PubMed Health⌕ Search

Biomedical subjects

Theo Thien

Publications and source records attributed to Theo Thien.

17 recordsLinked to original sources
PubMed2006

Bromide as a marker to measure adherence to drug therapy.

OBJECTIVE: Several methods have been described to measure adherence to prescribed drug therapy. However, most of these have been shown to be inaccurate. Bromide is an anion that is readily absorbed in the gut and has an elimination half-life of about 12 days. In the present study, we investigated the pharmacokinetic properties of bromide with the objective to use it as a measure of drug adherence. METHODS: Three groups of each 8 healthy volunteers took 15, 24 or 30 mg potassium bromide, respectively, daily for 20 weeks. Serum concentrations of bromide were measured every two weeks. RESULTS: There was a linear relationship between the daily dosage taken and the mean increase of bromide concentration. In every group considerable inter-individual variability was seen. Correction for body weight resulted in an improved correlation between daily bromide dose and increase in concentration (r=0.78, p<0.01). CONCLUSIONS: Unfortunately, the inter-individual variability in clearance of bromide was considerable. This limits the use of bromide to primarily measuring adherence in individual patients during long term follow-up. Bromide appears to be a potentially useful marker to be added to drugs for assessment of individual adherence to long term drug therapy. This needs to be investigated in various patients, particularly for patients with relatively asymptomatic diseases (e.g. hypertension).

Bromides↗
PubMed2006

The optimal scheme of self blood pressure measurement as determined from ambulatory blood pressure recordings.

OBJECTIVE: To determine how many self-measurements of blood pressure (BP) should be taken at home in order to obtain a reliable estimate of a patient's BP. DESIGN: Participants performed self blood pressure measurement (SBPM) for 7 days (triplicate morning and evening readings). In all of them, office blood pressure (three consecutive readings) and 24-h ambulatory blood pressure were obtained as well. Average SBPM values, obtained from several combinations of readings, were correlated with the results of ambulatory blood pressure measurement (ABPM). In addition, we assessed whether certain patient characteristics would influence such correlations. SETTING: Patients were recruited at hospital or general practice. PATIENTS: A total of 216 untreated hypertensive patients. RESULTS: The average SBPM value calculated from day 3 to day 7, omitting the first measurement of each morning and evening session, gave the best correlation with 24-h ABPM (r = 0.70). However, similar results were obtained from a SBPM value averaged from day 3 until 5 without the first measurement of each triplicate session. Overall, younger patients had significantly better correlations than older ones. Women had significantly better correlations with ABPM than men for systolic morning and daytime SBPM, whereas men had significantly better correlations for daytime and evening diastolic SBPM (P < 0.001). In addition, all correlations increased with lower systolic office blood pressure measurement (OBPM) values. CONCLUSIONS: A minimum number of 5 days of measurement is recommended to obtain a reliable estimate of a patient's usual BP. On each day, three consecutive morning and evening measurements should be performed. For calculating the average SBPM, the first 2 days and the first measurement of each triplicate measurements should be discarded. Moreover, patient characteristics may have an impact on the number of necessary self-measurements. However, because adhering to these recommendations will make SBPM a time-consuming procedure, this type of measurement should be performed only when a decision about starting or changing antihypertensive therapy is needed or in the case of special patient groups.

Adult↗
PubMed2006

Prevalence of the white-coat effect at multiple visits before and during treatment.

OBJECTIVE: To investigate the prevalence and persistence of the white-coat effect (WCE) and white-coat hypertension (WCH) on multiple blood pressure measurement occasions in hypertensive patients with and without treatment. DESIGN: Essential hypertensive patients in whom we took office blood pressure measurements (OBPM) at eight visits (three readings per visit) performed self blood pressure measurements (SBPM) for 1 week prior to each visit (42 readings per week) over a period of 1 year. All measurements were performed with the same automatic device (Omron 705CP). In addition, 24-h ambulatory blood pressure monitoring (ABPM) was performed at the start and at the end of the study. At the start, patients did not use any medication but on subsequent visits they were treated on the basis of their SBPM values. WCH was defined as an OBPM-value > or = 140 and/or 90 mmHg and a SBPM or daytime ABPM value < 135/85 mmHg. This definition was used irrespective of treatment. We also determined the prevalence of a substantial WCE (OBPM 20 mmHg systolic or 10 mmHg diastolic higher than SBPM or daytime ABPM). SETTING: Patients were recruited at hospital or general practice. PATIENTS: A total of 163 mild-to-moderate essential hypertensive patients with a mean age of 56 years (56% males). RESULTS: At eight blood pressure (BP) measurement occasions, 75% of all patients had a substantial WCE at least once, while 57% had WCH at least once. One-third of the patients consistently had a substantial WCE and 14% consistently had WCH on three or more occasions The magnitude of the WCE was significantly related to the height of blood pressure in treated but not in untreated patients. CONCLUSION: In some patients, WCH or a substantial WCE occurs consistently on multiple OBPM visits. Especially in untreated patients, the magnitude of the WCE varies widely among individuals. These results support the incorporation of SBPM and/or ABPM into optimal management of hypertension, not only to prevent misdiagnosis in untreated patients but also to determine the need for adjusting antihypertensive therapy in treated subjects.

