The Importance of Hydration in Body Composition Assessment in Children Aged 6-16 Years

Body composition is associated with many noncommunicable diseases. The accuracy of many simple techniques used for the assessment of body composition is influenced by the fact that they do not take into account tissue hydration and this can be particularly problematic in paediatric populations. The aims of this study were: (1) to assess the agreement of two dual energy X-ray absorptiometry (DXA) systems for determining total and regional (arms, legs, trunk) fat, lean, and bone mass and (2) to compare lean soft tissue (LST) hydration correction methods in children. One hundred and twenty four healthy children aged between 6 and 16 years old underwent DXA scans using 2 GE healthcare Lunar systems (iDXA and Prodigy). Tissue hydration was either calculated by dividing total body water (TBW), by 4-component model derived fat free mass (HFFM_TBW) or by using the age and sex specific coefficients of Lohman, 1986 (HFFM_Lohman) and used to correct LST. Regression analysis was performed to develop cross-calibration equations between DXA systems and a paired samples t-test was conducted to assess the difference between LST hydration correction methods. iDXA resulted in significantly lower estimates of total and regional fat and lean mass, compared to Prodigy. HFFM_TBW showed a much larger age/sex related variability than HFFM_Lohman. A 2.0 % difference in LST was observed in the boys (34.5 kg vs 33.8 kg respectively, p < 0.05) and a 2.5% difference in the girls (28.2 kg vs 27.5 kg respectively, p < 0.05) when corrected using either HFFM_TBW or HFFM_Lohman. Care needs to be exercised when combining data from iDXA and Prodigy, as total and regional estimates of body composition can differ significantly. Furthermore, tissue hydration should be taken into account when assessing body composition as it can vary considerably within a healthy paediatric population even within specific age and/or sex groups.     

Dual X-Ray absorptiometry in pediatric studies: changing scan modes alters bone and body composition measurements.

The use of dual X-ray absorptiometry (DXA) for measurement of bone mineral and body composition in pediatric subjects faces a major technical issue: body size dictates choice of scan mode. However, different scan modes change results in the same subject, thus affecting the accuracy of bone/body composition measurements and especially the capacity to measure changes owing to either growth or intervention. To evaluate the effect of scan mode selections on measurements of bone mineral and body composition, 13 children with weights at the cutoff point between the pediatric large and adult medium scan modes of Lunar DPX or DPXL (Lunar, Madison, WI) with software 3.6 g (35.3 +/- 0.9 kg or 77.7 +/- 2.0 lb) were scanned by both modes. Adult medium mode gave significantly higher results than pediatric large mode for total body fat mass (11.1%), fat% (10.5%), bone mineral content (8.1%), and bone area (1.3%) (p < 0.02). The differences between pediatric large and adult medium modes in fat measurements increased with increasing body mass index ([BMI], kg/m(2)), body surface area ([BSA], m(2)), and trunk size (mm), whereas the differences in bone mineral measurement tended to be greater only with increasing BMI and BSA. None of the differences were correlated to body weight. This study suggests that scan mode selections based on trunk size, BMI, or BSA instead of body weight may improve continuity of bone and body composition measurements by the DXA technique in pediatric subjects.     

Is Discordance in Bone Measurements Affected by Body Composition or Anthropometry? A Comparative Study Between Peripheral and Central Devices

Screening of osteoporosis using peripheral bone measurements has become more common, even though diagnostic discrepancies are known to exist between peripheral dual-energy X-ray (pDXA) or quantitative ultrasound (QUS) and central DXA measurements. Values of diagnostic parameters such as bone mineral density, speed of (ultra)sound, and broadband ultrasound attenuation are affected by bone size and soft tissue composition. However, their significance for the discordance between peripheral and central techniques is unclear. In this study, bone status and total body composition of 139 women (mean age 68.3 yr [1.7 SD], mean body mass index 26.5 kg/m2 [3.6 SD]) were assessed by 3 GE Lunar devices. Heel pDXA and heel QUS were conducted using peripheral instantaneous X-ray imaging (PIXI) and Achilles, respectively, and central DXA measurements were taken at the posterior-anterior lumbar spine (L2-L4) and at the left femoral neck using Prodigy. Positive significant associations were found between body height or fat (%) and most DXA or QUS parameters. The discordance between the site-dependent DXA or QUS T-score values typically increased (p<0.05) as a function of body weight or fat (%), but not with body height. On an average, body adiposity accounted for less than 11% of the differences between the techniques; however, increase of total body fat from 20% to 45% led to a discrepancy of one T-score between DXA(HEEL) and QUS(HEEL). To avoid diagnostic bias, comparative assessment of the devices using the same population is recommended.     

