ZJ Part 1 Nutrition in the ICU Corrections 15 Nov. PDF

**TITLE: NUTRITIONAL CONSIDERATIONS FOR ICU PATIENTS.** **[(Part 1: When, what and how to feed)]{.smallcaps}** **TRAINEE:** Dr Gothyang Makuya **SUPERVISOR:** Dr [Z]{.smallcaps}ainub Jooma **EDITOR:** Dr Subramani Kandasamy **KEY POINTS** **INTRODUCTION** Nutrition plays a crucial role in the...

**TITLE: NUTRITIONAL CONSIDERATIONS FOR ICU PATIENTS.** **[(Part 1: When, what and how to feed)]{.smallcaps}** **TRAINEE:** Dr Gothyang Makuya **SUPERVISOR:** Dr [Z]{.smallcaps}ainub Jooma **EDITOR:** Dr Subramani Kandasamy **KEY POINTS** **INTRODUCTION** Nutrition plays a crucial role in the care of patients in the intensive care unit (ICU), where adequate nutrition support is essential for optimising outcomes and promoting recovery (1). Nutrition is no longer a support, but a therapy in critically ill patients. The European Society for Clinical Nutrition and Metabolism (ESPEN) categorises the stages of critical illness into three distinct phases: the early acute phase (1-2 days ICU), the acute late phase (3-7 days ICU), and the recovery phase (\>7 days-months) (2). During the early acute phase, there is an initial response to stress characterised by increased metabolic rate, hyperglycaemia, and insulin resistance; however, energy expenditure in this stage is decreased (3). The hypercatabolic phase follows in the acute late phase, marked by a sustained increase in metabolic rate, muscle protein breakdown, and ongoing inflammatory response, all causing a rise in energy expenditure. Finally, the recovery phase focuses on anabolic processes, tissue repair, and restoration of normal metabolic functions. Understanding the pathophysiology of the stages is crucial for tailoring nutrition interventions to meet critically ill patients\' changing metabolic and nutritional needs throughout their ICU stay, thus reducing morbidity and mortality related to inappropriate nutritional therapy (4). The time periods for the phases of critical illness are arbitrary, with no current biomarker or metabolic monitor to indicate the change from one phase to the next (5). Early identification of nutritional risk, appropriate assessment of energy expenditure, and timely initiation of nutrition interventions are key components of a comprehensive approach to nutrition care in the ICU (1). Medical nutritional therapy (MNT) is not only aimed at preventing malnutrition and micronutrient deficiencies but also at achieving metabolic optimisation, preserving gut integrity and attenuation of stress-induced immune response (6). **NUTRITIONAL RISK ASSESSMENT** Conducting a nutritional risk screening for patients in the ICU is a crucial aspect of their care. A systematic review found that the prevalence of malnutrition ranged between 38% to 78% of ICU patients (7). Malnutrition is a substantial predictive risk factor for critically ill patients, impacting important outcomes such as duration of hospitalisation, length of time on mechanical ventilation, rates of infection and mortality (8). Most nutritional scoring systems identify patients with cachexia, low BMI (≤18.5-20.5kg/m2), \>5% weight loss in the last month, and reduced general condition as severely malnourished and high risk for malnutrition and recommended early medical nutritional therapy (9). Nutritional assessment in clinical practice lacks standardisation. Various tools such as the Nutritional Risk Screening (NRS) 2002, Nutrition Risk in Critically Ill (NUTRIC) score, modified-NUTRIC, the Subjective Global Assessment (SGA), and Malnutrition Screening Tool (MUST) are available and can be used (1, 6). However, the NRS-2002 and m-NUTRIC scores were designed for critically ill patients and proved superior in predicting clinical outcomes in critically ill patients. Both scoring systems pay special attention to nutrition status and disease severity. The ESPEN guidelines recommend a thorough clinical assessment, including a detailed medical history, evaluation of muscle mass and strength, unintentional weight loss, and body composition. ESPEN also suggests using a practical approach, considering patients at risk for malnutrition if they are expected to stay in the ICU for more than 48 hours, on ventilator support, have severe infections or chronic diseases, or were undernourished for more than five days prior to ICU admission (1, 3). **DETERMINING ENERGY REQUIREMENTS** To determine energy requirements, both ESPEN and ASPEN recommend using indirect