Recommended Macronutrient Ratios for Patients Admitted with Infection
For patients admitted with infection, provide 25-30 kcal/kg/day total energy with protein at 1.3-2.0 g/kg/day, glucose comprising 30-70% of non-protein calories, and lipids providing 15-30% of non-protein calories. 1
Energy Distribution Framework
The American College of Chest Physicians established specific macronutrient proportions for infected patients that remain the consensus recommendation 1:
Protein Requirements
- Provide 1.3-2.0 g/kg body weight per day 1
- This represents approximately 20-30% of total calories when calculated at the higher end of energy provision 1
- Protein needs are calculated separately from non-protein calories because protein requirements in infected patients far exceed the proportional increase in energy expenditure 1
Carbohydrate (Glucose) Requirements
- Provide 30-70% of total non-protein calories from glucose 1
- The exact percentage depends on respiratory status: use lower carbohydrate ratios (closer to 30-50%) for ventilated patients to minimize CO2 production 1
- Maintain serum glucose below 225 mg/dl (though current practice favors tighter control at 81-180 mg/dl) 1, 2
- Minimum 2 g/kg/day of glucose to prevent protein catabolism 2
Lipid (Fat) Requirements
- Provide 15-30% of total non-protein calories from lipids 1
- Recent trends favor increasing the glucose:fat ratio from 50:50 toward 60:40 or even 70:30 to avoid complications of hyperlipidemia and fatty liver 1
- Reduce polyunsaturated fatty acids in septic patients while maintaining levels that prevent essential fatty acid deficiency (approximately 7% of total calories or 1 g/kg/day) 1
Practical Calculation Example
For a 70 kg patient with infection 1:
Total Energy: 25-30 kcal/kg = 1,750-2,100 kcal/day
Protein: 1.3-2.0 g/kg = 91-140 g/day (364-560 kcal from protein)
Non-protein calories: 1,386-1,540 kcal remaining
Glucose (at 60% of non-protein calories): 832-924 kcal = 208-231 g
Lipids (at 25% of non-protein calories): 347-385 kcal = 39-43 g
Critical Considerations for Infected Patients
Timing and Progression
- Start with lower energy provision (approximately 20 kcal/kg/day) during the acute phase (first 72-96 hours) to avoid overfeeding, as infected patients have intense endogenous energy substrate production 1, 2
- Gradually increase to target over 2-3 days as the patient stabilizes 2
- Full feeding in the first week may cause harm through metabolic complications 1, 3
Route of Delivery
- Enteral nutrition is strongly preferred over parenteral nutrition to maintain gut integrity and reduce infection rates 3
- If enteral feeding is not feasible after 3 days, initiate parenteral nutrition at approximately 50% of predicted needs 1
Monitoring Requirements
- Monitor blood glucose closely, maintaining between 81-180 mg/dl 2
- Check serum triglycerides when using lipid emulsions; avoid levels >5 mmol/dL 1
- Assess for refeeding syndrome risk, particularly monitoring potassium, phosphate, and magnesium 1
Common Pitfalls to Avoid
- Do not attempt full caloric feeding in the first 3-4 days of acute infection, as this increases complications without improving outcomes 1, 3
- Do not use the standard 0.8 g/kg protein recommendation for younger healthy adults; infected patients require substantially more protein 4, 5
- Do not provide excess polyunsaturated fatty acids in septic patients, as this may impair immune response 1
- Do not overlook non-nutritional calorie sources such as propofol or dextrose in IV fluids when calculating total energy delivery 1, 2
- Avoid aggressive early protein delivery in septic shock patients during the first week, as early aggressive feeding has not shown benefit and may worsen outcomes 3
Special Populations
Elderly Patients with Infection
- Protein requirements may increase to 1.2-1.5 g/kg/day due to age-related changes in protein metabolism and increased catabolism from infection 1, 4
- Energy needs remain at 27-30 kcal/kg/day for older adults 1