Bone mineral density and body composition in men with systemic lupus erythematosus: a case control study

OBJECTIVE: To study the bone mineral density (BMD) and body composition in men with systemic lupus erythematosus (SLE). METHODS: Consecutive male patients who fulfilled > or =4 ACR criteria for SLE and age-matched healthy men were recruited for measurement of BMD and body composition by DXA scan. Risk factors for low BMD in SLE patients were evaluated. RESULTS: 40 male SLE patients were studied (age 42.6+/-12 years; disease duration 84.7+/-79 months). 34 (85%) patients were treated with long-term glucocorticoids. Compared with 40 controls, SLE patients had a significantly lower BMD at the lumbar spine (0.96+/-0.16 vs 1.03+/-0.11 g/cm2; p=0.02) and the hip (0.87+/-0.14 vs 0.94+/-0.12 g/cm2; p=0.04). At the spine, 12 (30%) SLE patients had Z scores< - 2.0 and 2 (5%) had osteoporotic fractures. At the hip, 3 (7.5%) patients had Z scores< - 2.0 but none had hip fractures. The BMD Z scores at the femoral neck and spine were significantly lower in SLE patients than controls. The total lean body mass was also lower in patients than control subjects (46.4+/-7.3 vs 50.5+/-5.9 kg; p=0.01). Multiple regression revealed increasing age, habitual drinking, lower BMI and use of high-dose prednisolone were unfavorably associated with lower BMD at the spine in SLE patients. CONCLUSIONS: Reduced BMD and lean body mass are prevalent in men with SLE. Appropriate measures against osteoporosis should be undertaken, especially in older patients with low BMI who receive high-dose glucocorticoids.     

Pediatric in vivo cross-calibration between the GE Lunar Prodigy and DPX-L bone densitometers

Dual energy x-ray absorptiometry (DXA) machine cross-calibration is an important consideration when upgrading from old to new technology. In a recent cross-calibration study using adult subjects, close agreement between GE Lunar DPX-L and GE Lunar Prodigy scanners was reported. The aim of this work was to cross-calibrate the two machines for bone and body composition parameters for pediatrics from age 5 years onwards. One-hundred ten healthy volunteers aged 5–20 years had total body and lumbar spine densitometry performed on DPX-L and Prodigy densitometers. Cross-calibration was achieved using linear regression and Bland–Altman analysis. There was close agreement between the machines, with r² ranging from 0.85 to 0.99 for bone and body composition parameters. Paired t-tests demonstrated significant differences between machines that were dependent on scan acquisition mode, with the greatest differences reported for the smallest children. At the lumbar spine, Prodigy bone mineral density (BMD) values were on average 1.6% higher compared with DPX-L. For the total body, there were no significant differences in BMD; however, there were significant differences in bone mineral content (BMC) and bone area. For small children, the Prodigy measured lower BMC (9.4%) and bone area (5.8%), whereas for larger children the Prodigy measured both higher BMC (3.1%) and bone area (3.0%). A similar contrasting pattern was also observed for the body composition parameters. Prodigy values for lean body mass were higher (3.0%) for small children and lower (0.5%) for larger children, while fat body mass was lower (16.4%) for small children and higher (2.0%) for large children. Cross-calibration coefficients ranged from 0.84 to 1.12 and were significantly different from 1 (p<0.0001) for BMC and bone area. Bland–Altman plots showed that within the same scan acquisition modes, the magnitude of the difference increased with body weight. The results from this study suggest that the differences between machines are mainly due to differences in bone detection algorithms and that they vary with body weight and scan mode. In general, for population studies the differences are not clinically significant. However, for individual children being measured longitudinally, cross-over scanning may be required.     

Pneumothorax in the Intensive Care Unit: Incidence, Risk Factors, and Outcome

Background: The risk factors and outcomes of critically ill patients with iatrogenic pneumothorax (IP) have not been studied in a large unselected intensive care unit (ICU) population.

