Acute Pulmonary Oedema

Question 1

What is acute pulmonary oedema (APO)?

Answer 1

APO refers to the rapid build up of fluid in the alveoli and lung interstitium that has extravasated out of the pulmonary circulation. As the fluid accumulates, it impairs gas exchange and decreases lung compliance, producing dyspnoea and hypoxia. Can be cardiogenic or non-cardiogenic.

Question 2

What is cardiogenic APO and list some possible causes?

Answer 2

Cardiogenic APO occurs when cardiac output drops despite an increased systemic resistance, so that blood returning to the left atrium exceeds that leaving the left ventricle. As a result, pulmonary venous pressure increases, causing the capillary hydrostatic pressure in the lungs to exceed the oncotic pressure of the blood, leading to a net filtration of protein poor fluid out of the capillaries.

Examples:

1. Left ventricular failure - ACS, arrhythmia, pericarditis, myocarditis or endocarditis, valve dysfunction
2. Increased intravascular volume - fluid overload, non-compliance with fluid restriction or diuretics, renal failure
3. Pulmonary venous outflow obstructions - mitral valve stenosis

Question 3

What is non-cardiogenic APO and list some possible causes?

Answer 3

Pathological processes acting either directly or indirectly on the pulmonary vascular permeability are thought to cause this form of APO. As a result, proteins leak from the capillaries, increasing the interstitial oncotic pressure, so that is exceeds that of the blood and fluid is subsequently drawn from the capillaries.

Examples:

1. High output states - septicaemia, anaemia, thyrotoxicosis
2. Systemic increase of vascular permeability - pancreatitis, eclampsia, disseminated intravascular coagulation, burns
3. Toxins/environmental - immersion/submersion, toxic inhalation, high altitude pulmonary oedema (HAPE) & decompression illness
4. Other - head injury/intracranial haemorrhage, drugs (NSAIDS, calcium channel blockers & naloxone)
5. PE

Question 4

What are the clinical features of APO?

Answer 4

• Sudden onset of extreme breathlessness, anxiety, and the feeling of drowning
• Profuse diaphoresis
• Crackles are usually heard at the bases first; as the condition worsens, they progress to the apices
• Cough is a frequent complaint that suggests worsening pulmonary oedema in patients with chronic LV dysfunction
• Pink frothy sputum
• Tachypnoea & tachycardia
• Hypertension
• Hypotension indicates severe left ventricular cardiogenic shock
• Raised jugular venous pressure

Question 5

What is the primary goal of treatment in cardiogenic APO?

Answer 5

To reduce cardiac preload & afterload with nitrates.

Question 6

What is the primary goal of treatment in non-cardiogenic APO?

Answer 6

To provide respiratory support (with lung protection strategies) and treatment of the underlying cause.

Question 7

Outline the treatment strategy for cardiogenic APO?

Answer 7

Appropriate positioning (seated upright)

1. O2
2. Aspirin (PO)
3. GTN
4. 12-lead ECG
5. IPPV
6. PEEP
7. CPAP

Manage as per appropriate CPG:

• Relevant dysrhythmia
• ACS

Is the patient hypotensive?
If yes, manage as per Cardiogenic Shock

Question 8

Outline the treatment strategy for non-cardiogenic APO?

Answer 8

Appropriate positioning (seated upright)

1. O2
2. 12-lead ECG
3. IPPV
4. PEEP
5. CPAP

Mange as per appropriate CPG:

• Burns
• Post submersion
• Head injury
• Spinal injury
• Relevant toxicology/toxinology