Acute pulmonary edema is a common medical emergency which can be thought about by diverse causes. There is accumulation of extra-vascular fluid within the Lung. The mechanisms include rise in the dynamics of flow of fluids and protein through the capillary walls and changes in the interstitium. Fluid may accumulate in the interstitium or in the alveoli.
1. Left sided heart failure, eg, acute myocardial infarction, hypertensive cardiac failure or mitrial stenosis.
2. Aspiration of gastric contents (Mendelson's syndrome).
3. Neurogenic disorders such as subarachnoid hemorrhage, meningitis, encephalitis or brainstem injury with resultant depression of respiratory center.
4. Fluid overload, eg, over-transfusion of fluids, cute nephritic syndrome.
5. Drug hypersensitivity, eg, hexamethonium, nitrofurantoin, busulphan, etc.
6. Change in permeability of capillary wall, eg, acute glomerulonephritis.
7. Narcotic poisoning with depression of respiratory center.
8. Irritant gases, eg, phosgene, chlorine, acid fumes.
9. Other forms of poisoning like paraquat, weedicides, organophosphorus.
10. Pulmonary embolism.
11. Uremia, aspiration of Pleural effusion.
Rare causes are as follows;
hanging, high altitude pulmonary edema, hypoproteinamia, disseminated intravascular coagulation, falciparum malaria, near-drowning and Pneumothorax.
Acute pulmonary edema ushers in with intestine dyspnea, anxiety and sweating. At this early phase the only obvious abnormality may be tachypnea. When fluid collections in the alveoli, the patient expectorates copious amounts of white or pink frothy sputum. Auscultation reveals widespread rales and occasional rhonchi. Initially the lower lobes are affected. Cyanosis may develop and it becomes deeper, Death occurs due to respiratory failure. Examination of the heart may reveal evidence of left-sided heart failure such as gallop rhythm or the presence of valvular lesions.
Emergency management is indicated to save life. Cardiac causes have to be treated as for acute left-sided heart failure. The main steps in treatment include the administration of oxygen, frusemide, digitalis, aminophylline and vasodilator drugs. Physiological or open venesection may be required as an emergency rarely. The underlying purpose should be attended to, after instituting the life-saving emergency measures. When pulmonary edema flows the inhalation of irritant fumes, massive doses of corticosteroids may be beneficial. Aerosols of surface active agents have been tried with benefit. In narcotics poisoning use of antidotes such as naloxone may help in bringing about dramatic improvement. Artificial ventilation is indicated in cases where respiratory failure developments. In addition, all the general principals of management of poisoning have to be adopted.
Chronic Pulmonary edema. : This occurs in chronic heart failure caused by mitral stenosis or left ventricular cardiomyopathy. The lungs are edematous, congested and brown on section (brown induration). Hemosiderosis may occur in long standing cases. X-ray shows signs of chronic pulmonary venous congestion. Dilated interlobar septal lymphatics- Kerley's lines- are seen. When pulmonary hemosiderosis develops, military shadows are seen in the radiograph. Treatment of Cardiac failure clears the pulmonary edema as well, in early cases.
Hypostatic congestion : This condition may develop in chronically bed-ridden patients due to diminished circulation, local anoxia, and infection. Hypostatic congestion can be preceded by early ambulation, respiratory physiotherapy, and adequate treatment of infection.