastarch were risk factors for hemorrhage”

  9. Wilkes et al • Meta-analysis • “Postoperative blood loss is … lower in patients exposed to albumin than 6 % hetastarch.” Ann Thorac Surg 2001; 72:527-34

  10. Speakers • Charles C. Canver MD • Gary R. Haynes MD, PhD • William Sibbald MD

  11. 9 Reasons to Question Conclusions Based on Non-Randomized Trials

  12. Reason # 1 • The treatment arms may not be comparable • Different inclusion and exclusion criteria across trials • Different severity of illness scores (“risk adjustment”) • Different scoring systems used to assess risk

  13. Reason # 2 • Even with sophisticated statistical techniques, one can never be sure that key outcome predictors have been recognized and adjusted for • Recognized risk factors • Age, gender, severity of illness • Unrecognized/unmeasured risk factors • Genetic predisposition • Socio-economic status

  14. Reason # 3 • Standards of medical care change over time • Canver et al: Spanned 8 years

  15. Reason # 4 • Treatment endpoints vary between protocols • Knutson et al: • “No specific transfusion algorithms used during the study period” • “No rigorous guidelines for the infusion of hetastarch, albumin, or crystalloid”

  16. Reason # 5 • Patient selection and treatment can be biased • Canver et al: perfusionist selected which solution to use in the pump prime • HES might have been avoided in older patients, patients with renal failure

  17. Reason # 6 • Confounding is likely • Knudson et al: HES vs “non-HES” group • lower temperatures on bypass • longer times on bypass • higher frequency of preoperative anticoagulant use

  18. Reason # 6 (cont’d) • Confounding is likely • Cope et al: Volume expansion different across groups

  19. Reason # 6 (cont’d) • Confounding is likely • Pump prime • Cope et al: Albumin + crystalloid • Knutson et al: HES not used • Canver et al: HES, crystalloid, albumin, albumin + HES

  20. Adequate statistical power does not ensure lack of bias or confounding ~ 200 subjects required to detect an absolute 10% increase in blood loss Knutson et al (N=445): confounded with respect to CPB time and temperature Canver et al (N=887): biased with respect to patient selection and treatment Cope et al (N=189): confounded with respect to fluid management Reason # 7

  21. Reason # 8 • The quality of the data is often uneven • Endpoints • Different • Defined differently • Not pre-specified • Missing or inaccurate data not easily identifiable • Different variables collected

  22. Reason # 9 • Reporting bias is possible • Positive findings are reported whereas negative findings are not

  23. Conclusion • Non-randomized clinical trials tend to exaggerate effect size

  24. Questions for the Committee • 1. Is the evidence for excessive bleeding in cardiac surgery patients who receive 6 % hetastarch strong enough to warrant a warning statement in the hetastarch labeling? • 2. If there is insufficient evidence for a labeling change, should a randomized controlled trial(s) be conducted to answer this question? • If a trial(s) is warranted, please comment on • Inclusion and exclusion criteria • What endpoints and differences are clinically meaningful • Major predictors of blood loss

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