Week 9 - Clotting and Coagulation Flashcards
What is the best way to determine surgical bleeding risk?
Thorough history and physical –> During interview may aid in a decision to get labs drawn to if indicated
What things may patients complain about with undiagnosed coagulopathies during the interview?
Frequent hematomas, runaway bruising, and oozing after minor injuries
What are some physical signs of bleeding that warrants further investigation?
Bruising or petechial hemorrhages on chest, abdomen, or upper extremities
Where is vitamin K created?
Bacteria from the gut
What factors does vitamin K form?
Factors 2, 7, 9, 10, proteins C and S
What patient problems may be present in patients who are unable to form or use clotting factors?
LIVER DISEASES
What 2 things are important to ask the patient when assessing anticoagulant drugs they are taking?
What drug they are taking and when they took the last dose
How does Aspirin work?
Irreversibly inhibits cyclooxygenase which inhibits formation of prostaglandins and in turn Thromboxane A2 –> decreases function of the platelet
Patients should stop taking aspirin _____________ days prior to surgery
7-10 days
NSAIDS need to be withheld ______________ hours prior to surgery, why?
24-48 hours. These drugs reversibly block cyclooxygenase which prevents prostaglandin from forming, preventing the synthesis of thromboxane A2, so only a day or two is needed for platelets to regain function
Which herbal supplements can cause increased bleeding time?
All herbal supplements on table
What is a normal bleeding time?
3 - 7 minutes –> Qualitative assessment platelet count and function!
When can cryoprecipitate be given due to low fibrinogen levels?
80-100 mg / dL or less
What is a normal ACT?
80 - 150 seconds
What must the anesthesia provider do in an emergent or trauma situations that require surgery in regard to blood coagulation?
Must rely on on information supplied by family members, physical, and lab testing
Should coagulation labs be ordered on every patient prior to surgery?
No, only if indicated through doing a thorough history and physical
What can be done in a situation where a patient requires surgery, but not emergently. The patient presents with an elevated PT time
Administer vitamin K 4-6 hours prior to surgery for reversal –> 10-20 mg IM
If bleeding risk is moderate, what should be done prior to surgery? A type and crossmatch OR a type and screen?
Type and crossmatch
What should be done in an emergent surgery when the patient could be at an increased risk for bleeding?
Ordering all the blood components to have access to in the OR –> PRBCs, FFP, Platelets, and cryoprecipitate
What is the purpose of thromboxane A2 in the clotting process? What medications prevent this from occuring?
Constrict the vessel so vWF and platelets can adhere to the site of injury –> NSAIDS reversibly block this and ASA agents irreversibly block this
Prolonged bleeding will occur resulting in inadequate hemostasis
If a patient has a prolonged bleeding time, but hasn’t taken any medications that would cause this, what would be suspected? Should the case be cancelled?
Primary hemostasis abnormality –> Further investigation should be done
Just because a patient has a prolonged bleeding time DOES NOT mean they are at increased risk of bleeding or that an abnormality is present.
Is an isolated, slightly elevated bleeding time reason enough to cancel or delay a surgery?
No
Does a patient with a normal platelet count mean they have normal platelet function
No, only a representation of the quantity of platelets in the plasma with no correlation to function of the platelets
When is a patient considered throbocytopenic?
Counts less than 100,000
The patients platelet count drops below 50,000? What should be suspected?
You should suspect the patient will have prolonged bleeding under surgical conditions.
What platelet count is minimum for adequate hemostasis?
Greater than 100,000
When is a platelet count considered at a critical level? What can occur?
Less than 20,000. Spontaneous bleeding can occur
What does a PT time evaluate?
PET –> All extrinsic pathways and common pathways (3, 7, 10, 5, 1, and 2)
Most commonly used test to monitor oral anticoagulant therapy (Coumadin derivatives –> Warfarin)
Prolonged in deficiencies in these factors or warfarin.
What are some drawbacks to a PT test?
Not very sensitive. Does NOT tell you which clotting factor is deficient or what the issue is. Only which pathways (extrinsic and common)
What is considered mild thrombocytopenia?
50,000 - 100,000
How is a PT test preformed?
Patient plasma is incubated with source of tissue factor
What does a PTT test measure?
