Pulmonary edema is swelling and/or fluid accumulation in the lung(s). The resulting impairment of gas exchange can lead to respiratory failure, coma, and death, primarily due to hypoxia (a lack of adequate oxygen supply to the body or a part of the body). Pulmonary edema can be a consequence of direct damage to the lung (noncardiogenic), or of an increase in pulmonary vascular blood pressure due to the inability of the heart to adequately circulate blood through the lungs (cardiogenic).
Symptoms of pulmonary edema may include:
- difficulty breathing
- coughing up blood
- pink frothy sputum (coughed up saliva, mucus, and foreign material)
- excessive sweating
- pale skin
Symptoms of a gradual onset of edema may include:
- nocturia (frequent urination at night)
- paroxysmal nocturnal dyspnea (periods of severe sudden breathlessness at night)
- orthopnea (difficulty lying down flat due to breathlessness)
- ankle edema (swelling of the legs, usually of the kind in which the skin is slow to return to normal when pressed upon)
There are numerous causes of noncardiogenic pulmonary edema including infections, trauma, multiple blood transfusions, aspiration, inhalation of toxic gases, upper airway obstructions, ascent to high altitude and, of course, certain medications. These include:
There are also numerous causes of cardiogenic pulmonary edema, most of which have to do with problems with the heart such as heart attacks, hypertension, congestive heart failure, irregular heart beats, and pericardial effusion (abnormal amount and/or character of fluid in the space between the layers that surround the heart) with tamponade (enough pressure to affect the functioning of the heart). But it can also be caused by fluid overload such as from kidney failure or intravenous therapy.
Drugs can cause acute pulmonary edema principally in two ways: by injuring the capillary endothelium (a layer of flat cells that line the interior of these small blood vessels) and thereby causing a leakage of fluid and protein into the interstitum (connective tissue surrounding the alveoli) or by altering hemodynamics (blood pressure) that elevate microvascular pressure (blood pressure within the fine blood vessels in the lungs) thereby increasing the fluid filtration from vascular to alveolar and interstital spaces. The first mechanism results in permeability pulmonary edema, while the second results in hemodynamic pulmonary edema.
Drugs associated with acute permeability pulmonary edema include:
- Salicylates (aspirin, NSAIDs, etc.)
- Opiates (codeine, morphine, Fentanyl, Sublimaze)
- Radiographic contrast media (used to improve the visibility of internal bodily structures in MRI and X-ray images)
- Bleomycin sulfate
- Other cytotoxic agents (used in chemotherapy and radiation therapy for cancer patients)
- Nitrofurantoin (Furadantin, Macrobid, Macrodantin)
- Amiodarone (Cordarone)
Drugs associated with hemodynamic pulmonary edema include:
- Beta-Adrenergic blockers
- Calcium antagonists
- Doxorubicin hydrochloride (Adriamycin, Rubex), daunorubicin hydrochloride
- Colloid and crystalloid
- Beta-Adrenergic agonists
Diagnosis may involve a review of the medical history and physical examination of the patient, various blood tests, a complete blood count, coagulation studies, and a BNP test. Confirmation of the diagnosis and identification of the type of pulmonary edema may involve an x-ray, blood gas readings, an echocardiography, and/or a Swan-Ganz catheter (a thin tube is passed into the right side of the heart to observe blood movement through it).
In treating pulmonary edema, the first priority is on maintaining adequate oxygenation, usually through one or more of the following:
- High-flow oxygen
- Continuous positive airway pressure (CPAP)
- Variable positive airway pressure (VPAP)
- Mechanical ventilation (in extreme cases)
If circulatory causes led to the edema, the patient is usually treated with intravenous nitrates and loop diuretics to help improve cardiac function.
In most cases, direct tissue damage cannot be repaired. When lung tissue has been damaged, the most important measure is to treat the infection or remove any other cause.