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Biomedical subjects

M H Smolensky

Publications and source records attributed to M H Smolensky.

At least 19 recordsLinked to original sources
PubMed2001

Circadian rhythms and clinical medicine with applications to hypertension.

Circadian (24-h) rhythms are important to the practice of medicine. The phasing and amplitude of key physiologic and biochemical circadian rhythms contribute to predictable-in-time patterns in the manifestation and exacerbation of most medical conditions. Moreover, body rhythms can significantly affect responses of patients to diagnostic tests and medications. Rhythmicity in the pathophysiology of medical conditions is the rationale for chronotherapeutics--that is purposeful variance of the concentration of medicines in synchrony with biologic rhythm determinants of disease activity--to optimize treatment outcomes. This article discusses the concept of biologic time structure and its relevance to the practice of medicine, with a focus on hypertension and cardiovascular issues.

Antihypertensive Agents↗
PubMed2001

Circadian rhythms in medicine.

Circadian (24-hour) rhythms are important to the practice of medicine. The phasing and amplitude of key physiologic and biochemical circadian rhythms contribute to predictable-in-time patterns in the manifestation and exacerbation of most medical conditions. Moreover, body rhythms can significantly affect responses of patients to diagnostic tests and medications. Rhythmicity in the pathophysiology of medical conditions is the rationale for chronotherapeutics--the purposeful variance of the concentration of medicines in synchrony with biological rhythm--determinants of disease activity--to optimize treatment outcomes. This article discusses the concept of biological time structure and its relevance to the practice of medicine, with a focus on neurologic issues.

Journal Article↗
PubMed2001

Day-night variation in aggressive behavior among psychiatric inpatients.

Self-directed aggressive behaviors of human beings show a 24h pattern. The aim of this study was to evaluate if violence of psychiatric inpatients against one another and hospital staff varies over the 24h. The clock time occurrence of 334 episodes of assault behaviors by 119 psychiatric inpatients (78 males and 41 females, mean age 34.8+/-11.3 years) committed during a 5-year span in the psychiatric unit of the university-based hospital of Ferrara, Italy, was evaluated. The clock time of each event was categorized by hour during the 24h and into one of four 6h intervals for analysis of temporal variation by cosinor and chi2 tests, respectively. A significant 24h variation, characterized by an early afternoon peak, was detected irrespective of gender and number (single vs. repeated) of episodes committed. Changes during the 24h in ward activity, patient contact, and endogenous circadian rhythms are likely to contribute to the observed 24h pattern, although further study is needed to confirm our findings and to define causal factors.

Adult↗
PubMed2001

Seasonal variation in the effect of a fixed dose of heparin on activated clotting time in patients prepared for open-heart surgery.

We investigated the effect of an injected bolus of 5 mg kg(-1) heparin at one circadian stage (08:30 to 11:00) on blood coagulation during different months of the year. Activated clotting times (ACTs) were assessed before and 5 min after heparin dosing to ensure extracorporeal circulation during open-heart surgery. The ACT data of 1083 presumably day-active Turkish patients (816 men and 267 women, mostly older than 46 years) who underwent coronary bypass surgery between 08:30 and 11:00 in the years from 1994 to 1997 were analyzed for annual rhythmicity. The ACT values obtained just before and 5 min after heparinization were subjected to cosinor analysis using a 365.25-day period to assess seasonality in basal ACT level and heparin effect. A small-amplitude annual rhythm with a wintertime peak was documented in the morning ACT in the group of 1083 patients. Rhythms of similar magnitude and staging were also detected in heparin effect on ACT in the 1083 patients and in subgroups categorized by gender. Circannual rhythmicity in the heparin effect on ACT was also documented in the elderly (> or = 45 years old), but not young (18-45 years old) patients. The annual mean effect of heparin on the ACT was statistically significantly greater in younger than older patients. The relatively low-amplitude circannual rhythm in heparin effect on ACT (approximately 10% of the annual mean) is not viewed as being meaningful in patient preparation for bypass surgery for the 5 mg kg(-1) level of heparin dose.

Adolescent↗
PubMed2000

Day-night pattern in accidental exposures to blood-borne pathogens among medical students and residents.

