pulmonary circulation Flashcards
pulmonary embolism
-Complication of thrombus formation within the deep venous circulation
-US: estimated 100,000 deaths/year
-3rd leading cause of death among hospitalized patients
substances that can embolize to pulmonary circulation
-Thrombus*
-Air
-Amniotic fluid
-Fat
-Foreign bodies
-Parasite eggs
-Septic emboli
-Tumor cells
PE: thrombus
-MC
-Arises anywhere in venous circulation or heart
-Most often originates in deep veins of LE
-20% of calf vein thrombi propagate proximally to popliteal and ileofemoral veins
-May break off and embolize to pulmonary circulation
PE and DVT: risk factors
-PE and DVT are 2 manifestations of the same disease.
-70% patients with PE will have DVT on evaluation
-Same risk factors (Virchow’s triad)
-Venous stasis
-Injury to the vessel wall
-Hypercoagulability
what increases venous stasis
-immobility
-hyperviscosity
-increased central venous pressures
what damages vessels
prior thrombosis, orthopedic surgery, trauma
what causes hypercoagulability
-medications
-disease
-inherited genetic defects
pathophysiologic response to PE
-Pulmonary emboli are typically multiple, with the lower lobes* being involved in the majority of cases:
-Infarction - 2 circulation to to lungs so this is uncommon
-Abnormal gas exchange
-Cardiovascular compromise- right ventricular strain
PE acute/chronic
-Difficult to diagnose
-Depend on size of the embolus and the patient’s preexisting cardiopulmonary status
-Acute:
-develop symptoms and signs immediately after obstruction of pulmonary vessels
-Subacute:
-within days or weeks following the initial event
-Chronic
-slowly develop symptoms of pulmonary hypertension over many years (usually after PE that wasnt fully treated)
most common symptoms and signs of PE
-SYMPTOMS
-Dyspnea (rest or exertion) (73 percent)
-Pleuritic pain (44 percent)
-Calf or thigh pain (44 percent)
-Calf or thigh swelling (41 percent)
-Cough (34 percent)
->2-pillow orthopnea (28 percent)
-Wheezing (21 percent)
-SIGNS
-Tachypnea (54 percent)
-Tachycardia (24 percent)
-Rales (18 percent)
-Decreased breath sounds (17 percent)
-Accentuated pulmonic component of the second heart sound (15 percent)
-Jugular venous distension (14 percent)
hemodynamic stability
-Hemodynamically unstable PE is that which results in hypotension
-this is not good…
-Hypotension: systolic blood pressure <90 mmHg or
-Drop in systolic BP ≥40 mmHg from baseline for >15 minutes or
-Hypotension requiring vasopressors or inotropic support
-not due to other causes (sepsis, arrhythmia, LV dysfunction from acute myocardial ischemia or infarction, or hypovolemia)
PE-Wells criteria
PE dx tests and labs
-ECG abnormal (70%)
-Sinus tachycardia and nonspecific ST and T wave changes
-S1Q3T3 pattern
-ABG-Not diagnostic -> Usually hypoxemia, hypocapnia (low CO2), respiratory alkalosis
-Plasma D-dimer:
-sensitive but not specific test -> only helpful when its neg
-if its + it means nothing
-May be elevated in the presence of thrombus (non-specific)
-D-dimer <500 ng/ml has shown a sensitivity for absence of venous thromboembolism of 95–97%
-Leukocytosis, elevated ESR, LDH
PE imaging and special exams
-CXR:
-Exclude other common lung diseases
-Need for interpretation of V/ ˙Q scan
-Westermark’s sign-uncommon: A prominent central pulmonary artery with local oligemia
-Hampton’s hump-uncommon: Area of increased opacity that represent intraparenchymal infarct
lung scanning
-Perfusion scan:
-inject radiolabeled microaggregated albumin into the venous system, allowing the particles to embolize to the pulmonary capillary bed
-Ventilation scan:
-breathe a radioactive gas or aerosol while the distribution of radioactivity in the lungs is recorded.
-Both scans are interpreted together to give a high, low, or intermediate (indeterminate) probability that PE is the cause of the abnormalities
-look for places that are ventilated but not perfused
PE: lung scanning
-Normal perfusion scan: Excludes diagnosis of clinically significant PE
-High-probability scan:
-2 or more segmental perfusion defects in the presence of normal ventilation
-Sufficient for diagnosis of PE in most instances
-Most helpful: normal or high probability of PE
spiral CT pulmonary angiography
-MC evaluation
-has supplanted V˙ /Q˙ scanning as the initial diagnostic study
-Very sensitive: Thrombus in proximal pulmonary arteries
-Less sensitive: Distal arteries
pulmonary angiography
-Reference standard for the diagnosis of PE
-Definitive Dx:
-An intraluminal filling defect in more than one projection
-Secondary findings highly suggestive of PE:
-Abrupt arterial cutoff
-Asymmetry of blood flow—especially segmental oligemia
-Complications 5%
pulmonary angiography indications
-other testing is negative but high clinical suspicion
-Diagnosis of PE must be established with certainty
-Anticoagulation is contraindicated or placement of an inferior vena cava filter is contemplated
-Catheter Based Intervention- Catheter based extraction or thrombolysis
hemodynamically unstable PE that results in hypotension
-Hypotension: systolic blood pressure <90 mmHg or
-Drop in systolic BP ≥40 mmHg from baseline for >15 minutes or
-Hypotension requiring vasopressors or inotropic support not due to other causes (sepsis, arrhythmia, LV dysfunction from acute myocardial ischemia or infarction, or hypovolemia)
-look for right ventricle strian
approach to PE tx flow chart
tx-empiric therapy
-Supplemental oxygen: target an O2 sat ≥90%
-Mechanical ventilation
-Severe hypoxemia, hemodynamic collapse, or respiratory failure
-Assess bleeding risk to anticoagulate
-Low risk and stable: Empiric anticoagulation
-Moderate risk and stable: case by case
-High or absolute risk: no empiric therapy
tx: PE confirmed
-Approach to anticoagulation is based on hemodynamic stability, risk and size of PE
-Stable, low risk, nonmassive: continue anticoagulation in hospital and anticoagulation as outpatient once discharged
-Stable, high risk, nonmassive or contraindication to anticoagulation: inferior vena cava filter
-Stable, mod risk, nonmassive: case by case
-Approach is based on hemodynamic stability, risk and size of PE
-Stable, intermediate risk, submassive: anticoagulated in hospital and monitor closely for deterioration, consider thrombolytic
-Unstable:
-Thrombolytic therapy followed by anticoagulation
-Thrombolysis is contraindicated, surgical or catheter directed embolectomy
initial tx: anticoagulation
-Options for initial anticoagulation include the following:
-Low molecular weight (LMW) heparin- dosed by weight with no blood testing
-Fondaparinux
-Unfractionated heparin (UFH) - with extreme cases use this bc its backed with blood
-Oral factor 10a/Xa inhibitors or direct thrombin inhibitors -> Rivaroxabanandapixaban
