• Distinguish the milligram (mg), microgram (mcg), gram (g), and square meter (m2) units of measurement. • Evaluate orders for minimum and maximum pediatric SDR doses. • Calculate pediatric weight-based doses for oral and parenteral routes. • Calculate pediatric doses based on body surface area. • Calculate flow rates for IV volume-control devices. • State measures to prevent medication errors for pediatric patients. 1. Verifying that the order is within the SDR for the target population 2. Distinguishing microgram, milligram, and square meter units of measurement 3. Calculating accurate fractional doses and fluid needs for all routes 4. Identifying the correct patient when the patient cannot speak 5. Assessing side effects and complications in nonverbal patients The nurse has extra responsibilities to protect the safety of the pediatric patient. The preceding chapters provide a considerable foundation for mastering the calculations in this chapter. Weight-based orders and safe dose ranges for adults have been covered in Chapters 5 and 10. TABLE 13-1 IV Dose Comparison by Age Group for Selected Drugs *A neonate refers to an infant in the first 4 weeks of life. Consult drug references for child age-related dose guidelines. They vary. 1. Which of the recommended SDRs for amoxicillin is weight-based: the adult or the child? (Refer to Table 13-1) How many kilograms are equivalent to 5 lb 4 oz? First: Convert 5 lb 4 oz to pounds. Conversion factor: 16 oz = 1 lb The equation to convert ounces to pounds will be written like this: Total pounds = 5 lb + .3 lb = 5.3 lb. Next: Convert 5.3 lb to kilograms. Conversion factor: 2.2 lb = 1 kg. The final equation will be written like this: 1. Obtain the total body weight in the desired terms. 3. Compare and evaluate the order with the SDR. Contact the prescriber if the order is not within the SDR. Ordered: Drug Y, 60 mg PO per day in AM Patient’s wt: 26 lb 6oz SDR: 5-10 mg per kg per day in a single dose Supplied: Drug Y, 100 mg per 5 mL Conversion factors: 16 oz = 1 lb and 2.2 lb = 1 kg Total kg: (not needed for order; total lb to kg will be entered within SDR equation)* 3. Evaluation: It can be seen at a glance that the dose ordered is within the SDR for the total amount and the schedule. Medication is safe to give. Estimate: Will be giving less than 5 mL *Had the order been for mg per kg or mcg per kg, the lb to kg conversion would have been done separately first. • Note that once the total number of pounds is determined, it is entered in the SDR equations with the conversion formula to kilograms. 1. What are the four main steps in the sequence for evaluating and calculating the recommended safe dose? (State your answer using 1 to 3 key words for each step.) 1. A meter is just a little larger than a yard (1 meter = 1.09 yard). If you estimated your BSA in square yards, would you expect the amount to be very small? _____________________________________________ 2. What is my BSA? Use your weight and a calculator to apply one of the BSA formulas. Multiply the numerators, divide by the denominator, and then enter the square root sign. Does the term square meters provide a clue as to size of the result? Examine the following example. Patient’s BSA: 0.8 m2. SDR: 20 mg per m2 daily in 4 divided doses. SDR: 16 mg total per day divided in 4 doses Order: 16 mg total per day, 4 mg per dose Evaluation: The total dose and the frequency schedule are in accordance with the SDR. Give 4 mg. RAPID PRACTICE 13-5 Evaluating Pediatric SDR Estimated completion time: 15-20 minutes Answers on page 567 Directions: Evaluate the following orders. For BSA in square meters, read the nomogram in Figure 13-1 and calculate the safe dose. Set up a DA equation, and verify your answer with a calculator. State reason for giving or withholding the medication. SDR: 20,000 units per m2 q24h continues IV infusion a. BSA for this child: ________ b. SDR for this patient: ________ c. Evaluation: Safe to give or Hold and clarify promptly with prescriber? (Circle one and state reason.) _______________________________________________ a. BSA for this child: ________ b. SDR for this patient: ________ c. Evaluation: Safe to give or Hold and clarify promptly with prescriber? (Circle one and state reason.) _______________________________________________ a. BSA for this child: ________ b. SDR for this patient: ________ c. Evaluation: Safe to give or Hold and clarify promptly with prescriber? (Circle one and state reason.) _______________________________________________
Pediatric Medication Calculations
Introduction
Occasionally, young patients receive a higher-than-usual adult dose because of the severity of illness, the threat to life, or the lack of response to lower doses and other medications. The particular emphases for safe medication administration with pediatric populations, beyond the selection of appropriate equipment and sites for the medications, are:
Pediatric patients cannot protect themselves from medication errors. Many cannot identify themselves and are not in a position to question medications and medication orders or to verbalize physical complaints. In addition to using printed identification bracelets, bar codes, and other methods, the nurse should have a family member verify the identity of a pediatric patient.