Blood Pressure↗
PubMed2006

The position of the arm during blood pressure measurement in sitting position.

OBJECTIVE: Determining the influence of the position of the arm on blood pressure measurement in the sitting position. METHODS: Blood pressure of 128 individuals (the majority being treated hypertensive patients) visiting the outpatient clinic was measured simultaneously on both arms with arms in two different positions. First, both arms were placed at the chair support level and blood pressure was measured three times on both arms after 10 min of rest. Subsequently, while still remaining in the same sitting position, five blood pressure measurements were made simultaneously at both arms with one arm placed on the desk and one arm placed and supported at heart level (mid-sternal). The arm placed at heart level served as the reference arm. The choice of which arm was placed at desk level and which arm was placed at heart level was randomized. RESULTS: Both at desk level and at chair support level, mean (+/-SD) systolic and diastolic blood pressures were higher than blood pressure at heart level by 6.1/5.7+/-4.6/3.1 and 9.3/9.4+/-5.4/3.4 mmHg, respectively. The effect of the height differences between the arm positions on the blood pressure readings was smaller than predicted (0.49 mmHg/cm systolic and 0.47 mmHg/cm diastolic). No significant correlation was found between blood pressure difference in the different arm positions (desk and heart level) and age, sex, weight or baseline blood pressure. CONCLUSIONS: Different arm positions below heart level have significant effects on blood pressure readings. The leading guidelines about arm position during blood pressure measurement are not in accordance with the arm position used in the Framingham study, the most frequently used study for risk estimations.

Adult↗
PubMed2005

Side effects of ambulatory blood pressure monitoring.

OBJECTIVE: To study the experiences and complaints of patients who underwent 24 h blood pressure monitoring. METHODS: Two groups of hypertensive patients of a tertiary outpatient clinic were asked to fill in a nine-item questionnaire about the side effects of ambulatory blood pressure monitoring (ABPM). The first group (n=75) used the auscultatory Oxford Medilog device (OM) and the second group (n=110) the oscillometric Spacelabs 90207 (SL). RESULTS: The OM showed significantly less error readings (OM versus SL, 9 versus 19%; P=0.005) but was also less tolerated by the subjects. Sleep disturbance was noted in 53% of the OM patients group in comparison with 18% in the SL group (P<0.0001). Adjustment of daily activities occurred more often in the OM group (OM versus SL, 37 versus 19%; P=0.013) as did complaints of pain in the cuffed arm (OM versus SL, 31 versus 11 %; P=0.007). There was no difference in the proportion of patients that refused a second ABPM (OM versus SL, 11 versus 10%). Linear regression analyses showed that differences in side effects between the two devices were not due to differences in blood pressure, heart rate, age or sex. CONCLUSIONS: This study demonstrates that side effects of ABPM are not negligible and that there are differences between devices.

Activities of Daily Living↗
PubMed2005

Is the accuracy of blood pressure measuring devices underestimated at increasing blood pressure levels?

