The importance of metabolic rate and the folly of body surface area calculations

The error of estimated GFR in predialysis care

The error of estimated glomerular filtration rate (eGFR) and its consequences in predialysis are unknown. In this prospective multicentre study, 315 predialysis patients underwent measured GFR (mGFR) by the clearance of iohexol and eGFR by 52 formulas. Agreement between eGFR and mGFR was evaluated by concordance correlation coefficient (CCC), total deviation index (TDI) and coverage probability (CP). In a sub-analysis we assessed the impact of eGFR error on decision-making as (i) initiating dialysis, (ii) preparation for renal replacement therapy (RRT) and (iii) continuing clinical follow-up. For this sub-analysis, patients who started RRT due to clinical indications (uremia, fluid overload, etc.) were excluded. eGFR had scarce precision and accuracy in reflecting mGFR (average CCC 0.6, TDI 70% and cp 22%) both in creatinine- and cystatin-based formulas. Variations -larger than 10 ml/min- between mGFR and eGFR were frequent. The error of formulas would have suggested (a) premature preparation for RTT in 14% of stable patients evaluated by mGFR; (b) to continue clinical follow-up in 59% of subjects with indication for RTT preparation due to low GFRm and (c) to delay dialysis in all asymptomatic patients (n = 6) in whom RRT was indicated based on very low mGFR. The error of formulas in predialysis was frequent and large and may have consequences in clinical care.

The biological age model for evaluating the degree of aging in centenarians

BACKGROUND

Biological age (BA) has been used to assess individuals' aging conditions. However, few studies have evaluated BA models' applicability in centenarians.

METHODS

Important organ function examinations were performed in 1798 cases of the longevity population (80∼115 years old) in Hainan, China. Eighty indicators were selected that responded to nutritional status, cardiovascular function, liver and kidney function, bone metabolic function, endocrine system, hematological system, and immune system. BA models were constructed using multiple linear regression (MLR), principal component analysis (PCA), Klemera and Doubal method (KDM), random forest (RF), support vector machine (SVM), extreme gradient boosting (XGBoost), and light gradient boosting machine (lightGBM) methods. A tenfold crossover validated the efficacy of models.

RESULTS

A total of 1398 participants were enrolled, of whom centenarians accounted for 49.21%. Seven aging markers were obtained, including estimated glomerular filtration rate, albumin, pulse pressure, calf circumference, body surface area, fructosamine, and complement 4. Eight BA models were successfully constructed, namely MLR, PCA, KDM1, KDM2, RF, SVM, XGBoost and lightGBM, which had the worst R2 of 0.45 and the best R2 of 0.92. The best R2 for cross-validation was KDM2 (0.89), followed by PCA (0.62).

CONCLUSION

In this study, we successfully applied eight methods, including traditional methods and machine learning, to construct models of biological age, and the performance varied among the models.

Body surface area and treatment failure in peritoneal dialysis-associated peritonitis

INTRODUCTION

This study mainly discussed the relationship between body surface area (BSA) and treatment failure of peritoneal dialysis-associated peritonitis (PDAP).

METHODS

The exposures were BSA grouped by the tertiles of BSA levels. The association between BSA and the risk of treatment failure in PDAP, defined as the temporary or permanent switch to hemodialysis and kidney transplantation, was evaluated in Cox proportional hazards models.

RESULTS

A total of 483 episodes in 285 patients were recorded in our center. As a three-level categorical variable, in reference to G3, the G1 of BSA displayed a 4.054-fold increased venture of treatment failure in a fully adjusted model. In sensitivity analysis, a lower value of BSA (G1) was identified as an independent risk factor for peritonitis episodes (odds ratio = 2.433, 95% confidence interval: 1.184-4.999, p = 0.015).

CONCLUSION

A lower level of body surface area was remarkably associated with a higher incidence of treatment failure among peritoneal dialysis-associated peritonitis episodes.

