Anticoagulants

16/12/2009

 

  • anticoagulant
  • reduces risk of thrombus formation

 

Heparin Hemorrhage Risk Indicators

  • bleeding gums
  • hemotemesis
  • hematuria
  • melena

 

Diagnostics

  • aPTT = activated partial thromboplastin time or PTT = partial thromboplastin time
  • allows therapeutic heparin range to be monitored

 

Preexisting conditions that contraindicate heparin use:

  • threatened abortion
  • cerebral of aortic aneurysm
  • cerebrovascular hemorrhage
  • severe hypertension
  • blood dyscrasia
  • recent opthalmic surgery
  • recent neurosurgery

 

Preexisting conditions indicative of increased hemorrhage risk

  1. recent childbirth
  2. severe diabetes
  3. severe retanopathy
  4. hepatopathy
  5. severe trauma
  6. vasculitis
  7. active ulcer or GI lesion
  8. GU or Respiratory tract lesion

 

Over the counter medications which increase hemorrhage risk

  1. aspirin
  2. nonsteroidal antiinflammatories
  3. cephalosporins
  4. antithyroid agents
  5. probenecid
  6. thrombolytics
  7. garlic
  8. ginger
  9. ginkgo
  10. horse chestnut
  11. feverfew

 

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Cerebrovascular Accidents (Strokes)

27/11/2009

Ischemic Stroke: sudden loss of function resulting from disruption of the blood supply to a part of the brain. Neurons die when they can no longer maintain aerobic respiration.

  • Event usually the result of long-standing cerebrovascular disease
  • early Tx results in fewer symptoms and less functional loss

5 different types

  1. large thrombosis – 20%
  2. small penetrating artery thrombosis – 25%
  3. cardiogenic embolic stroke – 20%
  4. cryptogenic 30%
  5. Other – 5%

Large artery thrombosis strokes: due to atherosclerotic plaques in the large blood vessels of the brain. Thrombus formation and occlusion at the site af the atherosclerosis result in ischemia and infarction.

Small Penetrating artery thrombotic strokes: affect one or more vessels and are the most common type of ischemic stroke.

Aka lacunar strokes because of the cavity that is created once the infarcted brain tissue disintegrates.

Cardiogenic embolic strokes: are associated with cardiac dysrhythmias, usually atrial fibrillation. Emboli originate from the heart and circulate to the cerebral vasculature, most commonly the left middle cerebral artery, resulting in a stroke. Embolic strokes may be prevented by the use of anticoagulation therapy in patients with atrial fibrillation.

The 2 remaining categories of ischemic strokes are cryptogenic with no known cause and others causes such as cocaine, coagulopathies, migraine and spontaneous dissection of the carotid or vertebral arteries.

Pathophysiology:

Martin, Glenn and Porth, Carol, Mattson. 2009. Pathophysiology Concepts of Altered Health States. 8th ed. Lippincott Williams and Wilkins. Philadelphia


Scarvelis and Wells Clinical Assessment tool for Risk of Deep Vein Thrombosis

31/10/2009

Scarvelis and Wells Clinical Assessment tool for Risk of Deep Vein Thrombosis

  1. Active cancer (treatment within last 6 months or palliative) – 1 point
  2. Calf swelling >3 cm compared to other calf (measured 10 cm below tibial tuberosity) – 1 point
  3. Collateral superficial veins (non-varicose) – 1 point
  4. Pitting edema (confined to symptomatic leg) – 1 point
  5. Swelling of entire leg – 1 point
  6. Localized pain along distribution of deep venous system – 1 point
  7. Paralysis, paresis, or recent cast immobilization of lower extremities – 1 point
  8. Recently bedridden > 3 days, or major surgery requiring regional or general anesthetic in past 4 weeks – 1 point
  9. Alternative diagnosis at least as likely – Subtract 2 points

Assessment scoring guide:

  1. Score of 2 or higher – deep vein thrombosis is likely. Follow up with diagnostic tests – imaging the leg veins.

2. Score of less than 2 – deep vein thrombosis is unlikely.

Scarvelis, D and Wells, P, S. 2006. Diagnosis and Treatment of Deep Vein Thrombosis.Journal of the American Medical Association. 175 (9) 1087-1092.


Coagulation Disorders and Treatment

28/10/2009

The clotting factor cascade

Diseases of Hemostatsis

 Thromboembolic disorders

  • occur when undesirable clots are formed
  • Thrombus = stationary clot
  • Embolus = a travelling clot
  • Deep vein thrombosis = thrombi in veins, usually form in leg veins

  • thrombi can form in the atria during atrial fibrillation
  • R atrium thrombi can dislodge and travel to lungs = pulmonary embolism
  • L atrial thrombus can dislodge can cause CVA or arterial infarct elsewhere in the body

  • arterial thrombi and emboli can result from procedures involving arterial punctures such as angiography

 Thrombocytopenia

  • abnormal clot formation
  • deficiency of platelets
  • a result of bone marrow function is suppression
  • Etiology: chemotherapeutic agents and immunosuppressant

 Hemophilias

  • genetic clotting factor deficiency
  • classified by prolonged coagulation times that result in persistent bleeding that can be acute
  1. Hemophilia A
  • lack of clotting factor VIII
  • 80% of all cases

 2. Hemophilia B (Christmas Disease)

  • deficiency of factor IX
  • 20% of cases

Tx:

  • administration of the absent clotting factor

 3. von Willebrand’s disease (vWD)

  • decrease in the quantity or quality of von Willebrand factor, role in platelet aggregation
  • Tx: factor VIII concentrate
  • desmopressin, which promotes release of stored vWF
  • infusion of plasma products containing vWF

Four Mechanisms of hemostasis modification

Drug Classification Mechanism Type of Modification
Anticoagulants Inhibition of specific cloting factors Clot formation prevention
Anticoagulant/antiplatelets Inhibition of platelet actions Clot formation prevention
Thrombolytic Dissolution of clot thrombolytics
Antifibrinolytic Inhibition of the destruction of fibrin Antifibrinolytics – Promotion of thrombosis by inhibiting the normal removal of fibrin, keeping the clot in place for a longer period of time

Anticoagulants

  • prolong bleeding time in order to prevent clot formation
  • Tx of thromboembolic disease
  • Heparin
  • Warfarin

Mechanism of action:

  • exert a negative charge on the surface of the platelets
  • cell aggregation is inhibited

Heparin:

  • acts by enhancing the inhibitory actions of antithrombin III

Warfarin:

  • acts by inhibiting the hepatic synthesis of coagulation factors II, VII, IX and X

Low Molecular weight heparins (LMWHs)

  • inhibit active X factor
  • possess same anticoagulant activity as heparin
  • yet are less likely to thrombocytopenia
  • last 2-4 times longer than heparin

Thrombin Inhibitors

  • bind both clot-bound and circulating thrombin preventing the formation of fibrin clots

 Adams, Micheal, Patrick, Bostwick, Paula, Manuel, Holland, Leland, Norman jr, and King, Shirley, Linda. 2009. Pharmacology for Nurses: A pathological approach. Pearson Canada, Toronto.


Activated Partial Thromboplastin Time (aPTT )

23/10/2009

A blood test that measures the length of time (in seconds) that it takes for clotting to occur when certain substances are added to the liquid portion of blood in a test tube. It is used to detect clotting factor deficiencies and to monitor heparin’s effectiveness.

National Alliance for Thrombosis and Thrombophelia. 2009. GLossary of Blood Clot and CLotting Disorder Terms. Retrieved October 23, 2009 from http://www.stoptheclot.org/learn_more/glossary.htm