BACKGROUND: In validation studies reporting on the accuracy of blood pressure measuring devices (ambulatory and non-ambulatory systems), it is frequently stated that the accuracy of blood pressure devices seems to decrease at increasing blood pressure levels. This has been shown for several ambulatory devices in the past. Whether more recently validated devices are less accurate at increasing blood pressure levels is unknown, however. OBJECTIVES: We therefore retrospectively searched the literature for studies performed between 1993 and 2003, reporting on the accuracy of blood pressure measuring devices over different blood pressure levels. When needed, additional information from the authors was requested. METHODS: In total, 30 studies were selected. Of these, the studies reporting on the accuracy of 14 different ambulatory and nine different non-ambulatory devices were useful. For both ambulatory and non-ambulatory devices, accuracy appeared to decrease at increasing blood pressure levels. This was particularly shown for systolic blood pressure. RESULTS: We speculate whether this finding is due to the oscillometric method of blood pressure measurement. Another explanation may exist, however. Blood pressure variability increases with higher blood pressure. Further, the British Hypertension Society protocol 1993 uses sequential measurements. This may be the reason that, owing to the increased blood pressure variability, the accuracy of most devices tends to decrease at higher blood pressure levels. Consequently, the accuracy of blood pressure measuring devices may be underestimated at higher blood pressure levels. CONCLUSION: Currently used automated blood pressure measurement devices seem to be less accurate at increasing blood pressure levels. It is important to be aware of this phenomenon when treating hypertensive patients. The reported decrease in accuracy, however, may well be explained by the increasing blood pressure variability at increasing blood pressure and the use of sequential measurements. If this is the case, then the accuracy of these devices is perhaps underestimated.

Blood Pressure↗
PubMed2005

Long-term effect of inhibition of the angiotensin-converting enzyme (ACE) on cavernosal perfusion in men with atherosclerotic erectile dysfunction: a pilot study.

INTRODUCTION: Impaired perfusion of the corpora cavernosa is considered an important causal factor of erectile dysfunction (ED) in the aging male with atherosclerosis. Aim. On the basis of this notion, we hypothesized that inhibition of angiotensin-converting enzyme (ACE) may have a structural beneficial effect on cavernosal perfusion and subsequently on erectile function in men with impaired cavernosal perfusion. METHODS: A total of 59 men with atherosclerotic ED (mean age, 60.0 +/- 6.8 years) and impaired cavernosal perfusion, as demonstrated with penile-pharmaco duplex ultrasonography, were randomized between an ACE inhibitor and placebo treatment arm. The minimum period of intervention was 26 weeks (26-46 weeks). The goal of the study was to demonstrate an improvement of (i) cavernosal arterial perfusion demonstrated by a decrease of blood flow velocity waveform; and (ii) erectile function in the erection domain of the International Index of Erectile Function. RESULTS: Cavernosal perfusion improved significantly (paired samples t-test, P < 0.05) in both study arms, but the improvement did not differ significantly (anova, P > 0.05) between both arms. The number of sexually active men increased, and the severity of ED decreased in both groups. CONCLUSION: Although a persisting improvement of cavernosal perfusion by at least a 6 month-administration of an ACE inhibitor in men with advanced atherosclerotic ED could not be demonstrated in this pilot study, the beneficial effect on cavernosal perfusion, sexual activity, and erectile function in all participants of this study is remarkable. This pilot study warrants a follow-up study in sexually more active men with ED and less advanced atherosclerosis to show that ACE inhibition may result in persisting improvement of cavernosal perfusion.

Analysis of Variance↗
PubMed2005

The post-thrombotic syndrome: incidence and prognostic value of non-invasive venous examinations in a six-year follow-up study.

The ability to predict severity of the post-thrombotic syndrome (PTS) early after acute deep-vein thrombosis (DVT) is limited. The aim of our study was to examine the incidence of PTS prospectively and to evaluate the predictive value of non-invasive venous examinations shortly after DVT for the development of PTS. In 93 patients with DVT thrombosis score (TS), reflux, venous outflow resistance (VOR) and calf muscle pump dysfunction (CMP) were examined prospectively. After one, two and six years patients were evaluated for PTS using the clinical scale of the CEAP-classification (PTS present > or = 3 on a scale from 0 to 6). Area under the curves (AUC) were used to evaluate the predictive value of the non-invasive examinations at one and three months after diagnosis of DVT for future PTS. The cumulative incidence of PTS increased from 49% (32/65) after one year to 55% (36/65) and 56% (27/48) after two and six years, whereas the incidence of patients with PTS class 4 progressed from 20% after two years to 33% after six years. The prognostic value to predict PTS was highest for the combination of TS, VOR and reflux measured three months after diagnosis and showed an AUC of 0.77 (0.65-0.90) for PTS after one year. In conclusion, the incidence of PTS after DVT did not increase significantly after one year, whereas during longer follow-up the severity of PTS rose in patients with PTS. Moreover, measurement of TS, VOR and reflux three months after DVT could predict, with reasonable accuracy, the risk of PTS after one year of follow-up.