Light, Water, and Melatonin: The Synergistic Regulation of Phase Separation in Dementia

The swift rise in acceptance of molecular principles defining phase separation by a broad array of scientific disciplines is shadowed by increasing discoveries linking phase separation to pathological aggregations associated with numerous neurodegenerative disorders, including Alzheimer’s disease, that contribute to dementia. Phase separation is powered by multivalent macromolecular interactions. Importantly, the release of water molecules from protein hydration shells into bulk creates entropic gains that promote phase separation and the subsequent generation of insoluble cytotoxic aggregates that drive healthy brain cells into diseased states. Higher viscosity in interfacial waters and limited hydration in interiors of biomolecular condensates facilitate phase separation. Light, water, and melatonin constitute an ancient synergy that ensures adequate protein hydration to prevent aberrant phase separation. The 670 nm visible red wavelength found in sunlight and employed in photobiomodulation reduces interfacial and mitochondrial matrix viscosity to enhance ATP production via increasing ATP synthase motor efficiency. Melatonin is a potent antioxidant that lowers viscosity to increase ATP by scavenging excess reactive oxygen species and free radicals. Reduced viscosity by light and melatonin elevates the availability of free water molecules that allow melatonin to adopt favorable conformations that enhance intrinsic features, including binding interactions with adenosine that reinforces the adenosine moiety effect of ATP responsible for preventing water removal that causes hydrophobic collapse and aggregation in phase separation. Precise recalibration of interspecies melatonin dosages that account for differences in metabolic rates and bioavailability will ensure the efficacious reinstatement of the once-powerful ancient synergy between light, water, and melatonin in a modern world.

Body Surface Area (BSA) is a Better Osteoporosis Associated Anthropometric Parameter Than Other Anthropometric Parameters in Elderly Population

Body surface area (BSA) is widely used for adjusting drug dose, while few studies have yet systematically evaluated its association with osteoporosis and compared its advantage with other anthropometric parameters in osteoporotic risk prediction. A total of 10,021 Chinese individuals aged over 65 years were enrolled in our study. Bone mineral density (BMD) was measured, and demographic information was also collected. Pearson correlation analysis, receiver operating characteristic (ROC) curves and predictive analysis were performed to assess the clinical practice of BSA for osteoporosis. BSA had the strongest correlation with BMD (0.544, p < 0.001) compared with conventional anthropometric indices. Besides, BSA had the highest power in osteoporosis prediction, with an area under the curve (AUC) reaching 0.81. After incorporating BSA into the osteoporosis risk prediction model, the AUC improved from 0.82 to 0.83 (p < 0.01). We found BSA provided additional diagnostic value beyond conventional anthropometric information with continuous and category NRIs were 30.40% (p < 0.01) and 3.29% (p < 0.01), respectively, and the IDI was 1.85% (p < 0.01). BSA was positively associated with osteoporosis and showed superior discriminative ability for osteoporosis risk prediction compared with other anthropometric parameters in the Chinese elderly population.

Peripheral Oxygen Extraction and Exercise Limitation in Asymptomatic Patients with Diabetes Mellitus

Patients with diabetes mellitus (DM) frequently present reduced exercise capacity. We aimed to explore the extent to which peripheral extraction relates to exercise capacity in asymptomatic patients with DM. We prospectively enrolled 98 asymptomatic patients with type-2 DM (mean age of 59 ± 11 years and 56% male sex), and compared with 31 age, sex and body mass index-matched normoglycemic controls. Cardiopulmonary exercise testing with resting followed by stress echocardiography was performed. Exercise response was assessed using peak oxygen uptake (peak VO₂) and ventilatory efficiency was measured using the slope of the relationship between minute ventilation and carbon dioxide production (VE/VCO₂). Peripheral extraction was calculated as the ratio of VO₂ to cardiac output. Cardiac function was evaluated using left ventricular longitudinal strain, E/e', and relative wall thickness. Among patients with DM, 26 patients (27%) presented reduced percent-predicted-peak VO₂(<80%) and 18 (18%) presented abnormal VE/VCO₂slope (>34). There was no significant difference in peak cardiac output; however, peripheral extraction was lower in patients with DM compared to controls. Higher peak E/e' (beta = -0.24, p = 0.004) was associated with lower peak VO₂ along with age, sex and body mass index (R² = 0.53). A cluster analysis found left ventricular longitudinal strain, E/e', relative wall thickness and peak VO₂ in different clusters. In conclusion, impaired peripheral extraction may contribute to reduced peak VO₂in asymptomatic patients with DM. Furthermore, a cluster analysis suggests that cardiopulmonary exercise testing and echocardiography may be complementary for defining subclinical heart failure in patients with DM.

