Hypernatremia: Physiology Unreplaced H2O loss
Hypodipsia
H2O shift into cells
Severe exercise, electroshock induced seizures
Transient ↑ cell osmolality
Na+ overload
Inappropriate IV hypertonic solution, salt poisoning
Abbreviations:
H2O: Water
GI: Gastrointestinal
DM: Diabetes Mellitus
DI: Diabetes Insipidus
Na+: Sodium ion
IV: Intravenous
ADH: Antidiuretic Hormone LOC: Level of Consciousness
Skin
Sweat, burns
GI
Vomiting, bleeding, osmotic diarrhea
Fluid [Na+] < serum [Na+] ↑ H2O loss compared to Na+ loss Renal DM, Mannitol, Diuretics Absent thirst mechanism Hypothalamic lesion impairs normal drive for H2O intake Nephrogenic ↑ renal resistance to ADH H2O Deprivation Test + no AVP response ↓ access to H2O DI Central ↓ ADH secretion H2O Deprivation Test + AVP response ↑ [Na+] 10- 15 mEq/L within a few minutes Weakness, irritability, seizures, coma ↑ thirst, ↓ urinary frequency and volume Note: Hypernatremia Serum [Na+] > 145 mmol/L
Intracranial hemorrhage
Headache, vomiting, ↓ LOC
• Plasma [Na+] is regulated by water intake/excretion, not by changes in [Na+].
• Effects on plasma [Na+] of IV fluids or loss of bodily fluids is determined by the tonicity of the fluid, not the osmolality.
Authors: Mannat Dhillon Reviewers: Andrea Kuczynski Kevin McLaughlin* * MD at time of publication
Legend:
Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
Complications
Published January 11, 2019 on www.thecalgaryguide.com