Adolescent↗
PubMed2004

Accuracy of the Omron RX-M, an automated blood pressure measuring device, measuring blood pressure at the wrist, according to a modified British Hypertension Society protocol.

OBJECTIVE: To determine the accuracy of the Omron RX-M, a device measuring blood pressure oscillometrically at the wrist. METHODS: In 89 subjects (mean age 55+/-14 years) blood pressure measurements at the wrist with the Omron RX-M were compared to sequential blood pressure measurements with a mercury sphygmomanometer at the (same) upper-arm and to simultaneous measurements with the Omron HEM-705 CP at the opposite arm.Measurements with analyzed according to the British Hypertension Society (BHS) - protocol 1993, to the protocol of the Association for the Advancement of Medical Instrumentation (AAMI) and (retrospectively) to the new 'International Protocol'. RESULTS: Mean differences (+/-SD) between the measurements with the mercury sphygmomanometer and the Omron RX-M were -7.5+/-8.4 mmHg for diastolic blood pressure (DBP) and -2.5+/-12.2 mmHg for systolic blood pressure (SBP), thus not fulfilling the AAMI-criteria (< or =5+/-8). According to the BHS-criteria a grade D was achieved for both DBP and SBP. Compared to the Omron HEM 705 CP results were -6.3+/-7.1 for DBP (grade D) and -4.1+/-12.7 for SBP (grade D). The Omron RX-M also failed to pass the new 'International Protocol' in phase 1. CONCLUSION: Although easy to use, based on this study the Omron RX-M can not be recommended to determine blood pressure accurately.

Adult↗
PubMed2003

Only weak vasorelaxant properties of loop diuretics in isolated resistance arteries from man, rat and guinea pig.

Besides their diuretic action, loop diuretics may induce a rapid vasodilator effect that contribute to their short-term therapeutic properties. We examined the effects of furosemide (10(-6)-10(-3) mol l(-1)) in comparison with bumetanide (10(-6)-10(-4) mol l(-1)) on isolated resistance arteries from rat and guinea pig mesentery and human subcutaneous fat, and investigated the mechanism of the acute direct vasorelaxant action on an isometric microvascular myograph. Both loop diuretics induced concentration-dependent relaxation of resistance vessels irrespective of membrane potential. The maximal effect of furosemide was greatest in rat and least in human arteries. Both diuretics caused a rightward shift in the concentration-response curve to extracellular Ca(2+). Incubation with indomethacin (2 x 10(-5) mol l(-1)) or mechanical removal of the endothelium did not inhibit the loop diuretic-induced relaxation. At high concentrations (10(-4)-10(-3) mol l(-1)) loop diuretics exert only weak direct relaxant effects on isolated human subcutaneous resistance arteries compared to the vasorelaxant effects in rat and guinea pig mesenteric vessels.

Animals↗
PubMed2003

Low-dose aspirin for primary prevention of cardiovascular disease.

Progressive atherosclerosis followed by plaque rupture is the leading cause of acute cardiovascular events. Inhibition of platelet aggregation by acetylsalicylic acid (aspirin) reduces recurrent cardiovascular events in secondary prevention trials. By extracting data from available randomized trials that examined aspirin prevention in persons without previously known cardiovascular disease, we evaluated the use of aspirin as a primary prevention measure. Using the raw data presented in the source publication on death, fatal and nonfatal myocardial infarctions, and cerebrovascular accidents, all relative and absolute risk reductions were recalculated with confidence intervals. In healthy men above 45 years of age, men with an increased cardiovascular risk profile, and persons with diabetes mellitus or hypertension, the use of aspirin reduces the incidence of myocardial infarction and has a neutral effect on cerebrovascular events. The protective effect of aspirin is apparently most prominent in those persons with an increased risk of manifest atherosclerotic vascular disease. Notwithstanding these results, for each patient it remains essential to balance the cardiovascular risk profile against the small increased risk of bleeding complications when prescribing aspirin.

Aspirin↗
PubMed2002

The development of postthrombotic syndrome in relationship to venous reflux and calf muscle pump dysfunction at 2 years after the onset of deep venous thrombosis.

