Anticoagulation therapy
Posted by admin on May 12th, 2010Anticoagulation therapy: The mainstay of treatment is anticoagulation therapy, beginning with heparin and continuing with warfarin. Heparin is given s.c. q6h,IVt|4h,orby continuous IV infusion. If the continuous IV route is used, the patient must first receive a rapid infusion (bolus) of 5,000 lo IO.0(K) u. The initial infusion rate is usually 1000 u./h; thereafter, the rate is adjusted according Lo the partial thromboplastin lime, which should be kepi between 1.5 and 2.0 limes the normal control value. The partial thromboplastin time must be measured daily, since the necessary flow rate may change.
Conlinuous IV infusion offers the most flexibility in adjusting dose. Accurate infusion is critical; inadvertent increases in rate can lead to severe bleeding, and temporary interruptions of ihe infusion can lead lo inadequate anticoagulation within I h. When an IV infusion is restarted, a rapid infusion (bolus) of 5000 u. must generally be given. Recently, IV heparin 10,000 to 12,000 u. q 12 h has been found to be as effective as continuous IV The duration of heparinization is debatable, but one recommendation is 4 days for femoropopliteal thrombosis and 5 to 7 days for iliofemoral thrombosis.
Periodic platelet counts should be obtained in patients receiving heparin therapy, usually after 5 days of therapy. Heparin therapy should be discontinued if the patient develops thrombocytopenia, which occurs in about % of patients. A small proportion of them develop arterial and venous thrombi called Ihe syndrome of paradoxical thrombosis. Although the exact mechanism of this syndrome is not clear, heparin-dependenl platelet antibodies and abnormal amounts of immunoglobulin may deposit on endothelial cells. In the laboratory, the rale at which normal platelets release serotonin increases when they are exposed lo heparinized plasma from these patients.
