Nutrition

Contents

  1. 1 General Nutrition Guidelines
  2. 2 Gastric vs. Postpyloric Feeds
  3. 3 Vasoactives and Enteral Nutrition
  4. 4 Respiratory Quotient
    1. 4.1 Resting Energy Expenditure (REE)
  5. 5 References

General Nutrition Guidelines






1.          Calculation of maintenance fluids based on wt in kg.
        a) Over 24 hours:
                    i)  100 ml/kg for first 10 kg
ii) 50 ml/kg for next 10 kg
                    iii) 20 ml/kg for every kg above 20 kg.
                    iv) Divide by 24 for ml/hr or use 4 ml/kg for first 10 kg, 2 ml/kg for next 10 kg, and then 1 ml/kg for every kg above 20 kg.

            * If mechanically ventilated, the patient has minimal respiratory insensible losses due to the heated/humidified circuit. Thus, maintenance fluid requirements are generally ~80% of that calculated above.


2.          Fluids should be adjusted to take into account extra losses, fever, dehydration,additional volume from drips and other medications, fluid restriction, etc. Also paralyzed, 
            sedated, intubated patients have decreased insensible losses and thus decreased maintenance fluid requirements.


3.          Basic Nutrition Goals: for the critically ill intensive care patients:

a)  Energy Needs (Maintenance + Growth) 
                                                  Term Infant                                90‐120 kcal/kg/day
1‐3 yrs                                       75‐90  kcal/kg/day
4‐6 yrs                                       65‐75  kcal/kg/day
7‐10 yrs                                     55‐75  kcal/kg/day
11‐18 yrs                                   40‐45  kcal/kg/day
>18 yrs                                      20‐35  kcal/kg/day

b)          Protein Needs (Maintenance + Growth)
                                                            <1 yr                                         2‐4 gm/kg/day
1‐10 yrs                                     1‐1.2 gm/kg/day
Adolescent                               0.8‐0.9 gm/kg/day
> 1 yr Critically ill               1.5 times normal


Parenteral: 

Timing: Fivez et al, NEJM 2016, found in a RCT of 1440 PICU patients, improved clinical outcomes (shorter ICU stay (6.5 vs 9.2 days), less new infections (10.7 vs 18.5%), shorter hospital stay, less renal replacement therapy, and shorter duration of mechanical ventilation in patients started "late" (day 8 of ICU stay) vs early (within 24 hours of PICU admission). Basically, in general, starting TPN later is preferable based on the available evidence.

Reserved to patients in which enteral nutrition is contraindicated.

    1. Total needs and blood chemistry levels largely determine tolerance to parenteral 
    nutrition solutions. (Refer to TPN sheets for monitoring)

    a) Renal panel, Magnesium and Triglyceride should be checked daily until the patient is on 
        stable TPN.

    b) Blood sugars should be followed closely when on high GIR’s especially when weaning off 
        TPN in infants.

    2. Carbohydrates: GIR (glucose infusion rate) is the milligrams of dextrose delivered per 
        kilogram weight per minute:
            i) GIR = dextrose (gm/ml) x 1000 (mg/gm) x infusion rate (ml/hour)
               60 min/hour x wt (kg)

            ii)          Initial GIR needs
                                        Neonates                   6‐8 mg/kg/min   
                                        Infants                     5‐7 Mg/kg/min
Children                     3‐4 mg/kg/min
Adults                       1‐2 mg/kg/min
            iii)         Maximum GIR
                                        Infant/Pediatric Range  12‐14 mg/kg/min 
                                        Adult range         7 mg/kg/min

        a)          Increase by 20‐50%/day until at goal of total kcal
        b)          Should be up to 60‐70% of total calories
        c)          Excessive dextrose associated with fatty liver and increased VCO2
        d)          Calculate calories:
                (1)         grams of dextrose = total volume of TPN * Dextrose %
                (2)         Kcals from dextrose = grams of dextrose * 3.4 kcal/gm

    3. Amino Acids: Start at 1 gram protein/kg/day and advance by 0.5‐1 gm /kg/day until you 
        reach the goal unless contraindicated by alterations in protein metabolism, (ie. renal or liver 
        disease, inborn error of metabolism,...etc.).
              a)      Calculate calories
                    i)           gm/day AA = gm /kg/day * kg
                    ii)          kcal AA/day = gm/day AA * 4.3 kcal/gm

