Which of the following children should the nurse assess first?

The correct answer is A. The nurse should assess the toddler with a concussion and forceful vomiting first because vomiting after a head injury can be a sign of increased intracranial pressure, which is a medical emergency requiring immediate attention to prevent further complications. Assessing for signs of concussion worsening is crucial. The other choices do not present immediate life-threatening conditions that require urgent assessment. The adolescent in option B has already been placed in traction and pain can be managed after a brief assessment. The child in option C with glomerulonephritis may need further evaluation, but the urgency is lower compared to the toddler with a head injury. The adolescent in option D with infective endocarditis reporting a headache may need assessment for possible complications, but it is not as urgent as addressing the potential increased intracranial pressure in the toddler.