Hyponatremia Correction Infusate Rate Calculator

How does this hyponatremia correction infusate rate calculator work?

This health calculator determines the infusate rate and the serum Na change per liter based on the clinical data you input. It is a useful tool in establishing the correction to be applied to a hyponatremia case. In the following lines will discuss the data to be input and the formulas employed.

■ Serum Na change per hour – measured in mEq/L

■ Serum Na – measured in mEq/L

■ Water fract – to be chosen between the following cases: child, adult male and female, elderly male and female.

■ Weight – of the patient

■ IV Na – the intravenous solution of Na in different concentrations: 5% NaCl, 3% NaCl, 0.9% NaCl or Ringer Lactate solution

■ IV K – solution measured in mEq/L in order to avoid hypokalemia that could aggravate the brain effects of the Na deficit.

This hyponatremia correction infusate rate calculator also allows you to choose the units in which you want the result to be presented. For the infusate rate you can choose between mL/hr, L/min, L/sec, mL/min, mL/sec.

The formulas used are:

- Infusate Rate = (1000 * Serum Na Change Per Hr * ((Water Fract * Weight) + 1)) / (IVNa + IVK – Serum Na)
- Serum Na Change Per Liter = (IVNa + IVK – Serum Na) / ((Water Fract * Weight) + 1)

Medical implications of hyponatremia

■ This is a condition caused by a decrease in the concentration of serum Na below 136 mEq/L, everything below 125 mEq/L being considered severe hyponatremia.

■ The main causes of hyponatremia are vomiting, diarrhea, diuretic use, heart failure, burns, pancreatitis and renal disease. At the same time, many conditions are associated with low serum sodium, such as congestive heart failure, liver or renal failure.

■ Symptoms vary from nausea and a general bad feeling to lethargy and decreased consciousness. The clinical signs are primarily neurologic, including headache and confusion while is serious cases, seizures and coma may occur.

■ Classification is made between hypovolemic (decrease in both body water and sodium), euvolemic (normal body sodium, high body water levels), hypervolemic (increase in both body water and sodium).

■ Diagnosis is made by measuring serum Na, while the analysis or serum and urine electrolytes and osmolality indicate the cause. The classification by osmolality is between hypotonic, isotonic, hypertonic.

■ Corrective treatment starts by restricting water intake, replacing the Na deficit and working towards correcting the underlying cause. However, the rhythm of the correction should be closely monitored in order to avoid cerebral edema resulting in brain damage.

■ While in mild cases, water restriction should be enough to balance serum sodium, in more serious ones the corrective sodium rate should not exceed 8 mEq/L although the initial correction rate can begin at 1-2 mEq/L/hr.

Reference

Adrogue, HJ, Madias, NE. (2000) Primary Care: Hyponatremia. New England Journal of Medicine 2000; 342(20):1493-1499.