4.          Lipids: use the 20% solution at 0.5‐1gm/kg/day ...may increase to maximum of 3gm/kg/day
              a)    Calculate Calories: (25‐30% of total calories) There are 20 gms of lipid per 100 ml of 
                       20% lipid with 2 kcals/ml.
i)           ml of fat/day = total grams of fat/day * 5 ml/gm
ii)          kcal fat/day = ml/day x 2 kcal/ml
                b)    Lipids can be run over 12‐18 hours (in this institution). In neonates not to exceed 
                     0.15 gm/ml/hr.
                c)   Rapid infusion of lipids may be associated with a decreased lipid clearance &/or 
                       respiratory &/or platelet aggregation complications.


        Peripheral Parenteral Nutrition (PPN): may be use to support blood glucose levels &/or supply short 
        term nutrition support and may be use in transition to TPN (while waiting for central access).

        1.  Dextrose is usually not greater than 10% (final concentration) but can be maximized at 
             12.5 %.
        2.  The total osmotic limits of peripheral parenteral nutrition is near 800‐900 mOsm:
                a)          250 mOsm per 5% dextrose
                b)          100 mOsm per 1% amino acids
                c)          Pharmacy will determine if the components of the PPN affect the osmolality

Enteral Nutrition: 
    
    First choice whenever possible as it is associated with better patient tolerance 
    and outcomes and reduced risks. (Srinivasan et al, PCCM 2020)

1.          Feeding tubes may be placed in the stomach when the risk of aspiration or reflux is 
             relatively low
        a)          Transpyloric feeding tubes can be if there is altered G.I. function with delayed 
                     gastric emptying, (duodenal trophic feeding can be initiated even in the absence of bowel sounds).
        b)          Continuous delivery tube feedings are usually tolerated better that bolus feeding in 
                     the intensive care patients as this allows for slower delivery and minimal gastric distention.
        c)          When initiating tube feeds in the PICU please use the Gastric feeding protocol unless 
                     special circumstances (i.e. only giving trophic feeds, patients with known feeding issues)
2.          Formula Selection:
        a)          Most standard formulas are isotonic and appropriate for the majority of patients. 
                     Specialized formulas are indicated for problems of intolerance or special patient needs.
        b)          Hyperosmotic solutions can be used to reduce volume loads, yet some patients may 
                     occasionally develop diarrhea or delayed gastric emptying with these formulas, so individualized 
                     feeding rates may be necessary in these circumstances

3.          Infant formulas: are usually 20 kcal/oz (0.67 kcal/cc) in isotonic, starting solutions.
        a)           Breast milk is by far the best tolerated formula and should be utilized when ever 
                      possible. Powdered formula or fortifiers may be combined with pumped breast milk to increase the 
                 nutrient delivery in smaller volumes.
     b)          Cow milk based formulas such as: Enfamil & Similac are similar in composition to breast 
                 milk and are usually well tolerated.
     c)          Soy based formulas such as: Isomil & Prosobee are used for lactose intolerance or milk 
                     protein allergies (both are rare in infants).
        d)         Hypoallergenic formulas such as: Pregestimil, Nutramagen & Alimentum contain protein 
                     hydrolysates. Formulas such as Neocate and EleCare contain free amino acids and are indicated for 
                 infants sensitive to intact proteins, malabsorption and/or allergies.
        e)          Fat malabsorption due to damage to the lymphatic system or thoracic duct may require 
                     use of medium chain triglyceride containing formulas, such as: Portagen.

4.          Pediatric Formulas for 1‐10 years of age: are usually 1 kcal/ml (30 kcal/oz) in 
         isotonic, starting solutions
        a)          Pediasure & Nutren Jr. with fiber are lactose free and nutritionally complete in 1000 
                 ml for kids 1‐10 years of age.
       b)          Specialized Pediatric Formulas: Peptamen Jr., EleCare may be indicated for 
                     malabsorption, short bowel syndrome, and allergies.

5.           Adult Formulas (>10 yrs): are usually 1 kcal/ml & isotonic in the starting solutions.
        a)          Standard: Osmolite, Jevity contain fiber
        b)          Specialized formulas: i.e. high protein, low protein, high calorie may be used in 
                 special circumstances.

Source: Akron Children's PICU Resident Curriculum: https://www.akronchildrens.org/cms/resource_library/files/picu_curriculum/picucurriculum.pdf, accessed 3/8/2016.

