Case 47 - periop coagulopathies

Question 1

How would you assess a patient’s coagulation status?

Answer 1

• all preop coagulatoin evals begin with H&P, familiy hx of bleeding, med history.
• consider surgical bleeding risk as well

History

• known coagulpathy disorder
• epistaxis
• prolong bleeding (dental extraction)
• hepatic dysfunction (decreaes clotting factor)
• renal dysfucntion (PLT dysfunction)
• stroke, cardiac disease, GI bleed

PE

• brusing
• bleeding from mucous membrane
• petechiae

Question 2

What is the difference between extrinisic and intrinisc pathway?

Answer 2

Intrinsic pathway

• measured by PTT
• Common pathway (1, 2, 5, 10) + factor 8, 9, 11, 12
  
  • Factor 1 = fibrinogen
  • Factor 2 = prothrombin

PTT

• affected by common pathway deficiency and factor defiency ( hemophilia, hypofibrinogenmia)
• hypothermia, heparin

Extrinisc pathway

• measured by PT/INR
  
  • to overcome interlaboratory variation in PT cause by different reagents, INR arose
• Tissue factor activates factor VII –> goes to common pathway
  *

Question 3

Describe PLT mechanism of action in coagulation?

Answer 3

3 steps: adhesion, activation, aggregation

1) adhesion

• tissue injury exposes subendothelial layer
• Plt adhere to injured vessel wall using vWF as a bridge

2) activation

• PLT secrete chemical messengers to activate additonal PLT to site of injury (ex TxA2)
• also initiate coagulation cascade

3) aggregation

• PLT aggregate and bind to each other via receptor binding sites
• exposed PLT glyco iib/iiia recpetors allow for fibrin cross-linking

Question 4

Indications for Platelet transfusion?

Answer 4

Indications for Platelet Transfusion

1) Active Bleeding

• < 50,000/mm3 and not the result of immune mechanisms
• > 50,000/mm3 and a condition which impairs platelet function is present
• Do not give platelets for > 50,000/mm3 with normal function, or if thrombocytopenia is caused by antibody

2) Massive Transfusion
* < 50,000/mm3 and evidence of continued bleeding
3) Prophylaxis (without evidence of bleeding)

• < 5000/mm3
• < 20,000/mm3 and high-risk condition (ex. PUD, previous hemorrhage)
• Do not give platelets for < 20,000/mm3 (but > 5000/mm3) if no risk factors for bleeding are present
• < 50,000/mm3 and endoscopic biopsy, lumbar puncture, or major surgery are planned

Question 5

Describe dilutional coagulopathy?

Answer 5

Etiology

• massive transfusion
  
  • > 10 U of PRBC within 24 hrs
• coagulation is multifactorial
  
  • hemodilution of coagulation factors
  • fibrinolysis favored by hemodilution of inhibitors to tPA
  • hypothermia and acidosis –> impair thrombin generation

Labs

• hemodilutoin of everything
• Inc PT/INR, Inc PTT, dec fibrinogen, dec Plt

Tx:

• FFP
• cryo (fibrinogen and Factor 8)
• PLT
• consider antifibrinolytics (aminocaproic acid)

Question 6

Describe Platelet dysfunction

Answer 6

Etiology (congenital or acquired)

• hepatic or renal failure
• antiplatelet meds
• CPB
• ECMO
• HIT
• vWD defiency
• Hextend

Labs:

• normal PLT count (dec function) - vWD defiency
• thrombocytopenia - ECMO, CPB
• increase bleeding time - hextend, hepatic/renal dz

Tx:

• first check bleeding vs no bleeding
• consider transfusion if plt count < 50,000 and no immune mechanism
• > 50,000 and a condition which impairs platelet function is present

Question 7

Describe congential or aquired factor deficiency?

Answer 7

Etiology + lab + tx:

1) liver disease

• L: increase INR and PTT
• T: ffp, cryo, firbinogen concentrate

2) vit K antagonists (warfarin)

• L: increase INR, normal PTT
• Vit K, FFP

3) intrinisc pathway deficiency (hemophilia)

• L: nomral INR, increase PTT
• T: specific factor concentrate, FFP, cryo

4) Common pathway deficiency (hypofibrinogenemia)

• involves both extrinsic and intrinsic pathway
• L: inc INR, inc PTT
  *

Question 8

Describe acquired inhibitors

Answer 8

etiology

• antibodies that inhibit specific factor activity (can occur with eveyr factor)
• autoimmune disease (SLE, RA)
• malignancy
• factor VIII inhibitor (hemo A)

Labs:

• normal INR, increase PTT
• FVII inhibitor - inc INR, normal PTT

Question 9

Describe fibrinolysis

Answer 9

etiology

• plasminogen activation 2/2 to decrease plasminogen inhibtors or decrease plasminogen activator clearance
• dilutional coagulatipathy
• DIC
• liver disease

Labs:

• inc PT, inc PTT

Tx:

• maintain fibrinogen levels
• antifibrinolytics (amicar, transexaminc acid)

Question 10

describe DIC

Answer 10

etiology

• consumptive coagulopathy –< systemic activation of coagulation leading to thrombosis, organ failure, consumption of clotting factors, oozing from sites
• sepsis
• trauma
• burn
• aortic aneurysm
• allergic/immunologic rxn

Pathophys

• proinflammatory cytokine release leading to widespread tissue factor expression and resultant thrombin generation via extrinsic pathway.
• also assoc with deragnement of normal anticoagulant (C, S, AT III) –> leads to favoring thrombosis

Labs:

• inc INR, inc PTT
• dec PLT
• dec fibrinogen
• inc fibrin degrade products

tx:

• give everything
• maintain Plt > 50,000

Question 11

Describe thrombotic events

Answer 11

etiology

• typically manifest as DVT
• congential or acquired
• HIT
  
  • 5-14 days after heparin therapy
• Protein C, S, AT III deficiency
• immobilizatoin
• pregnancy (hypercoag state)
• malignancy

Labs:

• decrease bleeding time

Tx:

• thrombectomy
• fibrinolytic therapy
• anticoagulants

Question 12

what are the pitfalls of intraop coagulation testing?

