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Is it Possible and Necessary to Estimate Energy Requirements in the Critically Ill?

Is it Possible and Necessary to Estimate Energy Requirements in the Critically Ill?. Pete Turner Senior Nutritional Support Dietitian. Estimating energy requirements. This could be relatively easy in a healthy individual… Formulae to estimate BMR (REE) Schofield/Harris Benedict

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Is it Possible and Necessary to Estimate Energy Requirements in the Critically Ill?

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  1. Is it Possible and Necessary to Estimate Energy Requirements in the Critically Ill? Pete Turner Senior Nutritional Support Dietitian

  2. Estimating energy requirements • This could be relatively easy in a healthy individual… • Formulae to estimate BMR (REE) • Schofield/Harris Benedict • Activity factors / PARs • Is an ITU patient different?

  3. The ICU Patient

  4. The inflammatory response. • Similar responses seen in trauma, burns, sepsis and surgery. • Involves local and systemic reactions. • Extent of reaction proportional to severity of insult. • Excessive response can produce a systemic response e.g. SIRS and MODS.

  5. Inflammatory response. • Tissue injury results in release of cytokines. • Important cytokines include TNFα, IL-1, IL-2, IL-6, interferon and prostaglandins e.g. E2… regulate response. • Endocrine response includes the release of glucocorticoids eg cortisol…. Catabolic… insulin antagonism. • ?Proteolysis inducing factor (PIF) and intracellular catabolic processes in skeletal muscle (Curtis et al 2002, Nutrition 18, 971-977).

  6. Effects of inflammatory response • Catabolism… negative nitrogen balance (up to 20g /day, Campbell 1999). • Weight loss, ↓skeletal muscle & contractile proteins – weakness and fatigue (Curtis et al 2002) • Acute ICU patients can lose 5-10% muscle per week (Griffiths 2003) • Synthesis of acute phase proteins. • Lipolysis and gluconeogenesis. • Insulin resistance & hyperylcaemia • Hypermetabolism • Anorexia • ↑ vascular permeability and hypoalbuminaemia.

  7. Nutritional Support on ICU. • Can we completely reverse the malnutrition caused by the inflammatory response with nutritional support?

  8. Nutritional Support on ICU • It would seem logical to give as much energy and protein as possible to try to reverse these effects… • But several studies show aggressive nutritional support does not prevent loss of lean mass (Frankenfield et al 1997, JPEN, 21(6): 324-9, Shaw et al 1987, Ann Surg, 209, 63-72.) • Streat et al 1987, J. Trauma 27, 262-266. MOF patients lost 12.5% body protein despite 10 days of PN giving 2400kcal, 20gN.

  9. Energy Balance • Achieving energy balance does not prevent muscle wasting in critically ill. • Shown in 2 studies on mid arm circumference on ITUs (Reid et al Clin Nut 2004, 23(2) 273-80, Green et al Clin Nut 1995 11(6): 739-46 • Achieving energy balance may be over feeding • So what if we are overfeeding?

  10. Studies on outcome - TPN • Heyland meta-analyses in the critically ill and surgical patients (JAMA 1998 280(3) 2013-9. Can J Surg 2001 44(2) 102-11) • May↑morbidity compared to standard treatment, especially sepsis. • Only beneficial in malnourished surgical patients. • Did not recommend TPN in the critically ill. • Speculation that ↑morbidity due to excess energy as lipid or dextrose. • Can we explain these findings?

  11. Complications of TPN • Hyperglycaemia… sepsis • Hyperlipidaemia • Azotaemia • Hypercapnia • Abnormal LFTs • Hepatic steatosis • Impaired immune function. • Line sepsis. • Bacterial translocation (Deitch 2002, Surgery, 31(3) 241-4) • Klein 1998 JADA ,7, 795 – 806, Angelico et al Aliment Pharmacol Ther 2000 Supp 2: 54-57.