The purpose of this study was to determine whether the occurrence of accidental blood-borne pathogen exposure incidents in medical students and residents in training varies during the 24 h. A retrospective review of reported exposures was conducted in a large urban teaching institution--the University of Texas Health Science Center in Houston--between November 1993 and July 1998. Professional level (year of student or level of resident), time of exposure, means/route of exposure (needle stick, laceration, or splash), and type of medical service were recorded. Analysis of the clock time of the 745 reported blood-borne pathogen exposures showed they occurred more frequently during the day than night. Over the nearly 5-year span, 531 incidents took place between 06:00 and 17:59 in comparison to only 214 between 18:00 and 05:59. To account for the day-night difference in medical student and resident hospital staffing, the data were reexpressed as exposure rates, that is, in terms of the number of events per hour per 1000 medical students and residents. Based on the total number of reported exposures over the almost 5-year span of data collection, the average rate was 40 accidents per hour per 1000 doctors in training during the 12 h daytime span (6:00-17:59). It was 50% greater at night (18:00-05:59), with 60 incidents per hour per 1000 doctors in training. The day-night difference in rate of exposures was statistically significant (p < .04). The relative risk ratio for residents and students when working during the day shift compared to working the night shift was 0.67. This means that doctors in training are at a 1.50 higher risk of sustaining a blood-borne pathogen exposure when working nights than when working days.

Adult↗
PubMed2000

Hypertension, chronotherapy, and patient management.

This article highlights information from a symposium held at the 1999 National Conference for Nurse Practitioners, Washington, D.C., November 11, 1999, sponsored by The Nursing Institute and supported by an unrestricted educational grant from Schwarz Pharma Inc. "Hypertension" was the first topic and was discussed by Elijah Saunders, MD, FACC, FACP. "Medical Chronobiology and Chronotherapy" was the second topic and was discussed by Michael H. Smolensky, PhD. The third topic, "The Nurse Practitioner and the Hypertensive Patient," was discussed by Helen C. Noel, ANP, PhD. Dr. Noel also served as chair of the symposium.

Adult↗
PubMed1999

Chronopharmacology and chronotherapy of cardiovascular medications: relevance to prevention and treatment of coronary heart disease.

Biological functions and processes, including cardiovascular ones, exhibit significant circadian (24-hour) and other period rhythms. Ambulatory blood pressure assessment reveals marked circadian rhythms in blood pressure both in normotensive persons and hypertensive patients, whereas Holter monitoring substantiates day-night patterns in electrocardiographic events of patients with ischemic heart disease. The concept of homeostasis, that is, constancy of the milieu interne, which has dominated the teaching, research, and practice of medicine during the 20th century,is now being challenged by emerging concepts from the field of chronobiology-the science of biological rhythms. Epidemiologic studies document the heightened morning-time risk of angina, myocardial infarction, and stroke. Circadian rhythms in coronary tone and reactivity, plasma volume, blood pressure, heart rate, myocardial oxygen demand, blood coagulation, and neuroendocrine function plus day-night patterns in the nature and strength of environmental triggers all contribute to this morning vulnerability. Homeostatically devised pharmacotherapies, that is, medications formulated to ensure a near-constant drug concentration, may not be optimal to adequately control diseases that vary in risk and severity during the 24 hours. Moreover, circadian rhythms in the physiology of the gastrointestinal tract, vital organs, and body tissues may give rise to administration-time differences in the pharmacokinetics and effects of therapies. Thus the same medication consumed in the same dose under identical conditions in the evening and morning may not exhibit comparable pharmacokinetics and dynamics. New technology makes possible chronotherapy, that is, increase of the efficiency and safety of medications by proportioning their concentrations during the 24 hours in synchrony with biological rhythm determinants of disease. The chronotherapy of peptic ulcer disease achieved by the evening dosing of H 2-receptor antagonists and of asthma by the evening dosing of special drug delivery forms of theophylline and morning methylprednisolone administration has proven to be beneficial. Controlled-onset extended-release verapamil constitutes the first chronotherapy of essential hypertension and ischemic heart disease; once-a-day bedtime dosing results in a high drug concentration in the morning and afternoon and a reduced one overnight. Studies demonstrate effective 24-hour control of blood pressure, including the attenuation of its rapid rise in the morning, without induction of nighttime hypotension. Moreover, this formulation effectively controls angina, especially in the morning when the risk of ischemia is greatest. Determination of the role of verapamil chronotherapy in the primary prevention of cardiovascular morbidity and mortality awaits the results of the CONVINCE trial now in progress.