Assessment of factors affecting short-term pulmonary functions following cardiac surgery: A prospective observational study

BACKGROUND

Pulmonary complications after cardiac surgery are very common and lead to an increased incidence of post-operative morbidity and mortality. Several factors, either modifiable or non-modifiable, may contribute to the associated unfavorable consequences related to pulmonary function. This study was aimed to investigate the degree of alteration and factors influencing pulmonary function (forced expiratory volume in one second (FEV₁) and forced vital capacity), on third, fifth, and seventh post-operative days following cardiac surgery.

METHODS

This study was executed in 71 patients who underwent on-pump cardiac surgery. Pulmonary function was assessed before surgery and on the third, fifth, and seventh post-operative days. Data including surgical details, information about risk factors, and assessment of pulmonary function were obtained.

RESULTS

The FEV₁ and forced vital capacity were significantly impaired on post-operative days 3, 5, and 7 compared to pre-operative values. The reduction in FEV₁ was 41%, 29%, and 16% and in forced vital capacity was 42%, 29%, and 19% consecutively on post-operative days 3, 5, and 7. Multivariate analysis was done to detect the factors influencing post-operative FEV₁ and forced vital capacity.

DISCUSSION

This study observed a significant impairment in FEV₁ and forced vital capacity, which did not completely recover by the seventh post-operative day. Different factors affecting post-operative FEV₁ and forced vital capacity were pre-operative FEV₁, age ≥60, less body surface area, lower pre-operative chest expansion at the axillary level, and having more duration of cardiopulmonary bypass during surgery. Presence of these factors enhances the chance of developing post-operative pulmonary complications.

Clinical Significance of Paraspinal Muscle Parameters as a prognostic factor for survival in Gastric Cancer Patients who underwent Curative Surgical Resection

Background: The quantitative and qualitative skeletal muscle parameters have been proposed to predict the outcome of patients with gastric cancer. However, the evidence for their association with long-term survival is still conflicting. This study aimed to investigate the effect of paraspinal muscle parameters on overall survival (OS) and disease-free survival (DFS) in patients with gastric cancer who underwent curative resection.

Methods: Patients with stages I or II gastric cancer who underwent curative resection between October 2006 and June 2016 were identified from electrical medical records. Paraspinal muscle area and attenuation were measured at the level of the third lumbar vertebra using computerized tomography images. For the analysis of OS and DFS, proportional hazards model was used, incorporating demographic, pathologic, laboratory, and radiologic variables.

Results: This study enrolled 296 patients (192 men and 104 women). In the multivariate proportional hazards model, total gastrectomy (hazard ratio [HR], 2.65; 95% Confidence interval [CI], 1.36-5.19; p = 0.0044), neutrophil-lymphocyte ratio (NLR) (HR, 1.27; 95% CI, 1.06-1.51; p = 0.0081), serum albumin level (HR, 0.16; 95% CI, 0.07-0.39; p < 0.0001), paraspinal muscle area adjusted for body surface area (PMA_BSA) (HR, 3.06; 95% CI, 1.65-5.67; p = 0.0004), and mean attenuation in paraspinal muscle (PMMA) (HR, 3.38; 95% CI, 1.75-6.53; p = 0.0003) were prognostic factors for OS. Similarly, total gastrectomy (HR, 2.11; 95% CI, 1.10-4.06; p = 0.0243), NLR (HR, 1.25; 95% CI, 1.06-1.48; p = 0.0071), serum albumin level (HR, 0.22; 95% CI, 0.10-0.51; p = 0.0035), PMA_BSA (HR, 2.42; 95% CI, 1.34-4.37; p = 0.0035), and PMMA (HR, 3.19; 95% CI, 1.71-5.93; p = 0.0003) were prognostic factors for DFS.

