VASCULAR LUNG DISEASE: Pulmonary edema, Pulmonary embolism, Pulmonary hyptertension
o PULMONARY EDEMA: Fluid accumulation in the lung interstitium (i.e. extravascular space).
Ø PATHOPHYSIOLOGY: Pulmonary edema is either a result of inadequate functioning of the heart and circulatory system (i.e. cardiogenic) or due to direct damage to lung tissue (i.e. non-cardiogenic). The Starling equation, which explains fluid movement across capillary membrane as a result of filtration, can be used to describe pleural edema:
PLEURAL EFFUSION = Kf ([Pc + πi] − [Pi − πc])
Cardiogenic causes (due to ↑ Pc from backflow of fluid into the lung capillaries): HEART → H-heart failure, H-heart attack, H-hypertensive crisis, E-excessive fluid therapy, A-arrythmias (tachy- or bradycardia), R-renal failure causing fluid overload, cardiac T-tamponde (i.e. pericardial effusion).
v H _______________, _______________, _______________, _______________, _______________
v E _______________, _______________, _______________, _______________, _______________
v A _______________, _______________, _______________, _______________, _______________
v R _______________, _______________, _______________, _______________, _______________
v T _______________, _______________, _______________, _______________, _______________
Non-cardiogenic causes: This form is contiguous with ARDS.
v ↑ Kf (capillary permeability): Inhalation of toxic gases, Multiple blood transfusions, Severe infection (e.g. sepsis, pneumonia), Pulmonary contusion, Multitrauma, Neurogenic (e.g. subarachnoid hemorrhage), Aspiration (e.g drowning, gastric fluid), Certain medication (e.g. opiates), AVM.
v ↓ πc (capillary osmotic pressure): Hypoalbuminemia.
v ↓ Pi (interstitial hydrostatic pressure): Re-expansion (i.e. post pneumonectomy or large volume thoracentesis), Reperfusion injury (i.e. postpulmonary thromboendartectomy or lung transplantation).
v Other: HAPE (high altitude pulmonary edema): A life-threatening condition that occurs in otherwise healthy mountaineers at altitudes above > 2,500 meters. Epidemiology: Incidence: Occurs in < 1% of unacclimatized travelers exposed to high altitude (~4,000 m). Currently, it is not possible to predict individual susceptibility to HAPE. Pathophysiology: The initial insult that causes HAPE is a shortage of O2 caused by the lower air pressure at high altitudes, which lead to: 1) Hypoxic pulmonary vasoconstriction à ↑ Pc (i.e. pulmonary hypertension) 2) Idiopathic non-inflammatory ↑ permeability of the vascular endothelium (Kf). Treatment: Descend to lower altitude: At least 1000 meters as quickly as possible. This is the most important treatment, and symptoms tend to quickly improve. O2 supplement. Medications: Nifedipine, acetazolamide, dexamethasone, salmeterol or sildenafil may help.
Ø PRESENTATION: History: Cardiovascular disease, Dyspnea, coughing pink frothy sputum (classic sign, sweating, anxiety, pallor, fluid overload (e.g. ankle pitting edema, nocturia, orthopnea, and paroxysmal nocturnal dyspnea). Physical exam: Cyanosis, end-inspiratory crackles (characteristic for pulmonary edema), 3rd heart sound (S3 is predictive of cardiogenic pulmonary edema), and Cheyne-Stokes breathing (aka periodic breathing is characterized by oscillation of ventilation between apnea and hyperpnea, to compensate for changing serum partial pressures of O2 and CO2; it is seen with brain injury [e.g. strokes, traumatic brain injuries, brain tumors, toxic metabolic encephalopathy], CHF, and morphine administration). Untreated, it can lead to coma and death from hypoxia.
Ø DIAGNOSTIC EVALUATION: CBC. CMP: Check electrolytes, renal function, liver function. CRP/ESR. Coagulation studies: PT, aPTT. BNP (B-type natriuretic peptide): Check for CHF. CXR (confirm the diagnosis): Enlarged heart, prominent pulmonary vessels, pleural effusions, patchy alveolar infiltrates with air bronchograms, Kerley B lines (short parallel lines at the lung periphery at right angles to the pleura representing the interlobular septa; they are most frequently observed at the lung bases). ABG: ↓ PaO2. Echo: May strengthen the diagnosis by identifying cardiogenic causes. Swan-Ganz catheter: May be used to identify left ventricular dysfunction, thus confirm cardiogenic pulmonary edema.