Benefits of EN

  • Prevention of mucosal atrophy
  • Preservation of balanced gut flora
  • Reduced risk of infection
  • Ameliorate oxidative stress --> reduced gut permeability --> reduced bacterial translocation
  • Increases GI blood flow (postprandial hyperemic response)
  • Reduced mortality, hospital LOS, and cost associated w/ nutrition therapy

So we now know why it's important to start EN as soon as possible. But...

Gastric vs. Postpyloric Feeds

Theoretical benefit of reduced risk of aspiration with postpyloric feeds
  • HOWEVER: No clear evidence showing this is the case. In a randomized trial, Kamat et al (PCCM 2008) added methylene blue to feeds and then examined tracheal aspirates with spectrophotometry for evidence of aspiration. There was no difference in the rates of aspiration between postpyloric and NG groups. Furthermore, the PP group had a longer time to initiation of feeds and required more x-rays for confirmation of tube placement. 

  • Meert et al (Chest 2004 did a randomized trial comparing postpyloric to gastric feeds in 74 critically ill children who were mechanically ventilated. They used the presence of gastric pepsin via immunoassay in trachea aspirates to detect evidence of aspiration. They found no difference in rates of aspiration. However, the postpyloric feeding group did have less interruptions in delivery of nutrition and thus more of their daily caloric goal delivered than did patients fed gastrically. No differences were found in rates of feeding tube displacement, abdominal distension, vomiting, or diarrhea between groups

Vasoactives and Enteral Nutrition

 
Complications with EN While on Vasopressor/Inotropic Agents

  • "Steal" phenomenon
  • Increase in splanchnic blood flow from feeding without increase in overall cardiac output --> less blood to vital organs (clinical impact unclear)
  • Gut ischemia (without progression to necrosis)
  • Due to increased gut O2 demand vs. reperfusion injury
  • Incidence <1%
  • Evidence behind ischemia from animal studies only (unclear of clinical relevance in humans)
  • Small bowel necrosis
  • Most reported cases occurred with tube feeds (TF) through surgically placed jejunostomy tubes in surgery/trauma/burn pts
  • No reported cases in medical ICU pts without history of GI surgery
  • Very little documentation regarding an association with concomitant vasopressor use
  • Feeding intolerance
  • Most common complication
  • Defined as increased gastric aspirate volume vs. vomiting
  • Usually occurred within the first 48hrs of starting EN
  • Associated w/ aspiration PNA, longer LOS in the ICU, greater risk of mortality in 1 study

Overall, literature evaluating complications with EN + hemodynamic instability lacking and basically non-existent in the pediatric population. What are our current recommendations from the experts?
 
2009 Adult Guideline for Nutrition in the ICU

  • EN should be started within 24-48hrs following admission
  • EN should be withheld if:
  • Hypotensive
  • Initiating use of vasopressors (DA, NE, epi, phenyl)
  • Escalating dose of such agents
  • EN may be provided with caution if on stable or "low dose" of pressors (no explanation of "low dose")
  • Any sign of intolerance should be viewed as early signs of gut ischemia

2009 Pediatric Guideline for Nutrition in the PICU

  • No statement on whether EN can be initiated with vasopressor/inotropic agents

They're not very clear on whether EN should be started while on vasopressor/inotropic agents. What are the evidence behind starting vs. withholding EN in hemodynamically unstable pts?
 
2000 - EN in Adult Post-Cardiac Surgery Pts

  • Hemodynamically stable vs. unstable pts (requiring vasopressors) receiving EN
  • Unstable pts tolerated EN as well as the stable pts

2001 - Splanchnic Response to EN in Adult Post-Cardiac Surgery Pts on Pressors

  • EN not associated with decrease in gastric mucosal pH, suggesting lack of splanchnic ischemia
  • Actually showed increase in splanchnic blood flow

2004 - Enteral Nutrition and CV Meds in the PICU (JPEN), attached

  • Method
  • Retrospective analysis
  • 52 pts from single center receiving both EN (via NG, NJ, or oral) and cardiac meds (DA, dobut, epi, NE, phenyl) within the same 24hr period
  • Results
  • Most common pressors used = high dose DA; DA + NE (>70% of pts)
  • Only 29% of pts had feedings held for some time for perceived intolerance
  • 22% of pts had vomiting
  • Adverse events
  • 2 pts had clinically insignificant heme-positive stools
  • 2 pts had more extensive GIB but were also coagulopathic from liver failure/DIC
  • Bottom line
  • PICU pts tolerated EN well while on pressors without much adverse events