Pediatric patients suffer a much higher rate of medication errors than adults.
Comparing Adult and Pediatric Medication Doses and Schedules
Examine the selected examples in Table 13-1, and note the differences in dosing and units of measurement for adults and children.
Name of Drug
Dose Comparison
Potassium Chloride (KCl)*
SDR, Adult, Individualized: IV 20-60 mEq q24h
200 mEq per 24 hr for hypokalemia is usually not exceeded. 40 mEq dilution per liter preferred
SDR, Child, Individualized: IV 1-4 mEq per kg of body weight per 24 hr
OR
10 mEq per hr, whichever is less, not to exceed 40 mEq per 24 hr. Must be at least 40 mEq dilution per liter.
Monitor serum potassium levels.
Contact prescriber if patient is fluid-restricted.
Monitor ECG for symptoms of hypokalemia and hyperkalemia.
Pediatrics: KCl must be infused on electronic infusion pump. Obtain written order for each infusion.
Morphine Sulfate
Pain relief
Adult, IV: 2.5-15 mg q4h
Postoperative analgesia
Child, IV: 0.01-0.04 mg per kg per hr
Neonate, IV: 0.015-0.02 mg per kg per hr*
Severe chronic cancer pain
Child, IV: 0.025-2.6 mg per kg per hr
Prazosin HCl
Adult, PO: 1 mg at bedtime to start
Child, PO: 5 mcg per kg q6h to start
Amoxicillin
Adult, PO: 250-500 mg q8h
Child, PO: 25-50 mg per kg per d (max 60-80 mg per kg per d divided q8h)
Digoxin IV Injection
Initial loading (digitalizing dose)
Premature: 15-25 mcg per kg; 2-5 yrs: 25-35 mcg per kg; over 10 years: 8-12 mcg per kg
Taking 2 or 3 minutes to verify a safe dose order with a current pediatric drug reference and/or pharmacy may prevent a tragic error.
Calculating Kilograms to the Nearest Tenth from Pounds and Ounces
It is important to note that ounces must be converted to tenths of a pound before kilograms are calculated. 5 lb 4 oz is not equal to 5.4 lb.
Ounces must be converted to tenths of a pound before kilograms are calculated. 5 lb 4 oz is not equal to 5.4 pounds.
Sequence for Calculating Safe Dose Range (SDR)
Review the logic and example of the multi-step process for evaluating an order for safe dose. A calculator is helpful.
4 If the order is safe, estimate, calculate, and evaluate the dose.
Body Surface Area (BSA)
The nurse is expected to be able to define BSA, identify square meters, and, most important, distinguish among m2 and mg and mcg metric measurements when reading orders, medication records, and current drug references and when calculating SDR. The nurse rarely calculates the BSA. Pharmacy usually supplies it.
Calculating milligrams per square meter (mg per m2)
The calculation of milligrams per square meter is performed using a DA-style equation or simple multiplication, just as it is for calculating milligrams per kilogram (e.g., 2 mg per m2 means “2 milligrams of medicine for each square meter of body surface area”).
Pay close attention to the placement of decimal points. Square meters of BSA are very small amounts. A missing decimal point would result in a tenfold dose error.
Pediatric doses are calculated to the nearest hundredth of a mL. Check agency policies.
1 Ordered: An IV infusion of heparin 225 units per hr for a baby of normal height for weight weighing 10 lb.
2 Ordered: vincristine 1 mg IV once a week, for a child with Hodgkin’s disease of normal height for weight weighing 30 lb. SDR: 1.5-2 mg per m2 per week.
3 Ordered: methotrexate 15 mg PO daily, for a child with leukemia of normal height for weight weighing 70 lb. SDR: 3.3 mg per m2 per day.
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Cultural Note
Slashes (/) will be seen in printed drug references. Write out “per” for slashes to avoid misinterpretation and medication errors.
