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ACNP Pulmonary Cheat Sheet by

ACNP Student Pulmonary Rotation
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Pulmonary Embolism

Pathop­hys­iology
• A thrombus in another area of the body embo­lizes to the pulmonary vascul­ature via the RV and PA.
• Blood flow distal to the embolus is obstru­cted, causing incr­eased PVR, PA pressure, and RV pressu­re. If severe, acute cor pulmon­ale can occur.
• Blood flow decreases in some areas, dead space is created where there is vent­ilation but no perfus­ion.
Hypo­xemia and hyperc­arbia occur and drive tach­ypn­ea.
If dead space is large, signs are more overt (SOB). PE and DVT are on a continuum.
Source
• Most PE arise from thro­mboses of deep veins of lower extrem­ities above the knee (iliof­emoral DVT).
• Can also arise from deep veins of pelvis.
• Calf vein thrombi have a low incidence of embolizing to the lungs, but they can progress into the proximal veins and increase the risk of PE.
• Upper extremity DVT is rare (seen in IVDU).
Fat emboli from long bone fractures, amniotic fluid emboli during or after delivery, air emboli (trauma, lines), septic emboli (IVDU), schist­oso­miasis.
Sympotms
• Not a reliable indicator of the presence of PE.
Dyspnea (73%), cough (37%), pleuritic chest pain (65%), hemoptysis (13%).
• Only 1/3 of patients will have signs and symptoms of a DVT.
• Syncope seen in large PE.
Signs
Tach­ypnea (70%), rales (51%), tach­yca­rdia (30%), S4 (24%), increased P2 (23%).
• Shock with rapid circul­atory collapse in massive PE.
• Others include low-grade fever, decreased breath sounds, and dullness on percus­sion.
Risk Factors for DVT and PE.
• Age>60, mali­gna­ncy, prior history, heredi­tary, hyper coagulable states, prolonged immobi­liz­ation, cardiac disease (esp. CHF). obesity, neph­rotic syndro­me, major surgery (esp. pelvic or orthop­edic), major trauma, pregnancy, and estrogen use.
Prognosis
• PE is usually clinically silent.
• Recurr­ences are common, which can lead to chronic pulmonary HTN and chronic cor pulmon­ale.
• When undiag­nosed, mortality approaches 30%.
• When PE is diagnosed, mortality is 10% in first 60 minutes. Of those who survive initial event, 30% will die of recurrent PE if untreated.
• Most are recurrent in the first few hours.
• Treatment with anti­coa­gul­ation decreases mortality to 2-8%.
Diagnosis
• If suspected PE, stabilize with IVF and O2. {{nl}• }If PE is likely, start antico­agu­lation before diagnostic tests.
• If PE is unlikely, get testing first.
• If the patient has contra­ind­ica­tions to antico­agu­lation, get testing first and then consider IVC filter.
 

