Bioelectrical impedance plethysmographic analysis of body composition in critically injured and healthy subjects

Comparison of Bioelectrical Impedance Analysis (BIA)-Derived Parameters in Healthy Volunteers and Critically Ill Patients

OBJECTIVE

To compare bioelectrical impedance analysis (BIA)-derived parameters in healthy volunteers and critically ill patients and to assess its prognostic value in an ICU patient cohort.

DESIGN

Retrospective, observational data analysis.

SETTING

Single centre, tertiary-level ICU (Ziekenhuis Netwerk Antwerpen, ZNA Stuivenberg Hospital).

PATIENTS

101 patients and 101 healthy subjects, participants of International Fluid Academy Days.

MEASUREMENTS AND MAIN RESULTS

Compared to healthy volunteers, both male and female ICU patients had significantly higher values for total body water (TBW), extracellular water (ECW), extracellular fluid (ECF), plasma, and interstitial fluid volumes. The phase angle was significantly lower and the malnutrition index was significantly higher in ICU patients, regardless of gender. Non-survivors in the ICU had significantly higher extracellular water content (ECW, 50.7 ± 5.1 vs. 48.9 ± 4.3%, p = 0.047) and accordingly significantly lower intracellular water (ICW, 49.2 ± 5.1 vs. 51.1 ± 4.3%, p = 0.047). The malnutrition index was also significantly higher in non-survivors compared to survivors (0.94 ± 0.17 vs. 0.87 ± 0.16, p = 0.048), as was the capillary leak index (ECW/ICW).

CONCLUSIONS

Compared to healthy volunteers, this study observed a higher malnutrition index and TBW in ICU patients with an accumulation of fluids in the extracellular compartment. ICU non-survivors showed similar results, indicating that ICU patients and a fortiori non-survivors are generally overhydrated, with increased TBW and ECW, and more undernourished, as indicated by a higher malnutrition index.

Factors Related to the Assessment of Resting Metabolic Rate in Critically Ill Patients

BACKGROUND

Predicting resting metabolic rate (RMR) in mechanically ventilated, critically ill patients is an important part of the nutrition care in such patients.

METHODS

RMR and associated clinical data from various studies of mechanically ventilated, critically ill patients were combined, and the impact of body size, age, reason for admission, and sedation level were analyzed along with prediction methods of RMR (the American Society for Parenteral and Enteral Nutrition [ASPEN] standards and the Penn State equation).

RESULTS

Among 826 measurements, trauma patients had a higher RMR than surgical and medical patients (2077 ± 290 vs 1987 ± 282 kcal/d; P < .0001). RMR was not different in sedated vs unsedated patients. Wide ranges of weight (27-374 kg) and age (18-95 years) were captured. The relationships between weight and RMR and RMR and age were curvilinear. For weight-based ratio methods of RMR prediction, <50% of predictions were within the range in which they were designed to work. The accuracy of the Penn State equation was better in some weight categories than others. New equations based on a wider range of body weights and ages are presented.

CONCLUSIONS

Curvilinear functions exist for weight and age in relation to RMR, but extraordinary levels of each are required for the curve to become apparent. The ASPEN energy standards (kcal/kg body weight) fail to predict RMR because the relationship is more complex than a simple ratio. The Penn State equations are better able to model these relationships. The new versions of the equation presented here await validation.

Impact of Feeding on Resting Metabolic Rate and Gas Exchange in Critically Ill Patients

BACKGROUND

Feeding is understood to alter gas exchange and resting metabolic rate (RMR) in critically ill patients, but there are limited data describing such changes.

METHODS

A large collection of RMR measurements and energy intake was assembled in mechanically ventilated and critically ill patients. The data were used to explore differences in RMR, respiratory quotient (RQ), and carbon dioxide production (V̇co₂ ) related to feeding state.

