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Biomedical subjects

R Steffen

Publications and source records attributed to R Steffen.

At least 73 records · Page 4Linked to original sources
PubMed1998

Impact of melatonin on driving performance.

BACKGROUND: Because millions of people are self-prescribing melatonin for various indications, the safety aspects of this substance have become very important. The aim of our study was to determine whether or not melatonin impairs driving-related performance. METHODS: Twenty healthy men and women aged 21-57 years volunteered for this randomized, placebo-controlled, double-blind, crossover study. The crossover arms were separated by an interval of at least 4 weeks. On each testing day, melatonin 5 mg or placebo was taken at 1630 h; 60 minutes later a test series was performed, consisting of a medical examination, body sway measurement, and a standardized driving computer test battery to assess attention, reaction time, power of concentration, and sensomotor coordination. Subjective sleepiness was measured on three occasions during the test session using the Stanford Sleepiness Scale questionnaire. RESULTS: Just one of the 16 main variables of the driving computer test battery, the selective attention tested by signal-detection, was significantly affected by melatonin (p < .05). However, even those values were still within the normal range. Subjective sleepiness was increased by melatonin, although the result was significant only after the prolonged concentration task (p < .05). Neither the clinical examination nor the body sway test showed signs of any drug influence. CONCLUSIONS: The overall result of the computer test battery showed no objective adverse impact of melatonin on driving performance. However, due to the increased subjective sleepiness after administration of this hormone, caution should be exercised when driving under the influence of melatonin.

Adult↗
PubMed1998

Safety of mefloquine and other antimalarial agents in the first trimester of pregnancy.

BACKGROUND: Safe and effective antimalarials are required to protect pregnant women from the harmful effects of malaria. METHODS: Data were collected from two separate prospective cohorts to ascertain the safety of chloroquine-proguanil, sulfadoxine-pyrimethamine (SP), and mefloquine taken in the first trimester of pregnancy. RESULTS: In a traveler cohort of 236 pregnant women, spontaneous abortions were reported in 7.6% of 99 women taking chloroquine-proquanil, 0% of 19 taking sulfadoxine-pyrimethamine, and 9.1% of 118 women taking mefloquine. Anomalies were identified in 1.7%, 0% and 0% of the same cohort, respectively. Differences in rates of adverse outcomes between the three groups were not statistically significant. In a pharmaceutical database of 331 and 153 women exposed to mefloquine and SP, respectively, the overall rate of abnormal outcomes (spontaneous abortions plus fetal anomalies) was not significantly different (p=.29). Spontaneous abortions were significantly higher with mefloquine than SP (9.1% and 2.6%, respectively; p=.01), but the higher rate was comparable to background rates (7%-11%). Fetal anomalies in the mefloquine group (4.8%) were lower than the SP group (7.8%), but this was statistically not significant (p=.19), and was comparable with the background rate of 4.6% (p=.84). However, mefloquine exposure resulted in a significantly higher rate of therapeutically induced abortions, undertaken for perceived risk to the fetus, compared with SP (p<.0001). CONCLUSION: From the clinical data available, there is no indication that the risk of taking mefloquine in the first trimester of pregnancy is greater than that from any of the other antimalarials studied and the risk is considerably lower than that associated with falciparum malaria.

Abnormalities, Drug-Induced↗
PubMed1998

Effectiveness of personal protection measures against mosquito bites for malaria prophylaxis in travelers.

BACKGROUND: To determine the effectiveness of personal protection measures (PPM) against mosquito bites in travelers as tools of malaria prevention. METHODS: Two step questionnaire survey conducted in European tourists who visited East Africa: cross-sectional evaluation during the return flight with follow-up 12 weeks after return home. Among 100,336 tourists participating in a malaria survey, 89,617 had answered all questions relating to PPM and to malaria occurrence. The main outcome measure was the occurrence of malaria. RESULTS: Only 2% of tourists visiting East Africa regularly take all four of the most important PPM. Regular use of PPM resulted in a small, but significant reduction of malaria incidence when travelers were interviewed 12 weeks after returning home. Air-conditioned rooms and clothing which covered arms and legs were effective, whereas repellants, insecticides, coils, etc. showed no significant effect. CONCLUSIONS: In general, advice relating to all possible PPM in travelers should be concentrated on those who are at greatest risk of bites, and thus of malaria. For those at low and intermediate risk, preference should be given to convenient measures with proven effectiveness, such as using air-conditioned rooms and appropriate clothing.

Adolescent↗
PubMed1998

Are preventive HIV interventions at airports effective?

