You are discussing prevention of infective endocarditis with parents of a child with a complex congenital heart defect. A critical teaching point to emphasize includes:

Choice A reason: This is incorrect because the symptoms described by the mother are not typical of a formula allergy. A formula allergy would cause symptoms such as rash, hives, wheezing, or vomiting within minutes or hours of feeding. Switching to a soy based formula is not recommended without consulting a doctor, as some infants may also be allergic to soy.

Choice B reason: This is incorrect because feeding the infant after vomiting and diarrhea may worsen the condition and cause more dehydration. The infant should be given small amounts of oral rehydration solution (ORS) or breastmilk to prevent fluid loss. If the infant cannot tolerate oral fluids or shows signs of severe dehydration, such as sunken eyes, dry mouth, or lethargy, they should be taken to the emergency department for intravenous rehydration.

Choice C reason: This is incorrect because blood and mucous in the stool are not normal findings in infants and should be investigated promptly. They may indicate a serious condition such as intussusception, which is a telescoping of the bowel that causes obstruction and inflammation. The stool may look like currant jelly due to the presence of blood and mucous. Intussusception is a medical emergency that requires immediate treatment.

Choice D reason: This is correct because the infant's symptoms may indicate a serious condition such as intussusception, which can be life-threatening if left untreated. The infant should be taken to the emergency room for further evaluation and management. The nurse should also advise the mother to monitor the infant's vital signs, hydration status, and urine output until they reach the hospital.

Choice A reason: Slowing the heart rate does not increase diastolic filling time. Diastolic filling time is the time during which the ventricles are relaxed and filling with blood. Slowing the heart rate would decrease the cardiac output and worsen the heart failure.

Choice B reason: Increasing urine output does decrease pulmonary congestion, but it is not the primary effect of Captopril. Captopril is an angiotensin-converting enzyme (ACE) inhibitor, which blocks the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor. This reduces the blood pressure and the afterload on the heart. Diuretics are the drugs that increase urine output and reduce fluid overload.

Choice C reason: This is the correct choice. Decreasing the afterload means reducing the resistance that the heart has to overcome to pump blood to the body. This lowers the blood pressure and the workload on the heart, which improves the cardiac function and reduces the symptoms of heart failure.

Choice D reason: Increasing serum potassium does not improve cardiac performance. In fact, high levels of potassium can cause cardiac arrhythmias and cardiac arrest. Captopril can cause hyperkalemia (high potassium) as a side effect, which is why patients on this drug need to monitor their potassium levels and avoid potassium supplements or salt substitutes.