Methods: The authors studied a prospective cohort of adults admitted for more than 24 h. Data were collected at ICU admission and daily by senior physicians until ICU discharge. Risk factors for IP were identified in the entire cohort. A matched nested case-control study was used to evaluate the excess risk of IP in decedents.

Results: Of the 3,499 patients, 69 with pneumothorax before ICU admission were excluded. Of the remaining 3,430 patients, 94 experienced IP within 30 days (42 due to barotrauma and 52 due to invasive procedures). The cumulative incidence of IP was 1.4% (95% confidence interval [CI], 1.0-1.8) on day 5 and 3.0% (95% CI, 2.4-3.6) on day 30. Risk factors for IP (hazard ratio [95% CI]) were body weight less than 80 kg (2.4 [1.3-4.2]), history of adult immunodeficiency syndrome (2.8 [1.2-6.4]), diagnosis of acute respiratory distress syndrome (5.3 [2.6-11]) or cardiogenic pulmonary edema at admission (2.0 [1.1-3.6]), central vein or pulmonary artery catheter insertion (1.7 [1.0-2.7]), and use of inotropic agents during the first 24 h (2.1 [1.3-3.4]). Excess risk of IP in decedents was 2.6 (95% CI, 1.3-4.9; P = 0.004).     

A comparison of total body water measurements using whole-body magnetic resonance imaging versus tritium dilution in primates.

Standard techniques conventionally used to assess body composition have various drawbacks which include a requirement for specialized equipment and expertise not widely available, radiation exposure, extensive study time periods, and limited clinical utility. Anthropometric methods, which are more clinically feasible, also involve substantially greater calculation error. This study was designed to compare a newly developed whole-body magnetic resonance (MR) imaging technique with standard tritium dilution (THO) to measure total body water (TBW) in eight primates (Macaca fascicularis). Sedated primates underwent whole-body MR imaging (10-12 contiguous 50-mm slices) and TBW was computed using a previously validated program. After 5 days to allow for primate recovery and stabilization, TBW measurements were repeated using THO methodology. Linear regression analysis of TBWMRI (72.1 +/- 5.7% body wt) compared with TBWTHO (73.8 +/- 3.2% body wt) yielded a Pearson correlation of r = 0.8145, P = 0.02 with a mean squared error of 2.14. Whole-body MR imaging determination of TBW correlates well with THO, requires less time (20 min versus 24 hr), and does not expose the subject to radiation. This study suggests that whole-body MR imaging is an accurate technique for in vivo body composition analysis. As demonstrated by the body size of this investigational primate model, the technique maybe particularly applicable to the study of human infants.     

How to evaluate body composition in chronic kidney disease?

Onset of chronic kidney disease is rapidly followed by the occurrence of body composition alterations due to imbalance in sodium homeostasis and increased protein catabolism. These alterations lead to malnutrition and an increased cardiovascular risk and need to be accurately analysed. Numerous methods of body composition analysis are available but currently none is able to measure the five physiologic compartments -- extracellular fluid, intracellular fluid, body cell mass, bone mass and fat mass. Some are difficult to realize such the underwater weighing or neutron activation analysis, others are easier to do as skinfolds thickness or midarm muscle circumference measurements, dual energy X-ray absorptiometry (Dexa) or spectroscopic impedancemetry. These two techniques seem currently the most appropriate to measure fat mass, bone mass and lean mass for Dexa and body fluids for impedancemetry. The combination of Dexa and impedancemetry allows the calculation of body cell mass which is one of the most important parameter to evaluate nutritional status of patients with chronic kidney disease.     

