Clinical Scenario: 28 yo F with unknown medical history presents with multiple seizures. Routine BMP shows hyponatremia to 110. What is your next step for symptomatic hyponatremia?
Causes of hyponatremia:
- Hypervolemic Hyponatremia: congestive heart failure, cirrhosis, chronic renal failure
- Euvolemic Hyponatremia: SIADH, hypothyroidism, adrenal insufficiency
- Hypovolemic Hyponatreamia: fluid loss via the gastrointestinal tract, diuretics, renal tubular acidosis, pseudohyponatremia (hyperglycemia, hyperlipidemia, hyperproteinemia)
Step 1: Give 1-2cc/kg or 100cc -150 cc of 3% NS bolus over 5-10 minutes. If the patient is still seizing, repeat the same dose again.
- Each 100cc will raise serum sodium by 2-3 mmol/L
- Seizures induced by hyponatremia can be stopped by increasing serum sodium to 3-7 mmol/L.
- Most osmotic demyelination occurs after 9-12 mmol in 24 hours
- Hypertonic saline can be given through peripheral IVs, but it depends on the hospital and department policy.
- If 3% NS is not available, 50 cc of 8.4% of sodium bicarb can be given
Step 2: Fluid restrict patient. Goal: < 6 mEq/L in the initial 24 hours to prevent osmotic demyelination.
Step3: ICU admission and correction of underlying causes.
What labs do you send? CMP, osmolality, uric acid, TSH, cortisol, UA, urine lytes, urine urea, urine uric acid, urine osm, urine creatinine
What IV fluid do you give if the patient is hypotensive and has hypovolemic hyponatremia? Ringer’s lactate, because it has a sodium concentration of 128 mmol/L. It will not increase the serum sodium as fast as normal saline.
What is the role of DDAVP? One source suggests that DDAVP helps reverse, arrest, and prevent sodium over-correction. Another source suggests that the use of DDAVP with hypertonic saline can aggravate hyponatremia and water retention, which can subsequently cause pulmonary edema in elderly patients.
Adrogué , H.J. and Madias , N.E. Hyponatremia. New England Journal of Medicine 2000;342(21):1581-1589.
Adrogue, H.J. and Madias, N.E. The challenge of hyponatremia. Journal of the American Society of Nephrology : JASN 2012;23(7):1140-1148.
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