RESULTS

A total of 708 RMR measurements were available. No significant thermogenic effect of feeding could be appreciated. When controlled for body weight, the difference was 4.2% (1946 ± 400 kcal/d for unfed vs 2028 ± 341 kcal/d for fed patients; P = .299), and this small difference was fully eliminated when body temperature was also controlled for. RQ increased as carbohydrate and energy intake increased, but there was much variation in the relationship. Among 215 overfed patients, only 22 had RQ ≥1.0, and among 9 patients whose carbohydrate intake alone exceeded RMR, only 4 had an RQ ≥1.0. V̇co₂ was influenced mainly by the volume of oxygen consumed and to a lesser degree by carbohydrate intake.

CONCLUSIONS

No appreciable thermogenic effect of feeding occurs in continuously fed critically ill patients. This factor does not need to be considered in the assessment of resting energy needs. RQ is not a reliable indicator of overfeeding, and the ability of carbohydrate intake to alter V̇co₂ is small, although not absent.

Prediction of hemodialysis vascular access failure using segmental bioimpedance analysis parameters

PURPOSE

Segmental bioimpedance analysis (BIA) can identify fluid volume changes in the arms of patients on hemodialysis (HD) after vascular access surgery. We investigated whether the difference in fluid volumes between the arms of the patients using segmental BIA is associated with vascular access outcome.

METHODS

Body composition measurements were taken for 127 patients on HD with segmental, multi-frequency BIA equipment (InBody 1.0, Biospace Co. Ltd, Seoul, Korea). The difference in fluid volume between the arms of the patients was calculated from the fluid volume of the arm with the vascular access minus that of the other. The primary outcome was the loss of vascular access patency within 3 months of BIA measurement.

RESULTS

The median absolute and relative inter-arm fluid volume differences were 150 ml [interquartile range (IQR) 90-250 ml] and 9.6% (IQR 4.9-14.4%), respectively. Within 3 months of BIA measurement, 38 patients (30.0%) experienced vascular access failure. When the patients were divided into three groups based on the tertiles of relative inter-arm fluid volume differences (lowest tertile: < 6.8%; middle tertile: 6.8-12.7%; highest tertile: > 12.7%), greater difference in relative inter-arm fluid volume differences was associated with higher vascular access failure rates (14 vs. 28 vs. 48%, p value for trend across tertiles = 0.003).

CONCLUSIONS

We conclude that segmental BIA may be used as a tool that can predict vascular access failure in patients on HD by calculating the relative difference in fluid volume between the arms of the patients with and without vascular access.

Assessment of impairment and activity limitations in the critically ill: a systematic review of measurement instruments and their clinimetric properties

PURPOSE

To identify measures used to evaluate the broad constructs of functional impairment and limitations in the critically ill across the continuum of recovery, and to evaluate, synthesise and compare the clinimetric properties of the measures identified.

METHODS

A systematic review of articles was carried out using the databases Medline (1950-2014), CINAHL (1982-2014), EMBASE (1980-2014), Cochrane Library (2014) and Scopus (1960-2014). Additional studies were identified by searching personal files. Eligibility criteria for selection: Search 1: studies which assessed muscle mass, strength or function using objective non-laboratory measures; Search 2: studies which evaluated a clinimetric property (reliability, measurement error, validity or responsiveness) for one of the measures identified in search one. Two independent reviewers assessed articles for inclusion and assessed risk of bias using the consensus-based standards for selection of health status measurement instruments checklist.

RESULTS

Thirty-three measures were identified; however, only 20 had established clinimetric properties. Ultrasonography, dynamometry, physical function in intensive care test scored and the Chelsea critical care physical assessment tool performed the strongest for the measurement of impairment of body systems (muscle mass and strength) and activity limitations (physical function), respectively.

CONCLUSIONS

There is considerable variability in the type of measures utilized to measure physical impairments and limitations in survivors of critical illness. Future work should identify a core set of standardized measures, which can be utilized across the continuum of critical illness recovery embedded within the International Classification of Functioning framework. This will enable improved comparisons between future studies, which in turn will assist in identifying the most effective treatment strategies to ameliorate the devastating longer-term outcomes of a critical illness.

