Maintaining adequate hydration and electrolyte balance is crucial for patient recovery and well-being. The Maintenance IV Fluid Calculator helps healthcare professionals estimate the appropriate hourly intravenous (IV) fluid rate required for patients based on their individual needs. This calculator utilizes a common method that considers a patient's baseline fluid requirements and adjusts for ongoing losses and specific conditions.
The Basis: Holliday-Segar Method (Modified)
The foundation of many maintenance IV fluid calculations is the Holliday-Segar method, which assigns fluid requirements based on weight. A simplified approach often used in clinical practice is:
First 10 kg: 100 mL/kg/day
Next 10 kg: 50 mL/kg/day
Remaining weight (> 20 kg): 20 mL/kg/day
These daily totals are then divided by 24 to get an hourly rate. For example, a 50kg adult would have a baseline daily requirement of (10kg * 100mL) + (10kg * 50mL) + (30kg * 20mL) = 1000mL + 500mL + 600mL = 2100 mL/day, or approximately 87.5 mL/hour.
Adjustments for Physiological Losses
Patients often experience fluid losses beyond normal insensible losses, which need to be accounted for to prevent dehydration or fluid overload. This calculator incorporates common adjustments:
Fever: For every degree Celsius above 37°C, an additional 10% of the calculated maintenance fluid is often added. For example, a 38.5°C fever (1.5°C above normal) would add 15% of the maintenance rate.
Vomiting: A specific volume of fluid lost through vomiting needs to be replaced. This calculator uses the input Vomiting (mL) to add directly to the total deficit.
Diarrhea: Stools lead to significant fluid and electrolyte loss. The calculator estimates losses based on the frequency of stools. A common guideline is to replace 100-200 mL per diarrheal stool. This calculator uses an average of 150 mL per stool.
Other Insensible Losses: This accounts for losses not covered by fever, vomiting, or diarrhea, such as excessive sweating from other causes, wound drainage, or ostomy output.
Recent Fluid Resuscitation: If a patient has recently received a bolus of IV fluids (e.g., for shock), this might temporarily reduce the immediate need for maintenance fluids, though it's often accounted for in reassessment rather than a direct subtraction from maintenance rate itself. This calculator uses it as a factor to consider if prior fluid shifts are significant.
Calculation Logic (Simplified Example):
1. Calculate Baseline Maintenance: Determine the hourly maintenance fluid rate based on weight using the Holliday-Segar principles (or a simplified version).
2. Calculate Fever Adjustment: Add 10% of the baseline rate for each degree Celsius above 37°C.
3. Calculate Deficit Replacement: Sum up the fluid lost from vomiting, diarrhea (estimated), and other insensible losses.
4. Total Hourly Requirement: Baseline Maintenance Rate + Fever Adjustment + Deficit Replacement Rate. (Note: Some protocols add deficit replacement as a separate ongoing infusion or bolus, but this calculator integrates it into the hourly rate for simplicity of bedside management).
Disclaimer:
This calculator is intended for informational and educational purposes only. It is a tool to assist healthcare professionals and should not replace clinical judgment, established protocols, or physician orders. Always consider the individual patient's clinical status, comorbidities, and laboratory results when determining fluid management. Consult with a qualified healthcare provider for any medical advice or treatment.
function calculateMaintenanceFluids() {
var weightKg = parseFloat(document.getElementById("patientWeightKg").value);
var ageYears = parseFloat(document.getElementById("patientAgeYears").value);
var urinaryOutputMlHr = parseFloat(document.getElementById("patientUrinaryOutputMlHr").value);
var feverCelsius = parseFloat(document.getElementById("feverCelsius").value);
var vomitingMl = parseFloat(document.getElementById("vomitingMl").value);
var diarrheaStools = parseFloat(document.getElementById("diarrheaStools").value);
var insensibleLossMlHr = parseFloat(document.getElementById("insensibleLossMlHr").value);
var fluidResuscitationMl = parseFloat(document.getElementById("fluidResuscitationMl").value); // Used as a general consideration, not direct subtraction in this simplified model
var resultSection = document.getElementById("resultSection");
var calculationResult = document.getElementById("calculationResult");
var resultUnits = document.getElementById("resultUnits");
// Reset previous results
calculationResult.textContent = "";
resultUnits.textContent = "";
resultSection.style.display = "none";
// — Input Validation —
if (isNaN(weightKg) || weightKg <= 0) {
alert("Please enter a valid patient weight in kilograms.");
return;
}
if (isNaN(ageYears) || ageYears < 0) {
alert("Please enter a valid patient age in years.");
return;
}
if (isNaN(feverCelsius) || feverCelsius < 0) {
feverCelsius = 0; // Assume no fever if input is invalid or negative
}
if (isNaN(vomitingMl) || vomitingMl < 0) {
vomitingMl = 0;
}
if (isNaN(diarrheaStools) || diarrheaStools < 0) {
diarrheaStools = 0;
}
if (isNaN(insensibleLossMlHr) || insensibleLossMlHr < 0) {
insensibleLossMlHr = 0;
}
if (isNaN(fluidResuscitationMl) || fluidResuscitationMl < 0) {
fluidResuscitationMl = 0;
}
if (isNaN(urinaryOutputMlHr) || urinaryOutputMlHr < 0) {
// Urinary output is often monitored but not directly added to maintenance;
// invalid input here might indicate a need for closer monitoring, but doesn't stop calculation.
