Pulmonary embolism is most commonly produced by which of the following
|C||Thrombosis of pelvic vessels|
a. Pulmonary embolism is a spectrum of disease that ranges from the clinically insignificant pulmonary microembolus to a catastrophic instantaneously fatal massive pulmonary thrombus obstructing both pulmonary arteries.
b. Thrombi most commonly develop in the veins of the lower leg from stasis and a hypercoagulable state, and they propagate proximally to the deep veins of the leg and pelvis. As these clots become larger and as the veins become larger, the propensity for these clots to dislodge and embolize to the lungs increases.
c. Risk factors for pulmonary embolus may include high body-mass index, malignancy, cigarette smoking, hypertension, and surgery. Activated protein C is an extremely potent anticoagulant. Resistance to activated protein C may be transmitted as an autosomal dominant trait in some patients with a propensity for venous thrombosis.
d. Routine laboratory tests in the past for a hypercoagulable state or pulmonary embolus included an assay of antithrombin III, protein C, and protein S; however, deficiencies in these proteins rarely occur.
e. Currently, recommended testing includes the following:
i. Factor V Leiden mutation (the most common hypercoagulable statE.
ii. Hyperhomocystinemia (readily treated with B vitamins)
iii. Lupus anticoagulant (because intensive anticoagulation may be requireD.
b. IV fluids, monitoring of central venous pressures, or use of inotropes may be required as dictated by the clinical situation.
c. Heparin is the mainstay of treatment for pulmonary embolus. Heparin enhances antithrombin III activity to prevent propagation of the clot and to facilitate fibrinolysis. A bolus of heparin of 5000 to 10,000 units is given IV and followed by a continuous infusion of heparin (18 U/kg/hr; not to exceed 1600 U/hr).
d. After therapeutic partial thromboplastin times have been achieved (ratio of activated partial thromboplastin time to the control ranges from 1.5-2.5), oral anticoagulation may be started with warfarin