Malnutrition is a huge problem throughout the world, and it worsens in disaster situations. Estimates are that moderate-to-acute malnutrition affects around 10% of children <5 years old in low- and middle-income countries,¹ and contributes to more than half (54%) of the deaths in this group (Fig. 36-1). Among elderly patients in the US general population, the prevalence of malnutrition ranges from 12% to as high as 85% among the institutionalized elderly.² Malnutrition usually occurs in resource-poor situations. The keys are both to recognize it and to treat it effectively.

Malnutrition can be identified using mid-arm circumference (MAC) or by comparing a child’s weight and height with standard charts.

Mid-Arm Circumference

Measuring a child’s MAC helps to determine the degree of malnourishment. This technique is at least as good at predicting mortality from malnutrition as is a child’s position on a weight/height growth chart. Measure MAC, in centimeters, at the midpoint of the left upper arm, halfway between the point of the shoulder and the elbow. From 1 to 5 years of age, the mid-arm circumference remains fairly stable because the increasing growth in muscle mass is balanced by a decrease in arm fat. The median value for this age group is 16.5 cm. In the first 12 months of life, MAC changes so rapidly that it is not a reliable indicator of malnutrition. And, while skin thickness over the scapula or triceps can be measured, this requires the use of calipers and provides little additional information.³

To make the measurement, have the child keep the arm hanging straight down by his side (Fig. 36-2). If the MAC of a child between the ages of 1 and 5 years is <12.5 cm, he is severely malnourished. If it is between 12.5 and 14 cm, he is moderately malnourished. Above 14 cm is normal.^4,5

If a measuring tape is not available, one of the easiest measuring tools is to see which finger touches your thumb when wrapped around the child’s mid-arm. Predetermine measurements for each of your finger-to-thumb distances. Then you will know which combination indicates severe malnutrition (<12.5 cm), moderate (12.5-14 cm) and normal (>14 cm). Practice and teach this to others, using a roll of gauze as a surrogate arm.⁶ A marked piece of non-stretchable cloth or a string with knots at the appropriate distances can be used, although it may stretch a little. Another method is to use a strip of x-ray film. Scratch or paint the film at the 0-cm mark, and again at the 12.5- and 14-cm marks. For clarity, the area between the 0- and 12.5-cm marks can be colored red; the area between 12.5 and 14 cm, yellow; and the area above 14 cm, green.

The best parameters to determine nutritional risk in adults ≥65 years old are MAC and calf circumference.

Measure MAC as in a child. The standards for people at the 5th and 50th percentile are listed in Table 36-1. Those below the 50th percentile are at risk for malnutrition; those at or below the 5th percentile are seriously malnourished. For calf circumference, both the knee and ankle should be at 90-degree angles. In a sitting person, pass the measuring tape around the calf and move it along the calf to locate the largest circumference. If the person is supine, bend the knee to a 90-degree angle and support the foot so that it is also at 90 degrees before measuring the calf.⁷ The calf circumference which indicates that this group is at malnutrition risk is ≤31 cm.⁸

A child’s classification as malnourished depends on his or her position on the standard weight-height-for-age charts, which can be accessed at the Centers for Disease Control and Prevention: Growth Charts (www.cdc.gov/growthcharts/). Height (length for a supine infant) and weight can be measured using standard means or by the improvised methods described in Chapter 7. Interpret the results using the Welcome Classification system:

Severe malnutrition takes the form of either marasmus (wasting; Fig. 36-3) or kwashiorkor (edema; Fig. 36-4), or a combination of the two. The reasons for a progression of nutritional deficit into one form rather than the other are unclear and cannot be explained solely by the composition of the deficient diet.¹⁰