Frequency of Use of Suturing and Repair Techniques Preferred by Dermatologic Surgeons

BACKGROUND: There are many closure techniques and suture types available to cutaneous surgeons. Evidence-based data are not available regarding the frequency of use of these techniques by experienced practitioners. OBJECTIVE: To quantify, by anatomic site, the frequency of use of common closure techniques and suture types by cutaneous surgeons. METHOD: A prospective survey of the members of the Association of Academic Dermatologic Surgeons that used length-calibrated visual-analog scales to elicit the frequency of use of specific suture techniques. RESULTS: A response rate of 60% (61/101) indicated reliability of the received data. Epidermal layers were closed most often, in descending order, by simple interrupted sutures (38-50%), simple running sutures (37-42%), and vertical mattress sutures (3-8%), with subcuticular sutures used more often on the trunk and extremities (28%). The most commonly used superficial sutures were nylon (51%) and polypropylene (44%), and the most common absorbable suture was polyglactin 910 (73%). Bilayered closures, undermining, and electrocoagulation were used, on average, in 90% or more sutured repairs. The median diameters (defined as longest extent along any axis) of most final wound defects were 1.1 to 2.0 cm (56%) or 2.1 to 3.0 cm (37%). Fifty-four percent of wounds were repaired by primary closure, 20% with local flaps, and 10% with skin grafting, with the remaining 15% left to heal by second intent (10%) or referred for repair (5%). Experience-related differences were detected in defect size and closure technique: defects less than 2 cm in diameter were seen by less experienced surgeons, and defects greater than 2 cm by more experienced surgeons (Wilcoxon's rank-sum test: p=.02). But more experienced surgeons were less likely to use bilayered closures (r=-0.28, p=.036) and undermining (r=-0.28, p=.035). CONCLUSIONS: There is widespread consensus among cutaneous surgeons regarding optimal suture selection and closure technique by anatomic location. More experienced surgeons tend to repair larger defects but, possibly because of their increased confidence and skill, rely on less complicated repairs.     

The Official Positions of the International Society for Clinical Densitometry: Indications of Use and Reporting of DXA for Body Composition

The technique of body composition by dual-energy X-ray absorptiometry (DXA) has been used for several years in the research environment. Its ability to accurately and precisely measure lean, fat, and mineral composition in various body compartments has been well validated. Furthermore, the technique is widely available to clinical patients on existing DXA instruments throughout the world through the use of specific software packages and scanning algorithms. There have been few clear statements regarding the clinical indications for body composition measurement in patients outside the research setting. This is in part because of the lack of specific documented interventions that would be affected by body composition test results, beyond usual clinical advice. We have examined a few of the most common, specific scenarios (HIV therapy, sarcopenia, bariatric surgery, obesity) and proposed indications for body composition assessment. We have also discussed contraindications to body composition testing.     

Pneumothorax in the intensive care unit: incidence, risk factors, and outcome

BACKGROUND: The risk factors and outcomes of critically ill patients with iatrogenic pneumothorax (IP) have not been studied in a large unselected intensive care unit (ICU) population. METHODS: The authors studied a prospective cohort of adults admitted for more than 24 h. Data were collected at ICU admission and daily by senior physicians until ICU discharge. Risk factors for IP were identified in the entire cohort. A matched nested case-control study was used to evaluate the excess risk of IP in decedents. RESULTS: Of the 3,499 patients, 69 with pneumothorax before ICU admission were excluded. Of the remaining 3,430 patients, 94 experienced IP within 30 days (42 due to barotrauma and 52 due to invasive procedures). The cumulative incidence of IP was 1.4% (95% confidence interval [CI], 1.0-1.8) on day 5 and 3.0% (95% CI, 2.4-3.6) on day 30. Risk factors for IP (hazard ratio [95% CI]) were body weight less than 80 kg (2.4 [1.3-4.2]), history of adult immunodeficiency syndrome (2.8 [1.2-6.4]), diagnosis of acute respiratory distress syndrome (5.3 [2.6-11]) or cardiogenic pulmonary edema at admission (2.0 [1.1-3.6]), central vein or pulmonary artery catheter insertion (1.7 [1.0-2.7]), and use of inotropic agents during the first 24 h (2.1 [1.3-3.4]). Excess risk of IP in decedents was 2.6 (95% CI, 1.3-4.9; P = 0.004). CONCLUSION: Iatrogenic pneumothorax is a life-threatening complication seen in 3% of ICU patients. Incorporating risk factors for IP into preventive strategies should reduce the occurrence of IP.     

