Knowing a child’s age is important to determine normal vital signs, disease prevalence, and the appropriate medications. It is also an indicator of social milestones. The easiest way to determine a child’s age is to ask the parent or check available records. However, in cultures where birth records are unavailable, as well as during acute out-of-hospital or emergency department (ED) events, this information may not be easy to get.
Without records, one way to estimate a child’s approximate age is to count the number of teeth present and then add six to derive the age in months.1 Another way is to have the child sit upright (with the head in a neutral position), then raise one arm over his head and try to touch the opposite ear (Fig. 7-1). This “overhead test” has a sensitivity of 90% and a specificity of 78% (positive predictive value 93%, negative predictive value 68%). If the child successfully performs this test, he is most likely ≥6 years old, which is the age to begin school and to receive other benefits in many cultures. If a child fails this test, there is a good chance that he is <6 years old, but it is less clear, because other factors, such as malnutrition, may influence the results. The test works because a 6-year-old child’s humerus is long enough to raise the elbow so that the forearm extends across the head and allows the fingers to reach the opposite ear.2
A child <6 years old cannot reach his opposite ear.
Any firm surface can be marked in 1-cm (or 0.5-inch) increments to measure a patient’s height. For ambulatory patients, use a vertical surface, such as a wall or the side of a doorway. For infants, children, and bedridden patients, mark the side rails of stretchers and beds with indelible ink. Once a child’s height is known, the weight can be estimated.
Correct weight estimates are crucial in determining pediatric medication and fluid doses. When asked, the parents of children aged from 1 to 11 years old can estimate their child’s weight within 10% of the measured weight only 78% of the time. All other forms of guessing a child’s weight, including the Argyll, the Advanced Pediatric Life Support (APLS), and the Best Guess methods, perform poorly.3 If the parents aren’t available, use the following formula for children 1 to 13 years old:
This formula underestimates weight by about 7%, as opposed to > 33% for the APLS formula.4
Although many clinicians still use the Broselow tape, it is inaccurate in most children >10 years old, falls within 10% of the measured weight only 61% of the time, and is less accurate with older children.5,6,7,8,9 A much better method is to use the Mercy TAPE (Fig. 7-2), which integrates mid-arm circumference (MAC) and humeral length (HL), a surrogate of height, to dramatically improve its predictive performance.10 The Mercy TAPE works ...