SUR 126 - coagulation

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  1. what happens when damage occurs to blood vessels?
    body's coagulation mechanism begins clot formation to prevent excessive blood loss
  2. how are damaged blood vessels controlled intraoperatively?
    • thermal hemostasis (ESU)
    • mechanical hemostasis (ligatures or hemostatic clips)
  3. coagulants used on areas of capillary bleeding as an adjust to natural hemostasis
    topical hemostatics
  4. when natural coagulation factors are absent or insufficient...
    systemic coagulants used to restore or enhance coagulation process
  5. used to prevent or delay the onset of coagulation sequence during surgical procedures performed on blood vessels
    systemic anticoagulants
  6. administered IV topically from back table during peripheral and cardiovascular surgical procedures to prevent adverse clotting
    Heparin
  7. agents used to help speed the breakdown of existing blood clots
    thrombolytics
  8. what does damage to small blood vessel do?
    causes spasm, which causes platelet plug to form, which leads to coagulation
  9. 3 basic stages of clot formation
    • stage 1 - thromboplastin (prothrombin activator) formed
    • stage 2 - thromboplastin converts prothrombin (factor II) into thrombin
    • stage 3 - thrombin converts fibrinogen (factor I) into fibrin
  10. mesh of protein threads that traps blood cells to form a clot
    fibrin
  11. 2 mechanisms for formation of thromboplastin
    extrinsic pathway and intrinsic pathway
  12. pathway initiated by factors outside the blood
    extrinsic pathway
  13. what is extrinsic pathway triggered by?
    tissue thromboplastin (factor III) - released from damaged tissue
  14. how long does it take for extrinsic pathway to produce a clot?
    seconds
  15. in extrinsic pathway, factor III combines with what to activate Stuart-Prower factor X?
    antihemophilic factor VIII and calcium
  16. when Stuart-Prower factor X is activated in extrinsic pathway, what does factor X do?
    reacts with proaccelerin (factor V) and calcium to form thromboplastin
  17. what is intrinsic pathway initiated by?
    substances contained in the blood
  18. what is activated in intrinsic pathway when a blood vessel is damaged?
    Hageman factor (factor XII), which activates plasma thromboplastin component (PTC; factor IX), which combines with antihemophilic factor and calcium to activate factor X, which reacts with proaccelerin (factor V) and calcium to form thromboplastin
  19. abnormal clotting that takes place within an unbroken blood vessel
    thrombosis
  20. what happens if a thrombus forms in an artery?
    may cut off blood supply to an area
  21. what happens if a thrombus forms in a vein?
    may inhibit return of blood to systemic circulation
  22. clot-dissolving enzyme normally found in the blood
    fibrinolysin
  23. drugs that promote, accelerate, or make possible blood coagulation
    coagulants
  24. 2 major categories of coagulants
    • hemostatics
    • systemic coagulants
  25. agents that enhance or accelerate blood clotting at a surgical site
    hemostatics
  26. what does QuikClot treat?
    severe traumatic bleeding on the battlefield
  27. how are hemostatics applied in surgery?
    topically in form of films, powders, sponges or solutions
  28. agent thought to be mechanical rather than chemical applied topically with pressure to bleeding sites
    absorbable gelatin
  29. how long does it take for gelatin hemostatics to absorb completely?
    4 to 6 weeks
  30. how are gelatin hemostatics used?
    • dry or moistened with saline
    • never with infection or intravascularly
  31. examples of gelatin hemostatics
    • Gelfilm
    • Gelform powder and sponges
    • Surgifoam
  32. dry Gelfilm consistency and use
    • stiff cellophane
    • when moistened, becomes pliable and can be cut
  33. dry Gelfilm used in what types of surgeries?
    • neurosurgery
    • thoracic
    • ocular
  34. how is Gelfoam powder made into paste?
    by mixing with saline
  35. what does Gelfoam in powder form do?
    promotes granulation tissue - may be used on areas of skin ulceration
  36. types of surgeries Gelfoam used?
