Pediatric Medication and Fluid Calculations

Pediatric Medication and Fluid Calculations Pediatric Medication Calculations Pediatric medication dosages are based on the child’s weight. This has four major nursing implications: 1. The nurse must obtain the patient’s current and accurate weight immediately upon admission. 2. The nurse may have to convert weight in pounds to weight in kilograms. 3. The child’s length or height in inches or centimeters should also be obtained because the pharmacist needs both height and weight to calculate body surface area (BSA) and check the calculation of a correct dose. 4. The nurse must check the physician’s calculation of the manufacturer’s Recommended Safe Dose (RSD). This includes milligrams/kilogram/24 hour period. Here are a few examples: 1. The recommended initial dose of mercaptopurine is 2.5 mg/kg/day p.o. The child weighs 44 lbs. A) What is the child’s weight? 44lbs divided by 2.2 lbs/kg = 20 kg. B) What is the safe daily dosage for this child? 2.5mg/kg/day x 20kg = 50 mg/day. 2. For a child, the recommended safe dosage (RSD) of I.V. Vancomycin is 40mg/kg/day. Vancomycin 200mg I.V. q6h is ordered for a child weighing 38 lbs. A) What is the child’s weight in kg? 38 lbs divided by 2.2 lbs/kg = 17.2 kg B) What is the safe daily dosage for this child? 17.2 kg x 40mg/kg/day = 688mg/day. C) What is the divided dose? 24 hrs/q6h = 4 doses. 688 mg divided by 4 doses = 172 mg/dose. D) Is the dose ordered safe? No, it is too high a dose. Check with the prescriber. 3. The RSD of Dilantin is 4-8 mg/kg/day. Dilantin 25 mg p.o. q12h is ordered for a child weighing 11 lbs. A) What is the child’s weight in kg? 11 lbs divided by 2.2 lbs/kg = 5kg. B) What are the safe dose ranges for this child? 4mg/kg/day x 5kg = 20mg/day to 8mg/kg/day x 5kg = 40mg/day. C) Is the dose ordered safe? No. At 50mg/day it is over the safe range. D) Dilantin suspension is available in a dose strength of 30 mg/5ml. How many ml would you administer for one dose? 30mg /5ml = 6 mg/ml 25mg (desired dose) divided by 6 mg/ml = 4.16 mL 1 4. The physician orders Digoxin 30 mcg IV bid to be given to a 4 kg child with congestive heart failure. The vial is labeled Digoxin 0.1 mg/mL. How much Digoxin will you administer?  First convert dosages to same units of measurement (mcg to mg OR mg to mcg) 1 mcg = 0.001 mg so 30 mcg = 0.03 mg  Now calculate the amount of medication to administer 0.1 mg : 1 mL = 0.03 mg : X 0.03 mg divided by 0.1 mg x 1 = 0.1X = 0.03 OR 0.3 mL X = 0.3 mL 5. The doctor orders Clindamycin 500 mg intravenous piggyback to be infused over 40 minutes in 100 mL D5W. The intravenous microdrip tubing delivers 60 gtts/mL. How many gtts/min will the nurse infuse for this order?  Formula to use: Amount of fluid to administer times drip factor divided by infusion time X = 100 mL x 60 gtt/mL divided by 40 min X = 6000 divided by 40 X = 150 gtt/min 6. The doctor orders Azithromycin 900 mg intravenous piggyback in 150 mL D5W to run over 1 1/2hrs. What mL/hr rate will you set the pump at? 150 ml:60 min = X:90 min 9000 = 90X 100 mL/hr = X or 150 90 x 60 = 100 mL/hr Or Amt of solution /(min to adm/60) = ml/hr 150/ (90/60) = 150 = 100ml/hr 1.5 Pediatric Fluid Need Calculation Calculate the maintenance fluid needs of the child according to the following guideline: Usual weight Maintenance Amount Up to 10 Kg 100 ml/kg/24 hr 11 – 20 kg 1000ml + (50 ml/kg for weight above 10 kg)/24 hr Over 20 kg 1500ml + (20 ml/kg for weight above 20 kg)/24 hr Example: Vernon’s weight is 12kg. He needs 1000 ml + (50ml x 2kg), or 1100 ml/24hr for maintenance fluid. At home Oral Rehydration Therapy o For mildly dehydrated children is 50ml/kg over 4-6 hrs o For moderate dehydration, 100 ml/kg. o Losses from diarrhea may be replaced with 10ml/kg for each stool. 2 Some Approximate Equivalents by weight and volumes Liquid Volume ½ oz = 15ml 1 fluid oz = 30ml 1 tsp = 5ml Weights 1,000 mcg = 1 mg 1,000 mg = 1gram 2.2 lbs = 1kg *1 gm of diaper weight = 1 ml of urine. So weigh a dry diaper, then weigh a wet diaper and subtract. The difference is amount of ml of urine in that diaper. Additional Resources to work with outside of class: 3