Nutrition in Critical Illness — Part 4: Immunonutrition & Special Populations
Comprehensive guide to immunonutrition (arginine, glutamine, omega-3 fatty acids, antioxidants), and nutrition management in special ICU populations including sepsis, burns, trauma, TBI, acute pancreatitis, ECMO, obesity, chronic critical illness, open abdomen, and CRRT.
1. Immunonutrition — Overview
Immunonutrition refers to the provision of specific nutrients — including arginine, glutamine, omega-3 fatty acids, and antioxidant vitamins/minerals — at pharmacologic doses with the intent of modulating the immune response and improving clinical outcomes. The evidence for immunonutrition in critical illness is mixed and highly context-dependent. Specific nutrient effects may be beneficial in some populations and harmful in others.1 2 3
2. Arginine
2.1 Mechanism
Arginine is a conditionally essential amino acid in critical illness. It serves as a substrate for nitric oxide (NO) synthesis (via inducible nitric oxide synthase, iNOS), polyamine synthesis (cell proliferation), collagen deposition (wound healing), and T-lymphocyte proliferation. In critical illness, arginine depletion occurs due to increased consumption by iNOS and arginase pathways.1
2.2 Potential Benefits
- Enhanced T-cell-mediated immune function
- Improved wound healing (collagen synthesis)
- Improved nitrogen balance
- Enhanced microvascular perfusion (via NO)
2.3 Potential Risks
- In sepsis and septic shock, arginine supplementation may increase NO production via iNOS, leading to worsening vasodilation, hemodynamic instability, and potentially increased mortality
- Theoretical concern for enhanced peroxynitrite formation (oxidative damage)
2.4 Recommendations
| Population | Recommendation | Evidence |
|---|---|---|
| Surgical ICU (perioperative, elective major surgery) | Consider arginine-containing immune-modulating formula (as part of an immunonutrition cocktail with omega-3 and nucleotides) starting 5-7 days preoperatively and continuing 5-7 days postoperatively | Moderate — multiple meta-analyses show reduced infectious complications and LOS in surgical patients |
| Trauma (non-septic) | Consider arginine-supplemented formula | Low-Moderate |
| Sepsis / septic shock | Do NOT use arginine-supplemented formulas | Moderate — concern for hemodynamic instability and increased mortality |
| Medical ICU (general, non-surgical) | Not recommended routinely | Low — insufficient evidence of benefit |
3. Glutamine
3.1 Mechanism
Glutamine is the most abundant free amino acid in the body and is considered conditionally essential during critical illness. It serves as a fuel source for rapidly dividing cells (enterocytes, lymphocytes, macrophages), a precursor for glutathione synthesis (antioxidant defense), a regulator of heat shock protein expression (cellular stress response), and a substrate for renal ammoniagenesis (acid-base balance).4
3.2 Key Trials
REDOXS Trial (2013)
| Feature | Details |
|---|---|
| Design | Multicenter RCT; n = 1,223; critically ill adults with multi-organ failure (>= 2 organ failures) |
| Intervention | Glutamine (enteral + parenteral, total 0.5-0.8 g/kg/day) +/- antioxidants vs placebo |
| Primary outcome | No difference in 28-day mortality |
| Key findings | Trend toward increased mortality with glutamine supplementation at 6 months (37.2% vs 31.1% in the no-glutamine groups, p = 0.049 for the glutamine main effect); increased mortality particularly in patients with renal failure and multi-organ dysfunction |
| Interpretation | High-dose glutamine supplementation (especially combined enteral + parenteral) in patients with multi-organ failure is potentially harmful |
| Citation | Heyland DK, Muscedere J, Wischmeyer PE, et al. N Engl J Med. 2013;368(16):1489-1497 |
| DOI | 10.1056/NEJMoa1212722 |
MetaPlus Trial (2014)
| Feature | Details |
|---|---|
| Design | Multicenter RCT; n = 301; critically ill adults receiving EN |
| Intervention | EN supplemented with glutamine, omega-3 fatty acids, and antioxidants vs standard high-protein EN |
| Key findings | No benefit in overall population; increased 6-month mortality in the medical ICU subgroup receiving the supplemented formula (54.7% vs 35.5%, p = 0.04) |
| Citation | van Zanten AR, Sztark F, Kaisers UX, et al. Lancet. 2014;383(9921):1007-1016 |