Prevalence of low bone mineral density in a low‐income inner‐city population

Bone mineral density (BMD) is an important factor linked to bone health. Little is known of the prevalence of low BMD and its associated risk factors in an urban underserved population. Between 2001 and 2004, we recruited 338 subjects who completed drug use and medical history questionnaires, underwent hormonal measurements, and underwent whole‐body dual‐energy X‐ray absorptiometry (DXA) for evaluation of BMD and body composition. Of these, 132 subjects had site‐specific DXA (lumbar spine and hip) performed. Osteoporosis was defined as a T‐score of –2.5 or less for men 50 years of age and older and postmenopausal women and a Z‐score of –2.0 or less in men younger than 50 years of age and premenopausal women at either the lumbar spine, total hip, or femoral neck, according to National Osteoporosis Foundation (NOF) guidelines. The cohort consisted of mostly African‐American, middle‐aged people with a high prevalence of illicit drug use, 50% HIV⁺, and 39% hepatitis C⁺. Osteoporosis was identified in 22% of subjects (24 men, 5 women), with the majority of cases (90%) attributable to osteoporosis at the lumbar spine. Osteoporosis was more common in men than in women. Lower whole‐body BMD among women was associated with multiple risk factors, but only with lower lean mass among men. Osteoporosis was highly prevalent in men, mainly at the spine. The risk factors for bone loss in this population need to be further clarified. Screening men for osteoporosis starting at age 50 might be warranted in this population given the multiple risk factors and the unexpectedly high prevalence of low BMD. © 2011 American Society for Bone and Mineral Research.     

Association between body mass index and mortality is similar in the hemodialysis population and the general population at high age and equal duration of follow-up

The association of body mass index (BMI) with mortality in hemodialysis patients has been found to be reversed in comparison with the general population. This study examined the association of BMI with mortality in the hemodialysis population and the general population when age and time of follow-up were made strictly comparable. Hemodialysis patients who were aged 50 to 75 yr at the start of follow-up were selected from the Netherlands Cooperative Study on the Adequacy of Dialysis-2 (NECOSAD), a prospective cohort study in incident dialysis patients in the Netherlands (n = 722; age 66 +/- 7 yr; BMI 25.3 +/- 4.5 kg/m(2)), and compared with adults who were aged 50 to 75 yr and included in the Hoorn Study, a population-based prospective cohort study in the same country (n = 2436; age 62 +/- 7 yr; BMI 26.5 +/- 3.6 kg/m(2)). In both populations, 2- and 7-yr standardized mortality rates were calculated for categories of BMI. Adjusted hazard ratios (HR) of BMI categories were calculated with a BMI of 22.5 to 25 kg/m(2) as the reference category within each population. In 7 yr of follow-up, standardized mortality rates were approximately 10 times higher in the hemodialysis population than those in the general population. Compared with the reference category, the HR of BMI <18.5 kg/m(2) was 2.0 (95% confidence interval [CI]1.2 to 3.4) in the hemodialysis population and 2.3 (95% CI 0.7 to 7.5) in the general population. Obesity (BMI >or=30 kg/m(2)) was associated with a HR of 1.2 (95% CI 0.8 to 1.7) in the hemodialysis population and 1.3 (95% CI 0.9 to 2.0) in the general population. In conclusion, a hemodialysis population and a general population with comparable age and equal duration of follow-up showed similar mortality risk patterns associated with BMI. This suggests that there is no reverse epidemiology of BMI and mortality in hemodialysis patients. The clinical implication of this study is that to improve survival in the hemodialysis population, more attention should be paid to patients who are underweight instead of overweight.     

The influence of early steroid withdrawal on body composition and bone mineral density in renal transplantation patients

Corticosteroid treatment may have an important effect on body composition and bone mineral density (BMD) in renal transplantation (RTx) patients. We investigated the effect of early steroid withdrawal on body composition and BMD of RTx patients in a prospective design. Post-transplant immunosuppression consisted of tacrolimus, mycophenolate mofetil, and prednisolone. Three months after RTx, 27 patients participating in a multi-center trial were randomized either to continue steroids (at a dose of 10 mg/day, n=17; steroid+) or be withdrawn from steroids within 2 weeks (n=10; steroid-). Body composition and BMD (lumbar spine (L2-L4) and femoral neck) were measured by dual-energy X-ray absorptiometry (DEXA) just before and 3 months after randomization. With regard to body composition, fat mass tended to increase in the steroid+ group (1.1+/-2.3 kg; P=0.084), but did not change in the steroid- group. Increase in body fat percentage tended to be higher (P=0.08) in the steroid+ group (0.6+/-2.7%) than in the steroid- group (-0.7+/-2.1%). The change in lean body mass was not significantly different between the two groups. BMD of the lumbar spine and femoral neck decreased significantly in the steroid+ group (-1.4+/-3.2% and -2.3+/-2.9%, respectively, P<0.05) while no changes were observed in the steroid- group. The change in BMD of the lumbar spine was significantly different between the steroid+ and the steroid- group, whereas the change in BMD of the femoral neck was not significantly different. Thus, the increase in fat mass tended to be higher in the group continuing on steroids, though not significant, due to large inter-individual variation. In general, the effect of early steroid withdrawal on body composition after RTx appears to be modest. In addition, early steroid withdrawal seems to have beneficial effects on BMD in RTx patients, especially in the lumbar region.     

