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Biomedical subjects

S Koval

Publications and source records attributed to S Koval.

18 recordsLinked to original sources
PubMed2005

Bacteremia due to Pseudomonas aeruginosa: results from a 3-year national study in the Slovak Republic.

Risk factors, mortality and antimicrobial susceptibility of Pseudomonas aeruginosa bacteremias isolated from 148 patients from all University Hospitals in Slovakia were analyzed. Only 1.2% of 169 strains of P. aeruginosa were resistant to meropenem, 4.1% to piperacillin/tazobactam, 7.7% to ceftazidime as well as cefepime and 12% to amikacin. More than 30% of P. aeruginosa were resistant to ciprofloxacin. Our analysis of risk factors for antimicrobial resistance to the particular antimicrobials, indicated no difference in risk factors and outcome in cases infected with P. aeruginosa bacteremias resistant to amikacin, piperacillin/tazobactam or ceftazidime in comparison to episodes caused by P. aeruginosa due to susceptible isolates. When comparing risk factors for P. aeruginosa bacteremia in children vs. adults, cancer vs. non-cancer patients, several differences in risk factors were observed. Neither antimicrobial resistance to amikacin, ceftazidime or piperacillin/tazobactam, nor appropriateness of therapy according to two separate analyses were associated with better outcome.

Adult↗
PubMed2002

Ferroelectricity and isotope effects in hydrogen-bonded KDP crystals.

Based on an accurate first principles description of the energetics in H-bonded potassium-dihydrogen-phosphate crystals, we conduct a first study of nuclear quantum effects and of the changes brought about by deuteration. Tunneling is allowed only for clusters involving correlated protons and heavy ion displacements, the main effect of deuteration being a depletion of the proton probability density at the O-H-O bridge center, which in turn weakens its proton-mediated covalent bonding. The ensuing lattice expansion couples self-consistently with the proton off-centering, thus explaining both the giant isotope effect and its close connection with geometrical effects.

Journal Article↗
PubMed2002

[Regulation of respiration and its sleep-related disorders].

Four basic control mechanisms of breathing (brainstem respiratory centre, peripheral and central chemoreceptors, intero- and exteroceptive reflexes and suprapontine influences), as well as their sleep-related disorders are analysed. A decrease in central chemoreceptor sensitivity to CO2 and an increase in upper airway resistance during sleep result in hypoventilation and mild hypoxaemia already in physiological conditions. Compensatory increase in ventilatory effort with synchronous inhibition of pharyngeal dilators during sleep reduces the upper airway lumen manifesting with snoring, upper airway resistance syndrome, and OSA. The resulting hypoxaemia may cause marked cardiovascular, neuro-psychic, endocrine-metabolic and behavioural disorders. The augmented ventilatory effort and hypoxaemia evoke reflex dilation of airways and arousal from sleep, stimulating the sympatho-adrenal system, which provokes autoresuscitation by gasping preventing fatal asphyxia. Failure of this autoresuscitation mechanism seems to cause SIDS. Elimination of voluntary breathing by sleep either in Ondine's curse induced by lesions of respiratory centre, or in congenital central hypoventilation syndrome caused by insufficient central chemoreceptors result in respiratory failure and death. Nocturnal attacks of bronchial and cardiac asthma, lung oedema and other consequences of pulmonary congestion are also discussed. The pathomechanism of extreme daytime sleepiness, chronic fatigue, and disorders of memory, cognitive and other brain functions, are also analysed. Severe cardiovascular consequences of SAS may manifest acutely as angina pectoris, myocardial infarction. dysrhythmias, transient ischaemic attacks and even stroke or sudden cardiac death. OSAS may result also in development of hypertension, central obesity, diabetes mellitus, erectile dysfunction, depression, and various behavioural disorders.

Humans↗
PubMed2000

[Experience with polysomnography in the diagnosis of sleep apnea].

Whole-night recording of 9-30 parameters and calculation of various indices allow differentiation of various sleep related breathing disorders and estimation of their severity (Fig. 1, 2). Parallel monitoring of changes in ventilation, arterial oxygen saturation, ECG, EEG, EMG and others, give a possibility to appreciate the gradual development of cardiovascular, neuropsychic, endocrine-metabolic and other consequences of sleep related breathing disorders, their dependence on different phases and stages of sleep as well as their alterations by treatment.

Humans↗
PubMed1997

[Sleep-related breathing disorders--an interdisciplinary topic in undergraduate and postgraduate medical education].

Sleep-related breathing disorders (SRBD) include several disorders gradually developing from simple and loud snoring through upper airway resistance syndrome and sleep apnoea up to the Pickwickian syndrome. They are manifestant as a respiratory distress and apnoeic episodes, desaturation of oxygen in the blood and interruption of sleep. These symptoms are demonstrated in a case of a patient with the Pickwickian syndrome. SRBD may result in severe secondary life-threatening cardiovascular complications (nocturnal arrhythmias, sudden cardiac death, stroke and pulmonary oedema). They may contribute also to the development of important disorders of public health such as hypertension, obesity, and traffic accidents resulting from hypersomnolence and fatigue. (Tab. 1, Fig. 3, Ref. 46.)

