Providing appropriate response-contingent phase-specific nutrition therapy in critical illness

The pathogenesis of critical illness drives a dynamic cascade of clinical, metabolic, and immunologic abnormalities through the course of disease. Recent randomized trials show that early full-dose feeding for critically ill patients is ineffective and potentially harmful compared to trophic feeding. The aim of this review is to propose a response-contingent phase-specific strategy of nutrition therapy appropriate for this patient population.

Barriers to delivering effective nutritional therapy exist, ranging from bioenergetic failure related to mitochondrial dysfunction and gastrointestinal dysmotility with feeding intolerance, to microbial dysbiosis and impaired substrate utilization characterized by inefficient energy production and futile substrate cycling. Emerging concepts are helping to design more appropriate regimens, including estimation of potential benefit from nutritional therapy based on disease severity, risk of net harm, and determination of the stage of enteral nutrition responsiveness, which can be conceptualized as the capacity for achieving phase-specific goals within the constraints of physiologic state, metabolic capacity, safety, and feasibility.

Calibrating goals, dosage, monitoring strategies, and expectations from nutritional therapy is required to overcome barriers imposed by the underlying pathophysiology and to optimize support, as these complex patients transition through the acute phase of critical illness towards recovery and rehabilitation.