A Comparison of Dalteparin and Tinzaparin for Prevention of Blood Clots in Hemodialysis Patients on Oral Anticoagulants Having Surgery

A prospective multicenter randomised trial involving 60 consecutive eligible and consenting patients from teaching hospitals in Canada. Patients will be randomised to either tinzaparin or dalteparin to investigate the pharmacokinetics of both low molecular weight heparins (LMWH) perioperatively in a special population, namely end stage renal disease (ESRD) dialysis patients.

To date although there exists evidence to suggest tinzaparin may be safe in patients on hemodialysis, LMWHs as a group have not been investigated in the perioperative setting in these patients. This protocol has been developed so that the pharmacokinetic behaviour of tinzaparin and dalteparin can be compared but also so that the duration off warfarin is minimised. Therapeutic doses of LMWH are administered pre-procedure during as much time of the period as possible that oral anticoagulation is sub-therapeutic.

Inclusion criteria

• Informed consent
• Patients aged >= 18 with end stage renal disease requiring chronic hemodialysis (HD) three times a week and clinically stable on HD for 4 weeks (x 4 wks)
• Patients requiring active oral anticoagulation for prosthetic heart valves, recent deep vein thrombosis >= 1 month, or patients with atrial fibrillation and a major risk factor (previous transient ischemic attack [TIA] or stroke, high blood pressure, diabetes, aged >= 75, moderate/severe left ventricle dysfunction) who require elective non-cardiac surgery or an invasive procedure with reversal of their anticoagulant therapy.

Exclusion criteria

• Evidence of active bleeding prior to stopping warfarin
• Hemoglobin <= 90 or platelet count <= 100x10^9/L
• Uncontrolled hypertension or stroke within 6 months of study commencement
• Spinal or neurosurgery
• Eye surgery (excluding cataract surgery)
• Life expectancy less than 3 months
• Patients requiring cardiac surgery
• Presence of active duodenal ulcer