Adult↗
PubMed1997

[Hereditary hemorrhagic telangiectasis and the development of an arteriovenous fistula after 24 years].

The authors describe a unique pulmangiographic picture taken 24 years after the first angiographic examination made on account of repeated haemoptysis associated with Rendu-Osler-Weber s disease. Angiography revealed enlargement of the aneurysm in the lungs and dilatation of the afferent and efferent vessel of the aneurysm. The only treatment of pulmonary arteriovenous fistulas is surgical.

Arteriovenous Fistula↗
PubMed1996

[Treatment of autonomous thyroid gland nodules using percutaneous injections of ethanol under ultrasonography control--initial experience].

The authors treated nine women with autonomous adenomas of the thyroid gland by repeated ethanol injections under ultrasonographic control. In all patients clinical and laboratory characteristics of hyperthyroidism were present. After treatment is seven patients euthyroidism was induced, in two patients subclinical hypothyroidism which persisted also during the 6-month follow-up period. In all patients ultrasonographic changes in the nodes were recorded: a reduced echogenity the development of "halo"--hypoechogenic outlines--a change of the shape and on average a 37% reduction of the volume. Treatment was feasible also under out-patient conditions: it was well tolerated by the patients, undesirable effects were not serious and only transient and receded spontaneously.

Adenoma↗
PubMed1996

[Angiotensin converting enzyme inhibitors in ischemic heart disease].

Angiotensin formed in the renin-angiotensin system is involved in the genesis and development of atherosclerosis and coronary heart disease. It has a negative impact on the process of ischaemization/reperfusion. The renin-angiotensin system is activated during a new myocardial infarction and has an impact on the process of remodelling of the left ventricle after myocardial infarction which causes its dysfunction and heart failure. ACE inhibitors are one of the important means which influence the formation of angiotensin II and thus prevent its action on heart and vessels. They prevent the development of atherosclerosis, reduce the extent of necroses during myocardial infarction and reduce the extent of left ventricular dysfunction. They diminish also stunning of the heart muscle during ischaemia/reperfusion and significantly prolong the patients life after infarction. They do not influence the development of restenosis after percutaneous transluminal angioplasty. ACE inhibitors have a positive effect on heart failure, they reduce the rate of reinfarctions and the mortality rate.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1996

[Diagnosis of chronic massive pulmonary thromboembolism in elderly patients].

Chronic massive thromboembolism of the pulmonary artery is an occlusion of the major branches of the pulmonary artery which develops as a result of repeated embolisms, as a result of non-dissolution and organizing of a thrombus or retrograde growth of a thrombus. The authors observed four elderly patients with chronic massive pulmonary embolization. In their clinical picture dominated progressing dyspnoea and signs of right heart failure. In the diagnosis perfusion scan of the lungs and pulmoangiographic examination plays an important part as they revealed even unilateral absence of pulmonary circulation. This examination was stimulated by weaker respiration at the site of the lacking perfusion in a portion of the lungs.

Age Factors↗
PubMed1995

[Postischemic ("stunned") and chronic ischemic ("hibernating") cardiac muscle].

Stunning of the heart muscle is a postischaemic dysfunction observed after reperfusion. The stunned heart muscle is functional, the restoration of contractility is slow. The stunning of the heart muscle is probably due to a partial disorder of the electromechanical mechanisms caused by impaired calcium homeostasis. Substances which protect against the development of stunning are substances which eliminate oxygen radicals and calcium channel blockers which adjust the calcium homeostasis in cells. The "hibernating myocardium" is a state of contractile dysfunction during chronic hypoperfusion of the heart muscle. When the blood flow is restored, the contractility improves gradually. The second generation of calcium antagonists is effective in hibernated heart muscles due to their selective coronary artery dilating effect.

Animals↗
PubMedDate not supplied

[Obstructive sleep apnea as a cause of dysrhythmia in sudden cardiac death].

BACKGROUND: Sleep apnoea is often accompanied by severe disturbances in heart rate and cardiac rhythm. SUBJECTS AND METHODS: Various respiratory parameters were continuously recorded 6-9 hours during sleep in ten patients with sleep apnoea syndrome, paralley with direct ECG recording (8 cases) or Holter monitoring (2 cases). The rate, development and reversibility of various dysrrhythmias were evaluated. RESULTS: Obstructive, central and mixed sleep apnoeas (OSA, CSA, MSA) and hypopnoea occurred in each patient (52.5%, 3.5%, 10% and 34%, respectively). Lighter dysrrhythmias (sinus arrest, atrioventricular block and occasional supraventricular premature contractions) were in patients with frequent CSA, whereas the most severe ones (higher degrees of AVCB, premature ventricular contractions and tachyarrhythmias) occurred during OSA. Stronger hypoxaemia and myocardial acidosis, as well as severe alteration in sympathetic and vagal tone probably contributed to the development of life-threatening brady- and tachyarrhythmias in OSA, based on alteration in effective refractory period and reentry phenomenon. CONCLUSION: Dysrrhythmias often occur during OSA and they may result in acute cardiovascular complications. Due to their functional character and reversibility, the development of nocturnal dysrrhythmias can be prevented by early diagnosis and effective treatment of sleep related breathing disorders, which at the same time decreases, the risk of both cardiovascular complications and diseases.

Adult↗