• Haemorrhage
• Urinary loss
• Gastrointestinal fluid loss
• Cutaneous loss (e.g. burns)
• Third-space sequestration (e.g. acute pancreatitis)

Cardiac obstruction

• Pulmonary embolism (Chapter 57)
• Cardiac tamponade (Chapter 54)
• Tension pneumothorax (Chapter 64)

Cardiac pump failure (see Chapter49)

• Acute myocardial infarction (usually associated with pulmonary oedema, except when due to right ventricular infarction)
• Acute myocardial ischaemia (usually associated with pulmonary oedema)
• Arrhythmia (especially when associated with valve disorder, e.g. severe aortic stenosis, or impaired left ventricular function, in which case usually associated with pulmonary oedema)
• Acute aortic or mitral regurgitation (due to endocarditis, aortic dissection, papillary muscle or chordal rupture) (always associated with pulmonary oedema)
• Ventricular septal rupture complicating myocardial infarction (often associated with pulmonary oedema)

Vasodilatation

• Sepsis
• Drugs and toxins
• Anaphylaxis
• Acute adrenal insufficiency (Addisonian crisis)