Dose relation in the prevention of proximal vein thrombosis with a low molecular weight heparin (tinzaparin) in elective hip arthroplasty

This is a review of a double-blind, prospective study comparing the thrombo prophylactic efficacy and safety of two different prophylactic regimens of a low molecular weight heparin tinzaparin) in 250 consecutive patients (age d less than or equal to 18) undergoing primary elective hip arthroplasty. R egimen 1: 75 U anti-Xa/kg BW (actual range 63 to 91) once daily started 12 hours before operation; and regimen 2: 50 U anti-Xa/kg BW (actual range 41 to 71) once daily started 2 hours before operation. Both regimens were admi nistered in a weight-adjusted fashion and were continued for 7 days after o peration or until full mobilization. Efficacy was evaluated by occurrence o f postoperative deep vein thrombosis (DVT) diagnosed by bilateral ascending phlebography on day 7+/-2 after operation, and the venograms were evaluate d in an assessor blind fashion by a panel of three expert radiologists. Saf ety was evaluated by the amount of blood lost and transfusion requirements during and after the operation; all bleeding complications, reoperations, a dverse events and deaths were observed during the study. A 3-month follow-u p on survival and occurrence of thromboembolism was performed on all random ized patients. The result was a significantly better protective effect agai nst proximal DVT by regimen 1 compared with regimen 2. This was achieved wi th improved safety in terms of a significantly decreased need for blood tra nsfusions during operation and fewer wound complications in the postoperati ve period in favor of regimen 1. Therefore, tinzaparin administered in a dosage of 75 U anti-Xa/kg BW 12 hou rs before surgery is significantly more protective against proximal DVT and safer than the standard regimen of 50 U anti-Xa/kg BW started 2 hours befo re surgery in patients undergoing primary elective hip arthroplasty.