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Biomedical subjects

A E Meinders

Publications and source records attributed to A E Meinders.

At least 145 records · Page 8Linked to original sources
PubMed1994

Diurnal changes in heparin effect during continuous constant-rate infusion. A study in nine patients with venous thromboembolism.

OBJECTIVE: To evaluate the importance of diurnal variations in the effect of a continuous infusion of unfractionated heparin. DESIGN: Twenty-four-hour follow-up. SETTING: Tertiary referral centre. SUBJECTS: Patients (five male, four female) with acute venous thromboembolic diseases. MAIN OUTCOME MEASURES: Two-hourly measurement of anti-IIa activity, anti-Xa activity, APTT (Cephotest and automated APTT), antithrombin III and cortisol for 24 h. RESULTS: The maximum anticoagulant effect was found at 04.00-06.00 hours, and the minimum effect at 12.00 hours. The difference was 0.40 U ml-1 for anti-IIa activity (95% confidence interval (CI) 0.03-0.78; P < 0.05), 0.36 U ml-1 for anti-Xa activity (95% CI-0.05-0.72; not significant [NS]), 15.1 s for Cephotest APTT (95% CI 3.3-26.9; P < 0.03), and 112.9 s for automated APTT (95% CI 7.8-218.0; P < 0.05). Antithrombin III decreased from 97.9% at the start to 82.6% 24 h later (P = 0.001). Cortisol showed a typical diurnal rhythm. Expressed as a percentage of the individual 24-h mean, a maximum was found at 04.00 hours (anti-IIa activity), 06.00 hours (both APTTs), and 08.00 hours (anti-Xa activity) and a minimum at 12.00 hours (all variables). The difference was 26% for anti-IIa activity (P < 0.05) and anti-Xa activity (NS), 22% for APTT (Cephotest; P < 0.03), and 44% for APTT (automated APTT; P < 0.05). CONCLUSIONS: A continuous intravenous infusion of unfractionated heparin has a maximum anticoagulant effect between 04.00 and 8.00 hours and a minimum effect at noon. For individual patients the moment of minimum and maximum effect varies widely. Because the most impressive changes occur between 06.00 and 08.00 hours, laboratory control can best be performed at fixed times, e.g. at 10.00 and at 22.00 hours.

Adult↗
PubMed1994

Effect of insulin resistance, apoE2 allele, and smoking on combined hyperlipidemia.

Combined hyperlipidemia may result from the interaction of several metabolic and environmental factors. We explored to what extent fasting insulin concentration, apolipoprotein (apo) E2 frequency, and cigarette smoking explained the serum levels of triglyceride and high-density lipoprotein cholesterol (HDL-C) in patients with combined hyperlipidemia. Forty-nine untreated patients with combined hyperlipidemia were compared with 49 hypercholesterolemic patients who were matched for gender, age, and body mass index. All laboratory values were obtained after 9 weeks of standardized dietary intake and after an overnight fast. The patients with combined hyperlipidemia had a significantly higher (33 pmol/L, 50%) mean insulin concentration than matched hypercholesterolemic control subjects, indicating that the combined hyperlipidemic patients were more insulin resistant. However, the differences in the fasting insulin and triglyceride concentrations within the pairs were only slightly correlated (adjusted r = .29). The combined hyperlipidemic patients were also characterized by a higher frequency of apoE2 alleles (25% versus 6%) and smokers (41% versus 16%). In a matched multiple linear regression model, the differences in insulin concentration, apoE2 allele frequency, and smoking explained 12%, 8%, and 9%, respectively, of the mean paired difference in triglyceride concentration. The differences in insulin concentration or apoE2 allele frequency did not significantly explain the mean paired difference in HDL-C concentration, whereas smoking explained 17% of the difference. In conclusion, fasting insulin concentration, the presence of the apoE2 allele, and smoking may explain 30% of the hypertriglyceridemia and the low levels of HDL-C in nonobese patients with combined hyperlipidemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1994

Extraskeletal localization of 99mTc-labeled bone-seeking tracers in bone scintigraphy.

In this article clinical examples of extraskeletal localization of technetium-99m (99mTc)-labeled diphosphonate are described. In several of these cases this finding was relevant for clinical decision-making. 99mTc-labeled diphosphonates have been used for skeletal imaging since 1971, and from 1973 on many reports of extraskeletal localizations of these agents have been published. This visualization can be due to (1) an abnormality of the excretory route of 99mTc-labeled diphosphonate or (2) increased uptake in pathologically altered tissues and organs. The latter has been recorded in a multitude of disease processes, such as ischaemic injury, inflammatory processes, benign or malignant neoplasms, non-skeletal metastases, malignant pleuritis, scars, radiation injury and amyloidosis. Although the precise mechanism of extraskeletal uptake of 99mTc-labeled diphosphonate remains uncertain, binding of this radiopharmaceutical to calcium-containing compounds is thought to play a critical role.