Answer 12

Pitfalls:

• results unavailable for 30-60 min
• Abnromal results (ex inc PTT) are not diagnostic of underlying mechanim of coagulopathy (factor defiency, fibrinogen defiency, hypothermia)
• not detect effects of hypothermia because lab tests are performed at 37 C
• do not show mechanical properties of clot over time b/c PT and PTT terminate at low thrombin level and before fibrin is polymerized

Question 13

what does a thromboelastogram do?

Answer 13

TEG

• measure coagulation (viscoelasticity) of whole blood
• measures coagulation factor function (PT, PTT) as well as assess platelet function, clot strength, and fibrinolysis which these other tests cannot.

Question 14

what does the R value in the TEG represent?

Answer 14

1) R value (Reaction Time)

• Time from start of measurement until beginning of clot formation, initial fibrin formation.
• result
  
  • Increase r value = factor deficency
• Causes:
  
  • factor deficiency
  • heparin/anticoagulants
• Tx:
  
  • FFP

Question 15

What does K value in TEG represent?

Answer 15

K Value - clot kinetics

• time from end of R time to an amplitude of 20 mm
• reflects clot kinetics
• k and alpha angle show fibrinogen and coagulation formation
• result
  
  • increase K value -
    
    • Deficiency of thrombin formation
    • affected by any variable that would slow clot formation (factor defiency, heparin)
    • Lack of generation of fibrin from fibrinogen
• Tx
  
  • Cryo

Question 16

what does alpha angle in TEG mean?

Answer 16

Alpha angle - clot kinetics

• tangent of curve made as K is reached at 20 mm
• reflects kinetics of fibrin production and cross linking
• result
  
  • decrease alpha angle = hypofibringonemia
• Tx:
  
  • Cryo

Question 17

What is maximum amplitude in TEG represent?

Answer 17

MA (Maximum Amplitude) - clot strength

• indication of clot strength
• depends on both plt number and function, as well as adequate fibrinogen levels
• Result
  
  • decrease MA -
    
    • Thrombocytopenia
    • Thrombocytopathy (function defect)
    • Hypofibrinogenemia
• Tx:
  
  • PLTs
  • consider DDAVP

*

Question 18

what is MA 30 and MA 60 in TEG represent

Answer 18

MA 30+60 - Clot stability (clot lysis)

• reflects degree of fibrinoloysis
• 30 min vs 60 min after max amplitude (clot strength)
• Result
  
  • decease in MA 30 or MA 60:
    
    • abnormal fibrinolysis / excess plasminogen activity
• Tx:
  
  • Tx with FFP, cryo, platelets as indicated, possibly may need Factor VII, antifibrinolytic

Question 19

Review the following coagulation abnormalities and its corresponding TEG values

Answer 19

1) anticoagulants / hemophilia

• factor deficiency
• R & K - prolonged
• MA & alpha angle - decreased

2) PLT blockers

• thrombocytopenia/thrombocytopathy
• R - Normal; K - Prolonged
• MA - Decreased

3) Fibrinolysis

• tPA
• R - normal, MA - continuous decrease
• MA 30 and 60 - decreased

4) Hypercoagulation

• r & k - decrease
• MA & alpha angle - increased

5) DIC

• hypercoagulable state with secondary fibrinolysis
• r and k - decrease
• MA and alpha - increase
• MA 30 + 60 - decrease

Question 20

Pros and cons of FFP

Answer 20

Pros

• contains all components of coagulatoin found in pts plasma: factors, anticoagulants, natural antifibrinolytics

Cons

• risk of TRALI, viral transmission, volume overload
• in presence of factor inhibitors (heparin, direct thrombin inhibitor), FFp is infective to treat or prevent bleeding 2/2 inhibitor acting against FFP
• inadeaquate to provide increase fibrinogen plasma conc

Question 21

what is prothrombin complex concentrate?

Answer 21

• PCC contains factors II (prothrombin), IX, and X
• eliminates disadvantages of FFP - volume overloaad, hemodilution, infection, and need for crossmatching
• recommended - antagonize effects of warfarin and can tx specific factor deficiences

Question 22

what is recombinant activated factor VII (rFVIIa)?

Answer 22

• rFVIIa - thought to bind to tissue factor at site of vascular injury and amplify thrombin gneeration
• theoretical risk of thombotic complicatoins must be weighed against risk of ongoing hemorrhage
• off-label use during life-threatening hemorrhage that is unresponsive to convential management

Question 23

What is DDAVP?

Answer 23

• desmopressin
• V-2 receptor agonist
• stimulates release of vWF from endothelial cells & increases available FVIII
• use: hemophilia A (FVIII deficient) & vWD

Question 24

how do antifibrinolytics such as tranexamic acid or aminocaporic acid work? (mech of action)

Answer 24

• inhibit conversion of plasminogen to plasmin
• inhibit activity of plasmin
• Plasmin cleaves fibrin into fibrin degredation products