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Biomedical subjects

K Varughese

Publications and source records attributed to K Varughese.

7 recordsLinked to original sources
PubMed1999

Effect of experience with spinal anaesthesia on the development of post-dural puncture complications.

BACKGROUND: This clinical study was conducted in order to investigate the effect of operator experience with spinal anaesthesia (SA) on development of postural post-dural puncture headache (PPDPH) and postoperative backache. METHODS: The study was a cohort study of the first 100 SA performed by each of 5 trainees in anaesthesiology at the very beginning of their training period. SA was conducted with assistance and guidance according to usual departmental practice. In each SA, data regarding level of puncture, needle size, number of punctures, use of introducer and infiltration anaesthesia were recorded. In addition, usual problems and complications connected with dural puncture were registered. A visual analogue scale was used to record how difficult the procedure was experienced by the trainees. Postoperatively, the patients were contacted by the same trainee, usually by telephone. A semi-structured interview was conducted where occurrence and duration of headache, backache and other complaints were recorded. Headache was classified as PPDPH or non-PPDPH, and intensity of the headache was registered using a numerical rating scale (NRS) from 0 to 10. RESULTS: Five hundred SA in 495 patients with a mean age of 61.3 years were included in the study. Of these, 394 patients were completely followed-up postoperatively; the main reason for the drop-out was patient-related factors such as advanced age and dementia. Headache occurred in 56 patients postoperatively. PPDPH was diagnosed in 33 and non-PPDPH occurred in 23 patients. Postoperative backache was experienced by 27 patients. No significant effect experience with SA could be found regarding the occurrence of postoperative complications; 16 compared to 17 patients with PPDPH were found in the first and the last half of patients. A marked inter-individual difference in the occurrence of PPDPH was found in the patients treated by the 5 trainees. CONCLUSIONS: We could not demonstrate an effect of experience and training on development of complications after SA with regard to PPDPH and backache.

Aged↗
PubMed1982

Effect of fluoride on crystal growth of calcium apatites in the presence of a salivary inhibitor.

The effect of fluoride on the kinetics of crystal growth of calcium apatites was studied using seed crystals of hydroxyapatite coated with PRP-3, a proline-rich phosphoprotein salivary inhibitor of crystal growth. Initial precipitation rates in the presence of PRP-3, under conditions of partial inhibition, were enhanced by fluoride, effectively counteracting the inhibitory activity of the macromolecule. This rate enhancement is related to an increase in the precipitation driving force, i.e., the degree of supersaturation with respect to the precipitating phase; in this case a fluoridated hydroxyapatite. The growth of this phase takes place at the uncovered crystal growth sites which have been previously shown to be the same sites as the adsorption sites for the protein inhibitors. Explanations based on fluoride activation of secondary crystal growth sites and on the displacement of adsorbed inhibitor by fluoride are not substantiated by the present results. It has been demonstrated that under conditions of maximum coverage of available crystal growth sites by PRP-3, resulting in no apparent crystal growth, measurable crystal growth is observed upon the addition of fluoride (1 ppm). This phenomenon is best explained by the fact that at maximum PRP-3 coverage, a small number (16%) of crystal growth sites remain uncovered, which support an unmeasurable rate of crystal growth. Upon the addition of fluoride, this rate is significantly enhanced. It is suggested that the fraction of uncovered growth sites is related to steric interactions of the PRP-3 molecule in the adsorbed state. Overall, the results presented suggest that fluoride can accelerate crystal growth in an environment such as the enamel surface where the acquired pellicle is formed.

Crystallization↗
PubMed1982

In vitro evaluation of editempa on hydroxyapatite formation and its effects on dental enamel.

N,N,N',N' ethylene diamine tetra (methylene phosphonic acid)-Editempa inhibited the formation of hydroxyapatite (HA) in vitro at 4 ppm. In the seeded crystal growth of HA at 37 degrees C, it completely inhibited the crystal growth at 0.5 ppm. C14-Editempa adsorbed to HA crystal at 37 degrees C. The maximum adsorption was 1.29 mumol/m2 of HA and the adsorption was monolayer. Compared to the natural inhibitors of HA in saliva (Statherin and Proline-rich proteins), Editempa was more effective in vitro on weight basis. At 0.3 ppm, it inhibited growth rate of the crystals by 80% while 4 to 5 ppm of the natural inhibitors were needed to get the same effect. The inhibition of rates with Editempa was not directly proportional to the area covered by it on the HA seeds (occupied less than 10% of the surface). The natural inhibitors, on the other hand, seemed to cover all the available surface. These data indicate that the inhibition with Editempa was due to binding to specific sites on the surface of the seeds. The solutions up to 5% of Editempa did not damage or etch the surface of human dental enamel in vitro at pHs 5.0 and 7.5, as evaluated by scanning electron microscopy and calcium released in the exposed solutions.

Adsorption↗
PubMed1981

Crystal growth of calcium apatites in dilute solutions containing fluoride.

The kinetics of seeded crystal growth of calcium apatites were studied in dilute supersaturated solutions at various levels of fluoride concentrations. Initial precipitation rates were enhanced by fluoride concentrations higher than 0.05 ppm. The analytical results are consistent with the precipitation of fluoridated hydroxyapatites, Ca5Fx-(OH)1-x(PO4)3, FHA. The degree of fluoridation, X, appears to be determined by the activity of HF in solution, which varies for the various initial fluoride levels but remains fairly constant during precipitation. Thus the composition of the precipitating phase was the same for a given solution whether 25 or 10 mg of hydroxyapatite was added as seeds. All the experimental results are consistent with the BCF theory, which relates the mean linear rate of growth, RL, to the supersaturation, DS, by the expression RL = C1T(DS-1)1n(DS)tanh(C2/T 1n DS), in which DS is the supersaturation defined by mean molar activities with respect to the precipitating FHA, T the absolute temperature, and C1 and C2 are constants calculated from the experimental results. Consequently, the crystal growth appears to take place in surface kinks and to be controlled by surface diffusion. Since crystal growth in most biological systems takes place at fluoride concentrations within the experimental range used, it seems probable that it occurs along the model advanced in the present investigation.

Apatites↗
PubMed1979

Effect of human salivary proteins on the precipitation kinetics of calcium phosphate.

Inhibition of calcium phosphate precipitation in saliva, and prevention of the formation of mineral accretions on tooth surfaces, has been ascribed to the existence of inhibiting salivary macromolecules. Marked reductions in the crystal growth rate of hydroxyapatite (HA) seeds were measured in supersaturated solutions containing either of two proline-rich proteins, PRP1 or PRP3, or statherin; the three macromolecules were isolated from human parotid saliva. The reductions were also observed when the HA seeds were pretreated with solutions of the macromolecules before adding them to the supersaturated calcium phosphate solution. This effect was very similar in the case of the two PRPs and it was directly related to the extent of adsorption site coverage of these proteins on the HA seeds. The effect of statherin was larger than anticipated from its adsorption behavior. However, comparison on the basis of number of moles adsorbed per unit area of HA shows that the PRP are more effective inhibitors than statherin. The macromolecule concentrations used were considerably lower than those in the salivary secretions, therefore these macromolecules could readily prevent mineral accretion on tooth surfaces through their adsorption onto the enamel surface.

Adsorption↗