Adult↗
PubMed1994

Evaluation of an emergency medical system. The prognosis in patients with an out-of-hospital cardiac arrest.

In a retrospective chart review, we evaluated the efficiency of the emergency medical system of the Leiden area in patients with an out-of-hospital cardiac arrest. A total of 309 adult patients were included. Two hundred patients (64.7%) died in the emergency department and 67 (21.7%) died during subsequent hospital stay. Finally, 42 patients (13.6%) survived after hospital discharge. Favourable prognostic factors were the presence of witnesses at the time of arrest, a short call-response interval, an initial cardiac rhythm of ventricular fibrillation or tachycardia, and adequate advanced cardiac life support provided by the emergency medical system. We detected several shortcomings in the system such as an unacceptably prolonged call-response interval for some patients at the periphery of the Leiden area and a delay in the first defibrillation attempt. Improvement of this "pre-hospital chain of survival" is likely to result in a better outcome for these patients.

Adolescent↗
PubMed1993

[Good results of 100% oxygen treatment for acute carbon monoxide poisoning; temporarily no indication for hyperbaric oxygenation].

OBJECTIVE: To describe the complications in patients with acute carbon monoxide intoxication, if treated with 100% instead of hyperbaric oxygen. DESIGN: Retrospective chart review. PATIENTS: Thirty-three patients with acute-carbon monoxide intoxication admitted to the medical Intensive Care Unit of Leiden University Hospital. RESULTS: The mean carbon monoxide level of all patients was 29.4%. Ten patients had a carbon monoxide level above 40%. Seven patients (21%) were in coma on admission. Most complications occurred in the latter group. All patients were treated with normobaric 100% oxygen. Recovery was usually rapid. No patient showed neurological deficits at discharge. CONCLUSION: The short-term prognosis of patients with acute carbon monoxide intoxication is good, even if they are not treated with hyperbaric oxygen. There is still inconclusive evidence from the literature that hyperbaric oxygen improves the prognosis in these patients.

Acute Disease↗
PubMed1993

The cardiovascular risk factor plasminogen activator inhibitor type 1 is related to insulin resistance.

The cardiovascular risk factor plasminogen activator inhibitor type 1 (PAI-1) has been associated with abdominal obesity, hypertension, hypertriglyceridemia, hyperinsulinemia, glucose intolerance, and type II diabetes, conditions known to be linked with insulin resistance. To determine whether PAI-1 is related to insulin resistance, we studied nine obese nondiabetics and 10 obese type II diabetics by means of a sequential hyperinsulinemic euglycemic clamp study. Plasma PAI-1 antigen (Ag) correlated significantly with peripheral insulin resistance, represented by the insulin level at which peripheral glucose uptake (PGU) is half-maximal ([ED50PGU] r = .87, P < .001). Multiple regression analysis including indices of hepatic and peripheral insulin action, fasting plasma insulin levels, triglyceride levels, blood pressure (BP), waist to hip ratio (WHR), and body mass index (BMI) disclosed ED50PGU to account for 76% of the variance of PAI-1 Ag. We suggest that PAI-1 contributes to the increased cardiovascular risk encountered with insulin resistance.

Antigens↗
PubMed1993

Prolonged resuscitation efforts for cardiac arrest patients who cannot be resuscitated at the scene: who is likely to benefit?

STUDY OBJECTIVE: To determine who may benefit from prolonged resuscitation efforts after therapy by emergency medical services system (EMS) personnel has failed to restore vital signs. DESIGN: Retrospective chart review. TYPE OF PARTICIPANTS: Two hundred sixteen consecutive adult patients with out-of-hospital cardiac arrest who were admitted to the emergency department without vital signs. METHODS: Identification of prehospital resuscitation data, therapy in the ED, hospital course, and final outcome. RESULTS: Thirty-nine patients (18.1%) were resuscitated successfully. The odds ratio of successful resuscitation in the ED for the patients with ventricular fibrillation at the scene versus those with asystole or electromechanical dissociation was 3.4 (95% confidence interval, 1.5, 7.9). All patients with asystole or electromechanical dissociation, either at the scene or in the ED, died (95% confidence interval, 0, 4.3). CONCLUSION: Prolonged resuscitation efforts in the ED for patients with asystole or electromechanical dissociation usually are futile after previous efforts by the EMS personnel have failed to restore vital signs. Transportation to the hospital may not be indicated. However, for patients with persistent ventricular fibrillation, transport is indicated.

Adolescent↗
PubMed1993

Chronic stimulation of atrial natriuretic peptide attenuates the secretory response to postural changes.