Adrenergic beta-Antagonists↗
PubMed1999

Clinical chronobiology and chronotherapeutics with applications to asthma.

The concept of homeostasis (i.e., constancy of the milieu interne) has long dominated the teaching and practice of medicine. Concepts and findings from chronobiology, the scientific study of biological rhythms, challenge this construct. Biological processes and functions are not at all constant; rather, they are organized in time as rhythms with period lengths that range in duration from as short as a second or less to as long as a year. It is the body's circadian (24 h) rhythms that have been researched most intensely. The peak and trough of these rhythms are ordered rather precisely in time to support the biological requirements of activity during the day and sleep at night. The timing of the peak and trough plus the magnitude of variation (amplitude) of physiological and biochemical functions during the 24 h give rise to predictable-in-time, day-night patterns in the manifestation and exacerbation of many common medical conditions. Circadian rhythms also can influence the response of patients to diagnostic tests and therapeutic interventions according to their timing with reference to body rhythms. Rhythms in the pathophysiology of medical conditions and patient tolerance to medications constitute the basis for chronotherapeutics, the timing of treatment in relation to biological rhythm determinants as a means of optimizing beneficial effects and safety. The article discusses recent advances in medical chronobiology and chronotherapeutics and their relevance to clinical medicine in general and the management of asthma in particular. Indeed, since asthma is a disease that exhibits rather profound circadian rhythmicity, investigation of its pathophysiology and therapy necessitates a chronobiologic approach.

Anti-Asthmatic Agents↗
PubMed1999

Biologic rhythms in the immune system.

In all of its components, the immune system shows regularly recurring, rhythmic variations in numerous frequencies; the circadian (about 24 h) rhythms are the best explored. The circadian variations in immunocompetent cells circulating in the peripheral blood are of a magnitude to require attention in medical diagnostics. Both the humoral arm and the delayed (cellular) arm of the immune system function in a rhythmic manner. The response of the immune system to introduction of an antigen and to challenge of the sensitized organism varies in extent in the circadian frequency range and also in lower frequencies, for example, of about a week (circaseptan) or seasonally (circannual). The medical application of the biologic rhythms of the immune system extends to diagnostic measures, as well as treatment.

Animals↗
PubMed1999

Circadian rhythms in the pharmacokinetics and clinical effects of beta-agonist, theophylline, and anticholinergic medications in the treatment of nocturnal asthma.

Published asthma consensus reports now acknowledge that asthma is a nocturnal disease in as many as 75% of those afflicted by this medical condition. Nonetheless, the treatment of this chronic obstructive pulmonary disease in the clinic continues to be based primarily on homeostatic considerations in that it relies on long-acting bronchodilator and other therapies formulated and scheduled to ensure constant or near-constant levels of medication during the 24h. The need of asthma patients prone to nighttime attacks is not the same during the day and night; the therapeutic requirements of patients who experience nocturnal asthma, especially ones with the more severe forms of the disease, are often not satisfied by conventional medications. The therapeutic response and patient tolerance to bronchodilator medications can be improved markedly when the medications are proportioned during the 24h as a chronotherapy, that is, when more medication is delivered during nighttime sleep than daytime activity, as verified by numerous studies. This article reviews how the body's circadian rhythms influence the pharmacokinetics and effects of commonly prescribed asthma therapies and addresses why and how they must be taken into consideration to increase the effectiveness of asthma treatment.

Adrenergic beta-Agonists↗
PubMed1998

Knowledge and attitudes of American physicians and public about medical chronobiology and chronotherapeutics. Findings of two 1996 Gallup surveys.

