A 6-month-old infant is diagnosed with a congenital heart defect that causes a left-to-right shunt, resulting in increased pulmonary blood flow. Which of the following defects is most likely?

A. Visual Analog Scale (VAS) is incorrect because it requires the child to understand and mark a point on a line to represent pain intensity, which is often too complex for a 4-year-old, especially if they cannot verbalize pain reliably.

B. FLACC scale is correct. The FLACC (Face, Legs, Activity, Cry, Consolability) scale is an observational tool designed for children who cannot self-report pain. It assesses behavioral and physiological indicators of pain including facial expression, leg movement, activity level, crying, and consolability. Scores range from 0 to 10, allowing for objective assessment and monitoring of pain in young children, infants, or nonverbal patients.

C. Faces Pain Scale is incorrect because it relies on the child’s ability to understand and point to a facial expression that represents their pain. While appropriate for some preschoolers, a 4-year-old who cannot reliably verbalize or comprehend the scale may not use it accurately.

D. Numeric Rating Scale is incorrect because it requires the child to assign a number (0–10) to describe pain, which is generally suitable for children aged 7 and older who can understand abstract numerical concepts.

A. Hydralazine is incorrect because it is an antihypertensive used to lower blood pressure in preeclampsia or eclampsia, but it does not reverse magnesium sulfate toxicity, which is the immediate concern given the symptoms of respiratory depression, oliguria, and absent deep tendon reflexes.

B. Methylergonovine is incorrect because it is a uterotonic used to control postpartum hemorrhage. It is not indicated for magnesium toxicity and would not address the life-threatening respiratory and neuromuscular effects of magnesium sulfate overdose.

C. Calcium gluconate is correct because it is the antidote for magnesium sulfate toxicity. Symptoms of toxicity include respiratory depression (RR <12), oliguria (<30 mL/hr), absent deep tendon reflexes, and eventually cardiac arrhythmias or arrest. Administering 10 mL of 10% calcium gluconate IV over 3–5 minutes can rapidly reverse neuromuscular and cardiac effects while supportive care (e.g., stopping magnesium infusion and monitoring) is continued.

D. Narcan is incorrect because it is an opioid antagonist used to reverse opioid overdose. It has no effect on magnesium sulfate toxicity and would not address the neuromuscular or respiratory compromise in this patient.