Atrial natriuretic peptide (ANP), released upon pulmonary vasoconstriction, modulates pulmonary vascular tone through an increase of cellular guanosine 3',5'-cyclic monophosphate. In patients with cardiopulmonary disease, however, the plasma levels of ANP are relatively low, considering the high pulmonary arterial pressure. To evaluate the release mechanism of the hormone, plasma ANP levels were studied by the manipulation of right atrial stretch with different body postures. In healthy young subjects, the plasma ANP concentration significantly increased when posture changed from an upright to a supine position (p < 0.01). In contrast, plasma ANP concentrations were significantly higher in patients with chronic obstructive pulmonary disease and elderly subjects (p < 0.01), but the plasma levels did not increase upon the change in posture. Consistent with in vitro findings, the data indicate that chronic ANP stimulation attenuates the secretory response to acute stimuli. In addition, it was demonstrated that the ratio of guanosine 3',5'-cyclic monophosphate to ANP, reflecting the biologic effect of the hormone, was significantly lower in patients with chronic obstructive pulmonary disease as well as in the elderly (p < 0.05). This decreased biologic activity aggravated the blunted ANP response and may contribute to the development of pulmonary hypertension.

Adult↗
PubMed1993

Weight changes in critically ill patients evaluated by fluid balances and impedance measurements.

OBJECTIVE: To study simple, rapid, and predictive methods to determine body weight changes in critically ill patients. DESIGN: Prospective, consecutive sample. SETTING: Medical intensive care unit of a university hospital. PATIENTS: Thirty-one consecutive patients. INTERVENTIONS: Calculated weight changes, using day-to-day and cumulative fluid balances corrected (in two ways) for insensible losses, were compared with the actual weight changes (mattress bascule). A tetrapolar impedance technique measuring resistance was evaluated for estimating weight changes. MEASUREMENTS AND MAIN RESULTS: No reliable relationship was found between calculated weight changes using fluid balances corrected for insensible loss and the observed weight changes. An intraindividual relationship was found between actual weight changes and changes in resistance measured with the tetrapolar impedance technique in a group of 24 critically ill patients with large weight changes (11.1 +/- 6.7 kg). No such intraindividual relationship was found in seven patients with small weight changes (3.1 +/- 2.2 kg). In each patient, the slope coefficient of the change in weight and resistance relationship differed; this individual slope coefficient could be an indication for hydration. CONCLUSIONS: Calculated fluid balances are not predictive for actual weight changes in critically ill patients. Absolute weight measurements are indispensable. Changes in resistance correlated with weight changes in individual patients if weight changes were > 3 kg.

Adolescent↗
PubMed1993

Effects of hypoxia and atrial natriuretic peptide on aldosterone secretion in healthy subjects.

To evaluate the inhibitory effect of hypoxia and atrial natriuretic peptide (ANP) on aldosterone secretion, 11 healthy male subjects were infused with 5 ng.kg-1 x min-1 ANP or placebo. The subjects were exposed in a stepwise fashion to incremental hypobaric hypoxia, which decreased arterial oxygen saturation to 79 +/- 2% in the placebo and 84 +/- 2% in the ANP condition (P < 0.05). In the placebo condition, the plasma ANP concentration increased from 13.8 +/- 1.0 to 19.6 +/- 2.3 pmol/l (P < 0.01) at the lowest barometric pressure. Plasma renin activity did not change, whereas the plasma aldosterone levels increased consequent to the increase of plasma adrenocorticotropic hormone (ACTH). Continuous infusion of ANP increased the plasma levels twofold (P < 0.001) and the level of guanosine 3',5'-cyclic monophosphate threefold (P < 0.001). However, the plasma aldosterone concentrations were not different in the two experimental conditions. Administration of supplementary oxygen significantly decreased ACTH to baseline values (P < 0.01) together with a decrease in aldosterone. Free water clearance (P = 0.05) but not sodium excretion (P = NS) increased during continuous ANP infusion. The data indicate that the aldosterone secretion in hypoxia is not inhibited by (patho)physiological plasma ANP levels. The inhibition of aldosterone secretion may well be explained by a direct effect of hypoxia on the adrenal cells. ACTH is a major stimulus of aldosterone secretion in hypoxia, which overrides the natriuretic effect of ANP.

Adrenocorticotropic Hormone↗
PubMed1993

Atrial natriuretic peptide improves pulmonary gas exchange in subjects exposed to hypoxia.