Body cell mass evaluation in critically ill patients: killing two birds with one stone

Body cell mass (BCM) is the metabolically active cell mass involved in O₂ consumption, CO₂ production and energy expenditure. BCM measurement has been suggested as a tool for the evaluation of nutritional status. Since BCM is closely related to energy expenditure, it could also represent a good reference value for the calculation of nutrient needs. In a recent issue of Critical Care, Ismael and colleagues used bioelectrical impedance analysis parameters and anthropometric variables to evaluate BCM in patients with acute kidney injury, before and after a hemodialysis session. The results of this study suggest that BCM is relatively insensitive to major body fluid shifts, a well known factor interfering with nutritional evaluation/monitoring and energy need calculations in the ICU. Thus, BCM seems to be a more 'stable' nutritional variable, as it is apparently less influenced by non-nutritional factors. The results of this paper emphasize the need to identify biologically sound parameters for nutritional status evaluation and energy need calculation in critically ill patients; in this regard, BCM could fulfill these expectations.

The consequences of sudden fluid shifts on body composition in critically ill patients

INTRODUCTION

Estimation of body composition as fat-free mass (FFM) is subjected to many variations caused by injury and stress conditions in the intensive care unit (ICU). Body cell mass (BCM), the metabolically active part of FFM, is reported to be more specifically correlated to changes in nutritional status. Bedside estimation of BCM could help to provide more valuable markers of nutritional status and may promote understanding of metabolic consequences of energy deficit in the ICU patients. We aimed to quantify BCM, water compartments and FFM by methods usable at the bedside for evaluating the impact of sudden and massive fluid shifts on body composition in ICU patients.

METHODS

We conducted a prospective experimental study over an 6 month-period in a 18-bed ICU. Body composition of 31 consecutive hemodynamically stable patients requiring acute renal replacement therapy for fluid overload (ultrafiltration ≥5% body weight) was investigated before and after the hemodialysis session. Intra-(ICW) and extracellular (ECW) water volumes were calculated from the raw values of the low- and high-frequency resistances measured by multi-frequency bioelectrical impedance. BCM was assessed by a calculated method recently developed for ICU patients. FFM was derived from BCM and ECW.

RESULTS

Intradialytic weight loss was 3.8 ± 0.8 kg. Percentage changes of ECW (-7.99 ± 4.60%) and of ICW (-7.63 ± 5.11%) were similar, resulting ECW/ICW ratio constant (1.26 ± 0.20). The fall of FFM (-2.24 ± 1.56 kg, -4.43 ± 2.65%) was less pronounced than the decrease of ECW (P < 0.001) or ICW (P < 0.001). Intradialytic variation of BCM was clinically negligible (-0.38 ± 0.93 kg, -1.56 ± 3.94%) and was significantly less than FFM (P < 0.001).

CONCLUSIONS

BCM estimation is less driven by sudden massive fluid shifts than FMM. Assessment of BCM should be preferred to FFM when severe hydration disturbances are present in ICU patients.

Early rehabilitation in critical care (eRiCC): functional electrical stimulation with cycling protocol for a randomised controlled trial

INTRODUCTION

Intensive care-acquired weakness is a common problem, leads to significant impairment in physical functioning and muscle strength, and is prevalent in individuals with sepsis. Early rehabilitation has been shown to be safe and feasible; however, commencement is often delayed due to a patient's inability to co-operate. An intervention that begins early in an intensive care unit (ICU) admission without the need for patient volition may be beneficial in attenuating muscle wasting. The eRiCC (early rehabilitation in critical care) trial will investigate the effectiveness of functional electrical stimulation-assisted cycling and cycling alone, compared to standard care, in individuals with sepsis.

METHODS AND ANALYSIS

This is a single centre randomised controlled trial. Participants (n=80) aged ≥18 years, with a diagnosis of sepsis or severe sepsis, who are expected to be mechanically ventilated for ≥48 h and remain in the intensive care ≥4 days will be randomised within 72 h of admission to (1) standard care or (2) intervention where participants will receive functional electrical muscle stimulation-assisted supine cycling on one leg while the other leg undergoes cycling alone. Primary outcome measures include: muscle mass (quadriceps ultrasonography; bioelectrical impedance spectroscopy); muscle strength (Medical Research Council Scale; hand-held dynamometry) and physical function (Physical Function in Intensive Care Test; Functional Status Score in intensive care; 6 min walk test). Blinded outcome assessors will assess measures at baseline, weekly, at ICU discharge and acute hospital discharge. Secondary measures will be evaluated in a nested subgroup (n=20) and will consist of biochemical/histological analyses of collected muscle, urine and blood samples at baseline and at ICU discharge.

