Nutritional assessment is based on clinical factors such as history of
weight loss, vomiting, diarrhea or feeding intolerance. Physical examination may
show signs of muscle wasting. Height, weight and head circumference
normograms should be evaluated for signs of poor growth. Adequacy of nutrition
may also be judged by evaluation of serum proteins. The half-lives of serum
proteins aid interpretation of nutritional status: albumin, 18 days; transferrin, 8
days; pre-albumin, 3 days; and retinol binding protein, 12 hours. Understanding
the half-lives of these protiens explains why patients with a low pre-albumin may
be malnourished even if the albumin level is normal.
Patients in the intensive care unit often have specific needs because of
increased caloric requirements and negative protein balance. Caloric needs are
altered by several factors such as surgical procedures, stress, cold, infection,
and trauma. [ 1 ] Open wounds, such as the open abdomen or burn patients, have
additional protein losses, which may be significant. Protein losses in body fluids
can be measured but estimates range from 12-29 grams per liter. [ 2 , 3 ]
II. Maintenance Fluids
Maintenance fluid requirements for children and adults are calculated
based on the lean body weight or body surface area. Several issues can affect
the suggested rate of fluid administration including environment, patient-related
factors and disease-related factors. In addition, during the first week of life,
infants are expected to lose 10-15% of body weight and an even greater