BACKGROUND: Few empirical data exist on the impact of preventive human immunodeficiency virus (HIV) interventions on intended and actual sexual behavior of international tourists. The present cross-sectional study is based on a 2 3 2 design. METHODS: The sample consisted of departing and arriving passengers (n = 3100) at Zurich Airport with destinations in countries where heterosexual HIV transmission is dominant. While 41% of the tourists obtained information about safer sex, the remaining 59% without such intervention served as control group. Departing passengers completed a short questionnaire focusing on their planned sexual behavior. Arriving passengers were asked about their actual behavior during the journey. Subjects of the intervention group also evaluated the impact of the consultation. RESULTS: Most travelers appreciated the intervention and reported that they received important information. Members of the intervention group were better informed than those of the control group about the risk of heterosexually transmitted HIV infection (p <.01). They also indicated more often that they could imagine having casual sex abroad (23% vs 16%, p <.01). However, the two groups did not differ with regard to planned condom use or actual sexual behavior. Whereas most of departing passengers indicated that they would use condoms consistently, only half of the passengers who reported casual sex actually did so. Subjects who refused to participate in the intervention tended to consider it as irrelevant and reported less consistent condom use. CONCLUSIONS: Although travel health interventions focusing on casual sex are appreciated and increase the knowledge, they failed to result in significant behavior modification. Future projects should attempt to approach possible risk groups more specifically and to have more impact.

Adult↗
PubMed1998

Effects of a synthetic allosteric modifier of hemoglobin oxygen affinity on outcome from global cerebral ischemia in the rat.

BACKGROUND AND PURPOSE: Neuronal injury results from an insufficient supply of oxygen to the brain. This experiment examined whether a pharmacologically induced rightward shift of the partial pressure of oxygen at which 50% of hemoglobin is saturated (P50) would improve outcome from either incomplete and/or near-complete forebrain ischemia-induced hypoxia in the rat. METHODS: For incomplete ischemia (attenuated electroencephalogram), fasted rats (n = 17 to 19 per group) were given a synthetic allosteric modifier of hemoglobin affinity for oxygen (RSR13; 150 mg/kg IV) before or immediately after 20 minutes of bilateral carotid occlusion combined with a decrease in mean arterial pressure to 40 mm Hg. For near-complete ischemia (isoelectric electroencephalogram), rats (n = 15 per group) were given RSR13 (150 mg/kg) at onset of reperfusion after 10 minutes of bilateral carotid occlusion combined with a decrease in mean arterial pressure to 30 mm Hg. In both experiments, control rats were given vehicle (0.9% NaCl IV) only. Outcome (defined as percent dead hippocampal CA1 neurons) was determined at 5 days after ischemia. RESULTS: RSR13 (150 mg/kg) produced a 68% rightward shift of P50 (34+/-3 to 57+/-8 mm Hg). RSR13 reduced CA1 damage resulting from incomplete ischemia by 28% (P=0.02), but only when administered at the onset of reperfusion. RSR13 had no effect on outcome from near-complete ischemia. CONCLUSIONS: A postischemic pharmacologically induced increase in P50 may improve outcome from incomplete global cerebral ischemia. More severe (near-complete) ischemia negates this benefit.

Allosteric Regulation↗
PubMed1998

Infectious diseases presentations of Munchausen syndrome by proxy: case report and review of the literature.

Munchausen syndrome by proxy is a form of abuse, usually of a child by a parent, in which a factitious illness is reported or produced in the child, resulting in unnecessary medical evaluations and treatments. A dramatic case of a 17-month-old infant with recurrent polymicrobial bacteremia prompted a review of cases diagnosed by the Pediatric Infectious Diseases consultation service at our referral children's hospital and a review of the infectious diseases presentations in the medical literature. The infectious diseases presentations of the syndrome as well as criteria for the diagnosis are reviewed and discussed.

Child↗
PubMed1998

The putative sponge aggregation receptor. Isolation and characterization of a molecule composed of scavenger receptor cysteine-rich domains and short consensus repeats.