Testing

D-Dimer
Specific fibrin degrad­ation product whose levels can be elevated in PE or DVT.
• Sensitive (90-98%).
• If results are normal and clinical suspicion is low, PE is very unlikely.
Spec­ificity is low, as it can be elevated in MI, CHF, pneumonia, and postop.
• Any cause of clot or increased bleeding can elevate D-Dimer.
Venous Duplex Ultrasound
• If positive, treat with IV heparin.
• False positives will lead to antico­agu­lation in patients without PE.
• If negative, the test is of very little value and the patient may still have a PE (up to 50% of patients with PE).
Echoca­rdi­ogram
Acute massive PE is accomp­anied by RV dilation and failure due to RV outflow obstru­ction and increased PVR.
• The dilated RV pushes the septum towards the LV, causing further decrease in LV preload and CO.
• This shows up as dilated RV cavity and hypoki­nesis of the RV free wall with sparing of the apex (McC­onn­ell's sign).
Helical CT
>90% sensit­ivity and good specif­ici­ty.
• Can visualize very small clots (>2mm). Can miss clots in small sub segmental vessels.
Test of choice.
• If negative and high clinical probab­ility of PE, there is a 5% incidence of PE.
• Contra­ind­icated in patients with renal insuff­iciency because of IV contra­st.
CXR
• Usually normal. Atel­ectasis or pleural effusion may be present.
• Mainly useful to exclude competing diagnoses.
• Hampton's hump or Wester­mark's sign are rarely present
V/Q Scan
• Important when there is a contra­ind­ication to helical CT.
• Results can either be normal, low-pr­oba­bility, interm­edi­ate­-pr­oba­bility, or high-p­rob­abi­lity.
• A normal V/Q scan rules out PE and no further testing is needed.
• A high probab­ility scan is very sensitive for PE and indicates treatment with heparin.
• If low or interm­ediate probab­ility, clinical suspicion determines next step.
• If high, pulmonary angiog­raphy is indicated.
Arterial Blood Gas
• Not diagno­stic.
PaO2 and PaCO2 are low (latter due to hyperv­ent­ila­tion) and pH is high.
Typi­cally respir­atory alkalo­sis.
The A-a gradient is usually elevat­ed. A normal A-a gradient makes PE less likely but does not exclude it.
Pulmonary Angiog­raphy
Gold standa­rd. Defini­tively diagnoses or excludes PE.
• But the test is invasive. Contrast is injected into the PE branch after percut­aneous cather­ization of the femoral vein.
• Consider when noninv­asive testing is equivocal and risk of antico­agu­lation is high, or if the patient is unstable and embole­ctomy may be required. Rarely performed due to 0.5% mortality.
Rules Out PE
Normal or low-pr­oba­bility V/Q scan or helical scan and low clinical suspicion, negative pulmonary angiogram (defin­ite), and negative D-Dimer with low suspicion
Wells Criteria
Symptoms and signs of DVT (3 points), altern­ative diagnosis less likely than PE (3 points), HR>100 (1.5 points), immobi­liz­ation >3 days or surgery in last 4wks (1.5 points), previous DVT or PE (1.5 points), hemoptysis (1 point) and malignancy (1 point). If >4, PE is likely.
Indica­tions for Treatment
intral­uminal defects in central, segmental or lobular PAs on helical CT (or high probab­ility with a scan) and clinical suspicion, DVT diagnosed with clinical suspicion, and positive pulmonary angiogram (defin­itively proves PE).
 

Treatment

Oxygen Therapy
• To correct hypo­xem­ia.
• Severe hypoxemia or respir­atory failure requires intubation and mechanical ventil­ation.
Heparin
• Either unfrac­tio­nated or LMWH (enoxa­parin) to prevent recurr­ence.
• Prevents further clot formation but does not lyse existing emboli or diminish thrombus size.
• Start immedi­ately based clinical suspicion. Do not wait for studies if high.
• Give one bolus, followed by infusion for 5-10days.
• Goal aPTT of 1.5-2.5x normal.
• Acts by prom­oting antith­rombin III.
• Contra­ind­ica­tions include active bleeding, uncont­rolled HTN, recent stroke, and HIT.
• LMWH has less compli­cations but NOT used in ESRD.
Warfarin
• For long-term treatment. Can start with heparin on day 1.
• Goal INR is 2-3. Continue for 3-6 months depending on risk factors.
• Some patients with signif­icant risk for recurrence (malig­nancy, hyper coagulable state) should receive lifelong therapy.
Thromb­olytic Therapy
• Strept­oki­nase, TPA.
Speed up lysis of clots.
• Does not improve mortality rates.
• Should be considered for use in patients with massive PE who are unst­able, and patients with evidence of RHF.
IVC Filter
• Have not been proven to reduce mortality.
• Patients are at a higher risk of recurrent DVT but lower risk of recurrent PE.
• Compli­cations include filter migration or mispla­cement, filter erosion and perfor­ation of IVC, and IVC obstru­ction due to filter thromb­osis.
• Indicated for patients with contra­ind­ica­tions to antico­agu­lation, compli­cation of current antico­agu­lation, failure of adequate antico­agu­lation evidence by recurr­ence, and low pulmonary reserve (high risk of death due to PE).
NOACs
Fondap­arinox is an injectable factor Xa inhibitor. Rivaro­xaban is an oral factor Xa inhibitor. Neither can be used in severe CKD (GFR<30). Epixaban is approved for use in CKD.

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