Among patients who require nutritional resuscitation in an intensive care unit, the best evidence that nutritional support is adequate is: (A) Urinary nitrogen excretion levels, (B) Total serum protein level, (C) Serum albumin level, (D) Serum transferrin levels
Answer is C. The serum albumin level provides a rough estimate of protein nutritional adequacy. The accuracy of this estimate is affected by the long half-life of albumin (3 week) and vagaries of hemodilution. The acute-phase serum proteins have a very short half-life (hours) and may also provide good short-term indications of nutritional status. Transferrin is one of these acute-phase proteins, but unfortunately its levels too are influenced by changes in intravascular volume and, along with the other acute-phase reactants, rise nonspecifically during acute illness. All the listed responses provide some useful information about nutrition and adequacy of replacement.