Porifera (sponges) are the oldest extant metazoan phylum. Dissociated sponge cells serve as a classic system to study processes of cell reaggregation. The reaggregation of dissociated cells is mediated by an extracellularly localized aggregation factor (AF), based on heterophilic interactions of the third order; the AF bridges two cells by ligating a cell-surface-bound aggregation receptor (AR). In the present study we report cloning, expression and immunohistochemical localization of a polypeptide from the marine sponge Geodia cydonium, which very likely represents the AR. The presumed AR gene gives rise to at least three forms of alternatively spliced transcripts of 6.5, 4.9 and 3.9 kb, as detected by northern blotting. Two cDNA clones corresponding to the shorter forms were already reported earlier; here we present an analysis of the largest. All three putative polypeptides feature scavenger receptor cysteine-rich (SRCR) domains. The largest form, SRCR-SCR-Car, is a cell-surface receptor of molecular mass 220 kDa, which is assumed to be the cell-adhesion receptor AR; the second form, SRCR-Re, is also a putative receptor of 166 kDa, while the third form, SRCR-Mo, is a soluble molecule of 129 kDa. The SRCR-SCR-Car molecule consists of fourteen SRCR domains, six short consensus repeats (SCRs), a C-terminal transmembrane domain and a cytoplasmic tail; its fourteenth SRCR domain features an Arg-Gly-Asp tripeptide. To obtain monoclonal antibodies, a 170-amino-acid-long polypeptide that is found in all three forms of the SRCR-containing proteins was expressed in E. coli. In a western blot of sponge cells lysate the monoclonal antibody raised against the recombinant polypeptide recognized two major immuno-reacting polypeptides (220 and 117 kDa) and two minor bands (36 and 32 kDa). The antibody was found to react with antigen(s) predominantly localized on the plasma membranes of cells, especially those of spherulous cells. In a functional assay Fab' fragments of the antibodies suppressed AF-mediated cell-cell reaggregation. Additionally, a recombinant SRCR-soluble fragment effectively inhibited AF-mediated cell-cell reaggregation. We conclude that the 220 kDa SRCR-containing protein of the sponge G. cydonium is very likely the AR.

Amino Acid Sequence↗
PubMed1998

Reproducibility of 24-hour intraesophageal pH monitoring in pediatric patients.

OBJECTIVE: Despite the widespread use of 24-hour intraesophageal pH monitoring for evaluation of gastroesophageal reflux in infants and children, there is little published information regarding the reproducibility of ambulatory pH studies in this patient population. The purpose of our study was to evaluate the reproducibility of 24-hour intraesophageal pH monitoring in pediatric patients. METHODS: We prospectively investigated 26 patients with symptoms suggestive of gastroesophageal reflux (14 females and 12 males) ranging in age from 1 month to 18 years (mean, 9.2 years). The patients underwent extended intraesophageal pH monitoring over two consecutive 24-hour periods. RESULTS: Data analysis revealed that the overall reproducibility of ambulatory 24-hour pH monitoring is only 69% (r = 0.32). Eight of 26 patients had conflicting results on day 1 compared with results on day 2. Of the 8 patients with conflicting results on day 1 versus day 2, 5 had normal studies on day 1, but demonstrated pathologic reflux on day 2. Thus, the false-negative rate for day 1 was 19.2%. The kappa statistic calculated for the total time the pH was abnormal was 0.32, with values < 0.4 representing poor correlation. Spearman correlation coefficients indicated that the percentage of time with pH < 4 (r = 0.64) and the number of reflux episodes (r = 0.71) per 24-hour period are the most reproducible pH parameters. CONCLUSION: The reproducibility of 24-hour intraesophageal pH monitoring in the pediatric population is suboptimal. The investigation should be extended or repeated if the result does not correlate with the patient's clinical history.

Adolescent↗
PubMed1998

Comparative study to determine the optimal melatonin dosage form for the alleviation of jet lag.

To compare the impact of various dosage forms of melatonin and placebo on jet lag symptoms, 320 volunteers who had flights over 6 to 8 time zones were recruited for a double-blind, randomized, placebo-controlled study. The volunteers received either melatonin 0.5-mg fast-release (FR) formulation, melatonin 5-mg FR formulation, melatonin 2-mg controlled-release (CR) formulation, or placebo. The study medication was taken once daily at bedtime during 4 days after an eastward flight. The volunteers completed the Profile of Mood States (POMS), sleep log, and symptoms questionnaires once daily and the Karolinska Sleepiness Scale (KSS) three times daily prior to departure and during the 4 days of medication intake postflight. A total of 234 (73.1%) participants were compliant and completed the study. The FR melatonin formulations were more effective than the slow-release formulation. The 5-mg FR formulation significantly improved the self-rated sleep quality (p < .05), shortened sleep latency (p < .05), and reduced fatigue and daytime sleepiness (p < .05) after intercontinental flight. The lower physiological dose of 0.5 mg was almost as effective as the pharmacological dose of 5.0 mg. Only the hypnotic properties of melatonin, sleep quality and sleep latency, were significantly greater with the 5.0-mg dose.