Conclusions: The pretreatment paraspinal muscle parameters such as PMA_BSA and PMMA along with total gastrectomy, NLR, and serum albumin level could predict OS and DFS in patients with stages I or II gastric cancer who underwent curative surgical resection. Because PMA_BSA and PMMA are newly characterized parameters in gastric cancer, the relationship with the survival of these parameters requires further validation in further studies before they are subjected to clinical applications.

Standard medical nutrition therapy of 25 kcal/kg ideal bodyweight/day often does not reach even resting energy expenditure for patients with type 2 diabetes

AIMS/INTRODUCTION

In Japan, an ideal bodyweight (IBW) calculated by 22 × height (m)2 has commonly been used in the planning of medical nutrition therapy (MNT). However, there have been concerns regarding calorie deficits in fulfilling resting energy expenditure (REE) for patients with type 2 diabetes undergoing MNT as defined by 25 kcal/kg IBW/day. The objective of the present study was to measure REE in patients with type 2 diabetes and verify the validity of MNT with 25 kcal/kg IBW/day.

MATERIALS AND METHODS

A retrospective cross-sectional study was carried out in 52 patients with type 2 diabetes (mean age was 65.9 ± 7.3 years, bodyweight 65.0 ± 11.3 kg, body mass index 24.9 ± 3.8 kg/m2 ). REE was measured by indirect calorimetry.

RESULTS

The mean REE was 1,601.0 ± 253.1 kcal/day. Assuming that all patients strictly observed daily energy intake as 25 kcal/kg IBW/day, 41 of 52 patients (78.9%) did not reach their REE. The greater the bodyweight, the greater the difference between assumed energy intake as 25 kcal/kg IBW and REE.

CONCLUSIONS

We call attention to the potential risk of total dietary energy intake set to 25 kcal/kg IBW/day. Clinicians should carefully plan MNT to not fall below a patient's REE to prevent sarcopenia and ensure MNT continuity.

Body surface area, height, and body fat percentage as more sensitive risk factors of cancer and cardiovascular disease

BACKGROUND

Limited studies have compared the association between various physical measurements and the risk of cancer or cardiovascular disease (CVD). We aim to explore the best-individualized indicators of cancer and CVD risk assessment.

METHODS

From May 2004 to December 2017, a community-based cohort in China involving 100 280 participants were enrolled. BMI, height, body surface area (BSA), and body fat percentage (BFP) were compared in parallel about cancer and CVD risk with the multivariable-adjusted Cox proportional hazard regression model.

RESULTS

Within the follow-up period, 3107 (3.10%) were diagnosed with cancer and 3721 (3.71%) had CVD. Per-level increased (in tertile: T1, T2, and T3 level) BSA, height, and BFP was positively associated with the risk of overall cancer [HR (95% CI): 1.10 (1.05-1.15), 1.12 (1.07-1.18), and 1.10 (1.03-1.16), respectively], whereas BMI was insignificant. Compared with the reference group (T2), the highest BSA level (T3) was positively associated with overall cancer incidence for both male [HR (95% CI): 1.28 (1.13-1.45)] and female [HR (95% CI): 1.13 (1.00-1.28)]. The BSA, height, and BFP also significantly associated with some site-specific cancers including thyroid, stomach, breast, urinary system, and skin cancer. Meanwhile, BFP presented a strong positive association with overall CVD [HR (95% CI): 1.22 (1.15-1.30) in trend] in both gender and associated with nearly all CVD subtypes especially the myocardial infarction and heart failure.

