pulmonary edema



OVERVIEW

Definition

Pulmonary edema is a clinical syndrome in which the balance of tissue fluid production and reflux in the lungs is imbalanced, and large amounts of tissue fluid accumulate in the alveoli, interstitium, and small bronchioles, resulting in a severe impairment of pulmonary ventilation and gas exchange.

Patients with coronary heart disease, hypertensive heart disease, rheumatic heart disease, myocarditis, lung infection, inhalation of toxic gases, severe burns, and allergic reactions are more likely to develop pulmonary edema.

Classification

Classification according to the cause

Cardiogenic pulmonary edema: also known as hydrostatic pulmonary edema.

Non-cardiogenic pulmonary edema: according to the specific cause, it can be classified into neurogenic pulmonary edema, infectious pulmonary edema, plateau pulmonary edema, pharmacogenic pulmonary edema, etc.

Classification according to mechanism

Hypertensive pulmonary edema: normal vascular barrier function, elevated microvascular pressure.

Normobaric pulmonary edema: normal microvascular pressure.

Negative-pressure pulmonary edema: increased absolute value of negative pressure in the chest cavity and/across the lungs.

Mixed pulmonary edema: elevated microvascular pressure with increased pulmonary capillary permeability.

Etiology

Causes

Cardiogenic pulmonary edema

Seen in severe mitral stenosis or mitral valve closure insufficiency, hypertensive heart disease, coronary artery disease, rheumatic heart disease, acute myocardial infarction, etc., when heart failure occurs.

Non-cardiogenic pulmonary edema

Neurogenic pulmonary edema: seen in head trauma or other brain lesions, such as craniocerebral trauma, encephalitis, brain tumor, cerebrovascular accident.

Infectious pulmonary edema: mostly seen in severe pneumonia.

Plateau pulmonary edema: mostly seen in those who live below 1000 meters above sea level and stay at 3500-4300 meters above sea level or above without acclimatization exercise before entering the plateau.

Pharmacogenic pulmonary edema: seen in the heavy use of anesthesia, sedative drugs, such as morphine, methadone, phenytoin sodium.

Others: inhalation of large amounts of irritating gases (such as sulfur dioxide, ammonia, etc.), infusion or transfusion of blood too fast, respiratory obstruction, metamorphosis, burns, drowning, organophosphorus pesticide poisoning, inhalation of gastric contents.

Pathogenesis

Pulmonary edema occurs when fluid enters the lungs faster than it can be removed. Elevated driving pressure or increased pulmonary capillary permeability, or both mechanisms, can cause pulmonary edema.

Elevated drive pressure

Elevated microvascular pressure: Pulmonary edema occurs when pulmonary microvascular pressure is elevated, fluid filtration from the vasculature increases rapidly, and the lung’s compensatory capacity to resist edema is inadequate.

Decrease in paravascular hydrostatic pressure: With a decrease in paravascular hydrostatic pressure, the total filtration drive increases, which results in increased filtration of fluid and proteins across the pulmonary microvascular barrier and the development of pulmonary edema.

Decreased osmotic pressure difference across the microvascular wall: a decrease in plasma protein concentration, or an increase in interstitial protein concentration, can lead to a decrease in the osmotic pressure difference between the inside and outside of the vasculature, resulting in an increase in the total drive pressure for the filtration of fluids and proteins out of the vasculature, and the occurrence of pulmonary edema.

Increased pulmonary capillary permeability

Increased pulmonary capillary permeability leads to an increase in the amount of fluid and protein filtering out of the vessels and pulmonary edema occurs.

Symptoms

Hypertensive pulmonary edema

In the interstitial phase of pulmonary edema, there may be coughing, chest tightness, and dyspnea, but because the edema fluid is mostly confined to the interstitial cavities, only mild shallow respiration is manifested, and no rales can be heard.

After the pulmonary edema fluid infiltrates into the alveoli, there may be coughing white or bloody foamy sputum, severe dyspnea and sedentary respiration, and wet rales can be heard all over both lungs.

Negative pressure pulmonary edema

It is often accompanied by acute airway obstruction and dyspnea.

There is often a painful, agitated facial expression and coughing up pink foamy sputum.

As the disease progresses, wet rales may be heard in the lungs, occasionally accompanied by rales.