OBJECTIVE: Postthrombotic syndrome (PTS) develops in 40% to 60% of patients with deep venous thrombosis. Factors that are important in the development of PTS include venous reflux, deep vein obstruction, and calf muscle pump dysfunction (CMD). METHODS: Reflux and CMD in relationship to the severity of PTS were evaluated in a 2-year follow-up study of patients with acute deep venous thrombosis. Duplex scanning was used to measure reflux. The supine venous pump function test (SVPT) measures CMD with strain-gauge plethysmography. The base-line examination was performed within 1 to 5 days after diagnosis. The next examinations were scheduled at 3, 6, 12, and 24 months. RESULTS: The study included 86 legs, and the 2-year follow-up period was completed for 70 legs. Significantly more reflux was found in previously thrombosed vein segments, with an odds ratio of 1.8 after 3 months, of 2.1 after 6 months, of 2.5 after 12 months, and of 3.2 after 24 months. Multiple regression results showed that the most important risk factor for early clinical signs of PTS was superficial reflux in months 3, 6, and 12 (P < or =.02). Deep reflux did not have a synergistic relationship with superficial reflux in correlation with the clinical signs of PTS. The SVPT was not able to predict the development of PTS. CONCLUSION: More reflux develops in previously thrombosed vein segments. As early as after the third month, patients with superficial reflux have an increased risk of development of the first clinical signs of PTS. Within 2 years, the SVPT shows no relationship with clinical signs of PTS.

Female↗
PubMed2002

Accuracy of the Welch Allyn Vital Signs Monitor 52000 automatic blood pressure measuring device according to a modified British Hypertension Society protocol.

The accuracy of the Welch Allyn Vital Signs Monitor, a compact device for the oscillometric measurement of blood pressure, was determined according to the British Hypertension Society protocol. The monitor achieved a grade C for diastolic and a grade D for systolic blood pressure. The device is suitable for monitoring a patient, for example post-operatively, in the emergency department or during an intervention. The device cannot, however, be recommended for an exact determination of blood pressure when compared with the mercury sphygmomanometer. In an earlier validation report, the Welch Allyn Vital Signs Monitor achieved a grade A for both diastolic and systolic blood pressure. After adjusting for the difference in method of calculating the grades used in the two studies, there remained a considerable difference in grading results, for which no clear reason could be found.

Adult↗
PubMedDate not supplied

Long-term outcome of cardiovascular prevention: a Nijmegen Academic Family Practices Network study.

CONTEXT: Cardiovascular disease is common and preventable. Primary care is the preferred setting for individual prevention and management. OBJECTIVE: This study analyzed the long-term outcome of cardiovascular risk in a family practice population. DESIGN: A longitudinal cohort analysis of cardiovascular outcome after 18 years, in participants of a randomized controlled trial (RCT) of cardiovascular prevention. In 1977, a RCT with cluster randomization at practice level assessed the effects of a 1-year preventive intervention in patients 20 to 50 years of age. Cardiovascular risk factors (smoking, body mass index, blood pressure, serum cholesterol, family history, and physical activity) were measured and intervention was a practice-nurse support for the follow-up of those at elevated risk. The control practices prescribed care as usual. Between 1994 and 1995, all participants were approached again, to analyze subsequent (cardiovascular) mortality and morbidity and their cardiovascular risk in a random sample. SETTING: The Nijmegen Academic Family Practices Network, The Netherlands. PARTICIPANTS: All participants (7092) of the 1977 screening for follow-up morbidity and mortality, 2600 for re-measurement risk factors. OUTCOME MEASURES: Cardiovascular risk factors; cardiovascular morbidity and mortality 1977-1995. RESULTS: Follow-up was achieved in 5945 participants (84%) and 2335 participated in the re-measurement (89%). No effects of the preventive intervention were found, but those initially at low risk profile were still so 18 years later. Risk of subsequent cardiovascular mortality and morbidity was related to baseline risk, but for women, the absolute risk was low in all risk strata and lower than predicted from international references. CONCLUSIONS: This study demonstrated the feasibility of family practice network research in pursuing longitudinal research. A single cardiovascular screening resulted in reliable risk assessment: those initially at low risk still were so after 18 years. Effects of a 1-year intensive intervention could no longer be demonstrated.

Adult↗