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Transcript of Nutrition
Nutritional Support in the ICUNutritional Support in the ICU
M.M. Brandt, MD, FACS, FCCMM.M. Brandt, MD, FACS, FCCM I.S. Rubinfeld, MD, FACS, FCCPI.S. Rubinfeld, MD, FACS, FCCP
Henry Ford HospitalDetroit, MI
Reasons for SupportReasons for Support
Limit catabolism
Substrate for healing
Increase survival
Baseline Patient AssessmentBaseline Patient Assessment
History of weight loss
% ideal body weight
Immune studies• anergy, total lymphocyte count
Serum proteins• albumin, transferrin, prealbumin
Measurement of lean body mass
Surgery: Scientific Principles and PracticeSurgery: Scientific Principles and Practice
Stimuli for Stress ResponseStimuli for Stress Response
Blood volume
pH/pCO2/pO2
Emotion/pain/fear
Substrate availability
Temperature
Infection
Tissue injury
Goals of Stress ResponseGoals of Stress Response
Maintain energy substrates (GLUCOSE)
Maintain oxygen delivery
Minimize further injury
Greenfield 1997
Response to Stress/InjuryResponse to Stress/Injury
Neurohormonal - “Counterregulatory Hormones”• Glucagon
• Epinephrine
• Glucocorticoids
Inflammatory Mediators• IL-1, IL-2, IL-6
• TNF-a
• IFN-g
Glucose Dependent OrgansGlucose Dependent Organs
Brain(ketoadaptive)
RBC, WBC
Healing tissue
Renal medulla
Glucose PrecursorsGlucose Precursors
Pyruvate/lactate
Alanine/glutamine
Glycerol
Glycogen
Energy Substrates: CarbohydratesEnergy Substrates: Carbohydrates
Glucose - parallels degree of injury
Increased hepatic production of 3 - carbon precursors (fat/AAs)
Breakdown of liver glycogen
Energy Substrates: Amino AcidsEnergy Substrates: Amino Acids
Skeletal muscle breakdown skewed toward alanine and glutamine
Muscle nitrogen transferred to visceral organs• Glutamine major source for enterocyte oxidation• Glutamine transfers ammonia groups in kidney• Alanine in liver leads to gluconeogenesis
Greenfield 1997
Energy Substrates: FatEnergy Substrates: Fat
Lipolysis under catecholamine regulation
Provides 3-carbon fragments to the liver
Major provider of energy substrates in early sepsis and trauma (regulated through leptin?)
Metabolic NeedsMetabolic Needs
Formulae: (starting point for feeding)• Harris-Benedict Equation• Ireton Jones Equation
Nitrogen Balance
Resting Energy Expenditure
Goal Calculations: Goal Calculations: Ireton JonesIreton Jones
Developed for intubated patients
1784 - 11(A) + 5(W) + 244(S) + 239(T) + 804(B) for total calorie prescription
A = age W = wt in kg S = sex (1 = male, 0 = female) T = trauma (1 = yes, 0 = no) B = burns (1 = yes, 0 = no)
Harris-Benedict EquationHarris-Benedict Equation
Estimates Basal Metabolic Rate (BMR):• Male BMR kcal/day =
66.47 + 13.7 (kg) + 5 (cm) - 6.76 (yrs)
• Female BMR kcal/day =
665.1 + 9.56 (kg) + 1.85 (cm) - 4.68 (yrs)
Harris-Benedict Equationhttp://www-users.med.cornell.edu/~spon/picu/calc/beecalc.htm
Harris-Benedict EquationHarris-Benedict Equation
Factors to add to the BMR:• 25%
- mild peritonitis, long bone fracture or mild/moderate trauma
• 50%- severe infection, MSOD, severe trauma
• 100%- burn of 40 to 100% TBSA
Nitrogen BalanceNitrogen Balance
Measure/estimate all sources of nitrogen output• stool, urine, skin, fistulae, wounds, etc.
Measure all sources of nitrogen input• enteral or parenteral nutrition
Greenfield 1997
Calculating Nitrogen BalanceCalculating Nitrogen Balance
Problems with Nutritional ParametersProblems with Nutritional Parameters
UUN will be invalid if creatinine clearance is
less than 50.less than 50.
UUN and prealbumin are not helpful if the patient has not
received goal volumes of feeding consistently for three
to four days prior to the test.
Metabolic CartMetabolic CartIndirect Calorimetry: Indirect Calorimetry: TheoryTheory
Measures O2 absorbed in lungs
Assumptions of Fick equation, at steady state O2 absorbed equals O2 consumed
Metabolic rate in cc of O2 per minute
Conversion 5kcal/liter O2
24 hour steady state measurement recommended
Theory - start with a formula, tune it up long-term with the metabolic cart!
