Acute & emergency · UKMLA & AKT
Dehydration
A free high-yield preview for the UKMLA Applied Knowledge Test, covering how to recognise this condition. The full SA Note notes add investigations, management and complications, with practice questions on this topic.
Key high-yield points
- 🥇 First-line
- U&E - raised urea/creatinine (pre-renal AKI), sodium level (hypernatraemia = hypotonic loss; hyponatraemia = isotonic/hypotonic loss), potassium (GI losses cause hypokalaemia)
- FBC - raised haematocrit/haemoglobin from haemoconcentration
- Urinalysis - concentrated urine (specific gravity >1.020) supports dehydration
- Blood glucose - exclude hyperglycaemia/osmotic diuresis
- Venous blood gas - pH (metabolic acidosis), lactate (poor tissue perfusion), bicarbonate
- 🏆 Gold standard
- Plasma osmolality - 90% sensitivity, 100% specificity; >295 mOsm/kg confirms hyperosmolar dehydration. Calculated as: 2[Na+] + glucose + urea (mmol/L)
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