Intrinsic and common pathway deficiencies or heparin therapy (12, 11, 9, 8, 10, 5, 2, 1, and ultimately 13) –> Also screens for acquired coagulation inhibitors like factor 8 antibodies and lupus anticoagulants
What factor would be missing in hemophiliacs?
Hemophilia A (Factor 8) and Hemophilia B (Factor 9)
Does a prolonged PTT always indicate a bleeding disorder?
No
What would be suspected if both a PT and PTT time were elevated?
Typically a common pathway deficiency –> Liver disease or DIC
What must occur within the body before a patient presenting with a prolonged PT or PTT time?
Factor that is deficient must be decreased by 30%
What factor deficiency won’t cause increased bleeding? Which ones will?
Factor 12 WILL NOT, Factors 9 and 8 WILL
What does an activated clotting time test?
Quick test used in surgery to monitor the ability of blood to clot –> Normal is 90 - 150 seconds
Most commonly used to guide anticoagulant dosing
What does thrombin time assess?
The ending phase of coagulation
What three things does a thromboelastogram (TEG) measure?
- Platelet reactions
- Coagulation
- Fibrinolysis
What does a normal TEG look like?
What would a hemophiliacs TEG look like?
What are some tests that can be used to evaluate fibrinolysis?
D-dimer, fibrin degradation products, and thromboelastogram (TEG –> Can be used to look at the whole coagulation process)
What is a therapuetic INR for patients taking warfarin?
2-3
What is a normal INR?
1.1 or less
INR formula
INR = (Patient PT / Mean normal PT)^ISI
Is a PT/INR sensitive to heparin?
No
What is an acceptable INR for a neuraxial block? What about a peripheral nerve block?
INR 1.4 or less, INR 1.6 or less
What do you do for a patient with an INR of 3 who needs an emergent surgery?
Give FFP
How do you interpret a TEG?
In RBC’s, what component decreases with increased length of storage but improves once transfused?
O2 carrying capacity –> Improves when 2,3 DPG regenerates during transfusion
What is the recommended dose for platelet replacement?
One concentrate per 10 kg of patient weight –> Should increase count by 5 - 10 K
Life span of transfused platelets?
4 - 5 days
Why might a platelet transfusion be indicated in a patient with a normal platelet count?
Potent anti-platelet agents, pulmonary bypass, congenital platelet dysfunction and bleeding –> Just because you have a “normal” platelet count doesn’t mean they are working correctly
Qualitative issue
When is a platelet transfusion usually recommended? When isn’t it?
It ISN’T generally indicated in surgical or obstetric patients with a platelet count greater than 100,000
It IS generally indicated with counts less than 50,000 in the presence of excessive bleeding
Can unmatched platelets be given?
Yes, but they should be matched because unmatched can result in quicker death of the transfused platelets
What needs to occur prior to discharge if pooled platelets are administered to women of child bearing years?
Administer RHOGAM (Rh immune globulin)
Surgeries involving the central nervous system should include a patient platelet count of at least
100,000 plts
Does FFP need to be ABO compatible?
Yes
Coagulation factors in one unit of FFP equals how many units of platelets and whole blood?
4-5 platelet concentrates or 1 unit of single donor apheresis or 1 unit of fresh whole blood
When has dilutional coagulopathy occurred within a patient?
Blood is diluted 30% or the patient has lost more than one volume of blood
What does cryoprecipitate contain?
Fibrinogen (200 mg), factor 8, vWF, and fibronectin
When treating vWD patients, what is the correct order of administering products?
- Desmopressin –> Increases vWF
- Subsequently administer specific vWF/factor 8 concentrate
- If no response to either, administer cryoprecipitate
What is a “transfusion trigger” for high risk pateints?
Hgb less than 7
What factor is approved for use in hemophilia A, B, factor 7 deficient, and universal hemostatic agent by the FDA?
Factor 7 –> VERY expensive
What two things can inhibit the administration of factor 7 concentrate?
Acidosis and hypothermia
What is thrombocytosis?
Too many platelets –> More than 440,000
Does a PT or PTT indicate the risk of perioperative bleeding?
NO
Two types of von Willebrand disease
Aquired –> AvWS, can be due to autoimmune clearance of vWF, increased binding of vWF to platelets, or increased proteolysis of vWF
Inherited –> Lifelong bleeders
Two purposes of vWF
Attach to walls for platelets to stick to and behave as a plasma carrier of factor 8
Where is wWF synthesized?
