The metabolic response to sepsis is complex and dynamic, requiring a tailored nutritional approach based on the disease phase. The goals of nutritional support shift from supportive during the initial hyperacute phase to restorative during the recovery phase. A one-size-fits-all strategy is ineffective, emphasizing the need for a careful assessment of a patient’s unique physiological state throughout their illness.
The Phased Approach to Nutritional Support
Nutritional management in sepsis is not a static process; it evolves with the patient's condition. Medical guidelines break down the nutritional strategy into distinct phases to match the body’s changing metabolic demands.
Phase 1: Acute and Resuscitation Phase (First 24–96 hours)
In the initial period of septic shock, the body's metabolic function is impaired, and energy metabolism is redirected to essential survival processes.
- Energy: Early, aggressive energy provision is not recommended and can be harmful due to impaired cellular metabolism. An exogenous energy supply of no more than 20 kcal/kg/day is generally advised. In well-nourished patients, endogenous energy reserves (glycogen, lipids) are utilized, and a period of relative underfeeding (permissive underfeeding) may be appropriate.
- Protein: Despite a lower caloric need, protein breakdown (proteolysis) is high, so adequate protein delivery is important from the start. An intake of at least 1.2 g/kg/day is recommended.
- Feeding Route: Early enteral nutrition (EN) should be initiated within 24–48 hours, provided the patient is hemodynamically stable. For patients with uncontrolled shock or severe gastrointestinal issues, early EN is contraindicated. In these cases, exclusive or supplemental parenteral nutrition (PN) can be considered, especially for severely malnourished patients.
Phase 2: Post-resuscitation and Chronic Phase
Once the patient is stabilized and shock is controlled, nutritional delivery needs to increase to counteract muscle loss and promote recovery.
- Energy: Caloric intake can be gradually increased to 25–30 kcal/kg/day to meet the heightened metabolic demands.
- Protein: Protein requirements also rise significantly in this phase to support tissue repair and build back lean body mass. Goals increase to 1.5–2.0 g/kg/day during recovery.
Phase 3: Recovery Phase (After ICU Discharge)
Nutritional support remains critical post-discharge to facilitate long-term recovery.
- High Protein and Energy: Patients require continued high protein and calorie intake for months to years to fully recover lost muscle mass and weight.
- Oral Nutritional Supplements (ONS): High-protein oral nutritional supplements are often essential to achieve adequate intake and are recommended for 3–12 months post-discharge, especially for frail or elderly patients.
The Route of Nutrition: Enteral vs. Parenteral
Choosing the right feeding route is a key aspect of managing sepsis. The decision hinges on the patient's hemodynamic stability and the functional integrity of their gastrointestinal tract.
| Feature | Enteral Nutrition (EN) | Parenteral Nutrition (PN) |
|---|---|---|
| Mechanism | Delivers nutrients directly to the stomach or intestine via feeding tube, leveraging the gastrointestinal tract. | Delivers nutrients directly into the bloodstream via an intravenous line, bypassing the GI tract entirely. |
| Advantages | Helps preserve gut barrier function and microflora, is generally safer, and is less expensive. | Can guarantee precise delivery of nutrients when the gut is not functional or cannot tolerate feeding. |
| Disadvantages | Associated with risks of aspiration, feeding intolerance (e.g., high gastric residual volume, diarrhea), and bowel ischemia in unstable patients. | Higher risk of central line infections, metabolic complications (e.g., hyperglycemia), and higher cost. |
| Timing in Sepsis | Start early (within 48 hours) once hemodynamically stable. Avoid during uncontrolled shock. | Use for severely malnourished patients or when EN is contraindicated or fails to meet goals after 3–7 days. |
Micronutrients and Immunonutrition
The role of specific micronutrient and immune-modulating formulas in sepsis has been a subject of extensive research, with many studies yielding conflicting results.
Vitamins
- Vitamin C: High-dose intravenous vitamin C has been studied extensively, with some trials showing reduced organ dysfunction, shorter vasopressor duration, and improved mortality, especially in sepsis-associated acute respiratory distress syndrome (ARDS). However, results are mixed, and routine use is not yet standard practice.
- Thiamine (B1): Thiamine deficiency is common in septic patients and can contribute to lactic acidosis. Supplementation has shown some benefit in lactate clearance and potentially reduced need for renal replacement therapy in deficient patients, but overall mortality benefits are unproven.
- Vitamin D: Low vitamin D levels are linked to poorer outcomes, but routine supplementation has not consistently shown clinical benefits, except possibly in severely deficient individuals.
Trace Elements
- Selenium: Routine supplementation with high-dose selenium is not recommended, as trials have shown conflicting results and potential harm.
- Zinc: Involved in immune function, but routine supplementation is not advised due to limited evidence and unclear benefits.
Other Immunonutrients
- Glutamine: Although traditionally considered beneficial, large trials have shown no benefit and potentially increased mortality with high-dose glutamine supplementation in critically ill patients. Low-dose intravenous glutamine may be used with PN.
- Arginine: Supplementation is generally not recommended in septic patients due to a lack of strong evidence and possible harm.
- Omega-3 Fatty Acids: Show mixed results. While some studies suggest benefits in ARDS, evidence for use in general sepsis is weak, and some enteral formulas with omega-3s have shown no improvement in outcome.
Conclusion
Nutritional management in sepsis is a dynamic process tailored to the patient’s clinical phase. Standard guidelines recommend starting early enteral nutrition in hemodynamically stable patients, with cautious advancement of caloric and protein intake. In cases of severe malnutrition or failed EN, parenteral nutrition is a viable and increasingly safer option, particularly with improved lipid formulations and infection control. The use of routine immunonutrition (glutamine, arginine, selenium, omega-3s) remains controversial, though focused micronutrient therapy like high-dose vitamin C continues to be investigated. Ultimately, nutritional therapy must be integrated into a comprehensive care plan, with goals shifting from permissive underfeeding during acute illness to aggressive repletion during recovery. A proactive, phase-specific strategy is essential for mitigating the profound catabolic effects of sepsis and optimizing long-term outcomes for survivors.
