Acute metabolic derangements - hypo- and hypernatraemia
Description
- Sodium concentration is a water problem, not a sodium problem
- Total body sodium determines volume status; water handling determines the concentration
- Both disorders are almost always disorders of ADH and of thirst/water access
Hyponatraemia
- Na <135; severe <125. Symptoms track the rate of fall, not the absolute value
- Mild: nausea, headache, unsteadiness, falls, poor concentration
- Severe: vomiting, confusion, seizures, coma, respiratory arrest (cerebral oedema)
- Chronic "asymptomatic" hyponatraemia still causes falls, fractures and osteoporosis
Hypernatraemia
- Na >145. Almost always inadequate water intake - the thirsty patient who cannot reach a glass
- Thirst, lethargy, irritability, weakness, seizures, coma
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