Therapeutic targets
- Correction of the sodium balance
- Rehydration (fluid balance), as necessary.
Therapy recommendations
- As far as a causal cause is present: Co-treatment of the causative disease (e.g. hypothyroidism/ hypothyroidism).
- Hyponatremia in hypovolemia: correction of volume depletion (water loss) with NaCl (0.9%) i. v.
- Hyponatremia in euvolemia:
- Mild clinical cases: Fluid restriction (≤ 1 L/d).
- severe clinical cases:
- Hypertonic NaCl infusions (3%); caveat: Na elevation too rapid (target < 8-12 mmol/L in first 24 h, not more than 18 mmol/L in 48 h).
- Emergency (seizure, severe intracranial pressure symptoms): bolus therapy, i.e., 1- 2 ml of 3% NaCl solution (saline) per kg/KG per hour for 2-4 hTarget in emergency: elevation of serum sodium by 2-4 mmol/L in 2-4 hRule of thumb: 1 ml/kgKG of 3% NaCl solution elevates S-Na by 1 mmol/L
Note: presence of disease (eg, hypothyroidism / hypothyroidism, etc.) and / or triggering drugs.
- Hyponatremia in hypervolemia: therapy of the underlying disease.
- SIAD (syndrome of inadequate ADH secretion): vasopressin V 2 receptor antagonists (vaptans): tolvaptanIndications:
- Chronic SIAD when other therapeutic approaches are unsuccessful or fluid restriction involves a significant reduction in quality of life
- If the above measure is ineffective, not indicated, or not feasible, a loop diuretic plus saline or, alternatively, urea can be used:In a retrospective case-control study, it was shown that urea therapy resulted in a significant increase in sodium concentration to approx. 6 mmol / l within 4 to 5 days; this was accompanied by an equally significant increase in urine concentration, without an increase in serum creatinine and without a decrease in glomerular filtration rate (GFR).
- Acute cases when substitution with 3% NaCl solution is detrimental (e.g., heart failure (cardiac insufficiency), liver cirrhosis/irreversible (non-reversible) damage to the liver associated with marked remodeling of liver tissue).
- Chronic SIAD when other therapeutic approaches are unsuccessful or fluid restriction involves a significant reduction in quality of life
Notice:
- If hyponatremia has developed within a short time (< 48 h), correction of sodium balance may be more aggressive than in chronic hyponatremia because brain adaptation to extracellular volume (ECV) hypoosmolarity is not yet complete. In these cases, clinical severe symptoms are usually present.
- Hyponatremia in asymptomatic patients can be approached slowly.
Correction of hyponatremia (sodium deficiency) and hypernatremia (sodium excess)
Formula: Δ [Na+] P = ([Na+] I + [K+] I – S-Na+) / (GKW + 1).
The formula describes the change in plasma concentration of sodium (Δ [Na+] P) after administration of an infusion solution containing a given concentration of sodium ([Na+] I ) and potassium ([K+] I ); all concentrations are in mmol/L, and total body water (GKW) is in liters. Total body water is 60% of body weight in middle-aged men, 50% in middle-aged women, 50% in older men, and 45% in older women. Extracellular volume (EZV) contributes 40% of total body water, and intracellular volume (IZV) contributes 60%.