Which of the following are early signs of heart failure that parents of children with congenital heart defects should look for?

Diaphoresis, or excessive sweating, can be an early sign of heart failure in children, particularly those with congenital heart defects. This can occur during physical activity or even at rest, as the heart struggles to pump effectively and the body tries to compensate by increasing sweat production. It's important for parents to monitor their children for this symptom, as it can indicate that the heart is under stress and not functioning optimally.

Other signs such as sudden weight gain, diminished urine output, or hypoxia are also important to recognize, but diaphoresis is particularly indicative of the heart's inability to meet the body’s demands, prompting a need for further evaluation and management by healthcare professionals.