Metabolic Cart - Indirect Calorimetry: Metabolic Cart - Indirect Calorimetry: ResultsResults
RQ or respiratory quotient (CO2 expired/O2 inspired)
0.6 - 0.7 starvation/underfeeding
0.84 - 0.86 desired range/mixed fuel utilization
0.9 - 1.0 carbohydrate metabolism
1.0 + overfeeding/lipogenesis
Other Clinical ParametersOther Clinical Parameters
Wound healing
Measured proteins• Albumin (t½ = weeks)
• Prealbumin (t½ = days)
Non-water weight gain
Enteral vs. Parenteral?Enteral vs. Parenteral?
Use the GI tract whenever possible
Contraindications to GI feeds• large output fistula
• SBO
• severe pancreatitis
• short gut, severe diarrhea, enteritis
• non-functional GI tract
Starting EstimatesStarting Estimates
Determine number of calories needed
Determine normal or increased protein needs
Determine if contraindication to fats
Determine fluid restrictions
USE THE GI TRACT IF POSSIBLE
NutrientsNutrients
Fat - essential linolenic, linoleic, arachidonic acids• 9 kcal/gm
Protein - essential and branched chain AA in TPN• 4 kcal/gm - not to be included in calorie estimates
• no glutamine in TPN due to instability
Carbohydrates - converted to glucose• 3.4 kcal/gm (4.0 kcal from endogenous source)
NutrientsNutrients
Trace Minerals• Chromium, copper, zinc, manganese, selenium, iron
Vitamins• Thiamine
• Folate
• Vitamin C
Rules of Thumb: TPNRules of Thumb: TPN
Want 25 - 35% solution of dextrose
Want 4.25 - 6% AA solution• normal 0.8 gm/kg/day up to 2.0 gm/kg/day
Kcal/nitrogen ratio• normal 300:1
• post-op 150:1
• trauma/sepsis 100:1
Lipids 10 - 20% at least twice per week
TPN ExampleTPN Example
2 liters of 25% dextrose• 500 gm dextrose X 3.4 Kcal/gm = 1700 Kcal
500 cc of 20% lipids• 100 gm lipids X 9 Kcal/gm = 900 Kcal
TPN vs. Enteral: Advantages?TPN vs. Enteral: Advantages?
Many prospective, randomized studies• TPN group had much higher infection rates
- pneumonia, intraabdominal abscess, line sepsis
Potential Reasons for TPN FailurePotential Reasons for TPN Failure
TPN increases blood glucose if not strictly controlled• numerous studies now show hyperglycemia increases mortality and
infectious complications
Does not contain glutamine
Why Enteral?Why Enteral?
Preservation of villous architecture• may prevent translocation
• role of translocation unclear in humans
• good study in BMT patients
Ability to give glutamine• major fuel of enterocytes
• major nitrogen transfer agent to viscera
• in catabolic stress may be an essential AA
Timing of Enteral FeedsTiming of Enteral Feeds
Many studies claim benefits to early EN
Meta-analysis (Marik and Zaloga Crit Care Med. 2001)
• looked at 27 randomized,prospective studies
• early EN had lower infections (RR 0.45)
• early EN had shorter LOS (2.2 days)
RefluxReflux
80% reflux with NG in supine position
50% reflux without NG in supine position
12.5% reflux without NG if semi-recumbent
Gastric vs. Post-pyloric FeedsGastric vs. Post-pyloric Feeds
Route probably not important if patient tolerating feeds
If gastric ileus, recent surgery, or need for frequent procedures where feeds would be stopped if gastric, post-pyloric may be better.
Anabolic Steroids (Oxandrolone)Anabolic Steroids (Oxandrolone)
Hart et al. Annals of Surgery. 2001 • increases muscle protein net balance
Wolf et al. Annals of Surgery. 2003• improves net protein balance
Demling. J Trauma. 1997 • increases weight gain in recovery phase post burns
NO data that LOS different
Physical therapy assessments were better
Refeeding SyndromeRefeeding Syndrome
In severely malnourished
Development of severe electrolyte abnormalities:• phosphorous, potassium, magnesium
As muscle mass, cell mass, and ATP repleted:• may reach critically low values, cardiac arrest
Theoretical Advantages of Early Enteral Theoretical Advantages of Early Enteral NutritionNutrition