| DOI | 10.1016/S0140-6736(14)60781-3 |
3.3 Recommendations
| Population | Recommendation | Evidence |
|---|---|---|
| Multi-organ failure (>= 2 organ failures) | Do NOT supplement glutamine | Strong (REDOXS) |
| Sepsis / septic shock | Do NOT supplement glutamine | Moderate |
| Burns (>= 20% TBSA) | May consider enteral glutamine supplementation (0.3-0.5 g/kg/day) | Low-Moderate — earlier trials in burns showed reduced infections; not replicated in large multicenter trials |
| Trauma | Insufficient evidence to recommend routinely | Low |
| Patients on exclusive PN (without organ failure) | May consider glutamine supplementation in the PN (0.2-0.3 g/kg/day of L-alanyl-L-glutamine) | Low — supported by earlier meta-analyses; post-REDOXS, exercise caution; avoid in renal failure |
| General medical ICU | Do NOT routinely supplement | Moderate |
4. Omega-3 Fatty Acids (Fish Oil — EPA/DHA)
4.1 Mechanism
Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are long-chain omega-3 polyunsaturated fatty acids that modulate inflammation by displacing arachidonic acid from cell membrane phospholipids, reducing pro-inflammatory eicosanoid (prostaglandin E2, thromboxane A2, leukotriene B4) synthesis, and promoting the production of specialized pro-resolving mediators (resolvins, protectins, maresins) that facilitate inflammation resolution.5
4.2 Routes of Delivery
| Route | Source | Considerations |
|---|---|---|
| Enteral | Fish oil supplements; omega-3-enriched EN formulas | Requires functional GI tract; absorption may be variable in critical illness |
| Parenteral | Fish oil-containing lipid emulsions (SMOF lipid, pure fish oil) | Bypasses GI absorption; more predictable delivery; used in PNALD treatment |
4.3 Key Evidence
| Indication | Evidence Summary | Recommendation |
|---|---|---|
| ARDS | Early trials (OMEGA trial, 2011) of omega-3 bolus supplements in ARDS showed no benefit and potential harm (more diarrhea, higher ICU mortality trend) compared to iso-caloric control; OMEGA trial was stopped early for futility | Do NOT use enteral omega-3 boluses for ARDS treatment |
| Surgical ICU | As part of immune-modulating formulas (arginine + omega-3 + nucleotides), perioperative use has shown reduced infections in some surgical populations | Consider as part of perioperative immunonutrition in elective GI surgery |
| PN lipid source | SMOF lipid (containing fish oil) may reduce hepatic complications compared to pure soybean oil emulsions | Prefer SMOF or mixed lipid emulsions over pure soybean oil for PN |
| Sepsis | Insufficient evidence for routine enteral omega-3 supplementation in sepsis | Not routinely recommended |
| TBI | Preclinical data suggest neuroprotective effects; human data are limited | Insufficient evidence to recommend; trials ongoing |
5. Antioxidant Supplementation
5.1 Rationale
Oxidative stress is a hallmark of critical illness. Reactive oxygen species (ROS) generated during the inflammatory response cause cellular injury, endothelial dysfunction, and organ damage. Antioxidant micronutrients (vitamin C, vitamin E, selenium, zinc) are rapidly depleted in critical illness. However, the clinical trials of pharmacologic-dose antioxidant supplementation have been largely disappointing.4
5.2 Key Evidence
- REDOXS trial (discussed above): Antioxidant cocktail (selenium 500 mcg, zinc 20 mg, beta-carotene 10 mg, vitamin E 500 mg, vitamin C 1,500 mg daily) showed no benefit; when combined with glutamine, there was a trend toward increased mortality
- LOVIT trial (discussed in Part 3): High-dose vitamin C in sepsis showed potential harm
- Selenium trials (meta-analyses): Mixed results; no clear mortality benefit with high-dose IV selenium
5.3 Recommendation
Standard-dose micronutrient supplementation (via MVI and trace element preparations in PN, or standard EN formulations) is recommended. Pharmacologic-dose antioxidant supplementation is NOT routinely recommended based on current evidence.1 2 4
6. Summary of Immunonutrition Recommendations
| Nutrient | Surgical ICU / Perioperative | Trauma (non-septic) | Sepsis / Septic Shock | Burns | Medical ICU (general) |
|---|---|---|---|---|---|
| Arginine | Consider (as part of immune-modulating formula) | Consider | Avoid | Insufficient data | Not recommended |