calorimetry (IC) as the gold standard (3). This non-invasive method measures the volumes of consumed oxygen (VO2) and exhaled carbon dioxide (VCO2) through a ventilatory circuit and thus estimates the patient's resting metabolic rate and total energy expenditure. The Fick method is another way to calculate energy expenditure, but it relies on the placement of a pulmonary artery catheter, which limits its applicability in clinical practice (3). The resting energy expenditure (REE) can be calculated using Weir's equation with or without nitrogen measurements. Nitrogen is assumed to be biologically inactive, eliminating the need for urine measurements. The (REE) formula is as follows (10): REE (kcal/day) = 1.44 × (\[VO2(ml/min)\] × 3.94\] + \[VCO2(ml/min) ×1.11\]) - 2.17 (UN) In the absence of IC, ESPEN recommends using exhaled CO2 from the ventilator (Figure 1). Assuming that the respiratory quotient (RQ) is normal, EE can be calculated by substituting the VO2 with the RQ value of 0.86. RQ is calculated as VCO2/VO2, depending on the proportion of carbohydrates, fat, and protein consumed. An RQ of 0.86 is characteristic of most nutritional products. This adjustment allows for the use of a modified Weir's equation (9): EE (kcal/day) = VCO2 (ml/min) × 8.19 **(Figure 1)** IC has some limitations that may lead to unreliable results e.g. patients requiring high oxygen demands, nitrous oxide usage, hemodynamic instability, or ventilator adjustments (10). In the absence of IC or VCO2, ESPEN recommends using a calorie intake formula based on weight. This entails limiting calorie consumption to 20-25 kcal/kg/d progressively during the acute phase and increasing intake to 25-30 kcal/kg/d during recovery. Weight-based formulas may not be adequate for all people, particularly those who are underweight or overweight (3). An alternative approach to estimating energy requirements involves the use of predictive equations. Several such equations exist, including the Penn State, Mifflin-St Jeor, and Ireton-Jones. While these equations are commonly employed, there is currently no conclusive evidence to suggest that they are more accurate than the revised Harris-Benedict (H-B) equation. However, it should be noted that the H-B equation is based on data from average individuals and may not accurately reflect the energy needs of all individuals, particularly those with atypical stress levels (11). Harris-Benedict equations: **(Table A)** To accurately estimate total daily calorie requirements, the H-B equation must incorporate both activity level and stress factors. The equation becomes: Daily Calorie Requirement = Resting Energy Expenditure (REE) × Activity Level × Stress Factor Activity level factors consider the patient\'s mobility (bed-bound or ambulatory), while stress factors account for the impact of illness or injury on metabolic rate (12). Predictive equations, with a potential error margin of up to 60%, may overestimate or underestimate energy requirements (11). In response, Pavlidou et al. have developed a revised H-B equation tailored to various populations, including individuals with specific diseases, ethnicities, life stages, and body compositions (13). Following the initial Tight Calorie Control Study (TICACOS), three subsequent studies have been published comparing a MNT guided by IC to a regimen based on predictive equations. The ESPEN guidelines incorporated a meta-analysis of four publications, which revealed a favourable trend regarding short-term mortality in patients receiving MNT guided by IC (RR 1.28, 95%CI 0.98-1.67, p= 0.07). However, they did not find any significant differences in long-term mortality, infection rates, or length of stay (3, 14). Recent literature suggests that the role IC guidance of MNT may be more appropriate later in the acute phase of critical illness although this has not been adopted into the current guidelines (5). **WHAT TO FEED** Tailoring nutrient intake to the specific needs of critically ill patients is paramount. Key considerations that require regular assessment include the stage of critical illness (acute vs post-acute), the ability of the gastrointestinal system and metabolism to tolerate substrates, the primary disease being treated, other health conditions, pre-existing nutrient deficiencies and the trajectory of the patient\'s illness. **Macronutrients** **WATER:** 30ml/kg/day. Fluids provided by medications and enteral nutrition (EN) or parenteral nutrition (PN) contribute to this