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Nutritional Requirements and Enteral Support of the Critically Ill,
Ventilated Patient
John P. Grant, MD, CNSPDirector Nutrition Support Service
Professor of SurgeryDuke University Medical Center
Durham, NC
Nutritional Requirements and Enteral Support of the Critically Ill,
Ventilated Patient
Slides available at:http://tpnteam.com
Optimal Metabolic Care of the Critically Ill, Ventilated Patient
Optimize milieu for cell metabolism
Minimize stress response
Provide adequate and appropriate nutritional support
Optimal Metabolic Care of the Critically Ill, Ventilated Patient
Provide Optimal Metabolic Milieu
Establish and maintain oxygenation
Adjust pH
Ensure adequate tissue perfusion
Control waste (dialysis)
Optimal Metabolic Care of the Critically Ill, Ventilated Patient
Provide Optimal Metabolic Milieu Minimize Metabolic Stress Response
Control painDebridement of necrotic/infected tissueDrain abscessesDress or cover wounds
Optimal Metabolic Care of the Critically Ill, Ventilated Patient
Optimize milieu for cell metabolism
Minimize stress response
Provide adequate and appropriate nutritional support
Importance of Adequate Nutrition
Nutrient balance and mortality in ICU patients
4/15 with positive caloric balance died (27%)
11/28 with 0 to -10,000 kcal balance died (39%)
12/14 with > -10,000 kcal balance died (86%)
Bartlett et al., Surgery 92:771, 1982
Caloric Balance and Outcome in ICU
A = positive caloric balance
B = 0 to -10,000 kcal balance
C = > -10,000 kcal balance
27%39%
86%
0102030405060708090
A B C
Caloric Balance vs % Mortality
Bartlett et al., Surgery 92:771, 1982
Days = { [(UBW X 2430) x K] - [(UBW - BW) x 2430]}
AEE - Ei
Where:
Days of Survival Without Nutrition
UBW = usual body weight in kgBW = current body weight in kg K = 0.35 with stress; 0.40 with simple starvation AEE = actual energy expenditure (kcal/d)Ei = energy intake (kcal/d)
Importance of Adequate Nutritionin Respirator Dependent Patients
Arora and Rochester evaluated the effects of malnutrition on diaphragmatic muscle dimensions at necropsy and in vivo function in patients after prolonged illness (75% UBW) as compared with well nourished patients
Diaphragmatic muscle mass
43% less
Max Inspiratory Vacuum 35% normal
Max Expiratory Pressure 59% normal
Max Ventilatory Volume 41% normal
Arora and Rochester: Am. Rev. Respir. Dis., 126:5-8, 1982.
Impact of Malnutrition on Pulmonary Function
Sahebjami and Wirman studied the lungs of adult rats subjected to 3 weeks of semi-starvation (approximately 40 percent loss of total body weight). They found:
• Marked emphysematous changes
• An increase in size of air spaces and reduction in alveolar wall surface tension
• Elastic fibers were shortened, irregular, and fewer in number
Sahebjami and Wirman: Am. Rev. Respir. Dis., 124:619-624, 1981.
Impact of Malnutrition on Pulmonary Function
• Reticular fibers were unchanged
• Biochemical measurements demonstrated a reduction in desaturated lecithin. Because lecithin is a major component of surfactant, it was proposed that alveolar collapse with emphysematous changes might be expected
• Refeeding the rats corrected desaturated lecithin concentrations but failed to reverse the morphological emphysematous changes
Sahebjami and Wirman: Am. Rev. Respir. Dis., 124:619-624, 1981.
Impact of Malnutrition on Pulmonary Function
Doekel et al. placed volunteers on a balanced 550 kcal/day diet for 10 days and demonstrated a 20% reduction in basal oxygen consumption and a 58% reduction in their ventilatory response to hypercapnea. (N. Engl. J. Med., 295:358-361, 1976)
Askanazi et al. fed volunteers a hypocaloric (550 Kcal/day), balanced diet for 10 days and demonstrated a 58% reduction in ventilatory response to hypoxia. (Anesthesiol. 53(Supp 1):185, 1980)
Refeeding in both studies restored normal function
Impact of Malnutrition on Pulmonary Function
Minnesota Experiment: Routine pulmonary function tests were performed before and after 24 weeks of semi-starvation
• Vital capacity, tidal volume, and minute ventilation decreased by 7, 19, and 31 percent, respectively
• Refeeding resulted in improvement but incomplete recovery, even after 12 weeks
Keys et al.: The Biology of Human Starvation. Minneapolis, University of Minnesota Press, 1950.