Endothelium and megakaryocytes
What patient population would you likely see a factor 11 deficiency?
Jewish population
What gender does hemophilia affect almost exclusively?
Males –> Although females can be carriers
What drug can be given to hemophiliacs to help with coagulation?
Desmopressin
In a hemophiliac, what factor can be given preop while the other factor should be given intraoperativley
Factor 8 preoperatively
Factor 7 intraoperatively –> Augments thrombin generation and deters bleeding
What is DIC?
Coagulation and fibrinolysis increased
Use up all of the clotting factors and causing microthrombi –> This causes thrombocytopenia, bleeding and end organ failure
Treatment of DIC
- Treat underlying cause
- Anticoagulation with heparin
- Platelet transfusion
- FFP
- Antithrombin III
What plays into the pathogenesis of DIC?
TF is released but TFPI doesn’t stop this like it normally should –> This leads to more clotting factors being activated than normal
After this, Plasminogen activator inhibitor type one is released, preventing the breakdown of the clot
THEN –> depletion off all the clotting factors leads to increased bleeding
What does a score of 6 indicate on the International society of thrombosis and haemostasis indicate regarding a potential DIC diagnosis
Anything 5 or more indicate overt DIC, less than 5 indicates non overt DIC
What may halt the progression of DIC in a septic patient?
Treatment with antibiotic therapy
What chromosome codes for the production of beta globin chains for the protein hemoglobin A?
Chromosome 11
Sickle cell anemia results in a variant hemoglobin _______
S
Who does sickle cell primarily affect?
African American population
What can trigger a sickle cell crisis?
Hypoxemia, hypothermia, acidosis, infection, dehydration, venous stasis
What is the most common procedure sickle cell patients undergo? Why?
Cholecystectomy, because of the excess bilirubin resulting from rapid breakdown of the sickle erythrocytes
Adequate anesthesia for a sickle cell patient includes
Providing adequate hydration, oxygen saturation, normothermia, acid base balance, and positioning
What types of surgeries cause an increased risk in sickle cell patients undergoing surgeries?
Surgeries that take longer because this can lead to hypoxemia and hypothermia –> Abdominal surgeries, intracranial surgeries, thoracic, certain orthopedic
What is HIT?
Heparin induced immune response that can lead to severe thrombosis, amputation, and death
What is an absolute contraindication to heparin therapy?
HIT
HIT should be suspected if a patient receives heparin and what happens?
Greater than 50% decrease of normal platelet count or total platelet count decreases below 100,000 within 5-10 days
What is the gold standard test assessing for HIT?
C serotonin release assay
Two types of HIT, which one is worse and why?
HIT type II –> Greatest morbidity and mortality, causes patient to develop IgG antibodies directed at heparin platelet factor 4 –> This causes platelet aggregation
Treatment for HIT
STOP heparin immediately, administer direct thrombin inhibitors (dibigatran, argatroban, lepirudin), SURGERY may be required to treat venous or arterial thrombosis (embolectomy)
What does desmopressin do?
Stimulates release of vWF from endothelial cells –> Used for von Willebrand disease and mild Hemophilia A
When can anticoagulants be resumed after surgery?
After adequate hemostasis has occurred they can restart 24 hours after surgery. (48-72 hours for larger doses)
What are the two most common complications associated with stent placement?
Acute stent thrombosis and stent restenosis
When does stent thrombosis generally occur?
Within 30 days of placement –> needs to be on long term anticoagulant therapy
What is the most common cause of acute stent thrombosis?
Premature withdrawal of anticoagulant therapy
How does a drug eluding stent work?
sirolimus or paclitaxel is slowly released from the stent to block endothelial growth proliferation.
Which stent holds increased risk with acute stent thrombosis?
DES –> Because of the delayed or incomplete endothelialization process
Can patients keep taking anticoagulants prior to surgery if they have had a stent placed within the last 6 months
Patient dependent. Some cardiologists will request that they do while others may be okay temporary withdrawal.
What can be done in between the period where anticoagulant therapy has been discontinued for surgery but you want to decrease the risk of thrombosis?
Bridge with LMWH or unfractionated heparin because of its short half life