CONCLUSION

BSA, height, and BFP have more sensitivity in assessing cancer risk and BFP shows the largest hazard ratios for CVD incident. We provided valuable evidence for the application of height, BSA, and BFP in routine healthcare practice. These encouraging findings should be tested in more well-defined studies for risk prediction.

Assessment of burn size in obese adults; a literature review

PURPOSE

Obesity causes changes in the total body surface area as well as the distribution of skin surfaces. In burn management, three methods are commonly used to determine the surface area burned: the patient's palm, the rule of nines, and the Lund-Browder chart. These methods rely on the distribution of skin surface, although none of these methods consider differences in body mass. This study investigates the relationship between body surfaces and body mass in the assessment of burn size to determine the validity of the conventional methods when applied to obese individuals.

METHODS

The current literature was reviewed using relevant electronic databases. The initial search yielded 247 results. Relevant articles were then reviewed. A total of seven publications fulfilled the inclusion criteria.

RESULTS

The palmar surface area ranged between 0.59%-1.22%, depending on BMI, gender, and ethnicity, compared to 1% according to conventional methods. The palmar surface area of obese individuals approximated 0.7% of the total body surface area in Caucasians. The surface areas comprised 5%-7.5% of the total body surface area for each arm, 15%-20% for each leg, and 40%-52% for the trunk in obese or morbidly obese individuals, compared to 9%, 18%, and 36%, respectively, for normal-weight adults.

CONCLUSIONS

The commonly used methods for assessment of burns should be used with caution when applied to obese burn patients, and the clinical parameters observed even more systematically.

Removal of body surface area normalisation improves raw-measured glomerular filtration rate estimation by the Chronic Kidney Disease Epidemiology Collaboration equation and drug dosing in the obese

BACKGROUND/AIM

We aimed to compared estimated glomerular filtration rate (eGFR) according to the Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI), with (mL/min/1.73 m(2) ) and without body surface area (BSA) normalisation (CKD-EPI_noBSA, mL/min) against measured (99m) Technetium - diethylenepentaacetic acid (Tc-DTPA GFR) (mL/min) in 222 individuals, including 80 with malignancy.

METHODS

BSA was calculated for each individual using the Du Bois equation. The CKD-EPI and CKD-EPI_noBSA equations were compared with measured Tc-DTPA GFR with respect to bias, proportion within 30% of GFR (P30) and root mean square error for predicting levels of GFR, and concordance in relation to carboplatin dosing.

RESULTS

The mean (SD) for BSA and measured GFR for the entire group was 1.99 (0.25) m(2) and 127 (41) mL/min respectively. The P30 for Tc-DTPA GFR was significantly higher with the CKD-EPI_noBSA (80%) than with the CKD-EPI equation (63%, P = 0.0001). In those with body mass index (BMI) > 30 kg/m(2) , the P30 values for the CKD-EPI_noBSA and CKD-EPI were 74% and 42% respectively (P < 0.0001). Carboplatin dosing concordance for the cancer patients using the CKD-EPI and CKD-EPI_noBSA equation was 71% and 56% respectively (P = 0.07). In 78 individuals with BMI > 30 kg/m(2) , concordance in relation to carboplatin dosing using CKD-EPI_noBSA was 65% compared with 26% with the CKD-EPI (P < 0.0001).

CONCLUSION

The CKD-EPI without normalisation (CKD-EPI_noBSA) equation was superior to the CKD-EPI equation in estimating raw-measured Tc-DTPA GFR (mL/min).

The effects of malnutrition on cardiac function in African children

OBJECTIVE

Cardiac dysfunction may contribute to high mortality in severely malnourished children. Our objective was to assess the effect of malnutrition on cardiac function in hospitalised African children.

DESIGN

Prospective cross-sectional study.

SETTING

Public referral hospital in Blantyre, Malawi.

PATIENTS

We enrolled 272 stable, hospitalised children ages 6-59 months, with and without WHO-defined severe acute malnutrition.