    • orthopedic
    • general
    • neurosurgical
    • otologic
  37. how is Gelfoam used in otologic surgeries?
    cut into pledgets used to pack the area around tympanic graft or apply very small amount of epinephrine on bleeding surfaces inside middle ear
  38. Gelfoam Plus
    combination of Gelfoam, thrombin, sterile saline, and 10-mL syringe
  39. what do flowable gelatins do?
    conforms to uneven bleeding surfaces and enables clot formation
  40. examples of flowable gelatins
    • Floseal
    • Surgiflo
  41. what does absorbable collagen sponges do when applied to bleeding surfaces?
    promotes platelet aggregation
  42. what does collagen do to bone cement?
    may reduce bonding strength, so it should not be applied to bone prior to placement of prosthesis requiring cement fixation
  43. examples of absorbable collagen
    • Collastat
    • Helistat
    • Hemopad
    • Instat
  44. dry, fibrous preparation of purified bovine corium collagen
    Avitene MCH
  45. to what instruments should Avitene be applied?
    dry instruments only - will adhere to wet surfaces
  46. onset of action of Instat MCH
    2-4 minutes
  47. what does oxidized cellulose do when applied to bleeding surfaces?
    it swells, becoming a gelatinous mass that serves as a nucleus for clotting
  48. how is fiber form of oxidized cellulose grasped?
    with dry tissue forceps in the specific amount needed
  49. surgeries in which oxidized cellulose is used
    • neurosurgery
    • otorhinolaryngology
  50. examples of oxidize regenerated cellulose
    • Surgicel gauze
    • Surgicel Nu-Knit
    • Surgicel Fibrillar
  51. Surgicel absorbable hemostat is effective against?
    • wide range of gram-positive and gram-negative microorganisms
    • bacteriocidal
  52. topical liquid hemostatic agent of bovine origin
    Thrombin (Thrombin-JMI, Thrombinar, Thrombostat)
  53. how does Thrombin work?
    by catalyzing conversion of fibrinogen to fibrin, increasing speed of natural clotting mechanism
  54. how is thrombin applied?
    topically in solution or as powder or in combination with gelatin sponge
  55. combination of bovine thrombin and calcium chloride freeze-dried into a gelatin sponge
    Thrombi-Gel
  56. in what form is Evithrom available?
    frozen solution that must be thawed prior to topical administration
  57. with what must Recothrom be constituted?
    sterile saline
  58. Recothrom is contraindicated for whom?
    patients with known hypersensitivity to hamster proteins or snake proteins
  59. thrombin combined with microfibrillar collagen that is combined with patient's own plasma
    Vitagel
  60. examples of fibrin sealants
    • Tisseel
    • Evicel
  61. topical agent made from beeswax
    bone wax
  62. bone wax used in what types of surgeries?
    • orthopedics
    • neurosurgery
  63. bone wax acts as?
    mechanical barrier rather than matrix for clotting
  64. complications of bone wax
    chronic inflammation and granuloma formation
  65. examples of hemostatic agents
    • tannic acid
    • silver nitrate
  66. powder made from astringent plant
    tannic acid
  67. when applied topically to mucous membranes, what does tannic acid do?
    helps stop capillary bleeding
  68. what is used after tonsillectomy as a vasoconstrictor?
    tannic acid in combination with 1% Neo-Synephrine
  69. what is silver nitrate sometimes mixed with?
    potassium nitrate
  70. silver nitrate used for?
    • cauterize wounds
    • remove granulation tissue or warts
  71. what should silver nitrate NOT be used around?
    eyes
  72. deep brown solution of ferrous sulfate, sulfuric acid and nitric acid diluted with water or available as paste
    Monsel solution
  73. Monsel solution used for?
    applied to bleeding surface remaining after cervical cone biopsy
  74. agents that replace deficiencies in natural clotting mechanism
    systemic coagulants
  75. systemic coagulants used to replace?
    calcium, vitamin K, some of coagulation factors in blood
  76. how are systemic coagulants administered?
