1. Clinical Assessment

A structured history and physical exam are the first steps in identifying malnutrition risks and signs of gastrointestinal (GI) dysfunction, which together guide the decision to initiate enteral nutrition support (ENS).

A. Nutritional History

• Weight Loss: Document any unintentional weight loss, particularly if greater than 5% in one month or 10% in six months, as these are strong indicators of nutritional risk.
• Dietary Intake: Estimate recent oral intake as a percentage of calculated energy and protein goals.
• GI Symptoms: Screen for anorexia, nausea, vomiting, dysphagia, or early satiety that may impede oral intake.

B. Anthropometric and Physical Exam

• Body Composition: Mid-arm circumference and triceps skinfold measurements can estimate muscle and fat stores, though their accuracy is limited by fluid shifts in critically ill patients.
• Muscle Wasting: Visually inspect for muscle loss in key areas like the temples and clavicular-scapular regions.
• Subcutaneous Fat Loss: Assess for diminished fat pads, which can indicate prolonged negative energy balance.

C. Functional and Contextual Assessments

• Functional Reserve: A formal swallow evaluation by a speech-language pathologist is critical for patients with suspected dysphagia. Hand-grip strength or ICU mobility scales can provide a baseline of functional capacity.
• Clinical Context: Consider conditions that inherently increase nutritional risk, such as neurologic injury, head/neck cancer, prolonged mechanical ventilation, chronic liver disease, or renal failure.

2. Laboratory and Imaging Modalities

Laboratory trends and targeted imaging studies help confirm the integrity of the GI tract, identify patients at risk for refeeding syndrome, and verify the correct placement of feeding tubes.

A. Laboratory Markers

While no single lab value defines nutritional status, trends in specific markers provide crucial information about inflammation, metabolic stress, and organ function.

B. Imaging Techniques

• Abdominal Radiograph: Remains the gold standard for confirming the distal tip position of a newly placed nasogastric or nasojejunal tube prior to initiating feeds.
• Contrast Studies: Can be used to delineate small-bowel anatomy and assess transit, but logistical challenges often limit their use in the ICU.
• Point-of-Care Ultrasound (POCUS): An emerging tool to non-invasively assess gastric residual volume and antral area, potentially guiding feed tolerance without interrupting nutrition.