This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Pediatrics
What is the most common cause of preload disorders in children? 
Select and explain. 
A. Distributive shock, B. Hypovolemic shock from vomiting and diarrhea, C. Congestive hea failure, D. Severe anemia
B: Hypovolemic shock from vomiting and diarrhea
Answer: B: Hypovolemic shock from vomiting and diarrhea 
Explanation: Preload is the amount of blood that the hea receives to distribute to the body. In addition to hea rate, afterload, and cardiac contractility, preload determines cardiac output. In children, the most common cause of decreased preload is hypovolemia, usually from vomiting and diarrhea. Distributive shock secondary to sepsis, neurogenic spinal shock, or anaphylaxis is a less common cause of preload reduction. Acute anemia may also be associated with decreased preload. Congestive hea failure is a frequent complication in children with congenital hea disease. Increased preload results in elevation of left atrial pressure leading to pulmonary edema and decreased oxygenation. Reference: GHAI Essential pediatrics, 8th edition