Infrared-spectrometric determination of D2O in biological fluids. Reappraisal of the method and application to the measurement of total body water and daily water turnover in the dog

Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectroscopy for the Quantitative Analysis of Deuterium in Plasma: Application to Total Body Water Determination in Humans and Other Animals

Conventional methods for measuring the concentration of deuterium in body fluids are by either isotope ratio mass spectrometry or Fourier transform infrared transmission (FT-IR) spectroscopy. The latter method is often preferred as it is less expensive and time consuming; however, having a lower sensitivity means a larger sample volume is required. This study investigated an alternative FT-IR spectroscopic method, attenuated total reflection Fourier transform infrared spectroscopy (ATR FT-IR), which has the potential to provide shorter analysis times while requiring smaller sample volumes. Deuterium was assayed using ATR FT-IR in plasma in the concentration range 0.5 to 2.5 mg mL^-1, typical of those observed in tracer dilution measurements of total body water. Minimal sample preparation was required and analysis time was substantially decreased compared to transmission FT-IR. Samples were analyzed with high precision (coefficient of variation (CV) < 0.5%). Precision of assay was maintained when assaying plasma volumes of only 10 µL. The application of the method to the determination of total body water in humans and animals (horses) was demonstrated. A rapid and simple method for the measurement of deuterium in plasma is described that only requires very small sample volumes, rendering the method suitable for use in pediatrics where blood sampling is required to be kept to a minimum.

Blood volume and body fluid compartments in lambs with aortopulmonary left-to-right shunts

A left-to-right shunt is accompanied by an increased plasma and blood volume. Since this is likely realized through renin/aldosterone-mediated salt and water retention, other body fluid compartments may be changed too. Therefore, we studied blood volume and body fluid compartments by a single-injection, triple-indicator dilution technique in nine 8-wk-old lambs with an aortopulmonary left-to-right shunt (55 +/- 3% of left ventricular output; mean +/- SEM) and in 11 control lambs, 2.5 wk after surgery. Systemic blood flow was maintained at the same level as in control lambs, but the aortic pressure of the shunt lambs was lower. Blood volume in shunt lambs was larger than in control lambs (110 +/- 6 vs. 84 +/- 7 ml/kg, P < 0.001) through an increase in plasma volume, which correlated significantly with the magnitude of the left-to-right shunt (r = 0.81, P < 0.01). Red blood cell volume was equal to that of control lambs. Evidence was obtained that the increase in plasma volume was induced by a transient increase in renin (8.0 +/- 2.2 vs. 1.6 +/- 0.2 nmol.l-1.h-1; P < 0.02) and aldosterone (0.51 +/- 0.14 vs. 0.24 +/- 0.09 nmol/liter) concentrations. Interstitial water volume, however, was not significantly different from that in control lambs. The amount of intravascular protein was significantly higher than in control lambs (5.0 +/- 0.3 vs. 3.5 +/- 0.2 g/kg body mass, P < 0.001). There were no significant differences in intracellular and total body water volumes between the two groups. We conclude that the increased amount of intravascular protein confines the fluid retained by the kidneys to the vascular compartment.

Weight loss in full-term negroid infants: relationship to body water compartments at birth?

The possible influence of the body fluid compartments at birth on postnatal weight loss was studied in normal term negroid infants when on a standardized oral fluid, sodium and energy regimen during the first three days of life. Measurements of plasma volume (PV), total body water (TBW), and extracellular water (ECW) were performed simultaneously on vaginally-born infants on the first day of life, by using a triple indicator (Evans blue, deuterium oxide and sucrose) single injection dilution technique. PV was 54 +/- 7 ml/kg (N = 9), TBW was 751 +/- 50 ml/kg (N = 13) and ECW was 311 +/- 61 ml/kg (N = 13) (mean +/- S.D.). Postnatal weight loss (3.7% of birth weight) occurred during the first two days. The postnatal weight loss was not related to any of the body water compartments. However, there was a highly significant correlation with the (cumulative) urine water excretion (r = 0.833, P less than 0.001 on day 1, with similar values for days 1 and 2).

Dissociation of body weight and lean body mass during cancer chemotherapy

Body weight and lean body mass are different reflections of the nutritional status of patients receiving cancer chemotherapy. In the present study, the relation between lean body mass and body weight during cytostatic treatment was investigated in 3 groups of newly-diagnosed children and young adults with acute lymphocytic leukemia, osteosarcoma, or a small round cell sarcoma. Body weight and lean body mass were determined before and after an initial period of cytostatic treatment. Lean body mass was derived from total body water volume, which was assessed by deuterium oxide dilution. A significant dissociation between body weight and lean body mass was observed in leukemia patients (n = 8, P = 0.008, paired t-test), and in osteosarcoma patients (n = 13, P = 0.001). No dissociation was found in patients with a small round cell sarcoma (n = 8, P = 0.839). We conclude that during cancer chemotherapy periodic assessment of body weight may give a false picture of the preservation of lean body mass. Considering the course of body weight alone may prevent the establishment of a timely diagnosis of malnutrition, which is mandatory for optimal supportive care.

Composition of postnatal weight loss and subsequent weight gain in small for dates newborn infants

Using a sucrose and deuterium oxide dilution technique body water compartments and solids were serially determined in small for dates newborn infants at birth, at the moment of maximum postnatal weight loss and on recovery of birth weight. Compositions of weight loss and subsequent weight gain were calculated from the differences in body water compartments and solids between the first and the second and the second and the third study, respectively. Birth weight of the infants was 1.55 +/- 0.46 kg (mean +/- SD) (N = 7), gestational age was 35.7 +/- 3.1 weeks. Results show that despite changes in extra- and intracellular water volumes during weight loss, total body water volume and solids per unit of body weight remained remarkably constant throughout the study. Compositions of weight loss and subsequent weight gain were similar to body composition. This suggests that in small for dates newborn infants postnatal weight loss is the result of catabolism rather than dehydration and subsequent weight gain is the result of growth rather than rehydration.

Simultaneous determination of dimethadione and trimethadione by infrared-spectrometry: application for mean intracellular pH measurement

A simple infrared-spectrometric method for the simultaneous determination of dimethadione and trimethadione in plasma is described. The method is based on the absorption band of the carbonyl group for trimethadione at the wavenumber of 1740 cm-1 and for dimethadione at the wavenumber of 1770 cm-1. The accuracy and precision of the method are excellent; at a dimethadione and trimethadione concentration of 0.5 mmol X 1(-1) the coefficient of variation for the determination of both compounds is less than 1%, which is better than that for the ultraviolet spectrometric or gas-liquid chromatographic methods. The method can be used for the determination of the ratio trimethadione/dimethadione in the clinical setting as a sensitive check of the patient's adherence to therapy. It can also be used for the determination of dimethadione as an indicator for the mean body intracellular pH.