Weiterentwicklung des transrektalen Ultraschalls Artifizielle neuronale Netzwerkanalyse (ANNA) in der Erkennung und Stadieneinteilung des Prostatakarzinoms

As a result of the enhanced clinical application of prostate specific antigen (PSA), an increasing number of men are becoming candidates for prostate cancer work-up. A high PSA value over 20 ng/ml is a good indicator of the presence of prostate cancer, but within the range of 4-10 ng/ml, it is rather unreliable. Even more alarming is the fact that prostate cancer has been found in 12-37% of patients with a "normal" PSA value of under 4 ng/ml (Hybritech). While PSA is capable of indicating a statistical risk of prostate cancer in a defined patient population, it is not able to localize cancer within the prostate gland or guide a biopsy needle to a suspicious area. This necessitates an additional effective diagnostic technique that is able to localize or rule out a malignant growth within the prostate. The methods available for the detection of these prostate cancers are digital rectal examination (DRE) and Transrectal ultrasound (TRUS). DRE is not suitable for early detection, as about 70% of the palpable malignancies have already spread beyond the prostate. The classic problem of visual interpretation of TRUS images is that hypoechoic areas suspicious for cancer may be either normal or cancerous histologically. Moreover, about 25% of all cancers have been found to be isoechoic and therefore not distinguishable from normal-appearing areas. None of the current biopsy or imaging techniques are able to cope with this dilemma. Artificial neural networks (ANN) are complex nonlinear computational models, designed much like the neuronal organization of a brain. These networks are able to model complicated biologic relationships without making assumptions based on conventional statistical distributions. Applications in Medicine and Urology have been promising. One example of such an application will be discussed in detail: A new method of Artificial Neural Network Analysis (ANNA) was employed in an attempt to obtain existing subvisual information, other than the gray scale, from conventional TRUS and to improve the accuracy of prostate cancer identification.     

Oncologic clearance with preservation of reconstructive options: literature review and the ‘delayed reconstruction after pathology evaluation (DRAPE)’ technique

Intraoperative frozen section and Mohs' micrographic surgery (MMS) are two techniques used to ensure oncological clearance without resorting to unnecessarily wide margins that might compromise reconstructive options for definitive wound closure. In addition to some technical issues, these techniques are suboptimal for resection of tumours such as melanoma, where specific tissue margins at histopathology are required to ensure minimal risk of local recurrence. We describe a technique that minimizes the amount of tissue excised and uses definitive paraffin sections interpreted in a pathology laboratory in order to delay reconstruction until after clear oncologic margins are obtained. This ‘delayed reconstruction after pathology evaluation (DRAPE)’ technique is particularly directed at extensive and complicated skin lesions, located in areas of the body that can be difficult to reconstruct and are prone to disfigurement and/or loss of function. A review of the literature is undertaken, establishing the role of each technique in achieving clear surgical margins. A case example is presented, highlighting the role of the DRAPE approach. The DRAPE technique is presented as a useful option for high‐risk lesions, especially within aesthetically sensitive regions or for complex reconstructions, and when reconstruction can be reasonably delayed while tumour clearance is established.     

