samisaf/nephcalc

Nephrology Calculators

Dysnatremias and Renal Replacement

Severe dysnatremias are perplexing problems in patients undergoing renal replacement therapy on a chronic or acute basis. The ability to manipulate sodium concentration in the dialysate or replacement solutions is limited.

Below are simple formulas to help determine the rate of hypotonic or hypertonic solutions needed to mitigate rapid correction of dysnatremias. These formulas can be used readily by the clinician at bedside.

Hyponatremia in hemodialysis patients

Formula 1: Increase in serum sodium at the end of hemodialysis session

Formula 2: Blood flow rate (Qb) needed for a slow rise in serum sodium

Formula 3: Volume of D5W needed to slow down the rate of serum sodium rise

Hypernatremia in hemodialysis patients

Formula 4: Volume of 3% saline needed to slow down rapid the rate of serum sodium decline

Hyponatremia in CRRT

Formula 5: Volume of D5W needed to slow the rate of serum sodium rise in CVVH

Formula 6: Volume of D5W needed to slow the rate of serum sodium rise in CVVHDF

Formula 7: Increase in serum na after 1 hour of CRRT

Hypernatremia in CRRT

Formula 8: Volume of 3% saline to slow the decline in serum sodium in CVVHDF

Formula 9: Decrease in serum sodium after 1 hour of CRRT

Tinawi, Mohammad, and Bahar Bastani. "A mathematical approach to severe hyponatremia and hypernatremia in renal replacement therapies." Seminars in Dialysis. 2020.