The Hypermetabolic Response and Its Impact on Nutrition
Following a severe burn injury, the body's metabolic rate can increase dramatically, entering a state of hypermetabolism. This response is triggered by a systemic inflammatory reaction and a surge of stress hormones, including catecholamines and corticosteroids, which can remain elevated for months or even years post-injury. This creates a high-energy demand that, if not met, results in significant protein and muscle wasting, compromised immune function, and delayed wound healing. The primary goal of nutritional therapy is to combat this severe catabolic state and its devastating effects on the patient's body.
The Importance of Early Enteral Nutrition
The timing and route of feeding are critical factors in burn patient care. Consensus and guidelines strongly recommend starting nutritional support early, ideally within 24 hours of admission, provided the patient is hemodynamically stable.
- Attenuation of the Stress Response: Early enteral nutrition (EN), delivered directly to the gastrointestinal tract, helps to mitigate the severity and duration of the hypermetabolic response, reducing the release of stress hormones.
- Preserving Gut Integrity: Enteral feeding helps maintain the health and function of the intestinal mucosal barrier. This is vital for reducing the risk of bacterial translocation, a process where bacteria leak from the gut into the bloodstream, which can lead to sepsis.
- Improved Outcomes: Multiple studies have shown that early EN can decrease wound infection rates, shorten the length of intensive care unit stays, and improve overall patient survival.
Macronutrient Requirements
Burn patients require a diet that is high in calories and protein, with a specific ratio of macronutrients to best support healing and prevent further tissue breakdown. Energy needs are determined by factors including the patient's weight, height, age, and the extent of the burn.
- Protein: Burn patients lose a significant amount of protein through wound exudate and muscle breakdown, with some experiencing losses of up to 150 grams daily. To compensate, protein intake for adults is typically 1.5–2.0 g/kg/day, and even higher for children. This extra protein is essential for rebuilding lost muscle mass, promoting wound healing, and supporting immune function.
- Carbohydrates: As the primary fuel for wound healing, carbohydrates should constitute the bulk of the patient's energy intake, often comprising 60–65% of total calories. This high-carbohydrate, low-fat approach is preferred because it spares protein from being used for energy and has been linked to better outcomes.
- Fats: While fat is needed for essential fatty acids and extra calories, intake is intentionally kept low, typically below 15% of total energy intake for severely burned patients. Excess fat can weaken the immune system, and some omega-3 fatty acid sources may be preferable to modulate inflammatory responses.
Micronutrient Requirements
Burn injuries deplete the body's stores of many essential vitamins and minerals, which are crucial for tissue repair and immune function. Supplementation is often required.
- Antioxidants: Vitamins C, E, and the trace elements zinc and selenium are potent antioxidants that help combat oxidative stress caused by the injury. High doses of Vitamin C, for instance, are needed for collagen synthesis.
- Vitamin A: This nutrient is important for epithelial growth and immune function, both vital for effective wound healing.
- Zinc: Involved in protein synthesis, immune function, and cell replication, zinc levels drop significantly after a burn, making supplementation critical for proper healing.
- Glutamine: Considered a conditionally essential amino acid after burn injury, glutamine supplementation may help reduce infection rates and shorten hospital stays by preserving gut integrity and fueling immune cells.
Monitoring Nutritional Support and Management Methods
Effective nutritional support requires constant monitoring and adjustment. Indirect calorimetry is the gold standard for measuring a patient's energy expenditure, though formulas can also be used. Other methods include monitoring weight, although fluid shifts can make this unreliable, and assessing nitrogen balance to gauge protein status.
Comparison of Nutritional Support Methods
| Feature | Enteral Nutrition (EN) | Parenteral Nutrition (PN) |
|---|---|---|
| Route | Via feeding tube into the gastrointestinal tract (nasogastric, jejunal). | Via a central intravenous (IV) line, bypassing the digestive system. |
| Timing | Should be initiated early, within 24 hours of injury, provided stability. | Reserved for when EN is contraindicated, insufficient, or not tolerated. |
| Benefits | Preserves gut integrity, reduces infection and stress response, cost-effective. | Provides nutrients when GI tract is not functional, but carries higher risks. |
| Risks | Feeding intolerance (nausea, diarrhea), potential aspiration if gastric. | Higher risk of infection, liver complications, and metabolic issues. |
| Preferred Status | The preferred route for burn patients due to clear benefits. | Used only as a last resort or supplement when EN is not possible. |
Transitioning from Hospital to Home
Nutritional support continues long after the acute hospital phase. For major burns, the hypermetabolic state can persist for over a year. Patients are typically discharged on a high-protein, high-calorie diet and with supplemental nutrients to aid ongoing healing. A dietitian will manage the transition from tube feeds to oral intake and provide guidance on diet changes as metabolic needs decrease.
Conclusion
Nutritional support is an indispensable element of care for burn patients. The profound hypermetabolic and catabolic state induced by severe burns creates overwhelming energy and protein demands that must be met promptly and aggressively. Early initiation of enteral nutrition with a high-protein, high-carbohydrate, and low-fat diet, supplemented with specific vitamins and minerals, is the standard of care for mitigating complications, accelerating wound healing, and improving survival. The nutritional plan, customized to the individual's needs, requires diligent monitoring and adjustment throughout both the hospital stay and the subsequent rehabilitation period to ensure optimal outcomes.