Two Gallup telephone interview surveys were conducted during 1996 of 320 American primary care physicians and 1011 adults to assess their knowledge and attitudes about medical chronobiology and chronotherapeutics. Of the doctors, 88% claimed to possess at least some familiarity with the concept of chronobiology and circadian rhythms; however, many were not often able to identify correctly the time of day or night when common medical conditions and events most likely occur or worsen. Furthermore, a significant number of doctors believed that chronotherapies, special dosage forms that proportion medications during the day and night in synchrony to need with reference to 24 h patterns in the intensity of symptoms and risk of severe medical events, were already being marketed in the United States for angina pectoris, hypertension, respiratory allergies, and other medical conditions even though this was not the case at the time of the survey. On the other hand, the doctors were relatively unaware of those chronotherapies that actually did exist to treat asthma and peptic ulcer disease. American adults also lacked knowledge of temporal patterns in disease and were seldom able to identify the clock time when asthma and myocardial infarction are of greatest risk or when blood pressure is highest. Although neither the American physicians nor adults possessed knowledge of these facts, both had a strong positive attitude toward the concept of chronotherapeutics. Overall, the findings of these Gallup surveys indicate that a massive educational effort is necessary immediately to ensure new developments in medical chronobiology and chronotherapeutics are correctly comprehended and properly incorporated by physicians into clinical medicine and wisely utilized by patients.

Adult↗
PubMed1996

Ambulatory blood pressure monitoring. Application to clinical medicine and antihypertension medication trials.

The wide use of ABPM has resulted in greater appreciation of the circadian time structure of BP variability and its clinical relevance. It is now recognized that the day-night change in BP results from an interplay of circadian rhythms in neurohumoral mechanisms coupled with temporal patterns in physical activity and mental load. The composite effect and balance of these endogenous and exogenous cyclic phenomena give rise to elevated BP during diurnal activity and reduced BP during nighttime repose in both normotension and uncomplicated essential hypertension. The balance is frequently disturbed in complicated and secondary forms of hypertension causing gross alteration of the 24-hour BP profile. ABPM also reveals the efficiency of antihypertensive treatment throughout the 24 hours and as a function of drug administration time. The pharmacokinetics and/or pharmacodynamics of antihypertensive medications have been demonstrated to vary with ingestion time. Such time-dependencies arise from circadian rhythms in BP and underlying mechanisms. The effect of antihypertensive medications is not simply superimposed upon endogenous bioperiodicities. Rhythms in neurohumoral mechanisms of BP control may modulate treatment effect. Certain aspects of the shape of the 24-hour BP profile, such as the magnitude of the morning surge and nocturnal decrease, have been implicated as determinants of morbid and mortal cardiovascular events. One large clinical multicenter investigation, known as the CONVINCE (Controlled Onset Verapamil Investigation of Clinical Endpoints) trial, is aimed at assessing the impact (cardiovascular morbidity and mortality) of verapamil chronotherapy over standard diuretic or beta anatagonist treatment in hypertensive patients with at least one risk factor of coronary heart disease. ABPM will help ascertain to what extent depression of the morning surge in BP relates to reduction in cardiac morbidity and mortality in this as well as other such trials. In any event, the importance of ABPM and the indices derived from its application are just beginning to be appreciated and explored.

Antihypertensive Agents↗
PubMed1996

Chronobiology and chronotherapeutics. Applications to cardiovascular medicine.

The concept of homeostasis, ie, constancy of the milieu interne, has dominated the teaching, research, and practice of medicine during the 20th century. According to this theory, biologic functions and processes are maintained in relative constancy over time. The emerging concepts of chronobiology, the scientific discipline of biologic rhythm study, and the findings from research in this field challenge the construct of homeostasis. Epidemiology studies document that the occurrence and exacerbation of many human diseases vary predictably in time over 24 h, the menstrual cycle, and year due to underlying rhythms of corresponding period. Advances in the chronobiology of cardiovascular disease have proceeded rapidly during the past decade and have influenced the manner in which diagnostic procedures are conducted and interpreted. Twenty-four-hour ambulatory blood pressure (BP) monitoring and Holter monitoring reveal the marked circadian (24-h) rhythms in BP in hypertensive patients and electrocardiographic events in patients with ischemic heart disease. Homeostatically devised pharmacotherapies, ie, medications designed to ensure constant drug levels over time, may be inadequate to optimally control diseases whose courses vary in risk or severity during the 24-h period. Chronotherapies--medications formulated to deliver varying amounts of drug at different times during the 24 h period to correlate with biologic need--theoretically could offer improved efficacy. A chronotherapy for cardiovascular disease already exists in the form of the evening administration for lipid-lowering medications. The chronotherapy for hypertension and of ischemic heart disease is forthcoming.

