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jb124
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what happens when damage occurs to blood vessels?
body's coagulation mechanism begins clot formation to prevent excessive blood loss
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how are damaged blood vessels controlled intraoperatively?
- thermal hemostasis (ESU)
- mechanical hemostasis (ligatures or hemostatic clips)
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coagulants used on areas of capillary bleeding as an adjust to natural hemostasis
topical hemostatics
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when natural coagulation factors are absent or insufficient...
systemic coagulants used to restore or enhance coagulation process
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used to prevent or delay the onset of coagulation sequence during surgical procedures performed on blood vessels
systemic anticoagulants
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administered IV topically from back table during peripheral and cardiovascular surgical procedures to prevent adverse clotting
Heparin
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agents used to help speed the breakdown of existing blood clots
thrombolytics
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what does damage to small blood vessel do?
causes spasm, which causes platelet plug to form, which leads to coagulation
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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
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mesh of protein threads that traps blood cells to form a clot
fibrin
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2 mechanisms for formation of thromboplastin
extrinsic pathway and intrinsic pathway
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pathway initiated by factors outside the blood
extrinsic pathway
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what is extrinsic pathway triggered by?
tissue thromboplastin (factor III) - released from damaged tissue
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how long does it take for extrinsic pathway to produce a clot?
seconds
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in extrinsic pathway, factor III combines with what to activate Stuart-Prower factor X?
antihemophilic factor VIII and calcium
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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
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what is intrinsic pathway initiated by?
substances contained in the blood
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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
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abnormal clotting that takes place within an unbroken blood vessel
thrombosis
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what happens if a thrombus forms in an artery?
may cut off blood supply to an area
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what happens if a thrombus forms in a vein?
may inhibit return of blood to systemic circulation
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clot-dissolving enzyme normally found in the blood
fibrinolysin
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drugs that promote, accelerate, or make possible blood coagulation
coagulants
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2 major categories of coagulants
- hemostatics
- systemic coagulants
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agents that enhance or accelerate blood clotting at a surgical site
hemostatics
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what does QuikClot treat?
severe traumatic bleeding on the battlefield
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how are hemostatics applied in surgery?
topically in form of films, powders, sponges or solutions
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agent thought to be mechanical rather than chemical applied topically with pressure to bleeding sites
absorbable gelatin
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how long does it take for gelatin hemostatics to absorb completely?
4 to 6 weeks
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how are gelatin hemostatics used?
- dry or moistened with saline
- never with infection or intravascularly
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examples of gelatin hemostatics
- Gelfilm
- Gelform powder and sponges
- Surgifoam
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dry Gelfilm consistency and use
- stiff cellophane
- when moistened, becomes pliable and can be cut
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dry Gelfilm used in what types of surgeries?
- neurosurgery
- thoracic
- ocular
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how is Gelfoam powder made into paste?
by mixing with saline
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what does Gelfoam in powder form do?
promotes granulation tissue - may be used on areas of skin ulceration
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types of surgeries Gelfoam used?
- orthopedic
- general
- neurosurgical
- otologic
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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
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Gelfoam Plus
combination of Gelfoam, thrombin, sterile saline, and 10-mL syringe
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what do flowable gelatins do?
conforms to uneven bleeding surfaces and enables clot formation
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examples of flowable gelatins
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what does absorbable collagen sponges do when applied to bleeding surfaces?
promotes platelet aggregation
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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
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examples of absorbable collagen
- Collastat
- Helistat
- Hemopad
- Instat
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dry, fibrous preparation of purified bovine corium collagen
Avitene MCH
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to what instruments should Avitene be applied?
dry instruments only - will adhere to wet surfaces
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onset of action of Instat MCH
2-4 minutes
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what does oxidized cellulose do when applied to bleeding surfaces?
it swells, becoming a gelatinous mass that serves as a nucleus for clotting
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how is fiber form of oxidized cellulose grasped?
with dry tissue forceps in the specific amount needed
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surgeries in which oxidized cellulose is used
- neurosurgery
- otorhinolaryngology
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examples of oxidize regenerated cellulose
- Surgicel gauze
- Surgicel Nu-Knit
- Surgicel Fibrillar
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Surgicel absorbable hemostat is effective against?
- wide range of gram-positive and gram-negative microorganisms
- bacteriocidal
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topical liquid hemostatic agent of bovine origin
Thrombin (Thrombin-JMI, Thrombinar, Thrombostat)
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how does Thrombin work?
by catalyzing conversion of fibrinogen to fibrin, increasing speed of natural clotting mechanism
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how is thrombin applied?
topically in solution or as powder or in combination with gelatin sponge
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combination of bovine thrombin and calcium chloride freeze-dried into a gelatin sponge
Thrombi-Gel
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in what form is Evithrom available?
frozen solution that must be thawed prior to topical administration
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with what must Recothrom be constituted?
sterile saline
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Recothrom is contraindicated for whom?
patients with known hypersensitivity to hamster proteins or snake proteins
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thrombin combined with microfibrillar collagen that is combined with patient's own plasma
Vitagel
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examples of fibrin sealants
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topical agent made from beeswax
bone wax
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bone wax used in what types of surgeries?
