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Pulm > Lec 20 Pulmonary Thromboembolism > Flashcards

Lec 20 Pulmonary Thromboembolism Flashcards

1
Q

What is pulmonary thromboembolism?

A

movement of blood clot from systemic vein through R side of heart to pulmonary circulation

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2
Q

What is common source of thrombi to lung?

A

usually from lower extremities; rarely from arms, pelvis, R chambers of heart

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3
Q

What is virchow’s triad of risk factors for thrombosis?

A
  • hypercoagulability
  • damage to endothelium of vessel wall
  • stasis/stagnation of blood flow
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4
Q

What are some hereditary risk factors for hypercoagulability?

A
  • antithrombin deficiency
  • protein C deficiency
  • protein S deficiency
  • factor V leiden
  • prothrombin gene mutation
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5
Q

What are acquired risk factors for hypercoagulability?

A
  • advanced age
  • previous venous thromboembolus
  • cancer
  • obesity
  • surgery
  • immobilization –> long flight
  • pregnancy
  • estrogens
  • having a catheter
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6
Q

What is factor 5 leiden?

A
  • single base substitition –> factor Va resistant to action of protein C

het individuals have 3-5x increase risk of venous thromboembolism

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7
Q

What happens in prothrombin gene mutation?

A

G20210A mutation in untranslated region of prothrombin

het individuals have 30% increase in prothrombin and 2-3x increase risk of thromboembolism

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8
Q

What are sequalae of pulm embolism?

A
  • have hemodynamic perturbations and impaired gas exchange

b/c mechanical obstruction of vessels + thrombus releases mediators

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9
Q

How does PE cause vasoconstriction?

A

thrombus releases mediators serotonin and thromboxane A2 causes vasoconstriction

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10
Q

What 3 factors determine the hemodynamic effects of PE?

A
  • degree of cross sectional reduction of pulm vascular bed
  • preexisting status of cardiopulm system [worse if high pulm pressure to start]
  • physiologic consequences of hypoxic and neurohumorally mediated vasoconstriction
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11
Q

What happens if obstruction < 20%?

A

normal PAP and PVR b/c of recruitment and distension of pulm vessels
CO maintained

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12
Q

What happens if obstruction 30-40%?

A

increase PAP and modest increase RAP

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13
Q

What happens if obstruction > 50%?

A

compensatory mech overcome

CO begins to fall and RAP increases

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14
Q

What is maximum mean PAP right ventricle can generate in patient without prior cardiopulm disease?

A

40 mmHg

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15
Q

What happens to PaCO2 level in PE?

A

have increase dead space ventilation but also have increase in total minute ventilation

–> can get low CO2 [hypocapnia]

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16
Q

What are 5 mechanisms that can lead to hypoxemia?

A
  • hypoventilation
  • V/Q mismatch
  • shunt
  • diffusion impairment
  • low PIO2
17
Q

Does dead space ventilation cause hypoxemia?

A

nope! not on its own

18
Q

How do you get hypoxemia due to decrease CO in pulm embolism?

A

have decrease CO –> decrease O2 delivery but your tissues still taking up the O2 and consume it –> lower O2 sat –> decrease CaO2

19
Q

What are 4 mechs causing hypoxemia in pulm embolism?

A
  • increased PVR
  • decreased CO reducing the O2 in venous admixture
  • loss of pulm surfactant
  • bronchoconstriction
20
Q

What is mech of increase PVR causing hypoxemia in PE?

A
  • increased PVR –> causes increased perfusion to poorly ventilated areas and get V/Q mismatch + if really high PVR –> can get reverse shunt
21
Q

What is mech of loss of surfactant causing hypoxemia in PE?

A

-loss of pulm surfactant after 24 hrs of occlusion –> atelectasis and edema

hypoxemia if partial thrombus resolution of perfusion but now have lack of ventilation = shunt

22
Q

What is mech of bronchoconstriction in PE?

A

platelet mediators in thrombus cause vaso/bronchoconstriction

hypocapnia that occurs in PE also causes bronchoconstriction

23
Q

WHat are the 3 potential sources of O2 for pulmonary parenchyma?

A
  • airways
  • pulm arteries
  • bronchial arteries
24
Q

What are symptoms of PE?

A
  • acute onset dyspnea [most common]
  • pleuritic chest pain
  • hemoptysis
  • syncope [rare]
25
Q

WHat do you see in phyiscal exam with PE?

A
  • tachycardia, hypotension, tachypnea, hypoxemia
  • lung exam may be normal or may have rales, wheezing, findings of pleural effusion
  • cardiac: RV heave, split S2, loud P2, systolic TR murmur
  • extremities: tender, edema, palpable cord in vessel
26
Q

What is hampton’s hump?

A

shallow wedge-shaped opacity in periphery of lung with its base against pleural surface

represents lung infarction

27
Q

What is westmark’s sign?

A

localized area of decreased lung vascular markings

28
Q

What are advantages/ disadvantages of CT pulmonary angiography?

A

advantages: high quality visualization; quick
disadvantages: radiation exposure, requires IV contrast

29
Q

What is a ventilation perfusion scan?

A

perfusion: use radiolabeled macroaggregated albumin particle injected into peripheral vein; lodges in small vessels that are perfused
ventilation: inhale xenon radioisotope; asses which parts of lung ventilated

30
Q

What is use of lower extremity ultrasound in pulmonary thromboembolism?

A
  • if have DVT the vein will be non-compressible

if no thrombus –> will be able to compress easily

31
Q

What is D dimer test?

A

tests if you have any forming clots –> will have positive D dimers of fibrin that break down when you give plasmin

32
Q

What does positive D Dimer test tell you? negative?

A

positive = doesn’t tell you much = poor specificity

negative = very sensitive and tells you that its probably not a thrombus

33
Q

What is natural history of thromboembolism?

A
  • thrombus grows, propagates; have fibrinolysis or roganization/recanalization

resolves a lot in first week; gradual over next 4-8 wks

most pts able to restore normal pulm hemodynamics + gas exchange

34
Q

What is treatment for thromboembolism?

A
  • anticoagulation

- thrombolysis or surgery in big thromboembolus

35
Q

What are some examples of anti-coagulants?

A
  • heparin
  • warfarin
  • coumadin
36
Q

What are some examples of thrombolytics?

A
  • tPA
  • streptokinase
  • urokinase
37
Q

What is IVC filter? side effect?

A
  • traps thrombi from lower extremities en route to pulm circulation

increases risk of deep vein thrombosis

38
Q

What are indications for IVC filter?

A
  • if contraindicated to anticoagulant therapy
  • if thromboembolism recurs despite anticoagulation
  • if limited pulm vascular reserve [already have pulm HTN]

Pulm (24 decks)

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