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Hypernatremia Physiology

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