Impact of Malnutrition on Pulmonary Function
Duke data, unpublished: Recovery of Organ Function With 2 Weeks of TPN in 21 Malnourished, Non-stressed Patients
Impact of Malnutrition on Pulmonary Function
Recovery of Organ Function With 2 Weeks of TPN in 21 Malnourished, Non-stressed Patients. Duke data, unpublished
Function
Numberof
Patients
Pre-TPN
Post-TPN
PercentChange
p-value
Maximal expiratory pressure
21 59% 69% 17 <0.02
Maximal inspiratory vacuum
21 43% 52% 23 <0.002
Impact of Malnutrition on Pulmonary FunctionBassili and Deitel, and Mattar et al. evaluated
the effects of inadequate nutritional support on the ability to wean patients from mechanical ventilation. Combining their results:
22 of 25 patients (88%) who received adequate nutritional support could be weaned from the respirator, whereas only 10 of 31 patients (32%) who did not receive adequate support were able to be weaned (p < .001)
Bassili and Deitel: J.P.E.N. J. Parenter. Enteral Nutr., 5:161-163, 1981. Mattar et al.: J.P.E.N. J. Parenter. Enteral Nutr., 2:50, 1978.
Adequate Nutritional Support of Critically Ill, Ventilated Patients
Protein Support – normal - Adjust for co-existing illnesses and to achieve positive nitrogen balance, reduce for renal and hepatic dysfunction
No stress 0.7 to 0.8 g/kg/day
Mild Stress 0.8 to 1.0 g/kg/day
Moderate Stress 1.0 to 1.5 g/kg/day
Severe Stress 1.5 to 2.0 g/kg/day
- What to Give -
Adequate Nutritional Support of Critically Ill, Ventilated Patients
Caloric Support – Ireton-Jones formula
Recently re-designed, specifically for ventilator-dependent patients in the ICU:
BEE = 1784 - 11(A) + 5(W) + 244(S) 239(T) + 804(B)
Where: A = age in years, W = weight in kilograms,S = sex (male = 1, female = 0), and T = trauma and B = burn (present = 1, absent = 0)
Ireton-Jones, C., NCP, 17:29-31, 2002
Adequate Nutritional Support of Critically Ill, Ventilated Patients
Caloric Support – Cal Long Modification of H-B
AEE (men) = (66.47 + 13.75 W + 5.0 H - 6.76 A) x (activity factor) x (injury factor)
AEE (women) = (655.10 + 9.56 W + 1.85 H - 4.68 A) x (activity factor) x (injury factor)
Activity Factor Use Injury Factor Use
Confined to bed 1.2 Minor OR 1.2
Out of Bed 1.3 Skeletal Trauma 1.3
Major Sepsis 1.6
Severe Burn 2.1
Adequate Nutritional Support of Critically Ill, Ventilated Patients
Caloric Support – Swinamer formula
Specifically for critically ill ventilated patients in the ICU:
REE = BSA(941) + Tmax(104) + RR(24) +Vt(804) - 4243
Where: BSA = body surface area, T = temperature, RR = respiratory rate, Vt = tidal volume
Swinamer, D.L. et al. Crit. Care Med., 18:657-661, 1990
Adequate Nutritional Support of Critically Ill, Ventilated Patients
Excessive calories can result in excessive CO2
production, increased arterial pCO2, RQ > 1.0, and increased ventilatory demand in the already compromised ventilated patient.
May delay weaning
May render respiratory support difficult
Adequate Nutritional Support of Critically Ill, Ventilated Patients
In ventilatory dependent patients, a high
caloric load (2 X REE) has been shown to
result in significantly higher O2 consumption
and CO2 production than a moderate load
(1.5 X REE) in patients otherwise receiving an
identical diet
Van den Berg and Stam: Intensive Care Medicine, 14:206-211, 1988.
Adequate Nutritional Support of Critically Ill, Ventilated PatientsClearly, total caloric intake has a greater impact on CO2 production and respiratory function than does the ratio of CHO/fat (varying CHO content from 40-75% of total calories has little impact)
Recommend 1.2 to 1.5 times REE (up to 5 mg/kg/min CHO infusion – 40 to 50% of total calories as CHO)
Van den Berg and Stam: Intensive Care Medicine, 14:206-211, 1988.
Talpers et al: Chest, 102:551-555, 1992.