  12. Peritonitis (animal model) Peck et al 1989

  13. Intensive Insulin Therapy in Critically Ill PatientsVan den Berghe et al. NEJM 2001; 345:1359-1367. • PRCT in 1548 adults on surgical ICU. Insulin to maintain glucose <6.0 mmol vs. insulin to maintain glucose <12 mmol • Also reduced in-hospital mortality by 34%, bloodstream infections by 46%, ARF requiring haemo-filtration by 41%. P<0.005 P<0.04

  14. Overfeeding • Overfeeding increases morbidity in metabolically stressed patients. • Key paper: Changing concepts of nutrient requirements in disease. Elia 1995, Lancet 345, 1279-1284. • Energy requirements previously overestimated… infusion of large amounts of nutrients raises energy expenditure by up to 30%. • Hypermetabolism offset by inactivity.

  15. What should we do? • Impossible to reverse the catabolic response. • Overfeeding increases morbidity. • Provision of adequate nutrients to attenuate losses… • But not enough to cause problems of overfeeding. • Although we cannot stop catabolism we can reduce losses with feeding (Michie 1996 World J. Surg 20(4) 460-4, Shaw 1987) • ACCEPT study showed improved ICU survival when evidence based nutrition guideline is followed • Replete losses in recovery - when metabolically stable increase energy and nitrogen.

  16. Recommendations for energy • American College of Chest Physicians 25kcal/kg (Cerra, Chest 1997. 111: 769-78) • ASPEN (2002) 20 – 30kcal/kg (JPEN 26(1) Supp) • Muller (1995) 14kcal/kg • Patino et al ’99 20kcal/kg (World J Surg 23 (6) 553-9) • Pomposelli 1994 estimated BMR (New Horizons 2, 224 – 9) • Intensive Care Society (ICS) 2000 estimated BMR • ICS 2004. 25 kcal/kg (www.ics.ac.uk standards and publications) • Keep energy low while unstable - increase when recovering (Mechanick Crit Care Med 2002,18 (3) 597-618)

  17. Energy requirements • Many recommendations / methods • All ESTIMATE requirements • Just give a starting point • Should we just start at 1500kcal? • Or small, medium and large regimens? • Monitoring and adjusting MORE important • Requirements change • Patients can arrive looking like…

  18. And leave looking like…

  19. Most Recent Recommendations • ESPEN 2006 • Feeding more than 20 – 25kcal/kg may be associated with poor out come outcome when metabolically stressed • Give 25-30kcal/kg in the anabolic flow phase… 10 – 40 days • NICE 25-35kcal/kg when stable – less when metabolically stressed (e.g on ICU).

  20. Stress Factors • Controversial • Survey of 115 UK dietitians found a vast variation in stress factor use (AJ Green 2006) • Designed to estimate energy expenditure • Achieving energy balance is not beneficial • Stress factors add energy at the worst time – when patients are most metabolically stressed • ESPEN and NICE say give less energy when metabolically stressed.

  21. Example • 75kg severely septic male, 28 yrs old. • BMR = 15.1x 75=692 • Stress factor = 20% – 60% • 2190 – 2920kcal/day • Bed bound immobile + 10% • 2409 – 3212kcal/day • 32 – 43kcal/kg/day • Contrary to ESPEN and NICE

  22. Other Problems • AACN – equation predictions vary 15-20% in healthy… 30 – 40% in critically ill • Other Formulae e.g Ireton Jones? • Require accurate weight – oedema etc?

  23. Practical recommendations. • Feed to 20 – 25 kcal/kg or BMR by Schofeild or low starting point when metabolically unstable. • Monitor carefully for signs of overfeeding e.g. hyperglycaemia, hypercapnia, ↑lipids,↑LFTs. • Increase energy and nitrogen when recovering. • It is argued that patients build up a nutritional debt on the ICU that must be repaid (Villet et al 2005) • This debt can only be repaid when the bank is open… • i.e. when the patient is in an anabolic phase…

  24. Recognising recovery • Signs that a patient is entering an anabolic phase include: • Oedema resolving. • Hyperglycaemia resolving & ↓insulin requirements. • ↓C reactive protein levels (CRP) • Patient is mobilising. • Appetite returning • Serial prealbumin measurements may show the switch to anabolism. Weekly increase over 40mg/l Bernstein et al 1995, Nutrition11(2), 169-171.

  25. Conclusions • Impossible to calculate requirements • Many methods – huge variation • Just a staring point • Dietitians should be more involved with metabolic monitoring and adjusting • Keep energy low when stressed – increase in recovery • Energy expenditure and requirements – not the same • Stress factors add energy at the wrong time • Using them is contrary to ESPEN and NICE

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