ETHICS AND DISSEMINATION

Ethics approval has been obtained from the relevant institution, and results will be published to inform clinical practice in the care of patients with sepsis to optimise rehabilitation and physical function outcomes.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trials Registry ACTRN12612000528853.

Assessment of body cell mass at bedside in critically ill patients

Critical illness affects body composition profoundly, especially body cell mass (BCM). BCM loss reflects lean tissue wasting and could be a nutritional marker in critically ill patients. However, BCM assessment with usual isotopic or tracer methods is impractical in intensive care units (ICUs). We aimed to modelize the BCM of critically ill patients using variables available at bedside. Fat-free mass (FFM), bone mineral (Mo), and extracellular water (ECW) of 49 critically ill patients were measured prospectively by dual-energy X-ray absorptiometry and multifrequency bioimpedance. BCM was estimated according to the four-compartment cellular level: BCM = FFM - (ECW/0.98) - (0.73 × Mo). Variables that might influence the BCM were assessed, and multivariable analysis using fractional polynomials was conducted to determine the relations between BCM and these data. Bootstrap resampling was then used to estimate the most stable model predicting BCM. BCM was 22.7 ± 5.4 kg. The most frequent model included height (cm), leg circumference (cm), weight shift (Δ) between ICU admission and body composition assessment (kg), and trunk length (cm) as a linear function: BCM (kg) = 0.266 × height + 0.287 × leg circumference + 0.305 × Δweight - 0.406 × trunk length - 13.52. The fraction of variance explained by this model (adjusted r(2)) was 46%. Including bioelectrical impedance analysis variables in the model did not improve BCM prediction. In summary, our results suggest that BCM can be estimated at bedside, with an error lower than ±20% in 90% subjects, on the basis of static (height, trunk length), less stable (leg circumference), and dynamic biometric variables (Δweight) for critically ill patients.

[Quality assessment and improvement in the indication and management of parenteral nutrition in a general surgery unit]

OBJECTIVE

To analyze the degree of compliance with a variety of internationally accepted standards defined for Total Parenteral Nutrition (TPN) quality control in our Surgery Department.

PATIENTS AND METHOD

Prospective study of patients treated with TPN over two years in the department of surgery of a university teaching hospital (n = 72). Assessment of quality was performed by measurements of compliance using 19 criteria. The criteria were divided into three groups according to characteristics of TPN standardisation: this must be "appropriate" to the nutritional requirements of the patient, "safe" in order to prevent complications and "accurate" in its daily programming. Corrective measures aimed at resolving the quality problem were applied to the deficient criteria over six months, paying particular attention to those criteria which had the highest percentage of errors in the study carried out using a Pareto analysis. During a third period of six months the information on all 19 criteria was gathered again and the improvement with regard to the standard values and to the compliance in the first period (using the value of z) was evaluated.

RESULTS

The compliance with seven criteria was significantly below standard values: all those of the "appropriate" group, except the criteria "type of diet" and "composition of the diet", and the criteria "absence of complications" of the "safe" group, which was also the one with the highest number of grouped non-compliances. In the second period all the below standard criteria improved with compared to the first period. The criteria "time of fasting", "concordance" and "duration" were significantly improved. The criteria "time of fasting", "duration" and "latency" reached the standard. The rest of criteria that reached their standard in the first evaluation maintained the same results.

CONCLUSIONS

Corrective measures introduced were effective since all the below standard criteria improved, including metabolic complications. Notwithstanding, it is necessary to continue in this line to improve the criteria still below standard.

