What is the primary difference in cardiac output (CO) between infants and adults?

The primary difference in cardiac output between infants and adults lies in the fact that infants exhibit a higher heart rate and a relatively lower stroke volume compared to adults. In terms of overall cardiac output, infants may indeed have a cardiac output that can be equivalent to that of adults when adjusted for body surface area. This means that while absolute values of CO may seem lower in infants due to smaller heart sizes and volumes, if we consider factors such as body size and metabolic demand, the cardiac output can be effectively adjusted and compared.

The assertion that an infant's CO is twice that of an adult is not supported by physiological data. In actuality, cardiac output is influenced more by age-related factors than by a direct comparison to adult values. In adults, a typical cardiac output ranges from 4 to 8 liters per minute, while in infants, it can be less than that when taken as a raw number due to smaller body size.

Overall, while it might appear that infants have higher CO figures when adjusted for surface area and metabolic activity, the notion of CO being literally twice that of adults does not hold true; rather, it is more pivotal to understand that CO varies based on many physiological factors, making the differences complex rather than straightforwardly proportional.