Continuous blood pressure monitoring utilizing a CMOS tactile sensor

A novel tactile device based on a monolithically integrated sensor chip is presented for external blood pressure measurement. It uses a tonometric principle, thus allowing for continuous monitoring of the blood pressure without the need for an invasive catheter. On the chip, the deflection of membranes in an array is sensed capacitively and read out using a SigmaDelta-modulator. The membrane array and the modulator are fabricated on a single chip using an industrial CMOS (complementary metal oxide semiconductor) technology combined with post-process micromachining to achieve small and portable devices with low power consumption. The tested device is operated at a conversion rate of 1 kilosamples per second and is pressure biased to a 2000 hPa (1500 mmHg) reference point. The power consumption of the sensor chip is 11.5 mW with signal-to-noise ratio better than 72 dB. During testing a pressure resolution of approximately 8 hPa (6 mmHg) for one digit at the output of the SigmaDelta-modulator is achieved over the range of interest continuous blood pressure monitoring using this CMOS-based tactile device is successfully demonstrated. The characteristic features of a blood pressure waveform are clearly recognizable from the acquired data.

[Optimization of amoxicillin/clavulanate therapy based on pharmacokinetic/pharmacodynamic parameters in patients with diabetic foot infection]

AIM OF THE STUDY

Individualized optimization of amoxicillin/clavulanate (AMC) antimicrobial therapy in diabetic foot infection.

METHODS

Pharmacokinetic analysis of individual steady-state plasma amoxicillin concentrations was done both in the i.v. infusion phase and in the oral phase of AMC, administered on the basis of the quantitative susceptibility of the detected microbe(s). The in vitro growth/killing dynamic parameters on model of Staphylococcus aureus as the most frequent isolate were evaluated. Therapeutic protocol optimization, leading to prediction of the earliest time to reduce the number of viable bacteria to 10-6 as a surrogate criterion of efficacy, was performed.

RESULTS

Based on individual plasma amoxicillin oscillations in 17 patients suffering from infected diabetic foot ulcers and the model microbial dynamic parameters, the reduction of the number of viable bacteria was reached significantly earlier after the administration of continuous i.v. AMC infusion than after the same daily AMC dose administered intermittently. In case of highly susceptible staphylococcal strain, highly frequent oral therapy of AMC (not longer than 8 hrs dosing interval) was also sufficiently effective. Decreasing plasma amoxicillin concentrations exponentially extended the time required for effective reduction of microbes.

CONCLUSION

Individualized optimization of amoxicillin/clavulanate dosage on the basis of growth/killing microbial dynamic parameters and antibiotic concentration/time fluctuations may enhance the antimicrobial effect and the treatment of infected non-critical ischemic diabetic foot ulcers.

Nephrotoxicity of cyclosporin A in hereditary hypertriglyceridemic rats

It has been suggested that cyclosporin A (CsA) nephrotoxicity can be reduced by the concomitant administration of omega-3 fatty acids or vitamin E. The present study was designed to establish whether the effect of the above substances can also be demonstrated in rats with hereditary hypertriglyceridemia (HTG) whose sensitivity to the nephrotoxic effect is greater than in control AVN rats. CsA administration at a dose of 10 mg/kg/day to HTG rats resulted in a significant rise (p<0.001) in serum levels of creatinine (from 66.0+/-7.6 to 108.4+/-11.6 micromol/l) and urea (from 8.3+/-0.7 to 22.3+/-18 mmol/l) which was not found in AVN rats. The baseline values of systolic blood pressure (SBP) were significantly higher in HTG rats. However, in both strains CsA administration was associated with a similar SBP increase which was not prevented by omega-3 fatty acids (EPAX) or vitamin E administration. Concomitant administration of CsA with EPAX at a dose of 600 mg/kg b.w./day in HTG rats prevented the rise in the serum levels of creatinine (65.4+/-14.7 micromol/l) and reduced the increase in the serum urea levels (11.9+/-7.6 mmol/l). Concomitant administration of CsA and vitamin E (at a dose of 25 mg/kg/day) also reduced the increase (p<0.05) in the serum levels of creatinine (70.7+/-14.3 micromol/l) and urea (9.8+/-3.4 mmol/l) compared to the effects elicited by the administration of CsA alone (p<0.05). Administration of CsA alone or in combination with EPAX or vitamin E did not have a marked effect on diuresis, proteinuria, urinary osmolality, urinary excretion of urea, creatinine and potassium. Under all experimental conditions, the rate of urinary excretion of sodium in HTG rats was significantly lower (p<0.01) than in AVN rats. The results obtained support the assumption that omega-3 fatty acids and vitamin E at the doses used reduce CsA nephrotoxicity in rats with hereditary hypertriglyceridemia whose sensitivity to the nephrotoxic effect of CsA is significantly higher than in AVN rats.