| Glutamine | Not routinely | Not routinely | Avoid | May consider (enteral) | Avoid |
| Omega-3 FA | Consider (as part of perioperative formula) | Not routinely | Not routinely | Not routinely | Not recommended |
| Antioxidants (pharmacologic dose) | Not routinely | Not routinely | Avoid high-dose vitamin C | Not routinely | Not recommended |
7. Special Populations
7.1 Sepsis and Septic Shock
Nutrition management in sepsis and septic shock requires balancing the benefits of early gut stimulation against the risks of GI intolerance, mesenteric ischemia, and overfeeding during the acute inflammatory response.1 2 7
| Parameter | Recommendation |
|---|---|
| EN timing | Early EN (within 24-48 hours) once hemodynamically stabilized (MAP at target, stable or decreasing vasopressor requirements) |
| Starting approach | Trophic feeding (10-20 mL/hr, ~500 kcal/day) for the first 48-72 hours; advance to full feeds over days 3-7 |
| Trophic vs full feeds (early) | Trophic feeding is non-inferior to full-dose EN in the first week based on the EDEN trial and supported by the PERMIT trial. The TARGET trial (2018) also showed no benefit of augmented caloric delivery (~100% of target) vs usual care (~70% of target) in a mixed ICU population. |
| Caloric target | 25-30 kcal/kg/day (advance toward this by end of first week); use IC if available |
| Protein | 1.2-2.0 g/kg/day; prioritize protein delivery even if caloric targets are not yet met |
| Vasopressors | See EN during vasopressor therapy (Part 2, Section 10) — trophic EN acceptable on low-moderate vasopressor doses; hold during hemodynamic instability or escalating pressors |
| PN | Avoid early PN (first 7 days) in well-nourished septic patients; consider earlier in malnourished patients |
| Immunonutrition | Avoid arginine, glutamine, and high-dose antioxidants in sepsis |
| Glycemic control | Target 140-180 mg/dL |
Key trial — TARGET (2018):
| Feature | Details |
|---|---|
| Design | Multicenter RCT; n = 3,957; critically ill adults expected to be ventilated > 2 days |
| Comparison | Energy-dense EN (~1.5 kcal/mL, targeting ~100% of estimated needs) vs routine care (~1.0 kcal/mL, targeting ~70% of estimated needs) |
| Primary outcome | No difference in 90-day mortality (26.8% vs 25.2%, p = 0.41) |
| Interpretation | Delivering more calories in the first week of critical illness does not improve mortality |
| Citation | Chapman MJ, Peake SL, Bellomo R, et al. N Engl J Med. 2018;378(1):11-22 |
| DOI | 10.1056/NEJMoa1811687 |
7.2 Burns
Burns represent the most hypermetabolic condition in critical illness, with REE reaching 140-200% of predicted basal metabolic rate in patients with > 40% TBSA burns. Nutrition requirements are the highest of any ICU population.8
| Parameter | Recommendation |
|---|---|
| Caloric target | IC is the gold standard. Predictive: Curreri formula [25 kcal x kg + 40 kcal x %TBSA burn] or Toronto formula [-4,343 + (10.5 x %TBSA) + (0.23 x caloric intake) + (0.84 x Harris-Benedict REE) + (114 x temperature C) - (4.5 x post-burn days)]. Weight-based: 25-30 kcal/kg/day initially; up to 35-40 kcal/kg/day for major burns. IC is preferred because predictive equations are particularly inaccurate in burns. |
| Protein | 1.5-2.0 g/kg/day (up to 2.5 g/kg/day in major burns > 40% TBSA) |
| EN timing | Within 6-12 hours of injury if possible (even earlier than general ICU recommendation) |
| Route | Gastric preferred; post-pyloric if gastroparesis develops (common in major burns) |
| Formula | Standard high-protein formula; some evidence supports glutamine-supplemented formulas in burns |
| Carbohydrate | Limit to < 5 mg/kg/min (glucose infusion rate) — burns patients are especially prone to stress hyperglycemia |
| Fat | Limit to < 20-25% of total calories — excess fat may impair immune function and worsen hypermetabolism |
| Micronutrients | Aggressive supplementation: zinc 25-40 mg/day, copper 2-4 mg/day, selenium 300-500 mcg/day, vitamin C 1,000-1,500 mg/day, vitamin A 10,000 IU/day (wound healing), vitamin D supplementation |
| Oxandrolone | Anabolic steroid (10 mg PO BID) — reduces muscle catabolism, improves nitrogen balance, and accelerates wound healing; considered in patients with > 20% TBSA burns who can take oral medications |
