Calculation of Maintenance Fluids

Maintenance Fluids Calculator (Holliday-Segar Method)

Calculation Results

Hourly Rate: mL/hr

Total Daily Requirement (24h): mL/day

Formula Breakdown:

function calculateMaintenanceFluids() { var weight = parseFloat(document.getElementById('patientWeight').value); var resultDiv = document.getElementById('fluidResult'); var hourlySpan = document.getElementById('hourlyRate'); var dailySpan = document.getElementById('dailyRate'); var breakdownUl = document.getElementById('formulaBreakdown'); if (isNaN(weight) || weight <= 0) { alert("Please enter a valid weight in kilograms."); resultDiv.style.display = "none"; return; } var hourly = 0; var daily = 0; var breakdown = ""; // Holliday-Segar / 4-2-1 Rule Calculation if (weight <= 10) { hourly = weight * 4; daily = weight * 100; breakdown = "

First 10kg: " + weight + "kg × 4mL = " + hourly + " mL/hr

"; } else if (weight <= 20) { var first10Hourly = 10 * 4; var remainingHourly = (weight – 10) * 2; hourly = first10Hourly + remainingHourly; var first10Daily = 10 * 100; var remainingDaily = (weight – 10) * 50; daily = first10Daily + remainingDaily; breakdown = "

First 10kg: 40 mL/hr

Next " + (weight – 10).toFixed(1) + "kg: " + remainingHourly.toFixed(1) + " mL/hr

"; } else { var first10Hourly = 40; var second10Hourly = 20; var remainingHourly = (weight – 20) * 1; hourly = first10Hourly + second10Hourly + remainingHourly; var first10Daily = 1000; var second10Daily = 500; var remainingDaily = (weight – 20) * 20; daily = first10Daily + second10Daily + remainingDaily; breakdown = "

First 10kg: 40 mL/hr

Next 10kg: 20 mL/hr

Remaining " + (weight – 20).toFixed(1) + "kg: " + remainingHourly.toFixed(1) + " mL/hr

"; } hourlySpan.innerText = hourly.toFixed(1); dailySpan.innerText = daily.toFixed(0); breakdownUl.innerHTML = breakdown; resultDiv.style.display = "block"; }

Understanding Maintenance Fluid Calculations

In clinical medicine, calculating maintenance fluids is critical for patients who cannot maintain adequate oral intake. The most widely accepted method for this calculation is the Holliday-Segar Method, also known as the 4-2-1 Rule. This formula estimates the volume of intravenous (IV) fluids required to replace the calories burned and water lost through normal physiological processes like breathing, sweating, and urination.

The 4-2-1 Rule Explained

The 4-2-1 rule simplifies the hourly fluid requirement based on the patient's body weight in kilograms:

• 4 mL/kg/hr for the first 10 kg of body weight.
• 2 mL/kg/hr for the next 10 kg of body weight (from 11kg to 20kg).
• 1 mL/kg/hr for every kilogram over 20 kg.

Example Calculation

If you have a pediatric patient weighing 25 kg, the hourly maintenance fluid rate would be calculated as follows:

1. First 10 kg: 10 kg × 4 mL/hr = 40 mL/hr
2. Next 10 kg: 10 kg × 2 mL/hr = 20 mL/hr
3. Remaining 5 kg: 5 kg × 1 mL/hr = 5 mL/hr
4. Total: 40 + 20 + 5 = 65 mL/hr

Daily (24-Hour) Fluid Requirements

While the 4-2-1 rule is standard for hourly rates, the 100/50/20 rule is often used to calculate total daily volume:

• 100 mL/kg for the first 10 kg.
• 50 mL/kg for the next 10 kg.
• 20 mL/kg for each kg thereafter.

Clinical Considerations

It is important to remember that the Holliday-Segar method provides an estimate for maintenance only. Clinical factors may require adjusting these rates:

• Dehydration: Patients with fluid deficits require additional replacement fluids.
• Ongoing Losses: Vomiting, diarrhea, or surgical drains may require "output-for-output" replacement.
• SIADH or Heart Failure: These conditions may require fluid restriction.
• Fever: Typically, fluid requirements increase by roughly 10-12% for every degree Celsius above normal body temperature.

Disclaimer: This calculator is for educational purposes for healthcare professionals and students. Always follow institutional protocols and clinical judgment when prescribing IV fluids.