// alert("Please enter a valid urinary output in mL/hr."); // Optional: uncomment to enforce
urinaryOutputMlHr = 0;
}
// — Calculation Logic —
// 1. Baseline Maintenance Fluid Calculation (Holliday-Segar Simplified Hourly)
var baselineHourlyMaintenance = 0;
if (weightKg <= 10) {
baselineHourlyMaintenance = (weightKg * 100) / 24;
} else if (weightKg <= 20) {
baselineHourlyMaintenance = (10 * 100 + (weightKg – 10) * 50) / 24;
} else {
baselineHourlyMaintenance = (10 * 100 + 10 * 50 + (weightKg – 20) * 20) / 24;
}
// 2. Fever Adjustment (Add 10% of baseline for each degree Celsius above 37°C)
var feverExcessCelsius = Math.max(0, feverCelsius – 37.0);
var feverAdjustment = baselineHourlyMaintenance * (feverExcessCelsius * 0.10);
// 3. Deficit/Ongoing Loss Replacement
// Vomiting: Direct replacement amount
var vomitingLossReplacement = vomitingMl; // Replace total loss
// Diarrhea: Estimate per stool (e.g., 150 mL per stool)
var diarrheaLossReplacement = diarrheaStools * 150; // Common estimate, adjust as per protocol
// Other Insensible Losses: Already provided in mL/hr
var otherInsensibleLossReplacement = insensibleLossMlHr * 1; // Already hourly
// Total fluid deficit to be replaced over a period (often 24 hrs, but here we add to hourly rate)
// For simplicity in hourly rate calculation, we can consider these losses occurring over the same period as the maintenance.
// A more complex model might calculate a separate deficit fluid to be given over time.
// Here, we will add these ongoing losses to the hourly rate calculation.
// Urinary output is a MEASURED loss, not typically added to the required *input* unless it's abnormally low.
// High urinary output might indicate need for more fluids, low output might mean dehydration.
// For basic maintenance, we focus on replacing normal losses + abnormal ones.
// Consider Fluid Resuscitation: If recent resuscitation was given, the immediate need might be less,
// but this calculator focuses on ongoing *maintenance* needs. We'll note it but not subtract.
// 4. Total Calculated Hourly IV Fluid Rate
// This is the sum of baseline maintenance, fever adjustment, and ongoing losses.
var totalHourlyRate = baselineHourlyMaintenance + feverAdjustment + otherInsensibleLossReplacement;
// Add deficit replacement (vomiting, diarrhea) to the hourly rate. This assumes these losses are continuous or need replacement concurrently.
// In practice, significant deficits might be replaced as boluses first. This simplifies it.
totalHourlyRate += (vomitingLossReplacement + diarrheaLossReplacement) / 24; // Distribute deficit replacement over 24 hours for hourly rate
// — Rounding and Display —
var finalRate = Math.round(totalHourlyRate * 10) / 10; // Round to one decimal place
// Display results
calculationResult.textContent = finalRate.toFixed(1);
resultUnits.textContent = "mL/hour";
resultSection.style.display = "block";
// Optional: Display individual components for clarity (can add more detail here if needed)
// console.log("Baseline Hourly Maintenance:", baselineHourlyMaintenance.toFixed(1));
// console.log("Fever Adjustment:", feverAdjustment.toFixed(1));
// console.log("Vomiting Replacement (Total):", vomitingLossReplacement);
// console.log("Diarrhea Replacement (Total):", diarrheaLossReplacement);
// console.log("Other Insensible (mL/hr):", otherInsensibleLossReplacement);
// console.log("Total deficit spread hourly:", ((vomitingLossReplacement + diarrheaLossReplacement) / 24).toFixed(1));
}