and should also be factored in the total fluid requirements (11). **ELECTROLYTES:** Sodium (Na+), Chloride (Cl--) = 1--2 mmol/kg/d Phosphate = 0.2--0.5 mmol/kg/d (11). **CARBOHYDRATES:** Carbohydrates accounts for 45-60% of calorie requirements (3, 15). Maximum recommended intake is 5mg/kg/min. **PROTEIN:** The suggested dose range is 0.8g/kg/day in the acute early phase and progressively increases to 1.3g/kg/day by day 4 of ICU. Frail and sarcopenic patients exhibit enhanced survival rates when consuming a protein intake of 1.3g/kg/day, as opposed to 0.8g/kg/day (3, 16). Conversely, septic patients demonstrate a lack of responsiveness to increased protein consumption. Increases up to 2g/kg/day later in critical illness may be necessary in obese, burns, and trauma patients (15). The EFFORT trial suggests that using high doses of protein (≥2.2g/kg/day) has not significantly improved mortality outcomes, with worse outcomes in cohorts of patients with acute kidney injury (AKI) and high multi-organ failure scores (SOFA score ≥9). These findings may be linked to the presence of anabolic resistance during the initial phases of critical illness (16, 17). **LIPIDS:** For intravenous lipids, the upper recommendation is 1g/kg/day with a tolerance of up to 1.5g/kg/day. Accounts for the remaining 30-40 % of the calorie requirement. Excess administration may lead to waste, storage, and toxicity. Propofol is a source of fatty acids that contain 1.1kcal/ml and can provide a significant energy load (3). **Micronutrients and** **Immunonutrition (INT):** Measuring of plasma levels of micronutrients in critical illness is unreliable as inflammation causes redistribution (5). Provision of maintenance doses of micronutrients is necessary (5). Most EN formulations are enriched with micronutrients, meeting the daily requirements of patients who consume ≥ 1500 kcal/d (18). However, additional supplementation may be necessary for special cases like trauma, major burns, and those requiring PN. Commercially available PN formulations lack micronutrients, including vitamins and trace elements, necessitating a separate prescription (3, 18). INT aims to provide specific nutrients that enhance immune function, reduce inflammatory responses, and support healing. INT components include glutamine, omega-3 fatty acids, arginine, antioxidants and nucleotides. Glutamine depletion is a common occurrence in critical illness, often linked to compromised immune function and intestinal barrier integrity. Glutamine supplementation may mitigate gut bacterial translocation, enhance immune cell activity, reduce proinflammatory cytokine production, and increase antioxidant levels. Enteral glutamine (0.2-0.3g/kg/d) can be considered for burn and trauma patients in the ICU for up to 5 days, potentially extending to 10-15 days in cases of complicated wound healing. However, its use in other ICU patients remains unestablished (3, 16). Fatty acids, including medium-chain triglycerides, omega-9, monounsaturated fatty acids, and omega-3 polyunsaturated fatty acids, play a role in critical illness. Omega-3 fatty acids, found in fish oils, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have documented anti-inflammatory properties and can modulate the production of inflammatory mediators, including eicosanoids and cytokines. Patients with conditions like adult respiratory distress syndrome, acute lung injury, and sepsis have shown improved outcomes in the length of stay, ventilator days and mortality with the use of enteral formulas enriched with borage oil and/or omega-3 fatty acids (19). The ESPEN practical guideline recommends considering omega-3 fatty acids supplementation for patients receiving EN (in nutritional doses) or patients requiring PN. However, high-dose omega-3 enriched enteral formulations should not be administered routinely or as bolus doses (3). Arginine has shown potential benefits in critically ill patients. However, caution is advised for patients with severe sepsis and septic shock due to its potential to increase nitric oxide production that can exacerbate hypotension (8). Antioxidant vitamins and trace elements, including vitamins C, D, and E, as well as zinc, copper, and selenium, are important in combating oxidative stress (20). (**Table B**) The guidelines currently do not recommend the routine use of INT in critically ill patient populations. Regular monitoring of nutritional status and immune function monitoring is crucial for optimising INT in ICU patients, and supplementation requires careful consideration on a case-by-case basis (21). **MODES OF NUTRITIONAL SUPPORT:** 1\. Oral: This is the most preferred method when the gastrointestinal tract (GIT) function is intact, and the patient can safely swallow and digest food and liquids without complications. 