The effect of the ultrashort beta-blocker esmolol on cardiac function recovery: an experimental study

OBJECTIVE

This is an experimental work designed to determine, using the isolated perfused rat heart, the effect of the ultra-short acting beta-blocker esmolol on cardiac arrest and cardiac function recovery following esmolol withdrawal.

METHODS

Changes in heart rate, coronary flow, diastolic pressure and the rate pressure product were evaluated on the isolated heart (Langendorff model). Esmolol concentrations of 125, 250, and 500 mg/l were tested. In another experiment using esmolol concentration of 250 mg/l, cardiac function recovery was assessed after 20- and 45-min arrest.

RESULTS

While concentrations of 250 and 500 mg/l are necessary to produce cardiac arrest, the concentration of 500 mg/l does not result in full cardiac function recovery following esmolol withdrawal. After the highest concentration of esmolol, coronary flow, heart rate and the rate-pressure product recovered to about 80, 70 and 60% of the initial control values, respectively. When comparing 20- and 45-min arrests we found cardiac function normalization occurs later after 45-min arrest.

CONCLUSION

The induction of cardiac arrest by esmolol is optimal at a concentration of 250 mg/l. A concentration of 125 mg/l does not result in cardiac arrest and produces bradycardia only, a concentration of 500 mg/l may be dangerous on account of persisting undesirable effects on the rat heart.

Changes in cyclosporine A kinetics after experimental reduction of renal parenchyma

Experimental chronic renal insufficiency (produced by 5/6 ablation of renal parenchyma) is associated with changes in the kinetics of oral (intragastric) cyclosporine A (CyA). Compared with animals with intact renal parenchyma, significantly lower levels of CyA are reached under these conditions. The factors responsible for reduced CyA availability under these conditions have not yet been identified.

[An experimental model of the effect of uremia on cyclosporin A availability]

BACKGROUND

The aim of the study was to determine whether or not uraemia has an effect on cyclosporine A intestinal resorption.

METHODS AND RESULTS

Model experiments were conducted in rats to monitor the effect of acute uraemia (bilateral nephrectomy) on the kinetics of cyclosporine A. Using intragastric tube, Cyclosporine A was administered to one group of rats in the form of Consupren (Galena, Czech Republic) and to another group in the form of Sandimmune (Sandoz, Switzerland), at a dose of 10 mg/kg/24 h either case. Blood levels of cyclosporine A were determined using RIA and specific and non-specific antibodies (cyclosporine and its metabolites). Cyclosporine A kinetics in nephrectomized rats was compared with that in control rats and in rats undergoing sham nephrectomy. The blood levels of cyclosporine A were significantly lower, and the area under the curve (AUC) of blood cyclosporine A in nephrectomized rats significantly smaller than in control rats. No significant differences in the evaluated parameters after Consupren or Sandimmune were observed.

CONCLUSIONS

Our findings support the hypothesis that uraemia decreases cyclosporine A availability. The results suggest that the changes in cyclosporine A kinetics in nephrectomized rats following Consupren and Sandimmune administration are of the same character.

[Preclinical modeling of the possible effect of acute uremia on drug resorption in the gastrointestinal tract]

The authors investigated in experiments on rats the course of serum concentrations of sulfisoxazole (S) and acetylsulfisoxazole (AS) in normal rats and in rats after bilateral nephrectomy after intra gastric administration of S. Serum concentrations of S and AS during the first three hours following administration did not differ significantly or were very close. During the subsequent hours the serum concentrations of S and AS in uraemic animals were significantly higher than in controls. The value of the absorption constant in the uraemic animals was on average higher and the absorption half-life lower than in controls. The assembled results suggest that in acute uraemia in rats the intestinal reabsorption of S and its metabolism in the liver are not reduced. The findings support the idea that the model used could be useful in preclinical research of drugs used in the treatment of acute uraemia.