Adult↗
PubMed1998

[Traveller's diarrhea: progress and lessons drawn from recent surveys].

Diarrhea among travellers continues to be as widespread as ever. A multicentric investigation carried out in Jamaica, Kenya, Goa (India) and Fortaleza (Brazil) indicates high incidence rates and enterotoxigenic Escherichia coli are the most common etiology for each destination.

Age Factors↗
PubMed1997

Update on the Epidemiology of Traveler's Diarrhea in East Africa.

Background: Traveler's diarrhea (TD), the most frequent health problem in visitors to subtropical and tropical regions, needs to be reassessed in view of the development of vaccines against its most frequent causative agent, enterotoxigenic Escherichia coli. Methods: Passengers returning from Mombasa to Europe were interviewed by self-applied questionnaires during the flights. Main outcome measures were subjective TD, defined as having had more diarrhea in East Africa than at home, objective TD as traditionally defined, and the cumulative incidence calculated by the method of Kaplan-Meier survival analysis. Results: Subjective TD was reported by 1117 (49.3%) of the 2268 tourists. The cumulative incidence of subjective TD reached 36.7% after a 1-week stay and 47.6% after 2 weeks. Conclusion: Subjective TD attack and incidence rates continue to be high even at frequently visited destinations.

Journal Article↗
PubMed1997

Tolerability and Effectiveness of Malaria Chemoprophylaxis with Mefloquine or Chloroquine with or without Co-medication.

Background: To determine the relevance of drug interactions with co-medication for effectiveness and tolerability of antimalarial chemoprophylaxis. Method: A database (MALPRO2) on travelers on their flight home from Africa to Europe between July 1988 and December 1991 was reanalyzed. It contains data on prophylaxis with mefloquine (n = 48,264), with chloroquine (6,752), with chloroquine plus proguanil (19,727), and with no prophylaxis (3,871). The comparison of rates of malaria incidence and adverse events (AEs) between users and nonusers of co-medication was expressed by relative risk (RR). Results: Fifty-three percent of travelers (63% of females, 43% of males) used co-medication in all prophylaxis groups, with an average of 1.35 additional drugs per person and about two AEs reported per person. With the exception of antidiarrheals plus mefloquine, malaria incidence with co-medication was lower (RR = 0.8) than without co-medication. In all regimens, the proportion of travelers reporting AEs was about 1.5-fold with co-medication (p<.01); that reporting severe AEs was twice as high as compared to with no co-medication. Mefloquine AE rates for various classes of co-medication were similar to that of chloroquine, with highest AE and severity rates with neuropsychiatric drugs (excluding antiepileptics, RR = 1.9 and 2.9), and lowest rates with cardiovasculars (RR = 1.1 and 1.0). Various co-medications were used with different frequencies in males and females, and the latter reported more AEs. Conclusion: These data suggest that co-medications commonly used by travelers have no significant clinical impact on safety and effectiveness of prophylaxis with mefloquine or chloroquine. Increased frequency and severity of AEs when using co-medication rather is explained by underlying illness.

Journal Article↗
PubMed1997

Impact of Travel-Related Health Impairments.

Background: Few recent data exist on the impact of travel-related health problems. Methods: A cohort study was conducted with follow-up by questionnaire of 2567 persons who had consulted the Zurich University Travel Clinic for travel health advice prior to visiting a developing country or eastern Europe. Of those questioned, 2109 (82.2%) could be evaluated. Results: More than one-third (800; 37.9%) had a health impairment, mainly illness leading to medical consultations in 224 (10.6%) individuals. Incapacitation was reported by 303 (14.4%) travelers, accounting for 2% of the total time abroad. The most frequent reasons for incapacitation were diarrhea and the common cold, particularly when accompanied by fever. Some 57 (7.1%) travelers consulted a doctor while abroad, and more than twice as many did so after returning home. Conclusions: This survey illustrates that despite efforts of travel medicine, the attack rate of health impairments remains virtually unchanged compared to 20 years ago. It provides one of the first overviews of incapacitation in travelers. To reduce the duration of incapacitation, one may wish to consider a travel kit which allows the patient self therapy for frequent and uncomplicated ailments.

Journal Article↗
PubMed1997

Verification of the position of pedicle screws in lumbar spinal fusion.