2\. Enteral: Nutrients delivered via a feeding tube directly into the GIT is a preferred method for patients unable to consume food orally or with difficulty swallowing but possessing intact gut function. Tubes can be inserted nasally, orally, or via the abdominal wall. ESPEN recommends establishing a gastrostomy or jejunostomy for patients anticipated to require enteral feeding for more than 3-4 weeks (22). 3\. Parenteral: Involves the direct infusion of artificial nutrients into the bloodstream via a vein. It is indicated when oral or enteral feeding is not feasible or contraindicated. PN encompasses two modalities: peripheral parenteral nutrition (PPN) and central parenteral nutrition (CPN). PPN is delivered through a peripheral intravenous catheter inserted into the arm or leg, while CPN requires a central venous catheter (CVC) or peripherally inserted central catheter (PICC) (22, 23). PPN can serve as a temporary nutritional supplement until enteral nutrition becomes feasible or as a rapid intervention when central venous access is unavailable. PPN offers several advantages over CPN, including reduced risks associated with central venous lines, minimised delays in nutritional support, and lower costs. However, PPN also carries certain drawbacks, such as a higher risk of thrombophlebitis, limitations in delivering a full complement of nutrients, unsuitability for prolonged feeding (4-7 days), and the need for solutions with lower osmolality compared to CPN (23). Central venous access devices for PN vary based on duration. Short-term catheters are non-tunnelled and intended for hospitalised patients requiring temporary nutrition. Medium-term catheters, such as PICCs and Hohn catheters, offer intermittent use and can support long-term PN for up to three months, both in and out of the hospital. PICCs are commonly used for home PN (HPN) but may pose challenges for self-care due to catheter placement. Long-term or home PN exceeding three months typically requires long-term venous access devices like cuffed tunnelled central catheters or implanted ports (22, 23). See Table 1. for a summary of indications, advantages and disadvantages of modes of MNT (3, 24). **(Table 1)** **WHEN AND HOW DO YOU DECIDE FEED TYPE** A comprehensive clinical assessment is essential for evaluating critically ill patients\' nutritional risk and severity of malnutrition. This assessment includes medical and weight loss history, physical examination, body composition analysis, and nutritional scoring. Patients staying in the ICU for more than 48 hours are at high risk of malnutrition and require priority attention to nutritional status. Oral intake should be prioritised over EN or PN for patients who can tolerate it. If oral feeding is not feasible, ESPEN recommends early initiation of low-dose EN within 48 hours, aiming to achieve the full energy target during the acute last phase of critical illness (5). PN may be considered as a last resort for severely malnourished patients when EN is contraindicated (3). However, PN should only be initiated during the acute **late phase** of critical illness (days 3-7) and after exhausting all reasonable strategies to improve enteral tolerance (3). Strategies include: - Temporarily stop EN or introduce EN at a low rate (trophic feeds) while monitoring for worsening symptoms of enteral feeding intolerance (EFI). - Patients at high risk for aspiration should be fed in a 35--40-degree head-up position - Use of prokinetics. ESPEN recommends using intravenous erythromycin as the first line of therapy, intravenous metoclopramide as a second line, or a combination of both. - Use of a jejunal tube, i.e. post-pyloric feeding. Post-pyloric tube placement demands specialised expertise; it may be less physiologically optimal than gastric EN and could pose risks in individuals with GIT motility issues beyond the stomach Post-pyloric feeding is advocated in patients with poor neurological status to reduce the risk of regurgitation. Consider supplementing with PN on a case-by-case basis in patients not tolerating full-dose EN during their initial ICU week, weighing safety and potential benefits (2, 