Atrial Natriuretic Peptide (ANP) is secreted in response to hypoxia and pulmonary vasoconstriction. The hormone modulates pulmonary vascular tone in vivo and decreases pulmonary edema in isolated lungs exposed to several toxic agents. In addition, ANP improves the barrier function of endothelial cell monolayers in vitro. The plasma levels of ANP are elevated in patients with high-altitude pulmonary edema. We hypothesized that under these circumstances, ANP improves pulmonary gas exchange by attenuating the transvascular permeation of plasma (water). Therefore, we studied the effect of low-dose ANP in 11 healthy mountaineers exposed to hypoxia in a single-blind, placebo-controlled, cross-over design. During four 1-h periods, the subjects were stepwise exposed to decreasing barometric pressure, with a minimum of 456 mm Hg (simulated altitude, 4,115 m). Infusion of 5 ng/kg/min human-ANP increased the plasma ANP concentrations approximately twofold. The plasma concentrations of cyclic GMP, which is the second messenger of ANP, rose approximately threefold. Infusion of ANP did not affect the hemodynamic or ventilatory response to hypoxia. The hemoglobin concentration, however, rose from 9.0 +/- 0.1 to 9.4 +/- 0.1 mmol/L (p < 0.01) during ANP infusion but not during placebo infusion. The change in plasma volume calculated from this hemoconcentration indicated that approximately 10% of the plasma volume had permeated into the interstitium. Despite the observed whole-body hemoconcentration, oxygen saturation was significantly higher during ANP infusion than during placebo infusion (84.7 +/- 1.7 versus 79.6 +/- 1.8%, p < 0.05), and the alveolar-arterial oxygen difference was significantly lower (3.5 +/- 0.7 versus 7.3 +/- 0.8 mm Hg, p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Sepsis syndrome and death after bronchoalveolar lavage.

Bronchoalveolar lavage is widely used in the management of patients with interstitial lung diseases and is considered a safe procedure. We describe a patient who died with a picture consistent with acute pulmonary edema and septic shock following bronchoalveolar lavage. This potential complication has not been previously reported.

Bronchoscopy↗
PubMed1993

The influence of serotonergic neurotransmission on pituitary hormone release in obese and non-obese females.

It has been suggested that a defect in hypothalamic serotonergic neurotransmission may be partly responsible for the impaired pituitary hormone release in obese subjects. In this study we investigated basal serum pituitary hormone concentrations and pituitary hormone release in response to the sequential injection of four hypothalamic releasing hormones before and after a seven-day course of fluoxetine, which inhibits serotonin re-uptake by presynaptic neurons and acts specifically in the brain. Ten obese women (body mass index (BMI) 35.6 +/- 1.0 kg/m2) and nine women of normal weight (BMI 22.9 +/- 0.9 kg/m2) were studied in the early and mid-follicular phases of the menstrual cycle. Basal concentrations of pituitary hormones were measured at 09.00. Subsequently 200 micrograms of TRH and 100 micrograms of CRH, GnRH and GHRH were injected intravenously. The pituitary hormone response was measured at regular intervals until 180 min after the four injections. The experiment was repeated after a seven-day course of 60 mg fluoxetine orally. We found the basal concentrations of prolactin (PRL) and growth hormone to be significantly lower in obese subjects than in the normal controls. Basal concentrations of ACTH, beta-endorphin, TSH, LH and FSH in the two groups were comparable. Releasing hormone-induced responses in the two groups were not significantly different. Administration of fluoxetine "restored" the basal PRL concentrations in obese subjects. It did not affect the other basal hormone concentrations. Furthermore, fluoxetine treatment reduced TRH-induced TSH release in both normal and obese subjects. It did not influence the other releasing hormone-induced responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗
PubMed1993

Evidence for brain serotonin-mediated control of carbohydrate consumption in normal weight and obese humans.

A plasma insulin and amino acid-mediated mechanism is thought to modulate brain serotonin concentration, thereby regulating carbohydrate consumption on a meal to meal basis. It has been suggested that obesity is associated with a defect in the appetite control system. Furthermore, post-absorptive plasma levels of several amino acids are increased in obese subjects, which is ascribed to obesity-associated insulin resistance and/or hyperinsulinemia. We studied breakfast-induced changes in plasma ratios of tryptophan to other large neutral amino acids and associated differences in macro-nutrient composition of lunch food in normal weight and obese human subjects. The study was randomized, double blind and cross-over with a 2 x 2 factorial design with drug/placebo and type of breakfast as factors. Nineteen healthy, non-obese (body mass index (BMI) 22.5 +/- 1.9 kg/m2, mean +/- s.d.) and 19 obese (BMI 34.7 +/- 6.2 kg/m2) female volunteers were treated with either 60 mg fluoxetine (FXT), a serotonin re-uptake blocker specifically acting in the brain, or placebo for four days with a wash-out period between treatments of four weeks. The subjects received either a carbohydrate (CHO) breakfast (80 g maltodextrin, 300 kcal) or a protein-rich (PROT) breakfast (60% milk protein and 40% CHO, 300 kcal) on two consecutive days (days 4 and 5 of each treatment period). Plasma glucose, insulin and amino acids were measured at several time points after breakfast. Three hours after breakfast, subjects were able to choose from 29 different food items. Total energy content and weight of lunch food and energy percentage of each macronutrient were calculated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