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Biomedical subjects

M S Mohan

Publications and source records attributed to M S Mohan.

13 recordsLinked to original sources

Neonatal ascites and hyponatraemia following umbilical venous catheterization.

The complications associated with umbilical venous catheterization in neonates range from pericardial effusion, portal hypertension, and peritoneal perforation with ascites, to Wharton's jelly embolism. The case of a term neonate who developed ascites and severe hyponatraemia (serum sodium 119 mmol/L) most probably following peritoneal perforation by an umbilical venous catheter is reported. The presenting feature was convulsions associated with dilutional hyponatraemia, probably following absorption of a large quantity of ascitic fluid across the peritoneum. Conservative management was associated with gradual recovery over 24 h. The case highlights that, irrespective of the route, excessive administration of salt-free fluids can lead to dilutional hyponatraemia with adverse consequences. The present case illustrates the importance of confirming intravascular positioning of umbilical catheters by ensuring free flow of blood on aspiration, to prevent/detect inadvertent peritoneal perforation. Ideally, echocardiographic confirmation of optimal intravascular placement of such catheters is preferred as radiographic confirmation is reported to be unreliable.

Ascites↗

Measurement of sodium in albumin solutions with ion-selective electrodes.

We have investigated the variations in the potentials of sodium-selective glass-membrane electrodes in various concentrations of albumin. These protein solutions serve as a simple model for measurements of electrolytes in whole blood, plasma, or serum with such an electrode. The results indicate that albumin-sodium binding and variations in liquid-junction potentials are of negligible importance. Mostly, the effect of albumin on the sodium glass-electrode potential is attributable to variations in the activity of sodium, determined by the water content of the solutions. We have calculated apparent fractional protein volumes in albumin solutions from measurements of sodium glass-electrode potential and find they compare well with the classical McLean-Hastings formulation. Our results indicate the need to correct experimentally determined potentiometric electrolyte concentrations for protein volumes.

Electrodes↗

Calibration of ion-selective electrodes for use in biological fluids.

We measured electromotive force at 37 degrees C with pH, sodium glass, valinomycin, and the Simon calcium electrodes in synthetic electrolyte mixtures simulating serum, in cells both with and without liquid junction. Evidently these electrodes respond in a near-Nernstian manner to changes in concentration of the ion sensed. We su-gest that such mixtures may serve as calibrating standards for ion-selective electrodes in clinical analysis. The effect of ionic strength on electrode response can be accounted for almost wholly by alterations in the activity coefficients. The lanthanum fluoride electrode activity coefficients. The lanthanum fluoride electrode shows promise as a reliable reference in cells without liquid junction.

Body Fluids↗

A study on zeta potential and dielectric constant of liposomes.

Zeta potential and dielectric constant of the liposomes were measured to study the effect of some of the formulation factors and in vitro ageing. Sonication affects zeta potential and dielectric constant of the liposomes. The ageing study showed an increase in the dielectric constant and zeta potential of liposomes at different storage temperatures. These two electrical parameters could be useful in studying structural alterations in liposomal vesicles and system as a function of different conditions. Particle size distribution and optical density were also measured, for comparison.

Chemical Phenomena↗