| Glycemic control | Tight-moderate control (target 140-180 mg/dL); insulin infusion; propranolol (non-selective beta-blocker) may reduce hypermetabolism and improve protein synthesis |
| Glutamine | May consider enteral glutamine 0.3-0.5 g/kg/day (earlier burn-specific trials suggested reduced infections) |
| Immunonutrition | No strong evidence for immune-modulating formulas in burns |
7.3 Trauma and Traumatic Brain Injury (TBI)
General Trauma
| Parameter | Recommendation |
|---|---|
| EN timing | Within 24-48 hours of admission; early EN is associated with reduced infectious complications in trauma |
| Caloric target | 25-30 kcal/kg/day (IC preferred) |
| Protein | 1.5-2.0 g/kg/day |
| Route | Gastric unless intolerant; post-pyloric for severe gastroparesis |
| Formula | Standard high-protein formula; consider immune-modulating formula (arginine + omega-3 + nucleotides) in non-septic trauma patients |
| PN | Only if EN is not feasible or insufficient after optimization |
Traumatic Brain Injury (TBI)
| Parameter | Recommendation |
|---|---|
| EN timing | Within 24-48 hours of injury; early EN is strongly recommended in TBI (associated with reduced mortality in observational studies) |
| Caloric target | 25-30 kcal/kg/day; IC is ideal because TBI patients have variable metabolic rates (may be hypermetabolic, especially with fever, posturing, or seizures; may be hypometabolic with barbiturate coma or hypothermia) |
| Protein | 1.5-2.5 g/kg/day (higher protein needs due to profound catabolism and nitrogen wasting) |
| Route | Gastric initially; post-pyloric often needed due to high prevalence of gastroparesis (up to 50% of moderate-severe TBI patients) |
| Prokinetics | Start early (metoclopramide 10 mg IV q6h) given the high rate of GI dysmotility |
| Barbiturate coma | Reduces REE by 30-50%; caloric targets should be reduced accordingly (IC is invaluable in this setting) |
| Targeted temperature management | Hypothermia (33-36 degrees C) reduces REE by ~10% per degree C below 37 degrees C; adjust caloric targets |
| Glycemic control | Target 140-180 mg/dL; hypoglycemia (< 70 mg/dL) is particularly harmful in TBI and must be avoided |
| Special nutrients | Zinc (12-25 mg/day) — some evidence for improved neurologic recovery. Omega-3 fatty acids — preclinical neuroprotection data; insufficient human evidence for routine recommendation. |
7.4 Acute Pancreatitis
The traditional practice of prolonged fasting (“pancreatic rest”) in acute pancreatitis has been definitively overturned by evidence demonstrating the safety and benefit of early enteral feeding.1 10
| Parameter | Recommendation |
|---|---|
| Mild acute pancreatitis | Initiate oral diet as tolerated (low-fat solid diet, not restricted to clear liquids) as soon as pain permits; most patients do not require EN |
| Moderate-to-severe acute pancreatitis | Early EN within 24-48 hours of admission is recommended; superior to PN and superior to delayed feeding |
| Route | Gastric feeding is acceptable in most patients — multiple RCTs have demonstrated equivalent safety and tolerance of nasogastric vs nasojejunal feeding. Nasojejunal feeding may be preferred in patients with gastric outlet obstruction or recurrent emesis. |
| Formula | Standard polymeric formula is appropriate for most patients; semi-elemental formulas may be considered but are not routinely superior |
| PN | Reserve for patients with complete EN failure (persistent ileus, complex pancreatic fistulae, or walled-off necrosis requiring surgery). If needed, initiate PN after 5-7 days of EN failure. |
| Caloric target | 25-30 kcal/kg/day |
| Protein | 1.2-1.5 g/kg/day |
| Monitoring | Lipase/amylase trends are not useful for guiding EN advancement; assess tolerance clinically (pain, vomiting, abdominal exam) |
| Immunonutrition | Glutamine and immunonutrition formulas are not recommended in acute pancreatitis |
| Probiotics | Do NOT use — the PROPATRIA trial demonstrated increased mortality with probiotic prophylaxis in severe acute pancreatitis (16% vs 6%, p = 0.01) |
Key point: The pancreas contributes only ~20% of overall pancreatic enzyme output in response to intragastric feeding. Trypsin output is primarily stimulated by duodenal and jejunal nutrient contact. Therefore, gastric feeding does not produce clinically significant pancreatic stimulation in most patients.
