a) Outline the metabolic changes seen in:
b) List the consequences of underfeeding in the critically ill.
Overall an adaptive hypometabolism whereby fat is used as the primary energy fuel and protein is relatively spared. (Essential point)
Increase in lipolysis and ketosis with marginal increase in catabolism, glycogenolysis or gluconeogensis.
Mobilization of protein, glucose and lipids is passive as a result of decrease in insulin levels.
After 24-48hrs gluconeogenesis does increase from peripherally released amino acids and glycerol (from lipolysis) -supplies glucose dependant tissues e.g. brain, immune system and renal medulla.
Beyond 48hrs ketosis occurs and FFAs are used for energy, which minimizes the need for amino acids and so preserves muscle.
Decrease energy expenditure with stable albumin initially. Urine urea low if adequate protein and energy stores.
Endogenous ‘stress’ mediators such as cortisol, catecholamines, GH, glucagon and cytokines are increased and contribute to the pattern of metabolism and mobilisation of the fuel required
Catabolism, glycogenolysis, and gluconeogenesis increased. Lipolysis with no increase in ketosis.
Mobilisation of protein is an active process. Energy expenditure is active.
Albumin levels drop precipitously.( negative acute phase reactant)
Gluconeogenesis decoupled from hormone control so can increase blood glucose levels Urine urea increases (>10g/day)
The physiological responses to starvation and the stress of critical illness are discussed elsewhere in gratuitous detail:
In point form, the answer would resemble this:
LITF as part of their Critical Care Compendium have excellent entries on both the starvation and stress repsonses, as a response to the stress of the 2013 CICM fellowship paper.
The consequences of malnutrition in critical illness are also discussed elsewhere.
The brief point-form list provided by the college will perhaps suffice.
In short, the consequences of malnutrition in critical illness are as follows:
Cahill GF; Parris, Edith E.; Cahill, George F. (1970). "Starvation in man". N Engl J Med 282 (12): 668–675.
Benedict, FG: A study of prolonged fasting. Washington DC Carnegie Institute, 1915 (Publication No. 203)
Klein S, Peters EJ, Shangraw RE, Wolfe RR. Lipolytic response to metabolic stress in critically ill patients. Crit Care Med. 1991 Jun;19(6):776-9.
Epstein, Jay, and Michael J. Breslow. "The stress response of critical illness."Critical care clinics 15.1 (1999): 17-33.
Charmandari, Evangelia, Constantine Tsigos, and George Chrousos. "Endocrinology of the stress response 1." Annu. Rev. Physiol. 67 (2005): 259-284.