Blood Pressure↗
PubMed1996

Sleep quality and physical and social well-being in North American petrochemical shift workers.

We modified a European questionnaire, the Standard Shiftwork Index, in syntax and length for application to workers of an American continuous operations petrochemical company in southeast Texas. Three groups of male employees--147 day workers, 107 8-hour backward rotating shift workers, and 107 12-hour shift workers--were surveyed for sleep quality, physical well-being, and time for family and personal pursuits. The groups were comparable in terms of travel time to work, marital status, age, number of children at home under the age of 18 years, history (years) of shift work, and proportion of partners working outside the home. Statistically significant group differences were detected in the mean responses between the 8-hour backward and the other groups for the indices of sleep quality, physical well-being (gastrointestinal and cardiovascular complaints), and time for family and personal pursuits. In all cases, the 8-hour backward shift work group fared worst. The differences between the groups are believed to reflect the stress of the respective work shift schedules.

Adult↗
PubMed1995

Twenty-four hour pattern in symptom intensity of viral and allergic rhinitis: treatment implications.

The symptoms of rhinorrhea secondary to influenza and cold virus or seasonal and perennial allergic rhinitis are circadian rhythmic. Cough frequency and handkerchief use by persons suffering from virus-induced rhinorrhea are more prominent during the daytime, especially during the initial hours after awakening from nocturnal sleep. The elevation in sublingual temperature as well as the decrement in mental alertness associated with influenza in particular are more profound at this time. Sneezing, blocked nose, and runny nose secondary to allergic rhinitis are also greater in intensity during the morning in approximately 70% of sufferers. The day-night variation in symptom intensity amounts to approximately 20% of the 24-hour mean level. The treatment of these diseases and their symptoms has traditionally involved equal-interval, equal-dose (homeostatic) medication schedules. The effects of antihistamine and antiinflammatory medicines may be enhanced by timing them to the day-night temporal pattern in symptom manifestation and intensity to achieve an optimization of their beneficial effects with control of toxicity, that is, as a chronotherapy.

Anti-Inflammatory Agents↗
PubMed1995

Bambuterol in the treatment of asthma. A placebo-controlled comparison of once-daily morning vs evening administration.

Once-daily morning (7 AM) vs evening (10 PM) administration of the terbutaline prodrug bambuterol (20-mg tablet dose) was investigated in a double-blind, cross-over, randomized, and placebo-controlled study involving 29 diurnally active patients with asthma. Terbutaline plasma concentration, spirometry, and drug tolerance were assessed during 39-h inpatient studies. A 7-day washout period separated each treatment. Mean 24-h plasma concentration was comparable for morning and evening bambuterol (13.2 vs 14.0 nmol/L). The Cmax for evening vs morning dosing was 17.2 vs 15.5 nmol/L (p < 0.02). The 24-h mean FEV1 was greater (p < 0.001) for bambuterol (morning: 3.2 L; evening: 3.4 L) vs placebo (2.9 L) as it was for FVC, FEF25-75%, and peak expiratory flow rate (PEFR), with the maximum effect at 4 AM independent of medication time. Evening dosing, however, resulted in greatest 7 AM (awakening) FEV1, FEV25-75, and PEFR (p < 0.03). With reference to corresponding-in-time placebo values, improvement in FEV1 at the end of the 24-h dosing intervals amounted to 0.34 L (13.5%) (p < 0.0004) and 0.35 L (15.9%) (p < 0.0012) with evening and morning bambuterol dosing, respectively. Side effects were greater for bambuterol than placebo, but not significantly so. Once-daily bambuterol therapy proved to be an effective treatment for asthma, whether administered in the evening or morning. Evening dosing seems best for nocturnal asthma since airway patency overnight and on awakening at 7 AM is most improved.

Adolescent↗