Pulmonary oedema

Pathophysiology
Pulmonary edema is caused because of transudation of fluid, RBCs and macromolecules from the pulmonary capillaries into the interstitium and then into the alveoli an bronchioles.

This takes place because of the following factors:
1.Increased pulmonary capillary pressure
2.Widening of the intercellular junctions between the pulmonary capillary endothelium
3.Disruption of the intercellular junctions


Causes
Cardiogenic pulmonary edema:
MS (mitral stenosis)
MR (mitral regurgitation)
MI (myocardial infarction)
Hypertensive heart disease

Non cardiogenic pulmonary edema:
ARDS
Narcotic overdose
Blockade of lymphatic drainage
Rapid evacuation of pleural effusion or pneumothorax


Stages
Interstitial edema
Alveolar edema


Symptoms
Severe dyspnea, orthopnea
Cough with copious, pink frothy sputum
Cyanosis, pallor- cold bluish extremities
Tachycardia, tachypnea
Sweating, anxiety
Bilateral rhonchi, bilateral basal crepitations
Patient may die because of respiratory arrest.


Investigations
ABG analysis: hypoxia, hypocapnia in early stages, hypercapnia in late stages

Radiological grading of pulmonary edema:
Grade 1– Prominence of upper lobe veins (reverse moustache sign or stag antler’s sign)

Grade 2 (interstitial edema) –
Kerley A lines,
Kerley B,
Endobronchial cuffing,
Blurring of the outline of Central pulmonary vessels and hilum due to perivascular edema

Grade 3 (alveolar edema) –
Bilateral fluffy shadows,
Bat’s wing appearance (bilateral perihilar opacity dense at the hilum), Pleural effusion at uncommon sites (interlobar fissure) which appears like a tumour on chest X-ray and disappears on administration of diuretics, hence called phantom tumour or vanishing tumour


Treatment (mnemonic is the alphabetical sequence –LMNOP)

L – Loop diuretics (Furosemide 40-100 mg iv)
Reduce the blood volume and have a venodilator action so as to reduce venous return.

M – Morphine 5mg iv to reduce venous return and anxiety

N – Nitrates, nitroprusside, nesiritide

Nitrates sublingual cause preload reduction

Nitroprusside helps in afterload reduction

Nesiritide is an arterial and venodilator, also it potentiate the action of diuretics

O – Oxygen 100% under positive pressure

P – Propped up position, Pressors like Dopamine, Dobutamine to increase the cardiac output

Monitor pulmonary vascular pressure using a Swan Ganz catheter in some cases.

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