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bone wax acts as?
mechanical barrier rather than matrix for clotting
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complications of bone wax
chronic inflammation and granuloma formation
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examples of hemostatic agents
- tannic acid
- silver nitrate
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powder made from astringent plant
tannic acid
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when applied topically to mucous membranes, what does tannic acid do?
helps stop capillary bleeding
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what is used after tonsillectomy as a vasoconstrictor?
tannic acid in combination with 1% Neo-Synephrine
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what is silver nitrate sometimes mixed with?
potassium nitrate
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silver nitrate used for?
- cauterize wounds
- remove granulation tissue or warts
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what should silver nitrate NOT be used around?
eyes
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deep brown solution of ferrous sulfate, sulfuric acid and nitric acid diluted with water or available as paste
Monsel solution
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Monsel solution used for?
applied to bleeding surface remaining after cervical cone biopsy
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agents that replace deficiencies in natural clotting mechanism
systemic coagulants
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systemic coagulants used to replace?
calcium, vitamin K, some of coagulation factors in blood
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how are systemic coagulants administered?
IV, IM, orally or subcutaneously
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body's most common mineral
calcium
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when would calcium salts be used?
if calcium levels fall during surgery
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dosage of calcium given intraoperatively
injection of 10% solution of calcium chloride
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fat-soluble vitamin that promotes blood clotting by increasing synthesis of coagulation factors
vitamin K
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what can vitamin K deficiency lead to in a surgical patient?
excessive bleeding
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how long does it take vitamin K to produce acceptable effect?
up to 24 hours
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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
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for what is vitamin K used in the medical setting?
to counteract anticoagulant-induced prothrombin deficiency
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what does vitamin K do?
stimulates prothrombin formation by the liver
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2 blood factors administered IV in medical setting
- factor VIII
- factor IX complex
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plasma protein essential for conversion of prothrombin to thrombin
factor VIII
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factor VIII is absent in whom?
patients with hemophilia A
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examples of antihemophilic factor
- Hemofil-M
- Koate-HS
- Monociate
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concentrate of dried plasma fractions, mainly coagulation factors II, VII, IX, and X
factor IX complex
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for whom is factor IX administered?
patients with hemophilia B
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what is factor IX complex used for?
to reverse coumarin-induced hemorrhage
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drugs that prevent or interfere with blood coagulation
anticoagulants
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why are anticoagulants administered?
to prevent venous thrombosis, pulmonary embolism, acute coronary occlusions after MI, and strokes caused by embolus or cerebral blood clot
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do anticoagulants dissolve existing clots?
negative - help prevent new clots from forming
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why are anticoagulants used in surgery?
to help prevent clot formation as response to trauma or manipulation of blood vessels
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most commonly used parenteral anticoagulant
heparin sodium
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how does heparin act?
- by binding to antithrombin III
- interferes with platelet aggregation
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onset and duration of heparin
- onset - 5 min
- duration - 2-4 hours
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adverse reactions of heparin
increased risk of hemorrhage and thrombocytopenia
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if high risk of PE or DVT exists, how is heparin administered?
preoperatively by subcu injection at least 1 hour prior to surgical procedure
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amount of time sufficient to allow systemic distribution of heparin
3 minutes
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antidote for heparin
protamine sulfate
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how is protamine administered?
by slow IV injection
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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
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what is enoxaparin used for?
to prevent postoperative DVT following hip or knee replacement
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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)
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what is Arixtra?
synthetic chemical, identical in structure to part of heparin molecule that binds with AT III
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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
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reversal agent for fondaparinux
none
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used for long-term medical management of thromboembolic disease such as DVT or PE
oral anticoagulants
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what is oral anticoagulant therapy used for?
to prevent blood clots associated with CV thromboembolic disease
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how does coumadin work?
act by inhibiting vitamin K activity in liver, preventing formation of coagulation factors II, VII, IX and X
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onset and duration of Coumadin
- onset - 12-72 hours
- duration - 5-7 days
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antidote for excessive warfarin anticoagulation
vitamin K
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what does aspirin do?
prevents clot formation by inhibiting platelet aggregation
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what does administration of 300 mg aspirin do?
double normal bleeding time for up to 7 days
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agents that activate plasminogen to form plasmin
thrombolytics
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what does plasmin do?
digests fibrin, which dissolves blood clot
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what are thrombolytics used to treat?
acute MI when coronary artery thrombosis is present
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what is used in conjunction with thrombolytic agents?
anticoagulation therapy
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first-generation thrombolytics
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second-generation thrombolytics
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