Which of the following statements best describes the pediatric compensatory response to decreased intravascular volume?

• A. Increasing heart rate
• B. Increasing stroke volume
• C. Vasodilation of peripheral vessels
• D. Respiratory rate increases

Answer: (A)

In children, the first protective response to decreased intravascular volume is to increase heart rate. This is because cardiac output (CO) is the product of heart rate and stroke volume (CO = HR × SV). When intravascular volume drops, stroke volume falls due to reduced preload, and the heart cannot easily augment SV quickly. To keep CO and thus maintain perfusion to vital organs, the body ramps up sympathetic activity and raises the heart rate. Peripheral vasoconstriction helps maintain blood pressure, but the key compensatory change that directly supports maintaining flow is the faster heart rate. A faster breathing rate can occur as a secondary response, but it does not restore CO the way an increased heart rate does. So increasing heart rate best describes the pediatric compensatory response to hypovolemia.