Chapters 1-5 ASPEN NS

TEE is divided into these 3 components

• BMR/RMR

• Thermogenic effect of food/digestion

• Physical activity (exercise and non-exercise)

BMR

Measured in a fasted state upon awakening before any physical activity is undertaken - typically requires it to be measured in a metabolic ward

RMR

Also measured in a fasted state but some movement is allowed before the measurement is taken. A 20-30 minute rest period is done prior to testing. The difference in RMR and BMR is small, usually RMR a little higher.

RMR is hard to measure in those receiving nutrition support because

They are usually receiving continuous feeds and therefore are never truly “fasted”. Instead, the RMR is adjusted to include the thermic effect of feeding

The majority of TEE is taken up by

RMR (65-75%)

Differences between RMR are found in

• Females and males - with females having lower RMR

• Older adults having decreased RMR

• Differences in lean mass - more lean mass = higher RMR

Thermic effect of digestion

Increases RMR 5-10% and is affected by multiple factors including ; size and composition of the meal, time of day eaten, stress, caffeine use, age, and smoking status

Studies have shown that the thermic effect of digestion does not apply to

Healthy and critically ill adults receiving continuous enteral infusion of formula

For those who are hospitalized and critically ill, certain activities such as wound care, turning, chest physiotherapy, or short-lived PT can greatly increase RMR, but this usually only has

A transient effect of 5-10% on TEE (as physical activity portion of TEE)

Hypermetabolism is considered

RMR greater than 10% of what is expected of a similar, healthy person

Differences of RMR in patients who are critically ill were eliminated when accounting for

Body temperature - someone with a higher body temp may have higher RMR

Direct Calorimetry

Measures heat and chemical energy released from the body - urine is collected to determine chemical energy given off. This is studied in a metabolic ward/thermal chamber isolated from the surrounding environment. The heat given off by the individual is taken up by machinery inside the chamber. These studies can last for days and take into account changes for sleep and physical activity.

Indirect Calorimetry

Measures gas exchange - oxygen intake vs carbon dioxide exhalation. Done for 30 minutes. Can even be done on patients not breathing room or atmospheric air.

Relative indications for Indirect Calorimetry

• BMI less than 20.5

• Body mass >80.5

• Concerns about overfeeding in a patient with unexplained high ventilator requirement, or who, for unknown reason cannot be liberated from the vent

• Unwanted weight loss over a period of time that is not explained by volume status in a patient who regularly receives near 100% of the target feediing

• Massive tissue loss from amputation

• Preadmission fluid overload (ascites, fluid resuscitation, “third spacing”) without a reliable reoprt of body weight at proper hydration

Contraindications for Indirect Calorimetry

• Air leak (chest tubes, cuff leak, any other leak around the ventilator circuit)

• ECMO

• Hemodialysis (during or for several hours after)

• For pts who are mechanically ventilated with a fractiion of inspired oxygen greater than 60%

• For patients who are spontaneously breathing (reliance on any supplemental oxygen, inability to cooperate with the measurement)

Modified Weir equation after IC measurement

RMR = [(vo2 × 3.94) + (vco2 × 1.11)] x 1.44 (RMR measured in kcal/day and VO2 and VCO2 measured in mL/min)

The modified Weir equation does not take into account

Urea excretion in urine

metabolic range of RQ is

between 0.67 and 1.3

RQ > 1 .0

Net fat synthesis (often taken as an indicator of overfeeding)

The RQ should not be used to assess the feeding status of patients who are

Mechanically ventilated

The RQ of mechanically ventilated patients is best used to determine if

Egregious errors are present, especially if the RQ is outside of physiological ranges (0.67-1.3)

IC only determines RMR in critically ill and mechanically ventilated patients for about

3-4 days, then measurement or recalculation should be done

The Harris-Benedict equation tends to overestimate

RMR - therefore should not be used as it is outdated

The Mifflin St. Jeor equation has been

Validated in men and women - including people with a BMI greater than the max BMI of 42. However, the accuracy does decrease in those with BMI greater than 30 compared to those with normal BMI

Which predictive equation is currently recommended in the AND care manual

Mifflin St. Jeor

The Livingstone equation is comparable to the

Mifflin St Jeor; but the MSJ was more accurate in those with obesity. The Livingston was more advantageous in those with BMI less than 20

Both ASPEN and ESPEN use the kg/kcal method but it is also

The most unreliable method for measuring RMR

What is the reason that ESPEN and ASPEN use kg/kcal to measure RMR despite it being an inaccurate measure?

to promote low energy intake early in the ICU stay to avoid full or overfeeding

AND does not recommend the following equations, and why

• Ireton-Jones Equation (low accuracy in critically ill and mechanically ventilated)

• Swinamer Equation (high error rate)

• Harris-Benedict (overestimates RMR)

• Livingston equation (similar to MSJ but MSJ more accurate)

The Penn-State Equation

Recommended by AND for critically ill patients, works best when recalculated daily rather than used for extended period

Predicts RMR with 80% accuracy in severe obesity, 72% in those with brain injuries, 73% accuracy in those with barbituate coma, lower accuracy in patients with BMI less than 20.5 and patients with cystic fibrosis

The Penn State equation may be more useful in patients with obesity than the

MSJ

The Penn-State equation is more useful than the MSJ in those who are

Acutely ill and spontaneously breathing - most accurate in those with a normal weight or who are overweight

Length of time before nutrition compromise due to inadequate energy intake depends on

• Initial nutrition status

• Size of the energy deficit

• Body component being catabolized

  • The critical deficit may be reached sooner in patients who are malnourished, those who are hypermetabolic (because they create larger deficits daily), and in cases where inflammatory conditions favor protein over fat catabolism.

Specific population and criteria for low/underfeeding

Patients receiving critical care in the first 7-10 days (3-7 days for ESPEN) - states that underfeeding is NOT WORSE than full feeding, does not state that underfeeding IS BETTER

For those who are critically ill after day 10, or for those who are acutely ill -

Few or no guidelines exist on recommended energy intake or how intake should be determined. It is assumed that energy balance is the goal unless weight loss is the clinical goal.