PROPATRIA citation: Besselink MG, van Santvoort HC, Buskens E, et al. “Probiotic prophylaxis in predicted severe acute pancreatitis: a randomised, double-blind, placebo-controlled trial.” Lancet. 2008;371(9613):651-659. DOI: 10.1016/S0140-6736(08)60207-X
7.5 ECMO (Extracorporeal Membrane Oxygenation)
Patients on ECMO present unique nutritional challenges due to altered metabolism, systemic inflammation, fluid shifts, and interactions between the circuit and nutrient delivery.11
| Parameter | Recommendation |
|---|---|
| EN feasibility | EN is feasible and recommended in most ECMO patients, including those on VA-ECMO. Early EN (within 24-48 hours of ECMO initiation) is generally safe. |
| VA-ECMO considerations | VA-ECMO provides non-pulsatile flow, which may compromise mesenteric perfusion. Risk of bowel ischemia is higher than in VV-ECMO. Initiate EN cautiously (trophic feeds), monitor closely, and avoid in patients with signs of mesenteric hypoperfusion (elevated lactate, abdominal distension, bloody stools). |
| VV-ECMO | EN is generally well-tolerated; treat similarly to ventilated ICU patients |
| Caloric assessment | Indirect calorimetry requires circuit-specific adjustments (VCO2 removal by the membrane oxygenator must be accounted for); consult calorimetry manufacturer guidelines or use validated correction formulas. If IC is not feasible, use 20-25 kcal/kg/day as a starting estimate. |
| Protein | 1.5-2.0 g/kg/day |
| PN | Use if EN is contraindicated or insufficient |
| Lipid clearance | Propofol use on ECMO contributes additional lipid load; ECMO circuits may sequester fat-soluble medications; monitor triglycerides |
| Micronutrients | Standard supplementation; consider that fat-soluble vitamins may be adsorbed by the ECMO circuit |
7.6 Obesity — High-Protein Hypocaloric Feeding
Detailed caloric and protein targets for obese ICU patients are provided in Part 1, Section 7. Key principles are summarized here.1 2
| BMI Category | Caloric Target | Protein Target | Strategy |
|---|---|---|---|
| BMI 30-39.9 | 11-14 kcal/kg actual BW/day | >= 2.0 g/kg IBW/day | High-protein, hypocaloric |
| BMI >= 40 | 11-14 kcal/kg actual BW/day | >= 2.5 g/kg IBW/day | High-protein, hypocaloric |
Additional considerations:
- Obese patients may be sarcopenic despite high BMI (sarcopenic obesity) — protein delivery is critical
- IC is particularly valuable in obesity because predictive equations are highly inaccurate
- Refeeding syndrome can occur in obese patients who have been fasting or have poor intake
- High-protein enteral formulas or modular protein supplementation is usually required to meet protein targets without exceeding caloric limits
- Monitor nitrogen balance weekly if feasible to ensure adequate protein provision
7.7 Chronic Critical Illness (CCI)
Chronic critical illness is typically defined as ICU stay > 14-21 days with ongoing organ dysfunction. These patients have transitioned from the acute catabolic phase to a persistent inflammation, immunosuppression, and catabolism syndrome (PICS) characterized by ongoing muscle wasting, immune dysregulation, and failure to recover.12
| Parameter | Recommendation |
|---|---|
| Caloric target | IC is essential — REE in CCI may be lower than expected due to reduced lean mass. 25-30 kcal/kg/day may overfeed patients with significant lean mass depletion. |
| Protein | 1.5-2.0 g/kg/day — continued high protein is essential to support any anabolic potential |
| Physical rehabilitation | Combined nutrition + early mobilization/rehabilitation is the most effective strategy for lean mass preservation and functional recovery |
| Anabolic agents | Consider oxandrolone or testosterone in select patients with profound sarcopenia (evidence limited to case series and small trials) |
| Micronutrients | Ensure adequate vitamin D, zinc, and B vitamins; deficiency is common with prolonged ICU stay |
| EN vs PN | EN preferred; many CCI patients tolerate enteral feeding. Transition to PEG if expected EN need > 4-6 weeks. |
| Oral diet | Transitioning from EN to oral intake requires speech-language pathology assessment, swallow evaluation, and careful monitoring of volitional intake adequacy |
| Key challenge | Metabolic resistance to feeding — CCI patients often fail to achieve positive nitrogen balance despite seemingly adequate protein delivery due to ongoing inflammation and anabolic resistance |
7.8 Open Abdomen