Pharmacokinetics of roxithromycin in kidney grafted patients under cyclosporin A or azathioprine immunosuppression and in healthy volunteers

The pharmacokinetics of roxithromycin was studied in 9 kidney grafted patients under cyclosporin A immunosuppression, in 10 transplanted patients with azathioprine, and in 6 healthy volunteers. The biological half-life (beta-phase) of roxithromycin in cyclosporin patients was 34.4 (+/- 12.25) h (mean +/- SD), in azathioprine patients 23.4 (+/- 8.18) h and in healthy volunteers 17.0 (+/- 3.8) h. The total elimination constant (k10) was 0.046 (+/- 0.014), 0.068 (+/- 0.019) and 0.084 (+/- 0.036) h, respectively. The total clearance was 0.79 (+/- 0.21), 1.45 (+/- 0.66) and 1.84 (+/- 0.56) l/h, respectively. The areas under the serum level curves were 407.6 (+/- 118.3), 251.0 (+/- 106.6) and 180.7 (+/- 73.2) mg.h/l, respectively. The differences in these parameters between healthy volunteers and cyclosporin patients were statistically significant, as well as those between cyclosporin and azathioprine patients. The differences between healthy volunteers and azathioprine patients were not statistically significant. The results cannot be interpreted unambiguously as an interaction between roxithromycin and cyclosporin; the effect of cyclosporin on the function of eliminating organs which causes the slowed-down elimination of roxithromycin could be taken into account.

Genetic differences in the resistance of rats to isoprenaline-induced heart lesions

Two strains of rats were obtained by selective breeding: the IR strain, resistant to isoprenaline-induced myocardial lesions and the IS strain, sensitive to this damage. The IR rats grew more slowly, the weight of their adipose tissue was higher and the weight of m. soleus was less than that of the IS rats. The IR rats had a higher content of triglycerides in the serum and a lower isoprenaline-stimulated lipolytic activity of adipose tissue in vitro. The basal NEFA level in the serum and its rise after the administration of isoprenaline in vivo did not differ between the strains. The IR rats had a higher content of glycogen in the heart and in the muscle. After the administration of isoprenaline the glycogen content decreased more slowly in IR rats. The findings indicate a considerable importance of the glycogen stores in the heart for the resistance of myocardium to damage.

Protective effect of isoprenaline pretreatment on the cardiotoxic effect of the same drug

The study deals with the development of increased resistance of the rat myocardium to ISO-induced injury after pretreatment with the same drug. Reduced sensitivity already developed after the first dose of ISO, whose effect was only slightly increased by subsequent repeated doses. The development of myocardial injury was completed significantly sooner in pretreated animals, and this resulted in a decrease of the extent of the lesion. The reduction of cardiotoxic effect of ISO could be achieved by pretreatment with very small doses of ISO (0.01 mg/kg). An increase in the pretreatment dose augmented the protective effect and, in particular, prolonged the duration of reduced sensitivity. The effect of pretreatment in older animals, which responded to ISO by greater damage, was more pronounced.

Studies on isoprenaline-induced myocardial lesions. 1. Quantitative evaluation by mercurascan uptake

For the quantitative evaluation of myocardial damage induced by isoprenaline (ISO) a method based on the uptake of 203Hg-labelled Mercurascan (MSC) in the heart was used. The increase of myocardial uptake of MSC in ISO-treated rats over control values was very rapid and might be directly proportional to the number of damaged myocardial cells actually present in the heart. MSC-uptake method of myocardial damage evaluation was more sensitive and precise than other methods tested (macroscopic evaluation according to Rona, increase of heart weight). Different modifications of MSC-uptake test may be selected in relation to experimental conditions. MSC test is especially useful for evaluation of early myocardial lesions induced by small doses of ISO (0.01 mg/kg).