MAIN OUTCOME MEASURES

Cardiac index, heart rate, mean arterial pressure, stroke volume index and systemic vascular resistance index were measured by the ultrasound cardiac output monitor (USCOM, New South Wales, Australia). We used linear regression with generalised estimating equations controlling for age, sex and anaemia.

RESULTS

Our primary outcome, cardiac index, was similar between those with and without severe malnutrition: difference=0.22 L/min/m(2) (95% CI -0.08 to 0.51). No difference was found in heart rate or stroke volume index. However, mean arterial pressure and systemic vascular resistance index were lower in children with severe malnutrition: difference=-8.6 mm Hg (95% CI -12.7 to -4.6) and difference=-200 dyne s/cm(5)/m(2) (95% CI -320 to -80), respectively.

CONCLUSIONS

In this largest study to date, we found no significant difference in cardiac function between hospitalised children with and without severe acute malnutrition. Further study is needed to determine if cardiac function is diminished in unstable malnourished children.

Coronary calcification with no flow limiting lesions: A potential cause for ischaemic dysfunction in syndrome X patients

Aim

Exertional angina in patients with no coronary flow limiting lesions remains a clinical puzzle. We aimed to assess the extent of coronary artery calcification (CAC) and its relationship to ventricular wall motion function using stress echocardiography in a group of patients limited by exertional angina, but no obstructive lesions.

Methods

We compared CT coronary calcium score (CACS) and dobutamine stress echocardiography in 55 patients (age 64.7 ± 7.7 years), divided into Group 1 (CACS ≤ 100) and Group 2 (CACS > 100). No patient had LV ejection fraction-EF < 55%, pulmonary hypertension, arrhythmia, renal failure or parathyroid disease. Multiple linear regression analysis was used to test the association between gender-standardized continuous echocardiographic parameters and patient groups adjusted for age, body surface area, osteoporosis and CV risk factors and CACS.

Results

At rest, LV long axis ‘subendocardial’ function was reduced (amplitude: β − 1.11 SD, p < 0.05, R² 0.6 and systolic velocity: β − 1.08 SD, p < 0.05, R² 0.44), left atrial (LA) indexed volume was raised (β 1.06 SD, p < 0.05, R² 0.37) and its systolic velocity decreased (β − 1.05 SD, p < 0.05, R² 0.35) in Group 2. With stress, wall motion score index increased (p < 0.05) and long axis disturbances worsened only in the same group. Multivariate analysis demonstrated clear relationship between ischaemic LV disturbances, reduced long axis amplitude, global longitudinal systolic strain and early diastolic strain rate. Resting and stress RV lengthening velocity also correlated with CAC score.

Conclusion

In symptomatic patients with no obstructive coronary lesions and with more than mild CAC, long axis disturbances and wall motion score index rise occur with stress, at the time of symptom development and correlate with severity of arterial calcification. These findings suggest CAC as a potential mechanism for coronary wall stiffness and consequently exertional ischaemic changes as a result of limited flow reserve.

Bone marrow uptake of ferumoxytol: a preliminary study in healthy human subjects

PURPOSE

To characterize the uptake and elimination of ferumoxytol, an ultrasmall superparamagnetic iron oxide (USPIO) agent, in bone marrow of healthy human subjects.

MATERIALS AND METHODS

Four men and two postmenopausal women, aged 22 to 57 years, were prospectively included. Simultaneous fat, water, and T2* mapping of the proximal femora was performed at 1.5 Tesla using a three-dimensional multiple gradient echo sequence. After baseline imaging, ferumoxytol (Feraheme/Rienso) was injected intravenously at a dose of 5 mg Fe/kg body weight. Imaging was repeated at 3 days, 1 month, 3 months, and 5 months after administration.