As increasing amounts of glucose are infused, a maximal rate of glucose oxidation and whole body protein synthesis is obtained at 5.0 to 6.0 mg/kg/min (~630 g/d for 80 kg patient)
Burke et al.,Ann Surg, 190:274, 1979
Use of Insulin to Stimulate Glucose Utilization
Does lower blood sugar in most cases
Drives glucose mainly into muscle
No documented increase in glucose oxidation or nitrogen sparing
Vary et al., JPEN 10:351, 1986
Use of Insulin in Glucose Utilization
Anaerobic Glycolysis
Pyruvate
Pyruvate Dehydrogenase
Krebs cycle Fat Synthesis
Insulin
Optimal Metabolic Care of the Critically Ill, Ventilated Patient
Benefits of
Early Enteral Nutrition
vs.
Parenteral Nutrition
Early Enteral Nutrition
Initiation of enteral nutrition within 24 to 48 hours of hospitalization or catastrophic event
Initiation of nutrition support after 72 hours may have no appreciable effect on morbidity
Early Enteral Nutrition
Reduces hypermetabolism in trauma, burn, and postoperative patients
Postburn Hypermetabolism and Early Enteral Feeding
30% BSA burn in guinea pigsEnteral feeding via g-tube at 2 or 72 hours following burnMucosal weight and thickness were similar
100
120
140
150
160
0 2 4 6 8 10 12
RME % Initial
Postburn day
175 Kcal - 72 h
200 Kcal - 72 h
175 Kcal - 2 h
Alexander, Ann. Surg., 200:297, 1984
130
110
Early Enteral Nutrition
Maintains gut mucosal barrier
Bulk stimulation
Fuel source for enterocyte - glutamine
TPN without glutamine = Intestinal atrophy – bacterial translocation
Glutamine in Cellular NutritionMajor Fuel For:
EnterocytesLymphocytesFibroblastsBone Marrow
PancreasLungTumor CellsRenal Tubular CellsVascular Epithelial Cells
GlutamineNecessary precursor for protein and nucleotide synthesis
Regulates acid-base balance through production of urinary ammonia
Major transporter of nitrogen (along with alanine)
Oxidation via Krebs cycle yields 30 mole ATP per mole glutamine (glucose = 36)
Glutamine MetabolismGut normally extracts 20 to 30% of glutamine from blood
During stress, muscle releases amino acids with glutamine and alanine making up 60% of total
Muscle glutamine concentration decreases by up to 50% and serum concentrations fall with prolonged stress
Adequate Nutritional Support of Respirator Dependent Patients
Content of Enteral Formulas
FormulaGlutamin
e g/LArginine
g/L% BCAA
AlitraQ 15 4.5 18.5
Immun-Aid 12.5 15.4 36.1
Pulmocare 5 3.3 19
Impact 5.9 14 17.1
Standard TF 3-6 1-2 17-22
Early Enteral Nutrition
Maintains GALT system
GALT SystemGut-associated lymphoid tissue
Intraepithelial lymphocytes
Lamina propria lymphoid tissue
Peyer’s patches
Mesenteric lymph nodes
GALT SystemIntraepithelial lymphocytes
First to recognize foreign antigens
Lamina propria lymphoid tissue
Source of IgA
Peyer’s patchesProcess antigens from intestinal lumen
GALT System
Responsible for reacting to harmful foreign antigens (e.g. bacterial or viral pathogens)
Must not react to non-threatening antigens to avoid chronic inflammatory condition
GALT System
Intravenous feeding with bowel rest and starvation result in significant suppression of the mass and function of GALT, with reduction in IgA secretion and increased gut permeability
Oral and enteral feedings preserve GALT mass and function
Li, J Trauma, 39:44, 1995
GALT SystemBowel rest (or an elemental diet) reduces intraluminal nutrients that bacteria need
Induces an adaptive response of bacteria to increase their adherence to the intestinal wall as a source of nutrients
Bacterial adherence causes cellular injury, or even bacterial penetration (translocation), with an adverse host response
Early Enteral Nutrition
Better maintenance of endogenous antioxidant pools
Helps reverse and prevent stress-induced splanchnic ischemia
Nutritional Support of the Critically Ill, Ventilated Patient
Problems with Enteral: Underfeeding
High gastric residuals
Fear of Aspiration
Constipation/Diarrhea
Abdominal distention
Nausea and vomiting
Nutritional Support of the Critically Ill, Ventilated Patient
Problems with Enteral: Underfeeding
McClave et al. prospectively evaluated enteral tube feedings in 44 medical ICU/coronary care unit patients (mean age, 57.8 years) who received nothing by mouth and were placed on enteral tube feeding
McClave et al.: Crit. Care Med., 27:1252-1256, 1999
Nutritional Support of the Critically Ill, Ventilated Patient
Physicians ordered a daily mean volume of enteral tube feeding that was only 65.6% of goal requirements
On average, only 78.1% of the volume ordered was actually infused
Thus, patients received a mean volume of enteral tube feeding that was only 51.6% of goal
McClave et al.: Crit. Care Med., 27:1252-1256, 1999
Nutritional Support of Critically Ill, Ventilated Patient
Only 14% of patients reached or exceeded 90% of goal feedings (for a single day) within 72 hours of the start of enteral tube feeding
Of 24 patients weighed before and after, 54% were lost weight on enteral tube feeding
Declining albumin levels correlated significantly with decreasing percent of goal calories infused
McClave et al.: Crit. Care Med., 27:1252-1256, 1999
Nutritional Support of Critically Ill, Ventilated Patient
NOTE: This may not be of major concern, perhaps it is actually beneficial – avoidance of overfeeding
Some contend that the problems with parenteral nutrition are due to overfeeding, since what is prescribed is more commonly given to the patient
Nutritional Support of the Critically Ill, Ventilated Patient
Problems with Enteral: Aspiration
Most feel TF is associated with an increased incidence of pneumonia – not aspiration
Most common event is aspiration of saliva
Consider use of feeding tube distal to stomach: Nasojejunal, gastrojejunal, or jejunostomy
Note: injection of Gastrografin to evaluate small bowel anatomy and motility.