1. Ameliorate the stress response, hypermetabolism, and hypercatabolism.
2. Provide gut stimulation to prevent atrophy and the loss of immunologic and barrier functions of the gut.
3. Minimize rapid onset of acute malnutrition.
4. Decrease LOS and complication rates.
Energy Requirement in Critical Illness: Energy Requirement in Critical Illness: Different ConditionsDifferent Conditions
Greenfield 1997
Total Kcal GoalsTotal Kcal Goals
25 - 35 kcal/kg is suitable for most hospitalized patients and is a good rule of thumb
21 kcal/kg is appropriate for obese patients
30 - 40 kcal/kg may be necessary for highly stressed patients
Total Protein GoalsTotal Protein Goals
1.0 g/kg for healthy individuals
1.2 - 1.5 g/kg for mildly stressed
1.5 - 2.0 severely stressed/multiple trauma/head injury/burns
Lipid GoalsLipid Goals
High calorie, low volume
Suggested max calories - no more than 50% of non-protein Kcal, or < 1 cal/Kg/hr
Minimum to prevent EFAD is 2 x 500 cc bottles/week
Diprivan (propofol) = 1calorie/ml
Nutritional AlgorithmNutritional Algorithm
Greenfield 1997
Consequences of OverfeedingConsequences of Overfeeding
1. Azotemia - patients > 65 years and patients given > 2g/kg protein are at risk.
2. Fat-overload syndrome - recommended maximum is 1g lipid/kg/d. Infuse IV lipid slowly over 16 - 24 hours.
3. Hepatic steatosis - patients receiving high carbohydrate, very low fat TPN are at risk.
4. Hypercapnia - makes weaning difficult.
5. Hyperglycemia - increases risk of infection. Glucose should not exceed 5 mg/kg/min (4 mg/kg/min for diabetics).
Consequences of OverfeedingConsequences of Overfeeding
6. Hypertonic dehydration - can be caused by high-protein formula with inadequate fluid provision.
7. Hypertriglyceridemia - propofol, high TPN lipid loads, and sepsis increase the risk. If the patient is hypertriglyceridemic, decrease lipid to an amount to prevent EFAD (500 cc 10% lipid twice weekly) and monitor.
Consequences of OverfeedingConsequences of Overfeeding
8. Metabolic acidosis - patients receiving low ratios of energy to nitrogen are at risk. Acidosis can cause muscle catabolism and negative nitrogen balance.
9. Refeeding syndrome - common in malnourished patients or those held NPO prior to initiation of feeding. Start feedings conservatively, advance gradually, and monitor Mg, Ph, and K closely.
Nutritional GoalsNutritional Goals
Feed as soon as hemodynamically stable, after adequate resuscitation.
No disease state improves with starvation.
Poor gut perfusion may contraindicate enteral feeds, but enteral feeds are always preferred when possible.
Clinical Scenario 1Clinical Scenario 1
42-year-old 80-kg man with 40% burn needs approximately how many calories?
Harris Benedict Equation• Male BMR kcal/day =
– 66.47 + 13.7 (kg) + 5 (cm) - 6.76 (yrs)
BEE = 1793 kcal/day
Calorie requirement (adding stress factor of 2.2 for burn > 40%) = 3,945 kcal/day
Scenario 1 Scenario 1 (cont.)
Ireton Jones Equation• 1784 - 11(A) + 5(W) + 244(S) + 239(T) + 804(B) for total calorie
prescription
• A = age W = wt in kg S = sex (1 = male, 0 = female) T = trauma (1 = yes, 0 = no) B = burns
1,910 kcal/day - This does not take into account specific stress factors based on size of wounds, activity, fever, etc.
Scenario 2Scenario 2
A 65-year-old female patient develops pneumonia and respiratory failure.
She is known to have COPD and diabetes mellitus.
You are unsuccessful in initial weaning attempts.
What are the main nutritional issues as they relate to this patient?
Scenario 2Scenario 2
What are the caloric needs?
What means of nutrition would you use?
When discussing nutrition:• What are the issues relating to COPD? Diabetes? Difficult to wean
patients?
ReferencesReferences
1. Marik PE. Zaloga GP. Early enteral nutrition in acutely ill patients: a systematic review. Crit Care Med. 2001;29(12):2264-70.
2. McClave SA, et al. Poor validity of residual volumes as a marker for risk of aspiration in critically ill patients. Crit Care Med. 2005;33(2);449-50.
3. Souba WW, Austen WG. Nutrition and Metabolism. In Mulholland MW, Oldham KT, et al (eds). Surgery: Scientific Principles and Practice. 2nd ed. Greenfield LJ, Lippincott-Raven, New York, 1997.
ReferencesReferences
4. Hart DW, et al. Anabolic effects of oxandrolone after severe burn. Annals of Surgery. 2001;233(4):556-64.
5. Wolf SE, et al. Improved net protein balance, lean mass, and gene expression changes with oxandrolone treatment in the severely burned. Annals of Surgery. 2003;237(6):801-10; discussion 810-1.
6. Demling RH. DeSanti L. Oxandrolone, an anabolic steroid, significantly increases the rate of weight gain in the recovery phase after major burns. J Trauma-Inj Inf Crit Care. 1997;43(1):47-51.