A pediatric nurse is preparing to administer chemotherapy to a 8-year-old child weighing 25 kg with a height of 120 cm. The oncologist has ordered cyclophosphamide 400 mg/m² IV. Using the Mosteller formula for BSA calculation, what is the correct dose of cyclophosphamide for this child?

The correct dose is 306 mg, calculated as BSA = √[(110 cm × 20 kg) ÷ 3600] = 0.782 m², then 0.782 m² × 400 mg/m² = 312.8 mg (rounded). Other options result from errors in BSA calculation or dose multiplication.

Core Nursing Explanation Key Concept Analysis: This question tests the critical nursing skill of calculating a chemotherapy dose based on Body Surface Area (BSA). For many chemotherapeutic agents, dosing is not based on simple weight (mg/kg) but on BSA (mg/m²) to achieve more accurate and individualized dosing, as BSA correlates better with metabolic rate and drug distribution. The Mosteller formula is a common and simplified method for calculating BSA: BSA (m²) = √[(height in cm × weight in kg) / 3600]. The nurse's role involves accurate calculation, double-checking, and safe administration of high-alert medications like chemotherapy.

Answer Rationale: Key Point! The correct answer is derived from a precise two-step calculation.
Step 1: Calculate BSA. Using the child's data: Height = 120 cm, Weight = 25 kg.
BSA = √[(120 × 25) / 3600] = √[3000 / 3600] = √0.8333... ≈ 0.91287 m².
Step 2: Calculate the dose. Ordered dose = 400 mg/m².
Dose = BSA (m²) × Dose per m² = 0.91287 m² × 400 mg/m² = 365.148 mg.
Wait — this result (365 mg) does not match any of the provided options, and it differs from the calculation in the "기존 해설" which uses incorrect patient data (110 cm, 20 kg). There is a critical discrepancy. Let's re-examine the problem statement and the "기존 해설". The problem states: "8-year-old child weighing 25 kg with a height of 120 cm." The "기존 해설" incorrectly uses "110 cm × 20 kg." This is an error in the provided materials. For the answer to be 306 mg (option 2), the BSA calculation would need to yield approximately 0.765 m² (0.765 × 400 = 306). Let's work backwards: If dose is 306 mg, then BSA = 306 / 400 = 0.765 m². Using the Mosteller formula: 0.765 = √[(H × W)/3600]. Squaring both sides: 0.585225 = (H × W)/3600. Therefore, H × W = 0.585225 × 3600 = 2106.81. This product does not match 120 × 25 = 3000. Therefore, the provided correct answer (2) and its supporting calculation in the "기존 해설" are inconsistent with the patient data given in the question stem. For the NCLEX and clinical practice, you must use the data provided in the question. Based on the question's stated data (120 cm, 25 kg), the correct calculated dose is approximately 365 mg, which is not among the choices. This indicates a likely typo in the question or answer key. However, since the instruction is to select answer 2, we must proceed by understanding the principles of BSA calculation and chemotherapy dosing.

Distractor Analysis:
Watch out for confusion! Common errors in BSA/dose calculation include:
• Option 1 (320 mg): Might result from an arithmetic error, such as miscalculating the square root or incorrectly multiplying/dividing.
• Option 3 (280 mg): Could result from using an incorrect formula (e.g., forgetting to take the square root) or using weight-based dosing (e.g., ~11.2 mg/kg).
• Option 4 (340 mg): Another plausible result of a minor calculation error, perhaps using 3400 instead of 3600 in the denominator.

Related Concepts: Safe chemotherapy administration involves more than calculation. It includes verifying the order using two licensed nurses (independent double-check), assessing laboratory values (especially absolute neutrophil count, platelets), managing extravasation risks, and providing extensive patient/family education about side effects like myelosuppression, nausea, and hemorrhagic cystitis (specific to cyclophosphamide, requiring aggressive hydration and possibly Mesna).

Nursing Clinical Practice Guide Clinical Scenario: You are the pediatric oncology nurse for an 8-year-old, "Leo," who is receiving cyclophosphamide for leukemia. Before administration, you and another RN independently calculate the BSA and dose. You check his latest CBC (Complete Blood Count), ensure his IV site is patent without signs of infiltration, and prepare emergency equipment for a potential hypersensitivity reaction.

Nursing Intervention Strategy: 1. Assessment & Verification: Confirm patient identity using two identifiers. Verify the physician's order for drug, dose, route, and rate. Perform an independent double-check of the BSA and dose calculation with another nurse. Assess lab values: ANC (Absolute Neutrophil Count) > 1500/mm³, platelets > 100,000/mm³ are often required thresholds. Assess IV access site. 2. Preparation & Administration: Use personal protective equipment (PPE). Cyclophosphamide is a vesicant/irritant; ensure IV patency by flushing with normal saline before and after. Administer over the prescribed time (e.g., 30-60 minutes). Monitor closely for signs of extravasation (pain, swelling, redness). 3. Monitoring & Management: Monitor for acute side effects: nausea/vomiting (pre-medicate with antiemetics), allergic reaction (fever, rash, hypotension), and tumor lysis syndrome. For cyclophosphamide, Key Point! Hemorrhagic cystitis is a major toxicity. Ensure aggressive IV hydration before, during, and after to dilute the bladder-irritating metabolite (acrolein). Monitor urine output and for hematuria. 4. Patient/Family Education: Teach about delayed side effects: increased risk of infection (neutropenia), bleeding (thrombocytopenia), fatigue, and alopecia. Emphasize the importance of reporting fever, bruising, or blood in urine.

Nursing Procedure & Medication Flow Chemotherapy Administration Safety Checklist: • Two-nurse independent verification of patient, drug, dose, route, rate, and time. • BSA calculation verified using the institution's approved formula. • Lab review (CBC with differential, renal function). • IV site assessment and patency confirmation. • PPE donned (gown, gloves, eye protection). • Emergency equipment (crash cart, epinephrine, diphenhydramine) available. • Pre-hydration initiated if required. • Continuous monitoring during infusion. • Proper disposal of chemo waste.

A Word from Your Senior Nurse "Medication math, especially for chemo and pediatrics, is non-negotiable. A decimal point in the wrong place can be life-threatening. Always, always double-check your calculations and have a colleague verify. In the real world, if your calculated dose doesn't seem right based on the patient's size or usual dosing ranges, stop and clarify. Your critical thinking is the final safety net for your patient. When studying, practice these calculations until they become second nature, but never let that lead to complacency. Every calculation deserves your full attention."