Patients managed with an open abdomen (e.g., damage-control surgery for trauma, abdominal compartment syndrome, or complicated intra-abdominal infection) have massive protein losses through the open peritoneal cavity and negative-pressure wound therapy (NPWT) effluent.13
| Parameter | Recommendation |
|---|---|
| EN | Early EN is recommended and is safe in most patients with an open abdomen, even without bowel continuity restoration (as long as there is enteral access proximal to any discontinuity). EN within 24-48 hours is associated with improved fascial closure rates and reduced complications. |
| Caloric target | 25-30 kcal/kg/day (may need to be higher; IC recommended) |
| Protein | 2.0-2.5 g/kg/day — massive protein losses from open peritoneum; NPWT effluent contains 1.5-3.5 g protein per liter. Measure protein content in NPWT effluent if possible and replace accordingly. |
| Nitrogen balance | Particularly inaccurate in open abdomen due to peritoneal nitrogen losses; clinical assessment and serial muscle mass evaluation (ultrasound) may be more useful |
| Volume | Patients often require large-volume fluid resuscitation; coordinate with nutrition to avoid overfeeding while accounting for massive fluid shifts |
| Formula | Standard high-protein formula; add modular protein as needed |
7.9 CRRT (Continuous Renal Replacement Therapy)
Patients receiving CRRT have significant nutrient losses through the dialysis effluent that must be accounted for in the nutrition prescription.1 2 3 14
| Nutrient | CRRT Losses | Compensation Strategy |
|---|---|---|
| Amino acids | 10-15 g/day (sieving coefficient ~0.8-1.0 for most amino acids) | Increase protein target to 1.5-2.5 g/kg/day |
| Glutamine | Significant losses (major constituent of effluent amino acids) | Do NOT supplement glutamine in patients with multi-organ failure (REDOXS) |
| Water-soluble vitamins | Vitamin C, B vitamins, folate are cleared by CRRT | Supplement with additional water-soluble vitamin preparation (double the standard MVI dose or add supplemental B vitamins and vitamin C 100-250 mg/day) |
| Trace elements | Selenium, zinc, copper may be lost in effluent; extent depends on protein binding and effluent rate | Standard trace element supplementation; consider checking levels weekly |
| Phosphate | Variable depending on CRRT solution composition — some solutions contain phosphate; others do not | Monitor phosphate frequently (every 6-12 hours during initiation); replace as needed; phosphate-containing CRRT solutions reduce the need for exogenous supplementation |
| Calories | CRRT with citrate anticoagulation provides additional calories from citrate metabolism (~300-500 kcal/day depending on flow rates and citrate load) | Account for citrate calories in total caloric prescription to avoid overfeeding |
| Electrolytes | Variable losses depending on CRRT modality, effluent rate, and solution composition | Frequent monitoring (every 6-8 hours); aggressive replacement |
Caloric target in CRRT:
- 25-30 kcal/kg/day (standard); adjust downward for citrate calories
- IC is ideal but requires accounting for CO2 removal by the CRRT circuit (generally less significant than ECMO)
Protein target in CRRT:
- 1.5-2.5 g/kg/day (actual body weight for non-obese; IBW for obese)
- Higher end of range for patients on high-volume CRRT (effluent rate > 35 mL/kg/hr) due to greater amino acid losses
- Do NOT restrict protein in an attempt to delay dialysis or reduce urea generation — this worsens sarcopenia without meaningful impact on RRT timing
7.10 Post-Cardiac Surgery
| Parameter | Recommendation |
|---|---|
| EN timing | Within 24 hours post-operatively in most patients |
| High risk for mesenteric ischemia | Patients with prolonged cardiopulmonary bypass, aortic cross-clamp, circulatory arrest, or requiring high-dose vasopressors post-operatively — initiate EN cautiously; trophic feeds; monitor closely |
| Caloric target | 25-30 kcal/kg/day |
| Protein | 1.2-2.0 g/kg/day |
| Extubation | Most cardiac surgery patients are extubated within 6-12 hours; transition to oral diet with swallow assessment |
8. Nutrition Quality Metrics and Monitoring Protocols
8.1 Key Performance Indicators
| Metric | Target | Rationale |
|---|---|---|
| Nutrition screening completion rate | > 90% of ICU admissions screened within 24-48 hours | Early identification of nutritional risk |
| Time to EN initiation | Within 24-48 hours of ICU admission (median) | Gut integrity, infection reduction |
| Caloric adequacy | >= 80% of caloric target delivered by day 3-5 | Adequate energy provision while avoiding overfeeding |
