Pulmonary Oedema

DEFINITION
The forcing of body fluid into the air sac spaces of the lung tissue, leading to severe shortness of breath worse of lying down, as a result of high pressures in the vessels of the lungs.
Here only management is discussed in detail.

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INCIDENCE
Varies by cause.
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AETIOLOGY
Varies by cause.
Most commonly relates to backed up pressure in pulmonary veins due to LV dysfunction.
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BIOLOGICAL BEHAVIOUR
Pathophysiology
Occurs when pulmonary capillary pressure >24 mmHg.
Fluid filters from capillaries.
--> through to interstitium first, particularly the interlobular septa.
--> as pressure increases further, fluid filters through to alveoli.
- iron containing proteins leak, accounting for hemosiderin-laden macrophages.
If oncotic pressure is low (eg hypoalbuminaemia), pulmonary oedema occurs at lower capillary pressures.

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MANIFESTATIONS
Symptoms
Local
Dyspnoea.
- especially if lying supine.
PND
Orthopneoa.

Signs
Observe
Pink blood-stained sputum.
Cyanosis.
Peripheral oedema if longstanding.
Raised JVP
Palpate
Cold, clammy peripheries, cyanosed if resp failure
Tachycardia
BP may be low if heart pumping impaired
- or high if secondary to vasoconstriction, elevated catecholamines.
Auscultate
Crackles of alveolar oedema.
+/- wheeze of bronchial congestion.
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INVESTIGATIONS
CXR
see card
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MANAGEMENT

Emergency
1. Rapidly secure ABCs and vital signs.
2. Sit patient upright.
- only if BP>100.
- legs over the bed.
3. O2 at highest possible concentration.
- aim sats >90%.
- consider CPAP, PPV or intubation if loses consciousness, cannot cough or severe resp failure.
4. Insert IV line, attach ECG.
5. GTN spray
- reduces preload.
- only if SBP>90.
- up to 4 doses under tongue every 15mins as BP allows.
- beware viagra interaction.
6. Morphine 2-4mg IV unless severe CORD.
- even if not in pain - dilates splanchnic vessels.
- over 3-5mins, counting RR every 5m.
- ensure naloxone available.
7. Frusemide -.5-1mg/kg IV.
**NB - recently thought less important**
- not orally as gut oedema reduces bioavailability.
- lower if frusemide naive, at least 1mg/kg if on already.
- very large doses if renal impairment eg 2mg/kg.
8. Consider dopamine if BP remapins <100mmHg.
9. Captopril 6.25mg
**NB - recently thought more important**
- if BP>120 or especially if high - reduces afterload.
- not if aortic stenosis.
10. Treat underlying cause.

If cardiac arrest occurs, survival is low - difficult to restore oxygen levels.

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