RESULTS

Imaging at 3 days revealed large increases in R2* ( =1/T2*) in hematopoietic marrow and lower average responses in fatty marrow, consistent with macrophage-specific uptake. However, certain regions of the diaphysis exhibited substantial R2* enhancement despite having very high fat content. This suggests the persistence of residual marrow stroma following adipose conversion, and may reflect the ability of diaphyseal marrow to adapt dynamically to fluctuating demand for hematopoiesis. Follow-up imaging demonstrated almost complete R2* recovery within 3 months.

CONCLUSION

The observed R2* enhancement characteristics support applications for ferumoxytol in distinguishing normal or hypercellular marrow from neoplasms, infection and inflammation. Further studies are warranted in specific patient populations.

A simple procedure for estimation of total body surface area and determination of a new value of Meeh's constant in rats

Precise calculation of total body surface area (TBSA) or premarked surface areas (P-MSAs) is of great importance in many biomedical applications. The aim of the paper was to present a simple procedure of measurement of P-MSAs in small animals and to determine a more accurate Meeh's constant (k), for a commonly used weight range of laboratory rats. A series of 30 Wistar rats, weighing 195-240 g, were anaesthetized and weighted. The TBSA of each animal was measured using a clear pocket and a planimeter. The data obtained were entered into the Meeh's formula (TBSA = kW(2/3)), the most commonly used for small experimental animals, so that a k value for each animal as well as a mean k value (9.83) were obtained. The TBSA of the animals was also calculated using the aforementioned mean k value and compared with that obtained using k values reported in previous studies. According to our findings, the new mean k value, determined with the use of our procedure of surface area measurement, ensured greater accuracy in the determination of the TBSA of experimental rats of a specific weight range. We also suggest a new procedure of surface area measurement which is easy, accurate and does not require animal sacrifice.

Body surface area prediction in normal, hypermuscular, and obese mice

BACKGROUND

Accurate determination of body surface area (BSA) in experimental animals is essential for modeling effects of burn injury or drug metabolism. Two-dimensional surface area is related to three-dimensional body volume, which in turn can be estimated from body mass. The Meeh equation relates body surface area to the two-thirds power of body mass, through a constant, k, which must be determined empirically by species and size. We found older values of k overestimated BSA in certain mice; thus we determined empirically k for various strains of normal, obese, and hypermuscular mice.

MATERIALS AND METHODS

BSA was computed from digitally scanned pelts and nonlinear regression analysis was used to determine the best-fit k.

RESULTS

The empirically determined k for C57BL/6J mice of 9.82 was not significantly different from other inbred and outbred mouse strains of normal body composition. However, mean k of the nearly spheroid, obese lepr(db/db) mice (k = 8.29) was significantly lower than for normals, as were values for dumbbell-shaped, hypermuscular mice with either targeted deletion of the myostatin gene (Mstn) (k = 8.48) or with skeletal muscle specific expression of a dominant negative myostatin receptor (Acvr2b) (k = 8.80).

CONCLUSIONS

Hypermuscular and obese mice differ substantially from normals in shape and density, resulting in considerably altered k values. This suggests Meeh constants should be determined empirically for animals of altered body composition. Use of these new, improved Meeh constants will allow greater accuracy in experimental models of burn injury and pharmacokinetics.

Accuracy of weight and height estimation in an intensive care unit: Implications for clinical practice and research

OBJECTIVE

Numerous calculations routinely used in the intensive care require the knowledge of patients' weight and height, although these measurements are not always made. Estimates by doctors or nurses are often substituted. This study sought to ascertain the accuracy of estimates of weight and height of patients made by intensive care unit (ICU) staff.

DESIGN

: Prospective clinical study.

SETTING

Sixteen-bed mixed medical and surgical ICU in a university teaching hospital.

PATIENTS

Fourteen patients had their height and weight estimated by 20 members of the medical and nursing staff.

MEASUREMENTS

After all estimates had been recorded, measurements of weight and height were obtained. Weight was measured by means of a patient hoist with a calibrated weighing facility and height using a steel tape measure.

