Yves W. Brans

A Noninvasive Approach to Body Composition in the Neonate: Dynamic Skinfold Measurements

Extract: Midtricipital (MT) and subscapular (SS) skinfolds were measured within 24 hr of birth in 23 normally grown mature (NG-M); 23 normally grown premature (NG-P); 6 intrauterine growth-retarded mature (IGR-M); and 7 intrauterine growth-retarded premature (IGR-P) infants. A rapid initial decrease in measured skinfold thickness (SFT) occurred after application of a Harpenden caliper, but readings stabilized by 60 s (SFT60). Measurements were recorded at 15 and 60 s. The difference between 15− and 60-s readings was expressed in percentage of the 15-s reading (percentage ΔSFT).The amount of subcutaneous fat, estimated from the SFT60 measurements, was affected by duration of gestation in the NG-M and NG-P and the IGR-M and IGR-P groups. In both NG groups, good linear correlations with birth weight (r = 0.852 at MT and 0.874 at SS, P < 0.001) and with gestational age (r = 0.842 at MT and r = 0.804 at SS, p < 0.001) were evident. Values for intrauterine growth-retarded infants deviated markedly from the mean SFT60 expected for their gestational age.Percentage ΔSFT was affected by duration of maturation but not by impaired intrauterine growth. It correlated with gestational age (r = −0.777 at MT and −0.773 at SS, P < 0.001) and with maximal postnatal weight loss (r = 0.579 at MT and 0.553 at SS, P < 0.001) in all groups and with birth weight in the premature groups only (r = −0.479 at MT and −0.520 at SS, P < 0.01). The similarity of these trends with those of direct extracellular water measurements suggested that percentage ΔSFT may be an estimate of subcutaneous interstitial water.Speculation: Changes in body composition during fetal life include fat deposition in the subcutaneous and internal body stores and a decrease in the proportion of body weight occupied by water. Intrauterine growth retardation results in lower fat stores and expansion of all body water compartments. The present data suggest that skinfold thickness recorded 60 s after caliper application and the difference between the 15-and 60-s readings provide estimates of fat stores and subcutaneous interstitial water, respectively. Caliper skinfold measurements can therefore be used for noninvasive studies of perinatal body composition and nutrition.

Effect of open-heart surgery on the body composition of infants and young children.

Summary: Body water content and distribution were determined in 16 children aged 2 wk to 28 months before and after open-heart surgery for correction of congenital cardiac defects. Operative procedures were performed using hypothermia and extracorporeal oxygenation. On the day before and the day after surgery, total body water was estimated as the antipyrine space (APS); extracellular water, as the corrected bromide space (CBS), and plasma volume, as the 10-min T-1824-albumin space. Intracellular water (ICW) was assumed to be the difference between APS and CBS; interstitial water was calculated from plasma volume and CBS. Before initiation and after completion of extracorporeal circulation, a pectoral muscle biopsy was performed, and a blood sample was obtained. Muscle total water (TW) content was determined by desiccation, extracellular water (ECW) was estimated as the corrected chloride space, and ICW was assumed to be the difference between TW and ECW. Plasma sodium, potassium, chloride, glucose, and osmolality contents were determined by routine methods. All studies were not completed in all patients.Although APS and CBS increased in eight of 11 children, mean APS (± S.E.) before and after surgery (662 ± 28.0 versus 714 ± 37.2 ml/kg) and mean CBS (335 ± 30.5 versus 358 ± 15.5 ml/kg) were not statistically different. Mean ICW changed neither in relation to body weight (328 ± 28.0 versus 355 ± 34.2 ml/kg) nor in relation to APS (ICW/APS ratio = 0.48 ± 0.040 versus 0.49 ± 0.010). Neither mean PV (54 ± 4.0 versus 56 ± 2.8 ml/kg) nor mean blood volume (92 ± 5.4 versus 90 ± 5.5 ml/kg) changed significantly. Mean interstitial water increased by 9 to 68% over preoperative values in all but one patient (238 ± 10.4 versus 305 ± 13.4 ml/kg; P < 0.01).Muscle composition was not affected by the procedure. Mean TW was 79 ± 1.3 ml/100 g before extracorporeal circulation and 78 ± 0.8 ml/100 g afterwards whereas ECW averaged 32 ± 4.4 and 36 ± 3.4 ml/100 g, and ICW averaged 48 ± 4.6 and 42 ± 2.9 ml/100 g. Mean ICW/TW ratios were 0.60 ± 0.055 and 0.54 ± 0.040 ml/100 g.Although mean plasma sodium (142 ± 3.5 versus 139 ± 2.4 mEq/liter) and potassium (3.3 ± 0.16 versus 3.6 ± 0.15 mEq/liter) concentrations did not change appreciably during extracorporeal circulation; mean plasma chloride content decreased (108 ± 2.9 versus 100 ± 2.0 mEq/liter; P < .002). Plasma glucose averaged 60 mg/dl more at completion of the procedure, increasing from a mean of 223 ± 25.6 mg/dl to a mean of 283 ± 5.3 mg/dl (P < 0.05). Plasma osmolality increased in five of eight children, but mean osmolalities were similar before and after extracorporeal circulation (301 ± 8.9 versus 303 ± 5.4 mOsm/kg).These data suggest that a childs organism does not react complacently to the invasive procedures associated with open-heart surgery. Further research into effects of these procedures and into means of minimizing undesirable homeostatic disturbances is warranted.Speculation: Body composition of adult patients has been shown to be acutely altered by open-heart surgery with hypothermia and extracorporeal circulation. Our data suggest that similar changes occur in young children who are subjected to these procedures. Because small children, especially those afflicted with major congenital defects, have limited homeostatic capabilities, the risk of these disturbances becoming life-threatening is increased. Means of minimizing them need be devised.