Note: injection of Gastrografin to evaluate small bowel anatomy and motility.
Fluoroscopic Placement Nasojejunal Tube
Adequate Nutritional Support of Respirator Dependent Patients
Use of Pulmonary Enteral Formulas
No clear benefit has been demonstrated
Problem of hypercarbia is due mostly to total caloric infusion rather than CHO/fat content
Effectiveness of fat in supporting the hypermetabolic response of critical illness and enhancing nitrogen balance remains in question
Malone, A.M.: Nutr. Clin. Pract. 12:168-171, 1997
Adequate Nutritional Support of Respirator Dependent PatientsAvailable “Pulmonary” Enteral Formulas
FormulaCHO
% caloriesProtein
% caloriesFat
% calories
Nutri-Vent 27 18 55
Pulmocare 28 17 55
Respalor 39 20 41
Regular TF 38-53 15-22 30-45
Adequate Nutritional Support of Respirator Dependent Patients
Use of Pulmonary Enteral Formulas
Disadvantages include:• Decreased gastric emptying
• Increased gastrointestinal side effects
• Possible inadequate CHO intake
• Significantly increased cost
Malone, A.M.: Nutr. Clin. Pract. 12:168-171, 1997
Adequate Nutritional Support of Respirator Dependent Patients
Use of Standard Enteral Formulas
Avoids above problems of Pulmonary Enteral Formulas
Formulas exist to adjust for liver and renal failure
Malone, A.M.: Nutr. Clin. Pract. 12:168-171, 1997
Adequate Nutritional Support of Respirator Dependent Patients
Use of specialized immunoenhancing products may be of some benefit – although not proven
Much concern recently over ratio of -3/-6 fatty acids
Optimal is about 1:2
Soy-based emulsions 1:5 TO 1:7
Malone, A.M.: Nutr. Clin. Pract. 12:168-171, 1997
Adequate Nutritional Support of Respirator Dependent Patients
Branched-Chain Amino Acids
Alanine
Leucine
Isoleucine
Organ Specific Substrate SupportBranched-Chain Amino Acids
Main energy source for skeletal muscle during stress and sepsis
Not metabolized by the liver: safe to give during liver failure
Give 30 - 40 grams/day: 100 -160 kcal/day (45% BCAA Solution)
Protein
BCAA can enhance nitrogen balance during periods of maximal stress
Cerra et al., Crit Care Med, 11:775, 1983
Nutritional Support of the Critically Ill, Ventilated Patient
Problems with Parenteral
Intestinal atrophy – bacterial translocation
Possible overfeeding
Catheter-related sepsis
Nutritional Support of the Critically Ill, Ventilated Patient
Problems with Parenteral
Immunosuppression – especially with lipids
No -3 rich lipid emulsion yet available
In Europe there is a 10% fish oil emulsion in use
Hamawy et al demonstrated deposition of lipid emulsions in macrophages with increased susceptibility of mice to pneumococcal infections
Hamawy et al: J.P.E.N. J. Parenter. Enteral Nutr., 9:559-565, 1985.
Nutritional Support of the Critically Ill, Ventilated Patient
Preferred Route for Nutritional Support
Some evidence that TPN is immunosuppressive and harmful
No real evidence that Enteral is better – but it probably is… and it is cheaper
Conclusion
Do what is effective in your clinical situation!
Nutritional Requirements and Enteral Support of the Critically Ill,
Ventilated PatientOptimize milieu for cell metabolism
Minimize stress response
Provide adequate and appropriate nutritional support
Standard Enteral Support > TPN