MAIN RESULTS

Estimation of weight was poor, with 47% of estimates at least 10% different and 19% of estimates at least 20% different from the measured values. The majority of height estimates were within 10% of the measured values.

CONCLUSIONS

Individual estimates of weight and height are frequently inaccurate. These errors of estimation could compromise application of effective therapies, as well as contribute to a reduction in design sensitivity of clinical trials.

Genetic effects on obesity assessed by bivariate genome scan: the Mexican-American coronary artery disease study

OBJECTIVE

To identify the genetic determinants of obesity using univariate and bivariate models in a genome scan.

RESEARCH METHODS AND PROCEDURES

We evaluated the genetic and environmental effects and performed a genome-wide linkage analysis of obesity-related traits in 478 subjects from 105 Mexican-American nuclear families ascertained through a proband with documented coronary artery disease. The available obesity traits include BMI, body surface area (BSA), waist-to-hip ratio (WHR), and trunk fat mass as percentage of body weight. Heritability estimates and multipoint linkage analysis were performed using a variance components procedure implemented in SOLAR software.

RESULTS

The heritability estimates were 0.62 for BMI, 0.73 for BSA, 0.40 for WHR, and 0.38 for trunk fat mass as percentage of body weight. Using a bivariate genetic model, we observed significant genetic correlations between BMI and other obesity-related traits (all p < 0.01). Evidence for univariate linkage was observed at 252 to approximately 267 cM on chromosome 2 for three obesity-related traits (except for WHR) and at 163 to approximately 167 cM on chromosome 5 for BMI and BSA, with the maximum logarithm of the odds ratio score of 3.12 (empirical p value, 0.002) for BSA on chromosome 2. Use of the bivariate linkage model yielded an additional peak (logarithm of the odds ratio = 3.25, empirical p value, 0.002) at 25 cM on chromosome 7 for the pair of BMI and BSA.

DISCUSSION

The evidence for linkage on chromosomes 2q36-37 and 5q36 is supported both by univariate and bivariate analysis, and an additional linkage peak at 7p15 was identified by the bivariate model. This suggests that use of the bivariate model provides additional information to identify linkage of genes responsible for obesity-related traits.

Determination of the site of tracheal tube impingement during nasotracheal fibreoptic intubation*

This study examines the incidence and site of tracheal tube impingement during nasotracheal fibreoptic intubation, and the efficacy of anticlockwise tube rotation to overcome the problem. Forty-three patients underwent fibreoptic-assisted nasotracheal intubation using a preformed nasal tube, and a second fibrescope was used to observe any obstruction to passage of the tracheal tube. Impingement occurred in 10 cases, with the most common site being the right arytenoid cartilage. Rotation resulted in successful intubation in all 10 cases, but proximal rotation did not always result in an equal degree of rotation at the tube tip. We conclude that the site of impingement for nasotracheal intubation with preformed nasal tubes is located at the posterior structures of the laryngeal inlet and that anticlockwise rotation is a simple and effective solution.

Accuracy of pulmonary function tests in predicted exercise capacity in COPD patients

PURPOSE

The purpose of this study was to examine exercise tolerance in patients with COPD from measurements of resting pulmonary function parameters.

METHODS

A total of 57 COPD patients were administered the pulmonary function test (PFT) and cardiopulmonary exercise test. The results were analyzed and essentially linear relationships emerged when each subject's VO2 peak was plotted against his individual PFT parameters. Those significant contributors were then introduced in a stepwise multiple regression analysis to determine the best predictor of the VO2 peak.

RESULTS

Stepwise multiple regressions in variables revealed that peak oxygen consumption (VO2 peak) was predicted best by the following equation: VO2 peak=(maximum voluntary ventilation x 0.024)+(forced mid-expiratory flow x 0.47)+(body surface area x 0.988)-0.913 (r=0.90; r2=0.81 SE=0.29 L/min).

CONCLUSION

We conclude that exercise capacity was predicted from measurements of resting pulmonary function parameters with excellent accuracy in the COPD patient.