Determination of body composition in growing rats by total body electrical conductivity.

Total body electrical conductivity (TOBEC), measured with an Em-Scan SA-1 analyzer, was evaluated as a means of estimating fat-free mass and total body water content noninvasively in small laboratory animals. Ninety-four rats whose weight ranged from 5.53 to 170.84 g at 0-50 days of age were studied. The animals were killed by intraperitoneal injection of a pentobarbital overdose. After weight, crown-rump length (CRL) and TOBEC were measured, and the animals were minced with scissors and desiccated to constant weight in a convection oven. Fat was extracted by multiple bathings in petroleum ether followed by Soxhlet extraction. Fifty-four rats were used to determine the relation between fat-free mass (FFM), total body water (TBW), and TOBEC# (E) by regression analysis. The best correlations were observed between FFM and (E x CRL)1/2 (r = 0.995, p less than 0.0001). Forty rats were used to determine the predictive value of TOBEC estimates. With this instrument, TOBEC tended to underestimate FFM by an average of 3.9% and TBW by 5.3%. Accuracy was questionable for animals smaller than 13 g and TOBEC did not provide useful estimates of total body fat. Subject to these limitations, TOBEC instruments should prove to be useful for sequential in vivo estimations of body composition during growth and development of small animals.

Perinatal mortality in a large perinatal center: five-year review of 31,000 births.

The perinatal mortality rate for 30,928 babies born at Medical Center Hospital, San Antonio, Texas, between 1978 and 1982, was 20.3/1,000 births. Neonatal and fetal mortality rates were, respectively, 10.1/1,000 live births and 10.4/1,000 births. Exclusion of babies who weighed less than 500 gm yielded adjusted fetal, neonatal, and perinatal mortality rates of, respectively, 9.2, 9.8, and 17.9. Birth weight-specific mortality rates were calculated by groups of 250 gm birth weight for all neonates and by increments of 100 gm for babies who weighed 500 to 1,499 gm. Male infants, intrauterine growth-retarded babies, and babies whose mothers were less than 15 years old contributed more deaths than would be expected from the characteristics of the obstetric population. Presumptive cause of fetal death was unknown in 32%, fetal anoxia in 21%, maternal pathologic conditions in 20%, inappropriate fetal growth in 13%, congenital malformations in 8%, and systemic fetal infections in 6%. Leading presumptive causes of neonatal death were immaturity (29%), congenital malformations (18%), hemorrhages (16%), and systemic infections (10%). Hyaline membrane disease and necrotizing enterocolitis contributed, respectively, 7% and 6% of deaths. Past and future trends of perinatal mortality are discussed.

