Hypernatraemia
OVERVIEW
Hypernatraemia can be caused by a number of critical illnesses
CAUSES
- water depletion (decreased intake, hypotonic fluid loss – renal/non-renal)
- solute excess (Na+ or other)
Decreased intake
- common
- elderly with altered cognitive function -> inappropriate response to thirst
H2O loss
- GI loss
- intrinsic renal disease
- hypercalcaemia
- hypokalaemia
- solute diuresis
- glucosuria
- diabetes insipidus (central or nephrogenic)
MANAGEMENT
Goals:
(1) correct H2O deficit
(2) reduce ongoing excessive urinary H2O losses
Calculate water deficit
Water deficit = 0.6 x premorbid weight x [1 – 140/serum Na+]
- formula assumes TBW = 60% and does not account for ongoing water losses
Treatment
- treat cause
- decreased intake: rehydration
- central DI: DDAVP (1-2mcg) + 5% dextrose to correct H20 deficit
- nephrogenic DI: Na+ restriction, thiazide diuretics, large doses of DDAVP
References and Links
- CCC – Hypernatraemia DDx
- CCC – Hypernatraemia Mind map (PDF)
- CCC – Hypernatraemia
- CCC – Hyponatraemia
- CCC – Hyponatraemia Mind map (PDF)
- CCC – Hyponatraemia Interpretation (PNG)
- CCC – SIADH – SIADH DDx
- CCC – Diabetes Insipidus Central – Diabetes Insipidus DDx
- Case – Exercise-associated Hyponatremia
- Case – Seizures, hyponatremia and ADH
- CCC – Sodium
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the Clinician Educator Incubator programme, and a CICM First Part Examiner.
He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.
His one great achievement is being the father of three amazing children.
On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.
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