What is acute pulmonary edema?
Acute pulmonary edema, also called acute lung edema (APS), is a medical emergency caused by the leakage of water from blood vessels into the lung tissue, making breathing difficult.
In practice, a patient with EAP has their alveoli filled with water and behaves as if they were drowning.
how does it arise
Lung edema has the same pathophysiological mechanism as any edema in our body, appearing whenever there is water leakage from blood vessels to some tissue.
Contrary to what you might imagine, our blood vessels are not impermeable tubes, they have pores that allow the exit and entry of cells, bacteria, proteins and water.
Lung edema basically occurs by two mechanisms:
Increased pressure within blood vessels
When the pressure inside the lung vessels is too high, the water in the blood tends to “sore” through the pores, going to accumulate inside the lung tissue, mainly in the alveoli, which are the structures that carry out gas exchange.
Increased vessel permeability
Some diseases that will be explained below cause an increase in the pores of blood vessels, making them more permeable, which facilitates the extravasation of water.
Congestive heart failure
The most common cause of pulmonary edema is heart failure . Let’s simply describe the cardiopulmonary circulation so that this mechanism is easily understood.
The left side of the heart is responsible for pumping oxygen-rich blood to the body. After nourishing all the tissues, the blood, now poor in oxygen and rich in carbon dioxide, returns to the right side of the heart and is immediately pumped into the lungs. In the lungs, the blood is oxygenated again and returns to the left side of the heart, where it will be pumped towards the rest of the body, restarting the process.
When the left side of the heart becomes weak, it finds it difficult to properly pump blood to the rest of the body. As the left side of the heart is responsible for pumping blood from the lungs, when the heart pump fails, there is congestion, causing blood to accumulate in the pulmonary vessels. This congestion causes an increase in blood pressure within the pulmonary vessels, favoring water leakage.
In heart failure, pulmonary edema develops slowly unless there is something that triggers an acute worsening of heart function.
Acute myocardial infarction
Acute myocardial infarction, popularly called a heart attack, can cause pulmonary edema if there is necrosis of a large area of the heart muscle on the left side of the heart, leading to sudden heart failure. If much of the heart muscle dies, the heart becomes unable to pump blood properly, causing it to retain it in the lungs. Acute pulmonary edema is one of the possible symptoms of a cardiac infarction.
Increased blood pressure is often a frequent cause of acute pulmonary edema, especially in patients who already have some degree of heart failure.
In normal situations, the heart of a patient with moderate heart failure may still be able to pump blood properly. However, a sudden rise in blood pressure is enough for an increase in blood flow resistance, requiring more work from the heart muscle. Some patients do not have a heart able to work against high blood pressure, which leads to pulmonary congestion.
Disease of the heart valves.
If the patient has a disease of the left heart valves, that is, the aortic or mitral valve, the heart may have difficulty pumping blood through them. Aortic stenosis and mitral stenosis are valve lesions that hinder its opening. If the heart valve does not open properly, blood cannot drain through it, causing pulmonary congestion.
Kidney failure leads to the accumulation of water and salt in the body, causing an increase in the volume of fluid inside the vessels. In some cases, especially if the patient no longer urinates adequate volumes, the amount of fluid retained in the vessels becomes so large that it starts to leak, causing edema in the body and pulmonary edema.
Some pulmonary infections, especially those of viral origin, can cause intense pulmonary inflammation, leading to an increase in vessel permeability and consequent leakage of fluid into the lung. This condition is usually called ARDS or SARS (acute respiratory distress syndrome).
Some people when exposed to altitudes above 2500 meters may develop pulmonary edema. The cause is not well known, but it is believed that there are changes in the pulmonary microvasculature that favor the leakage of fluid at high altitudes.
The risk factors for this type of acute pulmonary edema are:
- Get out of sea level and reach high altitudes in no time.
- Practicing physical effort at high altitudes without giving due time for acclimatization.
- Traveling to high altitudes already having a history of heart problems.
- Excessive alcohol intake without adequate altitude acclimatization time
Drugs and Medicines
The consumption of some drugs, such as heroin or cocaine, can provoke intense pulmonary inflammation, causing an increase in the permeability of the vessels and consequent acute pulmonary edema.
Aspirin intoxication (ASA) can also lead to acute pulmonary edema.
Some patients with severe neurological damage, such as head trauma, brain surgery, seizures, brain hemorrhage, etc., may develop lung edema. Edema arises from changes in pulmonary hemodynamics, with increased pressure and permeability in pulmonary vessels.
Depending on the cause, pulmonary edema may develop slowly or suddenly, the latter called acute pulmonary edema.
In patients who slowly and progressively accumulate fluid in the lung, the symptoms of pulmonary edema begin with intolerance to exertion, tiredness (even at rest), shortness of breath when lying down, requiring at least two pillows to sleep, edema in the feet and ankles and wheezing in the chest. This picture is typical in patients with heart failure, who experience a gradual worsening of heart function and progressive pulmonary congestion.
If this same patient described above has a decompensation factor for his heart failure, such as a heart attack, a hypertensive peak or even a severe infection, the heart suddenly becomes incapable of properly pumping blood to the body. acute lung fluid retention. In this case, the symptoms of acute pulmonary edema are intense shortness of breath, feeling of drowning, agitation, cough with frothy secretion, inability to lie down and tachycardia (rapid heart).
The water in the lung prevents oxygenation of the blood and basically acts as a drowning. Acute pulmonary edema is a medical emergency and if not treated in time, it will fatally lead to cardiorespiratory arrest.
The first step in the treatment of acute pulmonary edema is to provide the patient with oxygen. Usually, the patient arrives at the emergency room with hypoxemia, that is, with low levels of blood oxygenation. In some cases, pulmonary edema is so severe and oxygenation so low that the patient needs to be intubated and attached to a mechanical ventilator in order not to die.
The purpose of treatment is to remove water from the lung. If the patient urinates, diuretics are administered intravenously to act quickly Lowering blood pressure is also important to facilitate the work of the heart, so vasodilators are also often used.
If the patient does not urinate or does not respond adequately to diuretics, the option is urgent hemodialysis, a method capable of removing up to one liter of water from the lungs in just 20-30 minutes.
- Acute Pulmonary Edema: Pathology, Physiology and Clinical Management – Circulation.
- Noncardiogenic pulmonary edema – UpToDate.
- Pathophysiology of cardiogenic pulmonary edema – UpToDate.
- Cardiogenic Pulmonary Edema – Medscape.