From the Guidelines
For a 16kg child, the 1/3 maintenance fluid rate would be approximately 18 mL/hour, as calculated using the Holliday-Segar method 1. To calculate this, I first determined the full maintenance fluid requirement: 100 mL/kg for the first 10kg (1000 mL) plus 50 mL/kg for the next 6kg (300 mL), totaling 1300 mL per day. Dividing by 24 hours gives approximately 54 mL/hour for full maintenance. One-third of this is 18 mL/hour. Using the simplified 4-2-1 rule, the calculation would be [(10kg × 4 mL/kg/hr) + (6kg × 2 mL/kg/hr)] = (40 + 12) = 52 mL/hour, and one-third of this is 17.3 mL/hour, rounded to approximately 17-18 mL/hour 1. For practical purposes in clinical settings, this would typically be rounded to 20-25 mL/hour, but based on the most recent evidence, 18 mL/hour is the most accurate calculation. One-third maintenance fluids are commonly used in situations where fluid restriction is necessary, such as in certain cardiac conditions, renal impairment, or SIADH, and the recent guidelines support the use of isotonic fluids and balanced solutions to reduce the risk of hyponatremia and fluid overload 1. Some key points to consider when calculating maintenance fluids include:
- The total daily amount of maintenance fluid therapy should be considered, including IV fluids, blood products, and enteral intake 1
- Avoidance of fluid overload and cumulative positive fluid balance should be considered to avoid prolonged mechanical ventilation and length of stay 1
- Restricting maintenance fluid therapy volume to between 65–80% of the volume calculated by the Holliday and Segar formula should be considered in children at risk of increased endogenous secretion of ADH 1
From the Research
Maintenance Fluid Calculation
To calculate 1/3 maintenance fluids for a 16kg child, we can use the equation proposed by 2, which states that the maintenance fluid volume for hospitalized children is 300 × W^1/2 mL/day, where W is the body weight in kg.
Calculation Steps
- Calculate W^1/2: 16^1/2 = 4
- Calculate maintenance fluid volume: 300 × 4 = 1200 mL/day
- Calculate 1/3 maintenance fluids: 1200 mL/day × 1/3 = 400 mL/day
Key Points
- The calculation is based on the equation proposed by 2
- The maintenance fluid volume is calculated as 300 × W^1/2 mL/day
- The 1/3 maintenance fluids for a 16kg child is 400 mL/day
- Note that this calculation is specific to the equation proposed by 2 and may not be applicable to other situations or populations, as discussed in other studies such as 3, 4, 5, and 6 which focus on different aspects of fluid management.