Normobaric and mixed pulmonary edema

Depending on the cause of the disease and individual differences, they present different clinical manifestations.

Pulmonary edema due to inhalation of irritant gases

Cough, chest tightness, shortness of breath, and dry rales or rales in the lungs on auscultation.

Pulmonary edema caused by inhalation of stomach contents

The main symptoms are shortness of breath and cough, usually dry.

After passing through the acute pulmonary edema stage, purulent mucous sputum can be coughed out.

Pulmonary edema due to drowning

As it takes time for water to be absorbed from the alveoli, it may be characterized by coughing, intrapulmonary wet rales and persistent hypoxemia (pallor, dyspnea and cyanosis).

Some of the manifestations are metabolic acidosis, and rarely respiratory acidosis, which can be seen as accelerated and deepened respiration, palpitations, nausea and vomiting.

Plateau pulmonary edema

Symptoms occur within 12 hours to 3 days after arrival at plateau.

They are mainly cough, dyspnea, fatigue, hemoptysis, retrosternal discomfort, cyanosis and palpitations, which can be rapidly improved by oxygen intake or return to lower altitude.

Consultation

Department of Medicine

Respiratory Medicine

Prompt medical attention is recommended when coughing, chest tightness, shortness of breath, etc. occur.

Emergency Medicine

If you have difficulty breathing, coughing up pink foamy sputum, palpitations and cyanosis, we recommend that you consult the Emergency Department immediately.

Preparation

Preparing for your visit: registration, preparation of documents, common questions

Tips for seeking medical treatment

Chest X-rays or chest CT are often needed, so avoid wearing clothing made of metal, and those who are pregnant or planning to become pregnant should inform the doctor in a timely manner.

Preparation Checklist

Pay particular attention to the time of onset of symptoms and special signs and symptoms.

Is there a cough? How long has the cough lasted?

Is there phlegm? What kind of phlegm?

Is there any breathlessness or dyspnea?

Do you feel panicky?

How long have the symptoms been present?

Under what circumstances do the symptoms worsen or lessen?

Has there been any recent heavy infusion of fluids?

Has there been heavy use of drugs such as methadone, morphine, etc.?

Have you suffered from heart failure, kidney failure, pneumonia, etc.? Or have suffered head trauma?

Test results in the last six months, which can be brought to the doctor’s office

Laboratory tests: blood test, urine test, blood gas analysis

Imaging tests: Chest X-ray, Chest CT scan

Medications in the last 3 months, if available in boxes or packages, bring with you to the doctor’s office

Furosemide, nitroglycerin, terbutaline, aspirin, warfarin

Diagnosis

Diagnosis is based on

medical history

History of heart disease or lung infection.

History of head trauma.

History of heavy use of anesthetic and sedative drugs such as methadone, morphine, and phenytoin sodium.

Clinical manifestations

Symptoms such as chest tightness, fatigue, cough, dyspnea, coughing up white or bloody frothy sputum, and bruising of the skin, lips, and nail beds are present.

Wet rales or rales in the lungs may be heard. Early rales appear at the base of the lungs and may spread throughout the lungs as the disease progresses.

Turbidity is present on percussion.

Laboratory tests

Look for changes in red blood cells, white blood cells, and platelets.

May be used to determine infection.

No need to fast before the test.

To find out the changes of urine white blood cells, red blood cells, protein, specific gravity and tubular pattern.

It can be used to determine whether there is kidney damage.

Precautions: Clean mid-stream urine should be retained during the test, i.e., a portion of the urine should be discharged first, and then the urine should be caught in a urine cup, and the urine should be stopped before it is completely discharged.

Find out the partial pressure of oxygen, partial pressure of carbon dioxide, acidity and alkalinity in arterial blood.

Clarify the presence of acidosis or alkalosis and the severity or type of acidosis or alkalosis.

Precautions

Imaging

X-ray is the most important test for diagnosing pulmonary edema.

It can check the presence and degree of edema in the lungs and confirm the diagnosis of cardiogenic pulmonary edema.

X-rays may show “Kirschner’s B lines” or dense adenoidal shadows.

Precautions

It can show the distribution, extent and morphology of pulmonary edema, and can be sensitive enough to detect pulmonary edema and provide help for early diagnosis.

