1. Clinical Presentation and Signs/Symptoms

Refeeding syndrome typically emerges within 2–5 days of nutritional repletion in malnourished patients, driven by rapid intracellular shifts of phosphate, potassium, and magnesium, plus thiamine depletion. This leads to multisystem manifestations.

A. Neurologic

• New-onset weakness, paresthesias
• Delirium, confusion, agitation
• Seizures and Wernicke-like encephalopathy (thiamine deficiency)

B. Cardiovascular

• Hypotension and tachycardia from decreased myocardial contractility
• Arrhythmias (ventricular ectopy, QT prolongation) due to hypokalemia and hypomagnesemia
• Congestive features: peripheral edema, acute decompensated heart failure

C. Respiratory

• Respiratory muscle weakness, hypercapnia, difficulty weaning from mechanical ventilation
• Dyspnea and rapid shallow breathing

D. Hematologic and Fluid Balance

• Hemolysis, leukocyte dysfunction, and coagulopathy secondary to hypophosphatemia
• Sodium and water retention, leading to peripheral and pulmonary edema

2. Laboratory and Diagnostic Modalities

Serial biochemical monitoring and targeted imaging confirm the diagnosis, quantify severity, and exclude alternative etiologies.

A. Serial Serum Electrolytes

• Obtain baseline phosphate, potassium, and magnesium levels immediately before refeeding.
• Monitor every 12 hours for at least the first 72 hours in high-risk patients.
• A drop of >30% from baseline or any new organ dysfunction is considered severe.

B. Thiamine Assessment

• Do not wait for assay results. Empirically administer IV thiamine (e.g., 100 mg daily) before and during the initial days of feeding for all at-risk patients.

C. Metabolic Panels and Acid–Base Status

• Monitor blood glucose, renal, and hepatic panels to detect hyperglycemia, lactic acidosis, and organ dysfunction.
• An arterial blood gas (ABG) can reveal acid-base imbalances and assess respiratory compensation.

D. Imaging

• Echocardiography: May show reduced ejection fraction or diastolic dysfunction (“refeeding cardiomyopathy”).
• Chest Radiograph: Can identify pulmonary edema or pleural effusions resulting from fluid retention.

3. Risk Stratification and Classification Systems

Using validated criteria is essential to identify at-risk patients, guide the initial rate of feeding, determine monitoring intensity, and direct prophylactic supplementation.

A. NICE Criteria for Identifying At-Risk Patients

The UK’s National Institute for Health and Care Excellence (NICE) provides widely used criteria to determine if a patient is at high risk for refeeding syndrome.

B. ASPEN Severity Grading

The American Society for Parenteral and Enteral Nutrition (ASPEN) provides consensus recommendations for grading the severity of refeeding syndrome once it occurs, based on electrolyte drops or organ dysfunction.

C. Other Considerations

• Pediatric vs. Adult: Risk assessment in children uses different metrics, such as weight-for-length or BMI-for-age z-scores and shorter periods of intake deficits.
• Screening Tools: General malnutrition screening tools (e.g., NRS-2002, MUST) are useful for identifying at-risk populations but lack the specificity of the NICE criteria for predicting refeeding syndrome itself.