Maternal diabetes and neonatal macrosomia. II. Neonatal anthropometric measurements

Anthropometric measurements were obtained within 12 h of birth in 52 infants of non-diabetic mothers and 61 infants of diabetic mothers. Most of the diabetic patients were under good control, only ten of 61 having postpartum hemoglobin A1c levels in excess of normal. Neonates were grouped as normally-grown or macrosomic. Birthweight, crown-heel length, head circumference and skinfold thickness were measured. In each diabetes class, macrosomic neonates had larger mean length, head circumference and skinfold thickness than their normally-grown peers. At equal birthweight, neonates of gestational diabetic mothers and of non-diabetic mothers were similar in length, head circumference and skinfold thickness. Neonates of permanently insulin-requiring diabetics were similar to their non-diabetic peers in length and head circumference but had thicker skinfold thicknesses. Anthropometric measurements do not permit differentiation of the origin of neonatal macrosomia.

Total Body Electrical Conductivity Measurements: An Evaluation of Current Instrumentation for Infants

ABSTRACT: Quantitation of the bodys fat and lean masses is an important component of nutritional assessment. Such measurements, however, are difficult to conduct routinely in infants due to the numerous limitations of traditional methods. The application of total body electrical conductivity measurements for quantitating fat-free mass (FFM) overcomes many of these limitations. The instruments required to perform these measurements in pediatric patients (HP-2) have recently become commercially available, but their measurement performance has not been evaluated. In these studies, we compared the precision, day-to-day variability, and magnetic field profile of three HP-2 instruments. We also derived a new calibration equation that relates the FFM to the total body electrical conductivity measurement in piglets, and compared it with an equation (provided currently by the manufacturer) derived on a prototype instrument. The performance of the instruments was generally similar, although a significant difference in the magnetic field of one instrument was identified. The coefficient of variation of inanimate phantom measurements varied from ±0.2 to ±0.5%, and the day-to-day variability was generally similar. Such measurement error is significant (±0.035 to ±0.078 kg FFM) for small subjects. The new calibration equation was similar to the original equation; therefore, all the data were pooled to generate a new equation that is linear at least to 10 kg. Thus, the HP-2 total body electrical conductivity instruments, which can be safely and easily used to measure FFM and fat in infants through 1 y of age, proved to be reliable and precise, and results obtained from different instruments can be confidently compared.

Dynamic skinfold thickness measurements: a noninvasive estimate of neonatal extracellular water content.

Summary: Application of a Harpenden caliper to a neonates skinfold results in an exponential decline of the skinfold thickness, stabilizing within 50–60 sec. In order to elucidate the meaning of this decline, simultaneous measurements of skinfold thickness (SFT, by Harpenden caliper connected to a chart recorder), corrected bromide space (CBS, in ml/kg), plasma volume (ml/kg, by T-1824 dilution) and interstitial water (IW, ml/kg = CBS-plasma volume) were obtained in 18 term and 18 preterm neonates. Skinfold thickness was measured at the midtricipital (MT) and subscapular (SS) sites. The magnitude of SFT decline was estimated as the difference between 0–60 sec readings expressed in % of 0 second reading (%ΔSFT). The rate of SFT decline was estimated as the slope of the semilogarithmic plot from 4–20 sec after caliper application (SΔSFT).The 36 neonates whose birthweights ranged from 620–3700 g and whose gestational ages ranged from 27–41 wk were studied within 12 h of birth. Mean CBS, IW, %ΔMT, %ΔSS, SΔMT and SΔSS were higher in preterm than in term neonates (P < 0.001). Mean plasma volume was higher in preterm neonates (P = 0.009), but the difference disappeared after exclusion of six polycythemic term neonates from the calculations. The magnitude of SFT decline correlated well with both CBS (%ΔMT versus CBS: r = 0.71 and %ΔSS versus CBS: r = 0.71) and IW (%ΔMT versus IW: r = 0.71 and %ΔSS versus IW: r = 0.70). The rate of decline correlated moderately but highly significantly with both CBS (SΔMT versus CBS: r = 0.50 and SΔSS versus CBS: r = 0.42) and IW (SΔMT versus IW: r = 0.51 and SΔSS versus IW: r = 0.43). Exculsion of five neonates less than 30 wk in gestation improved the correlations with both %ΔSFT and SΔSFT.These data suggest that the decline in SFT measurements after caliper application results from the expression of subcutaneous IW from the skinfold and that both the amount of water expressed and the rate of its expression increase linearly with the amount of extracellular and IW in the body.Speculation: Both the magnitude and the rate of skinfold thickness compressibility or expressibility appear to be intimately related to extracellular and interstitial water contents of the neonatal body. Dynamic skinfold thickness measurements may therefore be noninvasive estimates that are representative of body hydration and that may be used in research on neonatal body composition as well as clinically to evaluate hydration status of sick neonates.

