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To determine the difference between total energy expenditure (TEE) and resting energy expenditure (REE) in a group of trauma patients and a group of septic patients with multiple organ dysfunction.

Definitions

• “Steady state” - not defined

Trauma Group

1. Understand and give written consent from a family member.
2. Admitted within 3 d of a blunt or penetrating injury with minimum Injury Severity Score (2) of 16.
3. Mechanically ventilated.
4. FIO₂ < 0.8
5. No air leaks in the ventilatory circuit
6. Expected to require parenteral nutrition
7. Not receiving ethanol for prophylaxis of delirium tremens

Septic Group

1. Understand and given written consent from a family member.
   • In addition to trauma groups criteria, this septic group had to meet the following conditions:
2. Documented or presumed infection:
   1. Leukocyte counts of >11,000 cells/mm²/L;
   2. Body temperature of >38.3 °C;
   3. Documented source of infection or deterioration in clinical course mandating immediate antibiotic therapy.
3. Hyperdynamic response:
   1. Heart rate of >90 beats/min;
   2. Cardiac index of >5.0 L/min/m² and either systemic vascular resistance index of <1100 dyne-sec/cm⁵.m² or oxygen consumption index >200 mL/min/m²
4. Dysfuction of at least 2 organ systems:
   1. Respiratory—mechanically ventilation required;
   2. Cardiovascular—inotropic support to maintain oxygen delivery of >/= 600mL/min/m²;
   3. Renal—dialysis required for fluid and azotemia control;
   4. Hepatic—total bilirubin concentration of > 2.5 mg/dL serum albumin of 2.8 g/dL;
   5. Gastrointestinal—failure to tolerate tube feedings or gastric drainage of >800 mL/day with distended abdomen;
   6. Coagulation—platelet count of <60,000 platelets/mm3 or platelet infusion required.

1. Refusal to consent
2. Not meeting inclusion criteria
3. Diabetes or other preexisting metabolic disorders

An indirect calorimeter was used to measure energy expenditure at rest (REE) 0700 and 1900 hrs. The energy expenditure measurement was then continued for up to 12 hrs (TEE)

2 comparisons were generated: a) 1 12-hr TEE with a controlled 20min-REE and b) a 12-hr TEE trend measurement during which generally more patient activity occurred (0700 to 1900) with a 12-hr TEE trend measurements during which less patient activity occurred (1900 go 0700). 

Data were collected for a maximum of 10 days per subject.

ANTHROPOMETRIC

• Ht measured? yes
• Wt measured? yes
• Fat-free mass measured? No
• Others: % ideal body wt, adjusted wt (ABW), body surface area(BSA)

CLINICAL

Clinical data was collected for computation of an illness severity score: blood gas analysis, electrolyte values, metabolic profiles, hematology and coagulation studies, ventilator settings, body temperature, cardiovascular and hemodynamic variables, sedative, narcotic, and inotropic drug administration

Resting energy expenditure

• IC type: Deltatrac MB100
• Equipment of Calibration: yes
• Coefficient of variation using std gases: not reported
• Rest before measure (state length of time rested if available): not specified
• Measurement length: 15-25 mins for REE; 12 hrs for TEE
• Steady state: not reported
• Fasting length: Not reported
• Exercise restrictions XX hr prior to test? not applicable
• Room temp: not reported
• No. of measures within the measurement period: Continuous
• Were some measures eliminated? Yes, a microprocessor in the metabolic monitor automatically discard all outlying data
• Were a set of measurements averaged? Not reported
• Coefficient of variation in subjects measures? No
• Training of measurer? Not reported
• Subject training of measuring process? Not reported

DIETARY

NPO

• Intervening factor:

Outcome(s) and other measures

1. Measured REE [(VO₂, l/min), VCO₂ (l/min; ml/kg/min), RQ, ventilation (l/min)].
2. Predicted RME using HB
3. Metabolically active wt was calculated for obese subjects from actual and ideal body wt.
4. Body surface area were calculated
5. Independent variables of weight, height, age

Blinding used: no

Total 33 patients

• 13 trauma patients
  • 10 M; 3 F
  • Mean age, y: 28±9
• 20 septic patients
  • 17M; 3F
  • Mean age, y: 32±11

Statistical tests

• The REE/TEE pairs were tested by Student’s paired t-test
• Difference between the trauma and septic groups and between day and night TEE were tested with Student’s independent t-test.  Significant was set at p<.05

Descriptive (mean ±SD)

	Trauma	Sepsis
Ht,cm	178±61	177±6
Wt,kg	75±18	83±17
%IBW	102±10	112±21
ABW	75±13	78±9
BSA	1.92±0.19	1.99±0.18

                             

REE/TEE

Septic subjects had a significant higher REE and TEE than trauma subjects. Mean REE was within 5% of mean TEE in both the trauma and septic groups. The difference between REE and TEE was statistically significant.  The ratio of REE to TEE ranged from 0.67 to 1.21.  In 10 (11.6%) of 86 trauma and 17 (11.0%) of 154 septic studies, REE exceeded TEE by more than the IC measurement error of 4%.

Diurnal Variation

TEE measured over the night hours (1900 to 0700) was not significantly different from TEE measured over the day hours (0700 to 1900).  REE at 0700 did not differ from REE at 1900 hrs.

