Core EM - Emergency Medicine Podcast

Episode 198: Hypernatremia

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We discuss the approach to diagnosing and managing hypernatremia in the emergency department.

Hosts:

Abigail Olinde, MD
Brian Gilberti, MD

https://media.blubrry.com/coreem/content.blubrry.com/coreem/Hypernatremia.mp3
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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.

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