Hematology 2 Flashcards
Normal blood vessels contain
Endothelial cells
Nitric Oxide
Prostacyclin
Nitric oxide
Vasodilates
Prostacyclin prevents
PLT Activation & aggregation (keeps plug from growing too big)
Binds PLT receptors
What happens when a blood vessel is injured?
Connective tissue & collagen is exposed
PLT adhere & rupture
Serotonin is released, a potent local vasoconstrictor
PLT plug & blood clot is created
Primary hemostasis includes
Adhesion
Activation
Aggregation
Adhesion is the formation of a
PLT plug
During adhesion, endothelial cells are synthesize &
There is a release of Factor 8, which is von Willebrand factor
What is von Willebrand disease?
Despite normal PLT count & clot retraction, there is no adhesion of PLT & increased bleeding time
Patients with von Willebrand disease can be given
DDAVP
Cryoprecipitate
DDAVP, given pre-op, will release
Endogenous stores of vWF
Cryoprecipitate will give the patient what factors?
1, 8, & 13
Activation process involves
Thrombin
Factor ____ & _____ binds thrombin receptor on PLT
2 & 2a
The activation stage involves the synthesis & release of
Thromboxane A2
Adenosine Diphosphate (ADP)
Additional PLTs
Promotes aggregation
ADP is attacked by
Plavix
PLT aggregation involves
Thromboxane A2 uncovers fibrinogen receptors
Fibrinogen binds & links PLTs
Water-soluble & friable PLT plug forms (temporary hemostasis)
Secondary hemostasis will
Create a more stable clot
Secondary hemostasis involves
Fibrin production, which involves the coagulation cascade (intrinsic, extrinsic, & final common pathway)
Secondary hemostasis contains
ALL clotting factors
What are the characteristics of fibrin fibers?
Woven net over PLT plug
RBCs trapped
Cross-linked & water insoluble
STABLE CLOT
Fibrinogen is factor
1 (final common)
Prothrombin/thrombin is factor
2 (final common)
Vit K dependent
Tissue factor/thromboplastin is factor
3 (vascular wall & injured cells)
Calcium is factor
4
Proaccelerin is factor
5
Proconvertin is factor
7
Vit K dependent
Antihemophiliac is factor
8c
von Willebrand is factor
8 (vascular endothelial cells)
Christmas is factor
9
Vit K dependent
Stuart Power is factor
10
Vit K dependent
Plasma thromboplastin antecedent is factor
11
Hageman is factor
12
Fibrin stabilizing is factor
13
Protein c & s are
Vit K dependent
What are the 3 phases of cell based coagulation?
Initiation
Amplification
Propagation
Initiation involves what pathway?
Extrinsic
Characteristics of Extrinsic pathway
Low level initiation occurs in normal conditions
Outside vascular compartment
Tissue factor (Thromboplastin or Factor 3)-primary initiator of coagulation
What factors are included in the extrinsic pathway
3–>7a
(+4)–>
10
Amplification pathway is
Intrinsic
Thrombin is amplified by factors
7, 9 & 11
What factors are involved in the intrinsic pathway?
12–>11
|
8c<–9
(+4)–>10
Approaching the final common pathway is called
Propagation
9a is generated by tissue factor
7a & 11a
9a +8a on PLT surface + Ca (4)=
Responsible for 10c
What factors are involved in the final common pathway?
10–>5
(+4)
–>2
–>1
+13
Factor 13 causes
Covalent bonding, creating a water soluble & stable clot
PT (prothrombin time) will test which pathway?
Extrinsic
Final common
PT will detect
& diagnose bleeding or excessive clotting disorders
Monitor Anticoagulation therapy
What is a normal PT
11-14 seconds
What is a normal INR?
0.8-1.1
What happens due to a prolonged PT?
Decreases in factor 2, 5, 7, & 10 (prothrombin)
Hepatic dysfunction
Which medication will prolong PT?
Warfarin, which is a Vit K antagonist
Activated Partial Thromboplastin Time (aPTT) test which pathway?
Intrinsic & final common
aPTT will
Detect bleeding disorders & thrombotic episodes
Monitor anticoagulation therapy
What is a normal aPTT?
25-35 seconds
A prolonged aPTT can be due to
Hepatic dysfunction
Leukemia
Intrinsic coagulation factor
Vit K deficiencies
What medication can prolong aPTT?
Heparin therapy & other anticoagulants
Active clotting time (ACT) measures which pathway?
Intrinsic & final common
ACT monitors
Heparinization & protamine antagonization
What can prolong ACT?
Hypothermia
Thrombocytopenia
Contact activation inhibitors (aprotinin)
Factor 1, 12, or 7 deficiencies
Bleeding time should be
3-10 minutes
PLT count should be
150,00-400,000 cell/mL
Thrombin time should be
<30 seconds
Fibrinogen should be
> 150mg/dL
Thromboelastography & Thromboelastometry measures
Coagulation time (onset of clot)
Clot formation time (angle formation): rate of fibrin polymerization
MAX clot firmness (max clot strength)
Lysis time (diagnosis of premature clot lysis & hyperfibrinolysis)
Anticoagulants
Decrease clotting
Naturally occurring heparin is release from
Mast cells during injury/inflammation
Heparin can be
Unfractionated (HMWH/LMWH)
Fractionated
What is the MOA of heparin?
Reversibly binds Antithrombin 3, increasing its activity 1,000-10,000 times
Heparin inhibits
Thrombin
Factor 10a, 12a, 11a, & 9a (7a, 2a)
PLT activation by fibrin
Onset of heparin IV? SC?
IV: immediate
SC: 1-2 hours
Heparin’s effectiveness is related to
Antithrombin 3 activity
Temperature
Protein binding
Individual response
Protein binding can cause
Heparin resistance
Dose fo heparin?
100units/kg IV initial bolus + 1,000 units/hr titrated to aPTT
What type of heparin should be used in PEDs?
Preservative free
What are characteristics of Heparin and pregnancy?
Lower plasma levels
Reduced efficacy
Monitor 10a
Doesn’t cross placenta
When performing neuraxial anesthesia, it is recommended to hold heparin for
> 4 hours
Neuraxial is avoided in coagulopathy
Low dose SubQ= no contraindication
What is the general rule for a patient on heparin & regional anesthesia?
No contraindications with low doses
When a patient is receiving heparin, you should monitor for
Neurological deficits (hematoma in epidural space)
Which lab values monitor heparin?
ACT
aPTT
Heparin blocks what pathways?
Intrinsic & Final
Heparin will prolong
ACT
aPTT