Body composition changes in the subtotally nephrectomized rat fed differing dietary proteins

Changes in body composition are found in chronic uraemia, but it is unclear if this results from poor nutrient intake or is a consequence of impaired renal function. To investigate this question, 31 female Wistar rats were allocated to undergo subtotal nephrectomy or sham operation and were fed diets of either 24% casein or 24% soya protein. Three months later measurements of inulin clearance were undertaken in the conscious animal and the carcass subsequently analyzed for body water and body fat. Subtotally nephrectomized animals had a significantly greater proportion of body water (p less than 0.001) and a lesser proportion of body fat (p less than 0.001) than control animals, and a significant correlation was found between glomerular filtration rate and body fat content (24% casein diet: r = 0.96; 24% soya diet: r = 0.71). The dietary protein source appeared not to influence the body composition. These results support the concept that altered body composition in uraemia is due to renal dysfunction rather than altered nutrient intake.     

Clinical applications of low flow and closed circuit anesthesia

Minimal Flow Anesthesia, an extreme technique of semiclosed use of rebreathing systems performed with a fresh gas flow of 0.5 l/min, can be managed with already available anesthesia machines. As a standardized fresh gas volume with fixed composition is used, due to the exponential decrease of the patient's gas uptake, the gas composition within the breathing system may change markedly during the time course of anaesthesia. Nevertheless, by this degree of fresh gas flow reduction, being very close to the patient's gas uptake, the advantages of the rebreathing technique can be achieved nearly extensively. Closed System Anesthesia, however, the anesthetic technique by which just these volumes of oxygen, nitrous oxide, and volatile anesthetics are applied, which are taken up by the patient at the particular time, can't be performed satisfactorily even if highly sophisticated equipment is used. The need for continuous adjustment of the fresh gas controls, the insufficient accuracy of the dosaging systems and the impossibility to calculate precisely the uptake figures in the individual case are essential obstacles for the routine use of this method. An account of the clinical realization of both techniques is given and the specific advantages and disadvantages are considered: although modern anesthesia machines are designed especially for the use of even lowest fresh gas flow rates, quantitative Closed System Anesthesia will not become a technique for routine clinical practice until apparatus with computer-aided closed loop feedback control of the fresh gas supply will be available.     

Volume status and body composition of chronic dialysis patients: utility of bioelectric impedance plethysmography

We assessed the utility of bioelectric impedance plethysmography (BIA) for measuring acute volume changes and body composition in patients with renal disease. Chronic hemodialysis and peritoneal dialysis patients were evaluated before and after dialysis. Total body water, as measured by BIA, predicts body weight. Acute changes in body water, induced by dialysis, are not predicted well by data derived from BIA. Body fat (%) and fat-free mass (%), determined by anthropometry, are predicted well by body composition data derived by BIA. BIA is useful for assessing body composition in this population, but must be cautiously applied to the measurement of acute volume changes.     

Body composition in renal transplant patients: bioimpedance analysis compared to isotope dilution, dual energy X-ray absorptiometry, and anthropometry

Whether multifrequency bioelectrical impedance analysis (MF-BIA), a relatively new method for measuring body composition, is also applicable for accurate body composition measurements in renal transplant (RTx) patients is not known. Therefore, the use of MF-BIA is validated in 77 RTx patients with a stable renal function at least 2 yr posttransplantation. MF-BIA is compared to isotope dilution techniques for measurement of body water compartments, and to dual energy x-ray absorptiometry (DEXA) and anthropometry for measurement of fat and fat free mass. Finally, DEXA and anthropometry are compared to each other. Method agreement is assessed by intraclass correlation coefficients (ICC) and plotted by Bland and Altman analysis. MF-BIA significantly underestimates total body water (TBW, 0.7+/-2.1 L) and overestimates the extracellular water (ECW, 3.3+/-1.8 L) compared to isotope dilution; the ICC between both techniques is 0.943 for TBW and 0.846 for ECW. The percentage body fat (BF) measured by MF-BIA is significantly higher than both BF measured by DEXA (3.4+/-4.7%) or by anthropometry (5.5+/-5.2%). The ICC between MF-BIA and DEXA is 0.887 and between MF-BIA and anthropometry 0.856. BF measured by DEXA is significantly higher than BF measured by anthropometry (2.1+/-4.4%); their ICC is 0.913. In conclusion, MF-BIA seems to be suitable for measurement of TBW in RTx patients; however, method agreement between isotope dilution and MF-BIA for the measurement of ECW is not satisfactory. In the assessment of fat and fat free mass, the reliability of MF-BIA appears to be questionable. Method agreement between DEXA and anthropometry seems to be slightly better.