	Trauma kcal/d	Sepsis kcal/d
0700REE	2753±355	3365±556
1900REE	2755±446	3442±691
Day TEE	2815±412	3570±691
Night TEE	2867±392	3475±551

Changes in REE/TEE Over Time

In 9 (69%) of 13 trauma subjects and 13 (65%) of 20 septic subjects, EE was measured for 4 days.  Comparing day 0,2,4, there was no significant changes in mean REE or TEE in both groups. However, individual difference ranged from 34 to 1424 kcal/day (i.e. up to 50% of initial measurement of REE)

In a subset of subjects (3 trauma and 9 septic patients), data were collected for 7 days. Neither mean REE nor mean TEE was significantly changed on day 7 compared with day 0. However, there was wide individual variation

Effects of Sedation and Neuromuscular Blockade in REE/TEE

All subjects received sedative medication, so an analysis of the difference between REE and TEE in sedated vs. nonsedated subjects could not be performed.

In the septic group, 42% of studies were performed during neuromuscular blockade plus sedation. Both REE and TEE were significantly higher in the medically paralyzed group than in the nonparalyzed group (about 120 kcal/day).

TEE was greater than REE in both the medically paralyzed and nonparalyzed studies.  There was a positive correlation between neuromuscular blocker dose (r²=.31) and TEE (r²=.32).

MEASUREMENT PROCESS

• Number of measurements
  • REE: minimum of 15 valid measurements
  • TEE: continuous measurements for up to 10 days.
• Length of measurements
  • REE: 15-25 min
  • TEE: 12 hrs
• Steady state: Not specified
• RQ: Not specified

MEASUREMENT TIMING

• Sleep or rest: Pt was not to be disturbed
• Physical activity: None
• Food intake: NPO; parenteral nutrition solutions were administered via continuous drip, and were not interrupted for the REE test
• Various times in the day:
  • REE at 0700 and 1899
  • TEE from 0700 to 1900 (day)
  • TEE from 1900 and 0700 (night)

INDIVIDUAL CHARACTERISTICS

• Circulatory hormones: Not reported
• Breathing ability: all patients were mechanically ventilated
• Medical tests/procedures: No major procedures were performed within 15 mins of the test
• Chemicals (medications/drugs/herbs, caffeine, nicotine, alcohol): Morphine and fentanyl was infused during 99% of studies.  Neuromuscular blocking agents were used in 42% of septic studies.

“In the current study, trauma and septic patients were markedly hypermetabolic, despite heavy sedation and in many cases medical paralysis. Additionally, a 20-min measurement of REE approximated a 12-hr measurement of TEE.  Mean REE/TEE of the groups were stable over several days of study, but there was wide individual variation.”

“REE in current study was 1.55 x predicted basal expenditure for trauma and 1.91 x predicted basal energy expenditure for sepsis.”

“REE generally approximated TEE in the current study, and both REE and TEE were significantly increased above predicted basal energy expenditure. In the current study, mean TEE (3273±647 kcal/day) was 1.037 x REE.”

“Although more activity occurs in the ICU during the day, TEE from 0700 to 1900 was not different from TEE measured from 1900 to 0700 hrs.”

“The frequency rate of REE exceeding TEE by more than the IC measurement error was ~11%). 3 types of errors were noted:

1. TEE decreased in relation to prior and subsequent TEE periods while REE remained stable (23% of trauma; 1.3% of septic)
2. TEE was stable but REE increased compared with prior measurements. Both TEE and REE remained elevated in subsequent study periods, with TEE greater than REE (3.4 % of trauma; 4.5% of septic)
3. REE increased in relation to prior and subsequent values of REE, while TEE remained stable (5.7% of trauma; 4.5% of septic).”

“Error type “a” cannot be explained, but since the decrease in TEE was transient (<12 hrs), the use of REE estimate TEE remains valid. Error type “b” seems to be not an error, but an actual physiologic change in metabolic rate that persisted into subsequent study periods. Error type “c” can be interpreted as an attempt to measure REE in patient who was not at rest.  It is the most significant error, because incorrect perception will be given of TEE leading to overfeeding. Although the rate of error type “c” is low, its occurrence is undetectable.”

“In subjects who remained in the study for at least 4 days, mean REE and TEE were stable from day 0 to day 2 to day 4.  Mean difference seemed clinically insignificant, but individual variation was wide (up to 50% from values recorded on day 1 of study), indicating that in individual patients, the difference in REE and TEE from day to day can be significantly significant. In patients who remained in the study for at least 7 days, there was no significant fluctuation in mean REE or TEE from day 0 to day 7, but again individual variation was great.”

“Although EE is stable for at least a week in population of trauma and septic patients, daily variation of EE in individual patients may be clinically significant, requiring frequent measurement by indirect calorimetry.  In most cases, a 20-min measurement of REE will be sufficient to assess TEE for the patients while the condition of severe stress and heavy sedation persist.”

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Strengths

• Inclusion/exclusion criteria are clear. Limit the possible confounding factors that might influence the IC results.
• Assess the effects of the sedation/medication on TEE/REE measurements.
• Great study design with appropriate statistics
• Addressed and discussed 3 types of errors of the situation when REE >TEE by more than the IC measurement error (the rate was ~ 11%)
• Conclusions were made in consideration to the daily variation in TEE/REE on individual basis, even though the mean TEE/REE (group variance) was stable for at least a week.

Generalizability/Weaknesses

• Results only applied to trauma and septic patients who are sedated, mechanically ventilated and on parenteral nutrition.
• Septic subjects seemed to weigh higher than trauma group (according to the descriptive data). Did not test or report if weight difference between groups was significant or not. Plus, weight status was not adjusted in the statistic analysis. Question if consistent higher REE/TEE in septic group is related to weight? (a possible confounder)