Nutritional Requirements and Enteral Support of the Critically Ill, Ventilated Patient John P. Grant, MD, CNSP Director Nutrition Support Service Professor

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


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


Provide Optimal Metabolic Milieu

Establish and maintain oxygenation

Adjust pH

Ensure adequate tissue perfusion

Control waste (dialysis)


Provide Optimal Metabolic Milieu Minimize Metabolic Stress Response

Control painDebridement of necrotic/infected tissueDrain abscessesDress or cover wounds


Optimize milieu for cell metabolism



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.


• 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.


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


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.


Duke data, unpublished: Recovery of Organ Function With 2 Weeks of TPN in 21 Malnourished, Non-stressed Patients


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 -


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


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


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


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


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


Benefits of

Early Enteral Nutrition

vs.

Parenteral 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


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


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


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


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


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


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


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


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


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


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


Use of Pulmonary Enteral Formulas

Disadvantages include:• Decreased gastric emptying

• Increased gastrointestinal side effects

• Possible inadequate CHO intake

• Significantly increased cost



Use of Standard Enteral Formulas

Avoids above problems of Pulmonary Enteral Formulas

Formulas exist to adjust for liver and renal failure



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



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


Problems with Parenteral

Intestinal atrophy – bacterial translocation

Possible overfeeding

Catheter-related sepsis


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.


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!


Ventilated PatientOptimize milieu for cell metabolism



Standard Enteral Support > TPN

Documents

Nutritional Requirements and Enteral Support of the Critically Ill, Ventilated Patient John P. Grant, MD, CNSP Director Nutrition Support Service Professor