| Protein adequacy | >= 80% of protein target delivered by day 3-5 | Critical for lean mass preservation |
| EN interruption rate | Minimize unnecessary holds (target: < 2 hours/day of non-essential holds) | Improve caloric delivery |
| Use of volume-based feeding protocol | Institution-specific adoption | Improved caloric delivery compared to rate-based protocols |
| IC utilization | Use IC in >= 50% of patients with mNUTRIC >= 5 or BMI >= 30 | Accurate energy target determination |
| Refeeding syndrome screening | 100% of at-risk patients identified and managed per protocol | Prevention of life-threatening electrolyte shifts |
| PN appropriateness | PN initiated only when EN is contraindicated, insufficient (< 60% target after day 3-7), or expected to be needed > 3-5 days | Avoid unnecessary PN use and associated complications |
8.2 Multidisciplinary Nutrition Team
Optimal ICU nutrition requires a multidisciplinary approach including:
| Team Member | Role |
|---|---|
| Intensivist | Overall nutrition strategy; integration with medical management; EN during vasopressors and prone positioning decisions |
| Registered Dietitian (RD) | Nutritional assessment (NUTRIC/mNUTRIC); caloric and protein calculations; IC interpretation; formula selection; refeeding risk assessment |
| Clinical Pharmacist | PN composition, compatibility, and stability review; drug-nutrient interactions; insulin management; prokinetic dosing |
| Nurse (ICU RN) | EN administration and advancement per protocol; GRV monitoring (if applicable); tolerance assessment; tube care and flushing; HOB management |
| Speech-Language Pathologist | Swallow assessment for patients transitioning from EN to oral diet (post-extubation, tracheostomy patients) |
| Physical/Occupational Therapist | Early mobilization programs that synergize with nutrition therapy for muscle preservation |
8.3 Daily Nutrition Rounding Checklist
| Question | Action |
|---|---|
| Is EN at goal rate? | If not, identify and address barriers (holds, intolerance, access issues) |
| Are protein targets being met? | If not, add protein modules or switch to high-protein formula |
| Is there abdominal intolerance? | Assess for distension, GRV (if checked), stool output; consider prokinetics |
| Is the patient on vasopressors? | Reassess EN safety per vasopressor dose and trend |
| Is the patient on propofol? | Calculate propofol lipid/caloric contribution; subtract from PN lipid dose |
| Are electrolytes (PO4, K, Mg) within target? | Replace aggressively; increase monitoring frequency if refeeding risk |
| Is blood glucose in target range (140-180 mg/dL)? | Adjust insulin; consider formula change or dextrose reduction in PN |
| Is PN still needed? | Transition to EN as soon as possible; taper PN when EN reaches > 60% of target |
| Has IC been performed (if indicated)? | Ensure IC in high-risk patients; repeat weekly or with significant clinical change |
| Are micronutrients and thiamine being supplemented? | Verify MVI and trace elements in PN; thiamine in refeeding risk patients |
9. EN/PN Holding Protocols for Procedures — Quick Reference
| Procedure | EN Hold Duration | PN Management | Post-Procedure Resumption |
|---|---|---|---|
| Elective intubation | 6-8 hours | Continue PN | Resume EN once secured and hemodynamically stable |
| Elective extubation | 4-6 hours | Continue PN | Resume EN or transition to oral diet after swallow assessment |
| Percutaneous tracheostomy | 6-8 hours | Continue PN | Resume EN 2-4 hours post-procedure |
| OR surgery (general anesthesia) | 6-8 hours | Continue PN (may need to adjust rate for OR) | Resume EN within 12-24 hours post-operatively |
| Bronchoscopy (diagnostic) | 4 hours (2 hours if post-pyloric) | Continue PN | Resume EN 1-2 hours after procedure |
| CT/MRI transport | No hold needed (may pause during transport for practical reasons) | No change | Resume immediately |
| Bedside procedures (arterial line, chest tube) | No hold | No change | — |
| Prone positioning (turning) | Hold 1 hour before turn | No change | Resume immediately after repositioning |
10. Summary of Special Population Recommendations
| Population | Caloric Target | Protein Target | Key Considerations |
|---|---|---|---|
| Sepsis | 25-30 kcal/kg/day (trophic first 48-72 hrs) | 1.2-2.0 g/kg/day | No immunonutrition; trophic early; monitor for mesenteric ischemia on pressors |
