1 23 Anticoagulants
2 Hemostasis: Three Events After InjuryVascular spasms: platelets release serotonin, which causes blood vessel to spasm and decrease blood loss until clotting occurs Platelet plug: platelets become sticky and adhere to vessel lining and each other, forming platelet plug, which is invaded by clotting factors
3 Hemostasis: Three Events After InjuryCoagulation: clot forms through chemical reactions that create netlike structure of fibrin, sealing off opening in injured vessel
4 Figure Hemostasis begins when a blood vessel is damaged and ends when the fibrin threads trap blood cells, forming a clot that seals the injured vessel.
5 Figure 23-2 Basic steps of hemostasis.
6 Mechanism of Action: HemostasisInvolves 11 plasma proteins (clotting factors) Most clotting proteins synthesized by liver Prothrombin activator, prothrombin, thrombin, fibrinogen, fibrin
7 Figure 23-3 The steps in the coagulation cascade.
8 Anticoagulants Medications that prolong bleeding timeDo not dissolve clots already formed, but may prevent clots from becoming larger Used to treat MI, venous thrombosis, pulmonary emboli Primarily used for thrombosis in veins
9 Table 23-1 Anticoagulants
10 Heparin: Uses Works by increasing length of coagulation; inhibits thrombi from forming or growing larger Treat emboli, thrombi, MI, and to prevent clotting during open-heart surgery, coronary artery bypass graft, and dialysis
11 Heparin: Adverse EffectsHemorrhage in urinary or GI tracts, subdural hematomas, hemorrhagic pancreatitis, hemarthrosis, ecchymosis
12 Heparin: ContraindicationsContraindicated in serious and intracranial bleeding, severe liver or kidney disease, malignant hypertension Interacts with aspirin, NSAIDs, anesthetics, valproic acid, thrombolytics, and other drugs
13 Heparin: Patient InformationTeach patients how to administer heparin subcutaneously. Advise patients to protect themselves from injury (e.g., use electric shaver). Warn patients to avoid aspirin and other OTC drugs. Instruct patients to report signs of bleeding.
14 Heparin in Older AdultsOlder adults are more susceptible to effects of anticoagulants. Signs of overdose include epistaxis, blood in stool or urine, excessive bruising, and prolonged bleeding. Overdose can be treated by slow infusion of 1% protamine sulfate.
15 Figure 23-4 Mechanism of action of anticoagulants.
16 LMWH: Uses Greater bioavailability and longer action than heparinMore effective in preventing and treating venous thromboembolism Less bleeding and fewer episodes of heparin-induced thrombocytopenia
17 Table 23-2 Common Low-Molecular-Weight Heparins
18 Warfarin (Coumadin): UsesInterferes with hepatic synthesis of vitamin K-dependent clotting factors (II, VII, IX, X) Used on inpatient and outpatient basis for long-term anticoagulation
19 Warfarin: Adverse EffectsHemorrhage Diarrhea Urticaria Alopecia Skin necrosis Dermatitis
20 Warfarin: ContraindicationsContraindicated in active or previous ulceration, hepatic or renal disease, malignant hypertension, bacterial endocarditis, chronic alcoholism, pregnancy Interacts with hepatic enzyme inhibitors, aspirin, NSAIDs, and thrombolytics
21 Warfarin: Patient InformationInstruct patients to report signs of bleeding; chest, abdominal, lumbar, or pelvic pain. Advise patient to stop drug immediately if signs of hepatitis occur. Advise female patients to avoid pregnancy with barrier contraceptive and to avoid breastfeeding.
22 Warfarin Tips for PatientsAdvise patients that 5 days prior to dental procedures, warfarin should be stopped. Supplemental intake of vitamin K can potentiate or inhibit oral anticoagulants.
23 Antiplatelets: Uses Prevent platelets from binding togetherUsed to prevent clot formation in arteries, in MI and stroke, and in PCTA Aspirin: low doses inhibit platelet aggregation and prolong bleeding time Ticlopidine (Ticlid) and clopidogrel (Plavix) irreversibly inhibit platelet activation
24 Antiplatelets: Uses Abciximab (ReoPro), eptifibatide (Integrilin) and tirofiban (Aggrastat) interrupt interaction of fibrinogen with clotting factors
25 Table 23-3 Antiplatelet Agents
26 Antiplatelets: Adverse EffectsEpigastric pain, heartburn, nausea, diarrhea, major or minor bleeding Abciximab: cardiac arrhythmias, abnormal thoughts, dizziness
27 Antiplatelets: ContraindicationsContraindicated in patients with history of peptic ulcer, hypertension, asthma, allergies, nasal polyps Interact with anticoagulants, thrombolytic agents, dextran, and other drugs
28 Antiplatelets: Patient InformationInstruct patients to report nausea, diarrhea, rash, sore throat, or infections; signs of bleeding; signs of hepatitis. Advise patients to avoid aspirin and antacids.
29 Garlic as AnticoagulantGarlic has been shown to decrease platelet aggregation. Use of garlic with anticoagulants may increase risk of bleeding complications.
30 Thrombolytics: Uses Used to prevent or treat excessive bleeding from surgical sites Facilitate conversion of plasminogen to plasmin, which hydrolyzes fibrin to dissolve blood clots Also called plasminogen activators
31 Table Thrombolytics
32 Thrombolytics: Adverse EffectsCommon: bleeding caused by fibrinogenolysis or fibrinolysis at site of injury Serious: intracranial bleeding
33 Thrombolytics: ContraindicationsContraindicated in active bleeding, pregnancy, lactation, intracranial trauma, vascular disease, and cancer Interact with anticoagulants, aspirin, and herbs such as feverfew, ginger, and ginkgo
34 Thrombolytics: Patient InformationInstruct patients to report signs of bleeding or changes in consciousness. Advise women to avoid breastfeeding.
35 Thrombocytopenia Platelet deficiency; most common cause of abnormal bleeding Hemophilia applies to several hereditary bleeding disorders that result from lack of factors needed for clotting.