Sodium Correction Rate Calculator

The rate at which sodium is corrected in dysnatremia is as clinically important as the direction and magnitude of the correction. Both over-rapid and excessively slow correction carry significant risks, and the optimal rate depends on the duration of the sodium disorder, the severity of symptoms, and whether the patient has hyponatremia or hypernatremia. For hyponatremia, the dominant safety concern is osmotic demyelination syndrome (ODS), formerly called central pontine myelinolysis. ODS results from the rapid shift of water out of brain cells when serum osmolality rises quickly. During chronic hyponatremia (present for more than 48 hours), brain cells have had time to extrude organic osmolytes to reduce cell swelling. When sodium is corrected rapidly, these cells cannot rehydrate fast enough, leading to demyelination of the myelin sheath in the pons and extrapontine regions. The result can be paraplegia, dysphagia, dysarthria, seizures, and death. The European clinical practice guideline (EASD/ERA-EDTA 2014) recommends a target correction rate of no more than 10 mEq/L in any 24-hour period for chronic hyponatremia, with some authorities citing 8 mEq/L as a more conservative target for high-risk patients. For acute hyponatremia (present for fewer than 48 hours), the brain has not had time to adapt, so the risk of ODS with rapid correction is substantially lower. However, the risk of fatal cerebral oedema from the hyponatremia itself is higher, particularly with rates of change exceeding 0.5 mEq/L per hour. In acute severe symptomatic hyponatremia (seizures, respiratory arrest, herniation), current guidelines recommend an initial bolus approach: 150 mL of 3% hypertonic saline over 20 minutes, repeated up to twice until symptoms resolve, targeting an initial rise of 1–2 mEq/L per hour for the first couple of hours. For hypernatremia, the risk of rapid correction is cerebral oedema. During chronic hypernatremia the brain has accumulated osmolytes to counteract cell shrinkage. Rapid infusion of free water causes cells to take up water faster than they can export these osmolytes, leading to cerebral swelling. The general recommendation is to correct no faster than 0.5 mEq/L per hour, with a maximum 24-hour decrease of 10–12 mEq/L. This calculator applies the following guideline-derived correction rates: for chronic hyponatremia — mild: 0.5 mEq/L/hr (max 8 mEq/24hr), moderate: 0.5 mEq/L/hr (max 10 mEq/24hr), severe: up to 1.0 mEq/L/hr initially (max 12 mEq/24hr); for acute hyponatremia — mild: 1.0 mEq/L/hr, moderate: 1.5 mEq/L/hr, severe: 2.0 mEq/L/hr initially. The infusion volume and rate are then computed from the target correction using the TBW deficit formula. All recommendations are starting points. Frequent sodium monitoring (every 4–6 hours during active correction) is essential to detect either over- or under-correction and to adjust the infusion rate accordingly.