| Burns (> 20% TBSA) | 25-40 kcal/kg/day (IC essential) | 1.5-2.5 g/kg/day | Earliest EN (6-12 hrs); aggressive micronutrients (Zn, Cu, Se, Vit C/A/D); limit fat < 25% calories |
| Trauma | 25-30 kcal/kg/day | 1.5-2.0 g/kg/day | Early EN; consider immune-modulating formula if non-septic |
| TBI | 25-30 kcal/kg/day (IC preferred) | 1.5-2.5 g/kg/day | Post-pyloric often needed; early prokinetics; avoid hypoglycemia |
| Acute pancreatitis | 25-30 kcal/kg/day | 1.2-1.5 g/kg/day | Early EN; gastric OK; avoid PN unless EN failure; no probiotics |
| ECMO | 20-25 kcal/kg/day (IC with corrections) | 1.5-2.0 g/kg/day | EN feasible; caution with VA-ECMO; account for CO2 removal on IC |
| Obesity (BMI 30-39.9) | 11-14 kcal/kg actual/day | >= 2.0 g/kg IBW/day | High-protein hypocaloric; IC valuable |
| Obesity (BMI >= 40) | 11-14 kcal/kg actual/day | >= 2.5 g/kg IBW/day | High-protein hypocaloric; refeeding risk possible |
| CCI (> 14-21 days) | IC-guided (avoid overfeeding) | 1.5-2.0 g/kg/day | Combine nutrition + rehabilitation; anabolic resistance |
| Open abdomen | 25-30 kcal/kg/day | 2.0-2.5 g/kg/day | Massive protein losses via peritoneum; early EN improves fascial closure |
| CRRT | 25-30 kcal/kg/day (subtract citrate kcal) | 1.5-2.5 g/kg/day | Compensate amino acid losses; do NOT restrict protein; supplement water-soluble vitamins |
References
McClave SA, Taylor BE, Martindale RG, et al. “Guidelines for the Provision and Assessment of Nutrition Support Therapy in the Adult Critically Ill Patient: Society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.).” JPEN J Parenter Enteral Nutr. 2016;40(2):159-211. DOI: 10.1177/0148607115621863 ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
Compher C, Bingham AL, McCall M, et al. “Guidelines for the Provision of Nutrition Support Therapy in the Adult Critically Ill Patient: The American Society for Parenteral and Enteral Nutrition.” JPEN J Parenter Enteral Nutr. 2022;46(1):12-41. DOI: 10.1002/jpen.2267 ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎ ↩︎
Singer P, Blaser AR, Berger MM, et al. “ESPEN guideline on clinical nutrition in the intensive care unit.” Clin Nutr. 2019;38(1):48-79. DOI: 10.1016/j.clnu.2018.08.037 ↩︎ ↩︎ ↩︎
Heyland DK, Muscedere J, Wischmeyer PE, et al. “A randomized trial of glutamine and antioxidants in critically ill patients (REDOXS).” N Engl J Med. 2013;368(16):1489-1497. DOI: 10.1056/NEJMoa1212722 ↩︎ ↩︎ ↩︎ ↩︎
Rice TW, Wheeler AP, Thompson BT, et al. “Enteral omega-3 fatty acid, gamma-linolenic acid, and antioxidant supplementation in acute lung injury.” JAMA. 2011;306(14):1574-1581. DOI: 10.1001/jama.2011.1435 ↩︎ ↩︎
Manzanares W, Dhaliwal R, Jurewitsch B, Stapleton RD, Jeejeebhoy KN, Heyland DK. “Parenteral fish oil lipid emulsions in the critically ill: a systematic review and meta-analysis.” JPEN J Parenter Enteral Nutr. 2014;38(1):20-28. DOI: 10.1177/0148607113486006 ↩︎
Reignier J, Boisrame-Helms J, Brisard L, et al. “Enteral versus parenteral early nutrition in ventilated adults with shock: a randomised, controlled, multicentre, open-label, parallel-group study (NUTRIREA-2).” Lancet. 2018;391(10116):133-143. DOI: 10.1016/S0140-6736(17)32146-3 ↩︎
Clark A, Imran J, Madni T, Wolf SE. “Nutrition and metabolism in burn patients.” Burns Trauma. 2017;5:11. DOI: 10.1186/s41038-017-0076-x ↩︎
Chapple LS, Deane AM, Heyland DK, et al. “Energy and protein deficits throughout hospitalization in patients admitted with a traumatic brain injury.” Clin Nutr. 2016;35(6):1315-1322. DOI: 10.1016/j.clnu.2016.02.009 ↩︎
Al-Omran M, Albalawi ZH, Tashkandi MF, Al-Ansary LA. “Enteral versus parenteral nutrition for acute pancreatitis.” Cochrane Database Syst Rev. 2010;(1):CD002837. DOI: 10.1002/14651858.CD002837.pub2 ↩︎
Bear DE, Smith E, Barrett NA. “Nutrition Support in Adult Patients Receiving Extracorporeal Membrane Oxygenation.” Nutr Clin Pract. 2018;33(6):738-746. DOI: 10.1002/ncp.10211 ↩︎
Mira JC, Brakenridge SC, Moldawer LL, Moore FA. “Persistent Inflammation, Immunosuppression and Catabolism Syndrome.” Crit Care Clin. 2017;33(2):245-258. DOI: 10.1016/j.ccc.2016.12.001 ↩︎
Dissanaike S, Pham T, Shalhub S, et al. “Effect of immediate enteral feeding on trauma patients with an open abdomen: protection from nosocomial infections.” J Am Coll Surg. 2008;207(5):690-697. DOI: 10.1016/j.jamcollsurg.2008.06.332 ↩︎
Bellomo R, Tan HK, Bhonagiri S, et al. “High protein intake during continuous hemodiafiltration: impact on amino acids and nitrogen balance.” Int J Artif Organs. 2002;25(4):261-268. DOI: 10.1177/039139880202500403 ↩︎