Valley Homeostasis Flashcards
What factor promotes platelet adhesion?
von Willebrand’s factor
Where is von Willebrand’s factor manufactured? Released?
vWF is both manufactured by and released from endothelial cells
What activates platelets?
Thrombin (aka: Factor IIa or activated factor II) activates platelets
What does the activated platelet synthesize? What is the effect?
activated platelets (think platelets that have changed shape) synthesize and release thromboxane A2 and ADP. Both of these promote platelet aggregation by binding to receptors and activating signal transduction.
What factor aggregates platelets?
Factor I - fibrinogen aggregates platelets.
Remember: Thromboxane A2 and ADP uncover the fibrinogen receptors
When the endothelial lining of the blood vessel is damaged, platelets adhere to the sub endothelial collagen. What substance anchors platelets to sub endothelial collagen?
Von Willebrand’s Factor
What clotting factor activates the platelet at the site of vascular injury?
Thrombin factor (IIa)
What two substances, released from the activated platelet, stimulate platelet aggregation?
Thromboxane A2 and ADP
What substance links platelets together (aggregates them)?
Fibrinogen (factor I)
What agents inhibit platelet aggregation by inhibiting cyclooxyegenase?
ASA and NSAIDs
What clotting factors are found in the extrinsic pathway?
III - aka tissue factor or thromboplastin
VII
What clotting factors are found in the intrinsic pathway?
XII
XI
IX
VIII
What clotting factor are found in the final common pathway?
I - fibrinogen II - prothrombin V X XIII - fibrin stabilizing factor
What clotting factor is considered the physiologic initiator of the coagulation cascade?
III - also known as tissue factor or thromboplastin
What clotting factor promotes fibrin cross-linking?
XIII - fibrin-stabilizing factor
Antithrombin III inhibits what five clotting factors? Which of these five is in the intrinsic pathway? What two of these five clotting factors are most profoundly inhibited?
II, IX, X, XI, and XII
IX, XI, and XII are in the intrinsic pathway
II and X are most profoundly inhibited
What four clotting factors are vitamin K dependent? Which of these is in the extrinsic pathway?
II, VII, IX, and X
VII is in the extrinsic pathway
How does heparin work?
heparin increases the activity of (turns on) antithrombin III
How does coumadin work?
coumadin competitively inhibits the vitamin-K dependent clotting factors
What anticoagulant affects the extrinsic and final common pathways?
warfarin (coumadin)
What anticoagulant affects the intrinsic and final common pathways?
heparin
What two coagulation tests asses the extrinsic pathway?
PT (prothrombin time) and INR (international normalized ratio)
What two coagulation tests assess the intrinsic pathway?
PTT (partial thromboplastin time) and activated coagulation time (ACT)
How does protamine work to reverse heparin? What kind of reaction is this?
protamine combines electrostatically with heparin (this is a neutralization reaction)
What enzyme is responsible for breaking down fibrin?
plasmin
What two pharmacological agents inhibit plasmin?
epsilon-aminocaproic acid (Amicar) and aprotinin (Trasylol)
Name three substances that convert plasminogen to plasmin.
urokinase plasminogen activator (uPA), tissue plasminogen activator (tPA), and streptokinase
When is aprotinin generally used in anesthesia? How does it work?
aprotinin is used for repeat sternotomies and works by inhibiting plasmin
What is the normal activated coagulation time (ACT)?
80-150 seconds
What is the best tests of primary hemostasis, or platelet function?
standardized skin bleeding time
What is the most common reason for coagulopathy after a massive blood transfusion?
lack of functioning platelets (thrombocytopenia)
What clotting factors are found in fresh frozen plasma?
all procoagulants
Cryoprecipitate contains what clotting factors?
factor I - fibrinogen
factor VIII - vWF
and factor XIII - fibrin-stabilizing factor
What are the typical manifestations of disseminated intravascular coagulopathy?
bleeding, with oozing from tubes, wounds, and vascular access sites
Transfused blood is deficient in what two coagulation factors?
factor V and factor VIII
What is the most common inherited coagulation defect?
Von Willebrand’s Disease
The patient with vW disease has not responded to desmopressin (DDAVP). What will you try next?
cryoprecipitate
What anti platelet agent prevents ADP-induced platelet aggregation?
ASA, IBP, Toradol, or Ticlopidine?
Ticlopidine
Which clotting factors are NOT made in the liver?
III - Tissue factor or Thromboplastin
IV - Calcium
VIII - vWF
The clotting factor that is responsible for cross-linking fibrin is?
XIII - fibrin-stabilizing factor
What anticoagulant works on the extrinsic pathway? and what test assesses the effectiveness?
Coumadin works on the extrinsic pathway.
PT (prothrombin time) /INR
What factors does cryoprecipitate contain?
I - fibrinogen
VIII - vWF
XIII - fibrin-stabiliing factor
When antithrombin is activated by heparin, antithrombin binds to what factors?
Binds factors II, IX, X, XI, and XII
A patient who is scheduled for CABG surgery is heparinized, and the ACT is less than 300 seconds. The result is the same after a second dose of heparin. Why is the patient unresponsive to heparin and what is your next action?
The patient has a deficiency of antithrombin III.
Give the patient FFP
Prothrombin time normally is what?
12-14 seconds
The reaction of protamine with heparin is what time of reaction?
a neutralization reaction
What substance convert fibrin to fibrin split products?
plasmin
What is aprotinin used for? And what should you be aware of when using aprotinin?
Aprotinin is used for patients undergoing a sternotomy for the second time.
A patient receiving aprotinin for the 1st time can have an allergic reaction.
A patient receiving aprotinin for the second time can have an anaphylactic reaction.
Post operative bleeding with continued oozing from wounds and catheter sites suggests what disorder?
Disseminated Inravascular Coagulopathy
What is increased in the patient with DIC?
Fibrin degradation products such as fibrin split products (FSP)
What is the major cause of diffuse bleeding after a massive blood transfusion?
Thrombocytopenia