Weight-adjusted resting energy expenditure is not constant in critically ill patients

OBJECTIVE

In critically ill patients, energy requirements are frequently calculated as a multiple of total body weight presuming a linear relationship between total body weight and resting energy expenditure (REE); however, it is doubtful if this estimation of energy needs should be applied to all patients, particularly to overweight patients, since adipose tissue has a low contribution to REE. This study was undertaken to test the hypothesis that REE adjusted for total body weight decreases with increasing body mass index in critically ill patients. Additionally, measured REE was compared with three predictive equations.

DESIGN AND SETTING

Clinical study in a university hospital intensive care unit.

PATIENTS

One hundred critically ill patients admitted to the intensive care unit.

MEASUREMENTS AND RESULTS

Patients were included into four groups according to their body mass index (normal weight, pre-obese, obese, and morbidly obese). Measured REE was assessed using indirect calorimetry. Energy needs were calculated using the basal metabolic rate, the Consensus Statement of the American College of Chest Physicians (REEacs), and 25[Symbol: see text]kcal/kg of ideal body weight (REEibw). Adjusted REE was 24.8 +/- 5.5 kcal/kg in normal weight, 22.0 +/- 3.7 kcal/kg in pre-obese, 20.4 +/- 2.6 kcal/kg in obese, and 16.3 +/- 2.3 kcal/kg in morbidly obese patients (p < 0.01). Basal metabolic rate underestimated measured REE in normal weight and pre-obese patients. REEacs and REEibw over- and underestimated measured REE in overweight patients, respectively.

CONCLUSIONS

Predictive equations were not able to estimate measured REE adequately in all the patients. Adjusted REE decreased with increasing body mass index; thus, a body mass index group-specific adaptation for the estimation of energy needs should be applied.

Can bioelectrical impedance analysis identify malnutrition in preoperative nutrition assessment?

OBJECTIVE

Malnutrition is characterized by changes in cellular membrane integrity and alterations in fluid balance, both of which can be detected by bioelectrical impedance analysis (BIA). We investigated whether BIA-measured variables could detect malnutrition, as defined by the Subjective Global Assessment (SGA), in preoperative surgical patients.

METHODS

We prospectively evaluated 279 patients hospitalized for elective gastrointestinal surgery during the first 72 h after admission. BIA estimates were used to derive body cell mass, ratio of extracellular mass to body cell mass, and phase angle. Malnutrition diagnosed with these measures was compared with the SGA score. Receiver operating characteristic curves also were formulated to explore alternative cutoff points for one measure, phase angle.

RESULTS

A linear trend for means across SGA categories was found for all indicators used, except percentage of body cell mass. However, there was only fair overall agreement between SGA and BIA estimates. The receiver operating characteristic curves for phase angle suggested that the test was too sensitive or too specific. No alternative cutoff points resulted in suitable tests that could provide an alternative to SGA.

CONCLUSIONS

Although not in close agreement with SGA, the results suggested that there are some alterations in tissue electrical properties with malnutrition that can be detected by BIA. New cutoff points may be needed for application of BIA as a complementary method in the nutrition assessment of surgical patients.

Fever and sepsis during neutropenia are associated with expansion of extracellular and loss of intracellular water

BACKGROUND AND AIMS

Shifts from intracellular to extracellular water are features of a catabolic reaction to sepsis. Bedside assessment of fluid shifts was carried out in neutropenic patients at high risk of systemic infection.

METHODS

Multifrequency bioelectrical impedance analysis was performed in 41 patients with leukemia or high-malignant lymphoma and chemotherapy-induced neutropenia.

RESULTS

Hydration was stable during afebrile periods except for transient intra- and extracellular dehydration after chemotherapy. The risk of over-hydration and dehydration increased 3-fold during fever. Over-hydration was more severe when occurring during fever. Extracellular water was highly variable and tended to increase, and intracellular water was slowly depleted. During sepsis, these alterations were enhanced. Changes in hydration status did not predict subsequent progression to sepsis because it developed more slowly than other symptoms of infection.

CONCLUSIONS

Extracellular over-hydration and intracellular dehydration are observed in febrile infection in neutropenia, similar to severe sepsis. If the technical limits of bioelectrical impedance are taken into account, this method may be useful for non-invasive monitoring of these features of metabolic stress.