Adult Male (0.6)
Adult Female / Elderly Male (0.5)
Elderly Female (0.45)
Children (0.6)
Calculation Results
function calculateHypertonicRate() {
var weight = parseFloat(document.getElementById('hs_weight').value);
var currentNa = parseFloat(document.getElementById('hs_currentNa').value);
var targetNa = parseFloat(document.getElementById('hs_targetNa').value);
var duration = parseFloat(document.getElementById('hs_duration').value);
var infusateNa = parseFloat(document.getElementById('hs_salineType').value);
var tbwCoeff = parseFloat(document.getElementById('hs_demographics').value);
var resultDiv = document.getElementById('hs_result');
var output = document.getElementById('hs_output_content');
if (!weight || !currentNa || !targetNa || !duration || weight <= 0 || duration <= 0) {
alert('Please enter valid positive numbers for all fields.');
return;
}
if (targetNa <= currentNa) {
alert('Target sodium must be higher than current sodium.');
return;
}
// Total Body Water
var tbw = weight * tbwCoeff;
// Adrogue-Madias Formula: Change in serum Na+ for 1L of infusate
// Change = (Infusate Na – Serum Na) / (TBW + 1)
var changePerLitre = (infusateNa – currentNa) / (tbw + 1);
// Total change needed
var totalChangeNeeded = targetNa – currentNa;
// Total volume in Liters
var totalVolumeL = totalChangeNeeded / changePerLitre;
// Convert to mL
var totalVolumemL = totalVolumeL * 1000;
// Infusion Rate (mL/hr)
var rate = totalVolumemL / duration;
// Change per hour
var changePerHour = totalChangeNeeded / duration;
resultDiv.style.display = 'block';
output.innerHTML = 'Total Body Water (TBW): ' + tbw.toFixed(1) + ' Liters' +
'Change per 1 Liter of Infusate: ' + changePerLitre.toFixed(2) + ' mEq/L' +
'Total Volume Required: ' + totalVolumemL.toFixed(0) + ' mL' +
'Infusion Rate:' + rate.toFixed(1) + ' mL/hr' +
'Sodium Rise Rate: ' + changePerHour.toFixed(2) + ' mEq/L/hr' +
'Note: Monitor serum sodium every 2-4 hours to prevent osmotic demyelination syndrome (ODS).';
}
Understanding Hypertonic Saline Infusion
Hypertonic saline (typically 3% NaCl) is a critical intervention in the management of severe symptomatic hyponatremia or elevated intracranial pressure. Because the sodium concentration in hypertonic saline is significantly higher than that of human extracellular fluid, precise calculation of the infusion rate is vital to avoid rapid overcorrection.
The Adrogue-Madias Formula
The calculation is based on the Adrogue-Madias formula, which estimates the effect of one liter of a specific intravenous fluid on the patient's serum sodium concentration. The formula is expressed as:
Change in Serum Na = (Infusate Na – Serum Na) / (TBW + 1)
Where TBW (Total Body Water) is calculated based on the patient's weight, sex, and age group.
Safety Limits and Monitoring
Clinical guidelines generally suggest that sodium correction should not exceed:
8-10 mEq/L in a 24-hour period.
18 mEq/L in a 48-hour period.
In cases of severe acute symptoms (e.g., seizures), a rapid rise of 4-6 mEq/L over 1-2 hours may be indicated, followed by a slower rate.
Overcorrection poses a high risk of Osmotic Demyelination Syndrome (ODS), formerly known as Central Pontine Myelinolysis, a devastating neurological condition.
Clinical Example
Consider a 70kg adult male with a serum sodium level of 110 mEq/L. The goal is to raise the sodium to 115 mEq/L over 10 hours using 3% saline.
TBW: 70kg × 0.6 = 42 Liters.
Infusate Na: 3% Saline contains 513 mEq/L.
Effect of 1L: (513 – 110) / (42 + 1) = 9.37 mEq/L rise per liter.
Required Rise: 5 mEq/L.
Total Volume: 5 / 9.37 = 0.533 Liters (533 mL).
Infusion Rate: 533 mL / 10 hours = 53.3 mL/hr.
Disclaimer
This calculator is for educational and informational purposes only. It is not a substitute for professional medical judgment. Clinical decisions should be based on real-time patient assessment, frequent lab monitoring, and institutional protocols.