3). Early initiation of full nutrition poses harm in a dose-dependent manner, regardless of the route of administration, and should be avoided (4, 5). This is due to the suppression of recovery pathways including autophagy and ketogenesis during the early catabolic phase (4, 5). Future research in the initiation of nutritional therapy needs to focus on identifying readiness for medical nutrition and monitoring response to nutritional therapy. Currently the use of biomarkers for this purpose has not been validated (5). Figures 2.1 and 2.2 summarises recommendations for deciding on nutritional therapy based on the ESPEN guidelines (3). **(Figures 2.1 and 2.2)** **SUMMARY** **MCQS** **REFERENCES** 1\. Moghaddam OM, Emam MH, Irandoost P, et al. Relation between nutritional status on clinical outcomes of critically ill patients: emphasizing nutritional screening tools in a prospective cohort investigation. *BMC Nutr*. 2024;10:69.2. Singer P, Blaser AR, Berger MM, et al. ESPEN guideline on clinical nutrition in the intensive care unit. *Clin Nutr*. 2019;38:48-79.3. Singer P, Blaser AR, Berger MM, et al. ESPEN practical and partially revised guideline: Clinical nutrition in the intensive care unit. *Clinical Nutrition*. 2023;42:1671-89.4. Gunst J, Casaer MP, Preiser JC, et al. Toward nutrition improving outcome of critically ill patients: How to interpret recent feeding RCTs? *Crit Care*. 2023;27:43.5. de Man AME, Gunst J, Reintam Blaser A. Nutrition in the intensive care unit: from the acute phase to beyond. *Intensive Care Med*. 2024;50:1035-48.6. Domenech-Briz V, Gea-Caballero V, Czapla M, et al. Importance of nutritional assessment tools in the critically ill patient: A systematic review. *Front Nutr*. 2022;9:1073782.7. Dixit SB, Tiwari NR, Zirpe KG, et al. How Have Nutrition Practices in the ICU Changed in the Last Decade (2011-2020): A Scoping Review. *Cureus*. 2021;13:e15422.8. Hill A, Elke G, Weimann A. Nutrition in the Intensive Care Unit-A Narrative Review. *Nutrients*. 2021;13.9. Narayan SK, Gudivada KK, Krishna B. Assessment of Nutritional Status in the Critically Ill. *Indian J Crit Care Med*. 2020;24:S152-S6.10. Moonen H, Beckers KJH, van Zanten ARH. Energy expenditure and indirect calorimetry in critical illness and convalescence: current evidence and practical considerations. *J Intensive Care*. 2021;9:8.11. Chowdhury R, Lobaz S. Nutrition in critical care. *BJA Educ*. 2019;19:90-5.12. Bendavid I, Lobo DN, Barazzoni R, et al. The centenary of the Harris-Benedict equations: How to assess energy requirements best? Recommendations from the ESPEN expert group. *Clin Nutr*. 2021;40:690-701.13. Pavlidou E, Papadopoulou SK, Seroglou K, et al. Revised Harris-Benedict Equation: New Human Resting Metabolic Rate Equation. *Metabolites*. 2023;13(2):189.14. Singer P, De Waele E, Sanchez C, et al. TICACOS international: A multi-center, randomized, prospective controlled study comparing tight calorie control versus Liberal calorie administration study. *Clin Nutr*. 2021;40:380-7.15. 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;40:159-211.16. Singer P. Protein metabolism and requirements in the ICU. *Clin Nutr ESPEN*. 2020;38:3-8.17. Heyland DK, Patel J, Compher C, et al. The effect of higher protein dosing in critically ill patients with high nutritional risk (EFFORT Protein): an international, multicentre, pragmatic, registry-based randomised trial. *Lancet*. 2023;401:568-76.18. Berger MM, Shenkin A, Dizdar OS, et al. ESPEN practical short micronutrient guideline. *Clinical Nutrition*. 2024;43:825-57.19. Weimann A, Braga M, Carli F, et al. ESPEN practical guideline: Clinical nutrition in surgery. *Clinical Nutrition*. 2021;40:4745-61.20. Manzanares W, Dhaliwal R, Jiang X, et al. Antioxidant micronutrients in the critically ill: a systematic review and meta-analysis. *Crit Care*. 2012;16:R66.21. Ay N, Derbent A, Kiyak H, et al. Evaluation of immunomodulatory nutrients in critically ill patients in the intensive care unit. *North Clin Istanb*. 2022;9:557-64.22. Pittiruti M, Hamilton H, Biffi R, et al. ESPEN Guidelines on Parenteral Nutrition: central venous catheters (access, care, diagnosis and therapy of complications). *Clin Nutr*. 2009;28:365-77.23. Khan A, Laing E, Beaumont A, et al. Peripheral parenteral nutrition in surgery - a systematic review and meta-analysis. *Clin Nutr ESPEN*. 2023;54:337-48.24. Farkas J. Critical Care Nutrition. Available from: https://emcrit.org/ibcc/food/. \[Accessed on 12 June 2024\]