What is pulmonary edema? Cardiology Basics

What is pulmonary edema? Cardiology Basics

Pulmonary edema is collection of fluid within the lung alveoli.
The most important cause of pulmonary edema is heart failure, specifically, left ventricular failure. Pulmonary edema can also occur when there is fluid overload in the body as in renal failure.
Other causes of pulmonary edema are mitral stenosis, pulmonary venous obstruction and increased permeability of the pulmonary capillaries. Increased permeability of the pulmonary capillaries occurs in noncardiogenic pulmonary edema – e.g. adult respiratory distress syndrome or ARDS.

Sudden breathlessness is the most important symptom of pulmonary edema as the lungs become heavier and alveolar gas exchange poor. Cough with pink frothy sputum is another association of pulmonary edema. There is rapid fall in the oxygen saturation in pulmonary edema and it is a serious life threatening condition. In cardiogenic pulmonary edema, fluid transudation into the alveoli occur due to elevated pulmonary capillary pressure.

Immediate hospitalisation and treatment are lifesaving. Oxygen is routinely given as the blood oxygen levels are low. Rapidly acting diuretics like loop diuretics relieve the pulmonary congestion. Pulmonary venodilator action of frusemide occurs even before the diuretic effect, relieving the pressure in the pulmonary capillaries. When pulmonary capillary pressure is reduced below the level of plasma oncotic pressure, there is no more transudation of fluid into the alveoli, as per the Frank-Starling mechanism. Afterload and preload reducing agents like nitroglycerine infusion are also useful in pulmonary edema due to acute left ventricular failure.

Severe cases of pulmonary edema may need endotracheal intubation and positive pressure mechanical ventilation. Positive end expiratory pressure may also be useful. Pulmonary edema due to fluid overload in renal failure may need hemodialysis. Another option in refractory cardiogenic pulmonary edema is removal of excess fluid by ultrafiltration. Ultrafiltration is done by applying negative pressure across the dialysis membrane during hemodialysis. Cause of the pulmonary edema has to be identified and treated to prevent recurrence of pulmonary edema.