    IV, IM, orally or subcutaneously
  77. body's most common mineral
    calcium
  78. when would calcium salts be used?
    if calcium levels fall during surgery
  79. dosage of calcium given intraoperatively
    injection of 10% solution of calcium chloride
  80. fat-soluble vitamin that promotes blood clotting by increasing synthesis of coagulation factors
    vitamin K
  81. what can vitamin K deficiency lead to in a surgical patient?
    excessive bleeding
  82. how long does it take vitamin K to produce acceptable effect?
    up to 24 hours
  83. what is given if emergency surgery is necessary and cannot be delayed for vitamin K?
    fresh frozen plasma may be administered 10-15 mL/kg for immediate hemostasis
  84. for what is vitamin K used in the medical setting?
    to counteract anticoagulant-induced prothrombin deficiency
  85. what does vitamin K do?
    stimulates prothrombin formation by the liver
  86. 2 blood factors administered IV in medical setting
    • factor VIII
    • factor IX complex
  87. plasma protein essential for conversion of prothrombin to thrombin
    factor VIII
  88. factor VIII is absent in whom?
    patients with hemophilia A
  89. examples of antihemophilic factor
    • Hemofil-M
    • Koate-HS
    • Monociate
  90. concentrate of dried plasma fractions, mainly coagulation factors II, VII, IX, and X
    factor IX complex
  91. for whom is factor IX administered?
    patients with hemophilia B
  92. what is factor IX complex used for?
    to reverse coumarin-induced hemorrhage
  93. drugs that prevent or interfere with blood coagulation
    anticoagulants
  94. why are anticoagulants administered?
    to prevent venous thrombosis, pulmonary embolism, acute coronary occlusions after MI, and strokes caused by embolus or cerebral blood clot
  95. do anticoagulants dissolve existing clots?
    negative - help prevent new clots from forming
  96. why are anticoagulants used in surgery?
    to help prevent clot formation as response to trauma or manipulation of blood vessels
  97. most commonly used parenteral anticoagulant
    heparin sodium
  98. how does heparin act?
    • by binding to antithrombin III
    • interferes with platelet aggregation
  99. onset and duration of heparin
    • onset - 5 min
    • duration - 2-4 hours
  100. adverse reactions of heparin
    increased risk of hemorrhage and thrombocytopenia
  101. if high risk of PE or DVT exists, how is heparin administered?
    preoperatively by subcu injection at least 1 hour prior to surgical procedure
  102. amount of time sufficient to allow systemic distribution of heparin
    3 minutes
  103. antidote for heparin
    protamine sulfate
  104. how is protamine administered?
    by slow IV injection
  105. why are low-molecular-weight heparins used more often?
    they also bind to AT III but they have a lower affinity for plasma protein binding and there is less variability among patients
  106. what is enoxaparin used for?
    to prevent postoperative DVT following hip or knee replacement
  107. factor Xa inhibitor used for postoperative and long-term prophylaxis of DVT and PE in orthopedic fracture, total joint and abdominal surgical patients
    Fondaparinux (Arixtra)
  108. what is Arixtra?
    synthetic chemical, identical in structure to part of heparin molecule that binds with AT III
  109. how is fondaparinux administered?
    • subcu ONLY
    • no earlier than 6-8 hours after surgery once daily in a dose of 2.5 mg/day for 5-9 days
  110. reversal agent for fondaparinux
    none
  111. used for long-term medical management of thromboembolic disease such as DVT or PE
    oral anticoagulants
  112. what is oral anticoagulant therapy used for?
    to prevent blood clots associated with CV thromboembolic disease
  113. how does coumadin work?
    act by inhibiting vitamin K activity in liver, preventing formation of coagulation factors II, VII, IX and X
  114. onset and duration of Coumadin
    • onset - 12-72 hours
    • duration - 5-7 days
  115. antidote for excessive warfarin anticoagulation
    vitamin K
  116. what does aspirin do?
    prevents clot formation by inhibiting platelet aggregation
  117. what does administration of 300 mg aspirin do?
    double normal bleeding time for up to 7 days
  118. agents that activate plasminogen to form plasmin
    thrombolytics
  119. what does plasmin do?
    digests fibrin, which dissolves blood clot
  120. what are thrombolytics used to treat?
    acute MI when coronary artery thrombosis is present
  121. what is used in conjunction with thrombolytic agents?
    anticoagulation therapy
  122. first-generation thrombolytics
    • streptokinase
    • urokinase
  123. second-generation thrombolytics
    • alteplase
    • tenecteplase

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Author:
 jb124
ID:
 182481
Filename:
 SUR 126 - coagulation
Updated:
2012-11-19 03:59:07
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coagulation
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coagulation
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