It can distinguish between pulmonary congestion and interstitial pulmonary edema.

Precautions: Remove metal objects, such as necklaces and earrings, from the body before the examination.

Others

Such as renal function tests, can understand the functional status of the kidneys.

Differential Diagnosis

Acute attack of bronchial asthma

Similarities: Both have symptoms such as coughing and difficulty in breathing.5

Differences: Acute attacks of bronchial asthma have a clear history of asthma and most often have clear triggers, which can be rapidly relieved by inhaled glucocorticoid therapy, and can be differentiated by chest X-ray and CT examination.

Pneumothorax

Similarities: Both have symptoms such as cough and dyspnea.

Difference: Pneumothorax has a clear history of trauma or underlying lung disease, and most of them have a rapid onset and sudden onset of pins and needles or knife-like chest pain on one side, which can be differentiated by chest X-ray and CT examination.

Treatment

The aim of treatment is to improve air exchange, rapidly reduce fluid accumulation and remove the cause of the disease.

General treatment

Body position

Acute pulmonary edema should be kept in the sitting or semi-recumbent position as much as possible, in order to reduce the volume of circulating blood in the lungs.

The venous return of blood to the heart can also be reduced by dropping the legs or rotating the venous tourniquets around the extremities.

Posture is more effective in those with volume overload or cardiogenic pulmonary edema.

Oxygen therapy

People with pulmonary edema usually require higher concentrations of inhaled oxygen to improve hypoxemia.

It is best to use a humidifier with 75% to 95% alcohol or 10% silicone built in to help eliminate foam and keep oxygen saturation (SpO2) above 90%.

Patients without hypoxemia (SpO2 ≥ 90%) do not require routine oxygen therapy to avoid vasoconstriction and decreased cardiac output.

Mechanical ventilation

It can relieve airway obstruction and correct hypoxemia.

Positive-pressure ventilation can reduce the venous return blood volume to the heart and reduce the blood volume in the pulmonary circulation, thus achieving the effect of treating pulmonary edema.

For acute pulmonary edema, mechanical ventilation via mask or artificial airway can be considered when the effect of conventional treatment is unsatisfactory.

When mechanical ventilation is performed in patients with comorbid shock, blood pressure should be monitored.

Treatment of etiologic factors

The active elimination and control of triggering factors are important in the treatment of pulmonary edema.

For drug-induced cases, the use of suspected drugs should be stopped immediately, and gastric lavage or antidote should be given if necessary.

In the case of rapid infusion, the infusion should be stopped or slowed down immediately.

For uremia, dialysis may be required.

If the infection is caused by the disease, the patient should be treated with anti-infection therapy.

Inhalation of toxic gases should be removed from the scene immediately and an antidote given.

For those at risk of hypertension, reduce blood pressure to a safe range (systolic blood pressure <180 mmHg) as soon as possible.

For cardiac causes, primary diseases (e.g. myocardial infarction, arrhythmia, etc.) should be treated aggressively.

Symptomatic treatment

Medications should be applied to improve the symptoms of pulmonary edema and prevent further deterioration of the condition.

Morphine

Reduce symptoms such as agitation and dyspnea.

Reduces peripheral vascular resistance through central sympathetic inhibition, causing blood to be transferred from the pulmonary circulation to the body circulation, and relaxes the smooth muscles of the airways to improve ventilation.

It is most effective in those caused by acute myocardial infarction. Contraindicated for those with shock, respiratory depression and chronic obstructive pulmonary disease combined with pulmonary edema.

Diuretics

It can rapidly diuretic, reduce circulating blood volume, reduce cardiac load, elevate plasma colloid osmotic pressure, reduce microvascular filtration fluid volume, and have certain vasodilator effect; it can also dilate the veins, reduce venous return, reduce pulmonary edema.

Commonly used drugs: furosemide.

Those who do not respond significantly to furosemide can be switched to other diuretics, such as bumetanide.

It should not be used in hypovolemic individuals and should be avoided in the absence of significant fluid overload.

Vasodilators

Can dilate blood vessels, rapidly reduce systemic resistance (cardiac afterload), is an effective drug in the treatment of acute hyperbaric pulmonary edema.

Commonly used drugs: nitroglycerin, sodium nitroprusside. Among them, sodium nitroprusside is suitable for pulmonary edema caused by severe hypertension, acute mitral regurgitation or acute aortic regurgitation.

