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Tags: Electorlye

Show Notes

Episode Overview:

• Introduction to Hypernatremia


• Definition and basic concepts


• Clinical presentation and risk factors


• Diagnosis and management strategies


• Special considerations and potential complications

Definition and Pathophysiology:

• Hypernatremia is defined as a serum sodium level over 145 mEq/L.


• It can be acute or chronic, with chronic cases being more common.


• Symptoms range from nausea and vomiting to altered mental status and coma.

Causes of Hypernatremia based on urine studies:

• Urine Osmolality > 700 mosmol/kg
  
  
  
  • Causes:
    
    
    
    • Extrarenal Water Losses: Dehydration due to sweating, fever, or respiratory losses
    
    
    • Unreplaced GI Losses: Vomiting, diarrhea
    
    
    • Unreplaced Insensible Losses: Burns, extensive skin diseases
    
    
    • Renal Water Losses with Intact AVP Response:
    
    
    • Diuretic phase of acute kidney injury
    
    
    • Recovery phase of acute tubular necrosis
    
    
    • Postobstructive diuresis
    
    
    
    
  
  
  
  


• Urine Osmolality 300-600 mosmol/kg
  
  
  
  • Causes:
    
    
    
    • Osmotic Diuresis: High glucose (diabetes mellitus), mannitol, high urea
    
    
    • Partial AVP Deficiency: Incomplete central diabetes insipidus
    
    
    • Partial AVP Resistance: Nephrogenic diabetes insipidus
    
    
    
    
  
  
  
  


• Urine Osmolality < 300 mosmol/kg
  
  
  
  • Causes:
    
    
    
    • Complete AVP Deficiency: Central diabetes insipidus
    
    
    • Complete AVP Resistance: Nephrogenic diabetes insipidus
    
    
    
    
  
  
  
  


• Urine Sodium < 25 mEq/L
  
  
  
  • Causes:
    
    
    
    • Extrarenal Water Losses with Volume Depletion: Vomiting, diarrhea, burns
    
    
    • Unreplaced Insensible Losses: Sweating, fever, respiratory losses
    
    
    
    
  
  
  
  


• Urine Sodium > 100 mEq/L
  
  
  
  • Causes:
    
    
    
    • Sodium Overload: Ingestion of salt tablets, hypertonic saline administration
    
    
    • Salt Poisoning: Deliberate or accidental ingestion of large amounts of salt
    
    
    
    
  
  
  
  


• Mixed or Variable Urine Sodium
  
  
  
  • Causes:
    
    
    
    • Diuretic Use: Loop diuretics, thiazides
    
    
    • Adrenal Insufficiency: Mineralocorticoid deficiency
    
    
    • Osmotic Diuresis with Renal Water Losses: High glucose, mannitol
    
    
    
    
  
  
  
  

Risk Factors:

• Patients with impaired thirst response or those unable to access water (e.g., altered or ventilated patients) are at higher risk.


• Important to consider underlying conditions affecting thirst mechanisms.

Diagnosis:

• Initial assessment includes history, physical examination, and laboratory tests.


• Key tests: urine osmolality and urine sodium levels.


• Lab errors should be considered if the clinical picture does not match the lab results.

Management Strategies:

• Calculate the Free Water Deficit (FWD) to guide treatment. 

• Administration routes include oral, NGT, G-tube, or IV with D5W for larger deficits.


• Safe correction rate is 10-12 mEq/L per day or 0.5 mEq/L per hour to avoid cerebral edema.


• Address hypovolemia with isotonic fluids before correcting sodium.

Monitoring and Follow-Up:

• Monitor sodium levels every 4-6 hours.


• Assess urine output and adjust free water administration as needed.


• Admission to ICU for symptomatic patients or those with severe hypernatremia (sodium >160 mEq/L).


• Decision to discharge vs admit is a complicated one that factors in symptoms, etiology, degree of hypernatremia, patient preference, access to follow up, etc.

Take Home Points:

• Hypernatremia is a serum sodium level over 145 mEq/L, with symptoms ranging from nausea to coma.


• It is primarily caused by water loss exceeding intake due to various factors like sweating, vomiting, diarrhea, and renal issues.


• Correcting hypernatremia too quickly can lead to cerebral edema, so a safe correction rate is essential.


• Initial treatment involves calculating the Free Water Deficit and selecting the appropriate administration route.


• Monitor sodium levels frequently and decide on admission or discharge based on symptoms, sodium levels, and patient’s ability to follow up.