Which of the following is a common cause of shock in an infant?

• A. Hypervolemia
• B. Dehydration from vomiting and diarrhea
• C. Hypoglycemia
• D. Seizure

Answer: (B)

In infants, shock most often results from hypovolemia due to dehydration from vomiting and diarrhea. When an infant loses fluids, the volume of blood in the vessels drops, lowering preload and cardiac output. The heart can temporarily compensate by beating faster and the vessels constrict, but soon perfusion to tissues declines, leading to shock. Infants are especially vulnerable because they have a high total body water content and limited ability to replace losses quickly, so GI losses can rapidly deplete intravascular volume. Early signs include a fast pulse, cool and clammy skin, delayed capillary refill, and listlessness or poor feeding. Hypervolemia would cause excess fluid in the body rather than a lack of circulating volume, and hypoglycemia or seizures are serious problems but do not describe the typical mechanism of shock in this GI-loss scenario.