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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