2010 - Early EN in Adult Pts with Pressors and Mechanical Ventilation (AJCC), attached

  • Methods
  • Retrospective analysis
  • 1174 medical ICU pts on DA, epi, NE, and/or phenyl during the first 2 days of ventilatory support divided into:
  • Early EN group (EN started within the first 2 days while on pressors)
  • Late EN group (after 2 days; may or may not be on pressors)
  • Results
  • Early EN group associated w/ lower risk of hospital mortality (35% decreased risk of death)
  • Survival difference evident within the first week of ventilation
  • Benefit of early EN more evident in the sickest pts who:
  • Received multiple pressors
  • Required pressors for >2 days
  • Results remained true at 28 days
  • Bottom line
  • EN within the first 2 days of mechanical ventilation was associated with reduction in hospital mortality in hemodynamically unstable pts

Bottom Line

  • Many benefits of early EN in kids and adults
  • Inotropes (Dobut, mil; increases CO --> increases splanchnic blood flow) should not dissuade us from initiating EN
  • Vasopressors (DA, Epi, NE, vaso, phenyl) should not entirely preclude clinicians from using EN, but risks may exist especially with NJ feeds
  • If pressor doses stable or low (very subjective), consider early EN feed
  • Worsening hemodynamic instability should warrant discontinuation of EN
  • Randomized controlled trials needed as evidence above are from retrospective analyses

Respiratory Quotient

  • "R" a dimensionless number that describes the ratio of CO2 eliminated to the amount of O2 consumed. It is used in the alveolar gas equation :PAO2= FiO2 (Patm - PH2O) - PaCO2/R 
  • R varies based on diet/what is being broken down
  • Normally, we assign a value of 0.8 to R to represent a normal diet

  • R can go above 1 in the setting of lipogenesis (ie due to overfeeding)
  • The respiratory quotient can become clinically relevant in a patient with difficulty ventilating as their nutritional intake and composition can significantly affect their CO2 production. In addition, medications such as propofol, delivered in lipids, can increase CO2 produced (even though the RQ of lipids/fat is 0.7).

Resting Energy Expenditure (REE)

  • REE = calories needed by the body at rest during a 24 hr period (~70% of calories used by the body)
  • Overfeeding --> increased CO2 production (can lead to resp failure), hyperglycemia, steatohepatitis
  • Underfeeding --> malnutrition, muscle weakness, impaired immunity
  • Good control of energy balance guided by indirect calorimetry (measures REE) --> decreased hospital mortality
  • Many equations exist to predict REE but were found to be inaccurate

  • REE determined by:  analyzing expired gas by looking at the volume and concentration of expired gas --> amount of O2 extracted (body burns fuel/energy using O2) and amount of CO2 expelled (byproduct of metabolism)
  • Limitation of measuring REE:  air leaks (from ventilator or chest tube), CO2 removal by CRRT/ECMO, or high vent settings that trigger a lot of air flow
  • Who benefits from measuring REE? Here's the ASPEN pt criteria:
    • underweight/overweight
    • fluctuating weights
    • failure to wean from vent
    • hypermetabolic state (dysautonomia, oncologic dx, seizure, hyperthermia, SIRS)
    • hypometabolic state (hypothermia, hypothyroidism, coma)
    • burn injury
    • in the ICU for >4 wks
  • 1 study found that ~70% of PICU pts meet the above criteria!
Reference for  general review (Sion-Sarid et al, Nutrition 2013)
One model of REE on ECMO (have to essentially treat the membrane oxygenator/sweep as another lung): (DeWaele et al, Acta Anesthesiologica Scand 2015)

References

1) Kamat P, Favaloro-Sabatier J, Rogers K, Stockwell JA. Use of methylene blue spectrophotometry to detect subclinical aspiration in enterally fed intubatedpediatric patients. Pediatr Crit Care Med. 2008 May;9(3):299-303.

2) Meert KL, Daphtary KM, Metheny NA: Gastric vs small bowel feeding in critically ill children receiving mechanical ventilation: A randomized control trial.Chest 2004; 126:872–878