Differentials
Dehydration
SIGNS / SYMPTOMS
Implies a loss of pure water, leading to hypertonicity and hypernatraemia.
The term is often misused to imply volume depletion.
However, volume depletion means both a salt and a water loss, leading to decreased intravascular volume.
Symptoms include fatigue, lethargy, dizziness, and increased thirst.
INVESTIGATIONS
Blood chemistry: hypernatraemia supports a diagnosis of dehydration.
Serum osmolality: elevated in dehydration. The hypertonicity exists due to an increased sodium concentration.
Heart failure
SIGNS / SYMPTOMS
Symptoms include exertional dyspnoea, orthopnea, paroxysmal nocturnal dyspnoea, and peripheral oedema.
Signs of volume overload such as pleural effusions, rales, distended neck veins, gallop rhythm, and peripheral oedema may be present in heart failure, which would not normally be present in volume-depleted patients.
Volume repletion may actually make heart failure worse if expansion leads to pulmonary oedema. When heart failure is accompanied by volume depletion from over-diuresis, only small amounts of volume resuscitation are necessary for management, in contrast to volume depletion without heart failure, when large volumes of fluid are appropriate.
INVESTIGATIONS
Echocardiogram: demonstrates a low ejection fraction.
Hepatorenal syndrome
SIGNS / SYMPTOMS
Volume depletion occurs as a result of shunting of blood to the splanchnic circulation. May have symptoms or signs of chronic hepatic disease (e.g., jaundice, spiders, ascites).
INVESTIGATIONS
Evidence of liver dysfunction; urine Na usually <10 mmol/L (mEq/L).
Cardiogenic shock
SIGNS / SYMPTOMS
May occur after an acute coronary syndrome, and potential findings include chest pain, dyspnoea, diaphoresis, nausea, or dusky extremities.
INVESTIGATIONS
Echocardiogram: demonstrates a low ejection fraction and possible structural damage or malfunction.
Biochemical cardiac markers: reveal elevated troponins and creatine kinase-MB.
Sepsis
Anaphylaxis
SIGNS / SYMPTOMS
Presents acutely with facial and neck swelling, difficulty breathing, and wheezing, and often with rash.[26]
INVESTIGATIONS
Anaphylaxis is a clinical diagnosis and the history is critical.
Drug adverse effect
SIGNS / SYMPTOMS
Variable presentation, depending on the specific offending drug.
INVESTIGATIONS
Trial withdrawal of offending drug: blood pressure improves on variable timescale, depending on the drug pharmacokinetics.
Volume resuscitation may be necessary until the drug is no longer causing hypotension.
Autonomic insufficiency
SIGNS / SYMPTOMS
Hypotension and tachycardia occur consistently with standing. Occasionally, the heart rate may not increase as blood pressure falls.
INVESTIGATIONS
There is no response to volume resuscitation.
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