Ritodrine hydrochloride infusion in pregnant baboons: II. Sodium and water compartment alterations☆☆☆

To evaluate the effects of intravenously administered ritodrine hydrochloride on sodium and water metabolism, a pregnant baboon model was studied. Animals given ritodrine retained significantly more sodium (p less than 0.001) and administered fluids (p less than 0.002) compared with control animals. Although plasma volume did not change significantly within or between the two groups, extracellular volume increased by a mean of 1,480 ml in those given ritodrine compared with 790 ml in the control animals. There was no significant difference between animals given ritodrine and their controls regarding serial hematocrits, serum sodium, or colloid oncotic pressures. From this we conclude that the retained sodium and water was in the interstitial space. Since plasma volume was unaltered by ritodrine administration it seems unlikely that pure volume overload can explain the pulmonary edema induced by beta-mimetics. Combined with the prior observation that direct pulmonary capillary membrane toxicity does not occur, the likely pathophysiology of beta-agonist-induced pulmonary edema involves left ventricular failure.

Amniotic fluid in baboon pregnancies with normal versus growth-retarded fetuses

Amniotic fluid samples from 12 pregnant baboons at 173 to 176 days of gestation were studied. Five fetuses were growth retarded and seven were normally developed. Mean amniotic fluid volumes and composition (osmolality, protein concentration, delta optical density at 450 nm, and amniotic fluid/maternal plasma creatinine ratio) were similar in the two groups. Growth-retarded fetuses had amniotic fluids with a lower mean (+/- SE) pH than their normally developed peers (7.50 +/- 0.083 versus 7.85 +/- 0.084, p = 0.023). Intrauterine growth-retarded fetuses appeared to ingest amniotic fluid at a slower mean rate than normally developed fetuses (609 +/- 50.9 versus 769 +/- 48.6 ml/day, p = 0.05), but the difference disappeared when the estimates were corrected for fetal weight. Whether these data may be extrapolated to human pregnancies is speculative but appears likely in view of the similarities between amniotic fluid volume and composition in normal baboon and human pregnancies.

Body water estimates in neonatal polycythemia.

To determine whether neonatal polycythemia and its treatment by partial exchange transfusion affect body water estimates, 10 normocythemic and eight polycythemic neonates were studied within 12 hours of birth. Total body water, extracellular water, and plasma volume were estimated immediately prior to and following exchange. Intracellular and interstitial water contents were calculated. There were no significant differences between normocythemic and preexchange polycythemic neonates in mean total body water, extracellular water, interstitial water, and intracellular water contents. In the polycythemic group, exchange did not affect mean total body water, but was associated with decreases in mean extracellular water and mean interstitial water and an increase in mean intracellular water. Mean transcapillary escape rate of T-1824 was not affected by exchange but was quite rapid both before (35 +/- SE 3%/hr) and after the procedure (30 +/- 4.9%/hr). These data suggest that moderate polycythemia in normal term neonates does not affect total and extravascular body water estimates, but that a fluid shift from the extracellular to the intracellular space may accompany the exchange procedure.