The Metabolic Cost of Critical Illness
Potential Harm From Nutritional Support
Timing, Route, and Dose of Feeding
Immune Modulating Enteral Formulations
GI Intolerance of Feeding
Prescribe a nutritional plan for the general medical ICU patient.
Describe common complications of enteral and parenteral nutrition, and list strategies for minimizing them.
Cite the differential diagnosis for diarrhea in the critically ill patient.
It has been difficult to demonstrate either the benefit or the harm to most nutritional practices in the ICU. This is likely caused in part by methodological limitations in the existing literature; however, our understanding of the interaction between nutrition and critical illness is also inadequate. A few recommendations can be made. The intensivist should be aware of the potential complications of feeding, including overfeeding syndrome and the refeeding syndrome. Enteral feeding should be started whenever possible within 24 to 48 h of admission to the ICU. There presently is insufficient evidence to recommend the use of one enteral feeding tube or location over another. Patients should be fed with the head of bed elevated. The optimal dose of nutrition is not known; however, the practice of using parenteral nutrition to supplement enteral nutrition early in the course of critical illness has been shown to cause harm and should be avoided. At the present time, the use of immune-modulating enteral formulations, such as those enriched with omega-3 fatty acids and γ-linolenic acid, cannot be recommended for patients with acute lung injury. Various forms of GI intolerance, including constipation, abdominal distension, and diarrhea, are common in critically ill patients. Metoclopramide and erythromycin may be used to facilitate enteral feeding. Diarrhea has many potential causes, including infection with Clostridium difficile and numerous commonly used medications. When diarrhea appears to be caused by enteral feeding, switching from intermittent bolus feeding to continuous feeding may help, as may changing the formulation to one with a lower osmolality. The blood glucose target for critically ill patients is approximately 140 to 180 mg/dL.