Blood volume and red cell mass in children with moderate and severe malaria measured by chromium‐53 dilution and gas chromatography/mass spectrometric analysis

Understanding blood volume changes in children with malaria is important for managing fluid status. Traditionally, blood/red cell volume measurements have used radioactive chromium isotopes. We applied an alternative approach, using non‐radioactive chromium‐53 labelling and mass spectrometry to investigate red cell volume (RCV) in Gabonese children with malaria. Nineteen children with malaria participated (10 severe, 9 moderately severe; ages 15 months to 7 years). Blood labelled with ⁵³Cr‐chromate ex vivo was re‐injected, then sampled 30 min later. Pre‐ and post‐injection ⁵³Cr content were measured by gas chromatography/electron ionisation mass spectrometry of the chromium‐trifluoroacetylacetone (TFA) chelate, calibrated against ⁵⁰Cr standards. Blood and red cell volumes were calculated from isotopic dilution in 15 of 19 children (in four, insufficient signal mitigated analysis). In this small pilot study, there were no significant differences between moderate and severe cases. Including all subjects, the mean RCV was reduced compared with predicted values (184 vs. 269 mL; p = 0.016) but blood volume, 71 ± 33 mL/kg (normalised for weight), was close to predicted, ～77 mL/kg, commensurate with reduced haematocrit. Blood lactate concentration correlated negatively with RCV/weight (r = ?0.56, p = 0.028), consistent with anaemia. In one case, sequential samples over 42 days gave an estimated rate of ⁵³Cr disappearance of 1.4%/day (equivalent half‐life: 70 days). ⁵³Cr‐labelling of red cells may be used to estimate blood and red cell volumes and can be used as an investigative tool in situations such as childhood diseases and resource‐constrained settings. Although the red cell mass is depleted in malaria, the blood volume appears relatively well preserved. Copyright © 2009 John Wiley & Sons, Ltd.     

Velocity Measurements for Arc Jets Produced by a DC Plasma Spray Torch

An optical method was used to determine the axial velocity of plasma jets produced by a DC plasma spray torch. Different experimental conditions were tested in order to systematically study the influence of the working parameters on the plasma velocity. In this way, the arc current ranged between 200 and 600 A, the gas flow rate between 30 and 80 slm, and the internal nozzle diameter between 6 and 10 mm; the plasma gases were either an Ar–H ₂ mixture or N ₂ . Rather well defined tendencies were observed and at the same time it appeared that the arc stability greatly influenced the fluctuations of the velocity.