Medial or lateral pedicle screw penetration with the potential to affect neural structures in a wellknown and frequent problem associated with posterior spinal fusion. We evaluated the placement of pedicle screws (n = 141) in 36 patients following posterior lumbar spinal fusion with Socon or Kluger instrumentation via a lateral transpedicular approach. The examination was based on CT and MR images performed after removal of the instrumentation, on average 1 year after implantation. We found seven pedicle screws with lateral cortical penetration of the pedicle and five screws with medial cortical penetration of the pedicle (8.5% pedicle penetration overall). No severe radicular complications accompanied these pedicle penetrations. The mean insertion angles of the pedicle screws at the L4 level were 22.6 degrees and 23.1 degrees for the left and the right side, respectively. At the L5 level the mean insertion angle was 20.5 degrees on the left side and 21.5 degrees on the right, and at the S1 level the mean angle was 16.2 degrees on the left and 15.2 degrees on the right. The results of this study indicate that the lateral transpedicular approach is a safe procedure for pedicle screw insertion.

Adult↗
PubMed1997

[Control measures in an influenza pandemic in Switzerland].

As an influenza pandemic is to be expected, contingency plans are being developed in industrialized nations. During the interpandemic phase the responsibilities are clearly defined and no shortage occurs with respect to vaccines and drugs. In contrast, a lack of material and of infrastructure must be expected in a pandemic which will stress public health and disrupt social and business life. This plan illustrates how with the available means we should attempt to the best possible primarily to reduce premature mortality, secondarily to diminish morbidity and to maintain essential public services and security. Options are described, for instance how an increased production of vaccine already during the interpandemic phase would probably reduce the impact of a pandemic.

Adult↗
PubMed1997

[Injection treatment of non-radicular lumbalgia].

Low back pain is the most expensive condition in industrialized countries. Approximately 65-80% of the population will be afflicted with low back pain at some point during their life. Low back pain has many causes and can originate from any of several pain-sensitive foci, among which are facet joints, sacroiliac joint, muscle and ligaments. Primary care in the acute phase consists of nonsteroidal anti-inflammatory drugs to address the biochemical and inflammatory mediators of pain or skeletal muscle spasmolytics to reduce low back pain symptoms. Injection procedures should be reserved for the patients with low back pain who fail to respond to a directed, conservative treatment trial and have had pain for at least 2 weeks duration. Eliminating sensation from a certain pain source has been proposed as a way to allow an examiner to determine if that joint is responsible for the patient's pain. Injections of local anesthetic into the facet joint or around its nerve supply are clinical methods of eliminating pain from focal areas such as facet joints or myofascial trigger points. When a particular joint is determined to be the source of pain, long-term relief can be sought by directing therapeutic interventions at that joint. The anatomic accessibility of the most common pain sources of low back pain make diagnostic blocks and therapeutic instillation of corticosteroids particularly appealing. If used, their potential benefit for the individual case needs to be carefully weighed. They should be used to facilitate more aggressive conservative care and not as an isolated treatment. Certainly, if response to corticosteroids does not occur after the first injection, no further administration of corticosteroids is indicated.

Adrenal Cortex Hormones↗
PubMed1997

Use of conscious sedation for lower and upper gastrointestinal endoscopic examinations in children, adolescents, and young adults: a twelve-year review.

BACKGROUND: Over the past decade, many pediatric endoscopists have replaced general anesthesia with conscious sedation. Sedation is commonly used to minimize discomfort. METHODS: To evaluate the safety and efficacy of conscious sedation we reviewed 2711 reports of lower and upper gastrointestinal endoscopic examinations performed in 2026 patients between July 1981 and December 1992. RESULTS: Intravenous sedation was accomplished using meperidine and diazepam (914 examinations, 35%) or meperidine and midazolam (1427 examinations, 55%). Single agents were used for 83 examinations (3%), and 96 examinations (3.5%) were performed with the patient under general anesthesia. In the lower endoscopy group sedated intravenously (n = 713), the cecum was reached in 82% of examinations. The procedure could not be completed in 17 cases in which patients were uncooperative despite sedation. In the upper endoscopy group sedated intravenously (N = 1653), all but 91 endoscopies were completed to the descending duodenum. Esophagoscopy had been planned in 76% of these procedures. Minor complications occurred in 7 patients (0.3%). This included two episodes of significant oxygen desaturation that responded to oxygen administration and narcotic reversal. A major complication occurred in 1 patient (0.04%) who had a gastric perforation during esophageal dilation over a defective guide wire. There were no deaths, episodes of cardiorespiratory arrest, or pulmonary aspirations in our series. The combined major and minor complication rate was 0.3%. CONCLUSIONS: Intravenous conscious sedation is safe and effective in children undergoing endoscopic examination of the gastrointestinal tract. Selected patients will require general anesthesia.

Adolescent↗