Agents Affecting Blood Clotting

Anticoagulant Agents Prevent the extension and formation of clots. Inhibition by interference with the ‘coagulation cascade’ – Drug Specific Usage – Thrombosis – Pulmonary Embolism – Myocardial Infarction

Clotting Cascade

Thromboembolism Consequences of Pulmonary Embolism - increased alveolar dead space, - pneumoconstriction - hypoxemia - hyperventilation. - regional loss of surfactant - pulmonary infarction.

Pulmonary emboli – Thrombus originating in the lower extremities  travels to the lung – lodges at the bifurcation of the main pulmonary artery/lobar branches  causes hemodynamic compromise i.e. - occlusion of smaller vessels in the lung periphery – produces pleuritic chest pain

Diagnosis of PE Missed in approximately 400,000 patients in the United States per year Approximately 100,000 deaths could be prevented Death from a massive PE is second only to the cardiac deaths - 10% of patients who develop PE die within the first hour -30% die subsequently from recurrent embolism  Anticoagulant treatment decreases the mortality rate to less than 5%.

Heparin Inhibits thrombin from converting to fibrinogen Also inactivates factors IXa, Xa, XIa and XIIa Inactivated by stomach acids so must be given parentally, not IM Prevention of a stable fibrin clot Metabolized in the liver; Excreted by the kidneys.

Additional Uses Out of body experiences (!) – Used to prevent clotting whenever the patient’s blood must circulate outside the body Used whenever prolonged coagulation is desired. – Central IV lines – Arterial lines – Some surgeries usually orthopedic DIC (Disseminated Intravascular Clotting) – Although bleeding is a symptom, the cause is hypercoagulation

Heparin Adverse Reactions: – Hemorrhage – Prolonged clotting time Bleeding gums Bloody noses Multiple bruises Black Stools Thrombocytopenia (low platelets) Necrosis of the skin Hypersensitivity reaction

Special Nursing Care Never give Heparin IM When injecting heparin subcutaneously, inject into the abdomen with a small gauge needle at a 90-degree angle Do not aspirate or rub the injection site

Heparin Drug Interactions Act synergistically with oral anticoagulants or antiplatelet drugs Risk of bleeding increases with usage of NSAIDs, Iron dextran, and ASA Drugs that inactivate or antagonize heparin Box 19-2 pg. 464 (Pharmocology) Protamine sulfate and administration of FFP are used as antidotes

Low Molecular Weight Anticoagulant Example: Enoxaparim (Lovenox) Chemically altered Heparin, actually broken down into smaller compounds. Used in prevention of thrombus especially after surgery. Prolonged circulating half life Blocks Xa factor, doesn’t affect fibrin formation

Oral Anticoagulants Warfarin (Coumadin) – Inhibits blood clotting by interfering with the synthesis of vitamin K-dependent clotting factors, VII, IX and X (which are formed in the liver) –  May be started concomitantly with Heparin therapy – Sometimes combined with antiplatelet drug such as aspirin, clopidogrel or dipyridamole to decrease arterial clotting.

Warfarin: Adverse Reactions Primary adverse reaction is minor bleeding Severe bleeding can occur, primarily in the GI tract or brain Bruises and hematomas may form at puncture sites (IV, Blood Gases, Lab draw) Necrosis or gangrene or the skin Can be reversed with vitamin K (phytonadione) and FFP

Drug Interactions Box 19-3, pg. 466, (Pharmacology Book) Quite the list! Important for patient teaching

Drug Interactions Drugs metabolized by the liver may increase or decrease the effectiveness of warfarin. – Box 19-4, pg. 467, (Pharmacology)  A diet high in vitamin K reduces the effectiveness of oral anticoagulants The risk of phenytoin (Dilantin) toxicity increases when phenytoin is taken with warfarin. Alcohol increases the risk of bleeding - especially chronic and acute alcohol poisoning.

Antiplatelet Agents Action: inhibit the aggregation of platelets – Prevent arterial thromboembolism – Target population: patients at risk for MI, stroke and arteriosclerosis Examples – Aspirin – Clopidogrel bisulfate (Plavix)

Antiplatelet Agents Uses – Useful in treating clients who have experienced CVAs or MI – Evidence suggests these agents may prevent recurrence Remember some drugs or herbs can induce bleeding or delay coagulation time (Box 19-1, pg 464, Pharmacology Book)

Thrombolytic Agents Action – Convert plasminogen to enzyme fibrinolysin; fibrinolysin dissolves clots Example – Streptokinase (IV) Pharmacokinetics – Cleared primarily by the liver Caution – Hemorrhage Uses – Used in an acute or emergency situation to dissolve a preexisting clot or thrombus

Tissue Plasminogen Activator (TPA) Thrombolytic brought to you by DNA technology Example: Activase – Effectiveness is dependent on how soon it is administered. – Within 6 hours of an MI, 71% of clients had improvement Side Effects: internal bleeding usually GI, GU, brain or retroperitoneal

Contraindications with thrombolytic drugs Active internal bleeding Intracranial neoplasm AV Malformation Aneurysm Severe uncontrolled hypertension History of recent stroke (within 2 months) Subarachnoid hemorrhage Bleeding Diathesis e.g. hemophilia Intraspinal or intracranial trauma Surgery within 2 months.

Precautions with Thrombolytic Drugs Can be used but watch closely – Undergone organ biopsy – Traumatic injury – GI or GU bleeding – Cerebrovascular diseases – Hypertension – Mitral stenosis or fibrillation that may lead to left-sided thrombus – Acute pericardiditis or endocardiditc – Septic thrombophlebitis – Diabetic retinopathy – Anticoagulantion therapy – Pregnancy – < 10 days postpartum – lactating

Nursing Interventions Important role in the health and well-being of clients – Education – S/Sx of bleeding – Bleeding from the nose or gums – Vital signs Weak, rapid pulse rate and restlessness are usually the first signs of shock.

Nursing Interventions Client education: – Advise to avoid situations that could lead to trauma – Talk with PMD before adding for subtracting any drug from their treatment program – Drastic changes in diet, laxatives, and mineral oil should be avoided – Identification and information about treatment should always be carried and/or a Medic Alert tag worn – Women on anticoagulants considering pregnancy must be referred to an obstetrician