Hypernatremic Dehydration
- Na level is more than 145 meq/L
Presentation
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May be nonspecific: irritable, lethargic, with doughy skin and a high-pitched cry, eventually having seizures
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CNS signs are first to develop due to intracellular dehydration of neurons
Replacement
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Done slowly over 48 hours with the aim of a fall in serum Na of less than 0.5 mmol/L/hr.
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Goal is to avoid a rapid drop of the serum Na+, which is a risk factor for central pontine demyelination and manifests as seizuresZ.
Causes
Water and Sodium Loss
- Gastroenteritis
- Burns
- DM
Water Deficit
- DI
- Phototherapy
- Inadequate intake (failed breastfeeding)
Excessive Sodium Intake
- Inappropriately prepared infant formula
- Salt poisoning
- Hypertonic IV
Lack of Response to ADH
- Polyuria, polydipsia: Hypernatremia if water is limited.
Central DI
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Lack of ADH secretion.
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Causes: Idiopathic, brain injury, surgery, infiltrative infections/tumors.
Nephrogenic DI
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ADH receptor/response defects
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Causes: Inherited receptor or aquaporin defects, acquired (drugs like lithium, foscarnet, clozapine), infiltrating infections, sickle cell, hypercalcemia/hypokalemia, pregnancy.