We discuss the approach to diagnosing and managing hypernatremia in the emergency department.
Hosts:
Abigail Olinde, MD
Brian Gilberti, MD
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
- Causes:
- 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
- Causes:
- Urine Osmolality < 300 mosmol/kg
- Causes:
- Complete AVP Deficiency: Central diabetes insipidus
- Complete AVP Resistance: Nephrogenic diabetes insipidus
- Causes:
- Urine Sodium < 25 mEq/L
- Causes:
- Extrarenal Water Losses with Volume Depletion: Vomiting, diarrhea, burns
- Unreplaced Insensible Losses: Sweating, fever, respiratory losses
- Causes:
- 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
- Causes:
- Mixed or Variable Urine Sodium
- Causes:
- Diuretic Use: Loop diuretics, thiazides
- Adrenal Insufficiency: Mineralocorticoid deficiency
- Osmotic Diuresis with Renal Water Losses: High glucose, mannitol
- Causes:
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.
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