Precautions

Cardiotonic agents

Mainly for pulmonary edema induced by rapid atrial fibrillation or flutter.

For cardiogenic shock or high volume states with systolic blood pressure <90 mm Hg, dobutamine, dobutamine, milrinone, and enoximone may also be used to promote cardiac contraction.

It may help to prevent pulmonary edema or accelerate the absorption and dissipation of pulmonary edema, and the efficacy needs to be further verified.

Commonly used drugs: nebulized inhalation of long-acting or short-acting beta2 agonists such as terbutaline or salmeterol.

Glucocorticoid

Can be applied to plateau pulmonary edema, toxic pulmonary edema and myocarditis combined pulmonary edema.

Commonly used drugs include dexamethasone and hydrocortisone.

Not suitable for long-term application.

Low molecular weight heparin

Prevent thromboembolism.

Commonly used drugs: antiplatelet drugs (clopidogrel, aspirin), oral anticoagulants (warfarin) or subcutaneous injection of low molecular heparin.

Enoxaparin can be used early if conditions permit.

Care should be taken to assess bleeding risk during treatment.

Other treatments

Hemodialysis

Hemodialysis treatment may be considered for acute pulmonary edema caused by volume overload when conventional treatment fails.

Combined shock is a relative contraindication to hemodialysis.

Extracorporeal membrane oxygenation (ECMO)

Extracorporeal membrane oxygenation (ECMO) in acute pulmonary edema due to acute cardiogenic shock may buy time for left heart assist device placement or for cardiac transplantation.

Prognosis

Cure

The prognosis of pulmonary edema is related to a variety of factors, including etiology. Early detection, diagnosis, and treatment can improve the prognosis of pulmonary edema.

The prognosis of pulmonary edema caused by acute left heart failure is poor.

Hazards

When pulmonary edema develops to a certain stage, gas exchange is severely impaired, which may lead to death.

Daily life

Daily life

Dietary management

Eat plenty of fresh fruits, vegetables, mushrooms, etc., and take care to supplement your diet with foods rich in high-quality proteins, vitamins, minerals and other nutrients.

Drink an appropriate amount of water, slowly and in small sips, and do not “drink from the cow”: also drink water on time, and do not wait until you feel thirsty to drink a large amount of water.

Limit salt intake to 3-4 grams per day; also pay attention to hidden salt in food, such as salt in pickled foods, processed meats, bread and crackers.

Do not eat spicy and stimulating, fried and barbecued, dry, hard and cold foods.

Life management

Keep the house clean and clean frequently.

Pay attention to the air circulation of the living environment, you can open the window frequently for ventilation.

Increase or decrease clothing according to climate change, do not catch cold.

Do more outdoor activities to strengthen your body.

Ensure sufficient sleep and do not stay up late.

Quit smoking and limit alcohol consumption.

Avoid going to crowded places in the fall and winter seasons, and take protective measures, such as wearing a mask, when you go out.

Adjustment of mindset

Avoid emotional fluctuations and keep a calm mind.

Listen to soothing music and read favorite books to relax your body and mind.

Family members should encourage and care for the patient.

Prevention

Life management

If you are allergic, you need to avoid contact with allergens (sensitizers).

When the climate changes, increase or decrease clothing in time and avoid getting wet or cold.

Avoid going to crowded places in winter and spring, and wear masks etc. when going out to prevent infection.

Prevent gas poisoning.

Active treatment of primary diseases

Promptly treat primary diseases such as coronary heart disease, hypertensive heart disease, rheumatic heart valve disease and myocarditis.

Treat and control lung infections in a timely manner.

Occupational protection

Workers in chemical plants are advised to wear gas masks to prevent inhalation of toxic gases during normal operation.

People concerned with contact with poisonous snakes, please wear protective clothing.

Others

Avoid prolonged inhalation of oxygen at high concentration.

Do not infuse fluids too fast, especially for the elderly and children.

Avoid taking large amounts of anesthetic and sedative drugs, such as morphine, methadone and phenytoin sodium.

Do a strict health check before entering the plateau. After entering the plateau, pay attention to keep warm, prevent from cold, pay attention to rest, reduce or avoid strenuous exercise.