Chapter 20: FLUIDS & ELECTROLYTES

MAINTENANCE IV FLUIDS (MIVF) AND DEHYDRATION

MAINTENANCE IV FLUIDS (MIVF)

There are multiple formulas that help to estimate the maintenance IV fluid (MIVF) requirement in a child. Become familiar with one and expect to use it on the pediatric boards because you are guaranteed to need this on the exam. Plus, these are quick and easy points!

• ONLINE HELP: www.pbrlinks.com/MIVF1
• HOURLY IV FLUIDS: 4 ml/kg for the first 10 kg + 2 ml/kg for the second 10 kg + 1 ml/kg for each additional kg
  • MNEMONIC: 4/2/1. 4 divided by 2 = 2. 2 divided by 2 = 1. Hence, 4/2/1.
  • SHORTCUT: For patients > 20 kg, the hourly IV fluid rate = 40 + WEIGHT IN KG. For a 20 kg patient, the hourly rate is 60 ml/hour when we add 40 + 20 kg! For a 50 kg patient, the hourly rate is 90 ml/hour using the 4/2/1 formula, and we also get the same rate of 90 ml/hour by using our formula and adding 40 to the WEIGHT IN KG, which is 50 kg!
• DAILY FLUID REQUIREMENT: 100 ml/kg/day for each of the first 10 kg + 50 ml/kg/day for each of the second 10 kg + 20 ml/kg/day for each kg beyond that (e.g., a 15 kg patient needs 1250 ml/day).
  • PEARL: FEEL FREE TO USE THE HOURLY IV FLUID RATE MULTIPLIED BY 24!
  • MNEMONIC: Use 100/50/25 instead. It’s easier to remember! 100/2 = 50. 50/2 = 25. Hence, 100/50/25! IT’S ALSO SIMILAR TO THE HOURLY RATE MNEMONIC AND IS THE SAME MNEMONIC, WITH THE SAME NUMBERS AS THAT OF CALORIC INTAKE (100/50/25)!
• RENAL FAILURE PATIENTS: (Likely low-yield) Keep strict ins/outs and replace urine cc for cc with D5 0.2 NS, and give an additional 1/3^rd of the calculated fluid requirement by weight (the latter is for insensible losses). Use a low sodium solution (D5 0.2 NS) because the total body sodium is normal and this is truly for maintenance fluid/water only.

DEHYDRATION

If the patient presents with mild to moderate dehydration, oral replacement should be tried first if the patient can tolerate small amounts of fluid (preferably with something like Oral Rehydration Solution, which has 2% glucose + 90 mEq NaCl per liter). If admitting into the hospital, give MIVF + FLUID DEFICIT. Give half of the deficit over 8 hours and the rest over the next 16 hours. If the patient is 10% or 15% dehydrated, first give boluses of isotonic fluid (NS or LR) and then subtract the total amount from the boluses from the 8-hour fluids.

• FLUID DEFICIT IN LITERS = % DEHYDRATION x WT IN KG.
  • 5% DEHYDRATION = Decreased tears
  • 10% DEHYDRATION = Sunken eyes and fontanelle. Poor turgor (assume 10% if hypERnatremia), dry mucus membranes, elevated heart rate.
  • 15% DEHYDRATION = Poor capillary refill + signs of shock

PEARL: On the exam, you will likely need to estimate the percentage of dehydration clinically. If they give you a recent weight, use the percentage of weight dropped as your % dehydration.