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Biomedical subjects

A Hoekstra

Publications and source records attributed to A Hoekstra.

At least 19 recordsLinked to original sources
PubMed2006

Participation of the general gynecologist in surgical staging of endometrial cancer: analysis of cost and perioperative outcomes.

OBJECTIVE: To compare the cost and perioperative outcomes of endometrial cancer staging when the procedure is performed by a gynecologic oncologist alone or when a general gynecologist participates in the procedure. METHODS: A retrospective analysis was performed on a series of women with clinical stage I endometrial cancer treated at a single institution between 1/98 and 12/00. The patients were grouped according to the participation of a general gynecologist in their surgery. The 48 patients in Group 1 underwent surgery with a general gynecologist who consulted a gynecologic oncologist intraoperatively. Group 2 included 77 patients whose procedure was performed completely by a gynecologic oncologist. The two groups were compared with the chi-square, Fisher's exact, and Wilcoxon rank sum tests. Cost analysis included total hospital costs (room, pharmacy, and ancillary services) and total surgical costs (anesthesia, operating room, procedure, and perioperative physician evaluation costs). RESULTS: The groups did not differ in age, type of surgeries performed, distribution of surgical stage, proportion of patients undergoing lymph node sampling (LNS), and length of follow-up. When LNS was performed, Group 2 had a significantly shorter median operative time (170 vs. 180 min; P=0.05) and shorter total time in the operating room (204 vs. 224 min; P=0.02). This group had a lower procedure cost when considered both in terms of payor's cost ($1,414 vs. $2,134; P<0.0001) and physician charge ($7,106 vs. $11,116; P<0.0001). Perioperative physician evaluation was reduced by almost half ($685 vs. $424; P<0.0001) in Group 2. Group 2 had a savings in total surgical cost by payor's cost ($9,142 vs. 10,294; P=0.005) or physician's charge ($14,546 vs. $19,276; P<0.0001), and in combined hospital and surgical cost by payor's cost ($15,664 vs. $17,346; P=0.004) or physician charge ($21,311 vs. $26,328; P<0.0001). Total hospital costs, however, did not differ between groups. CONCLUSION: Operative time and costs increase when general gynecologists participate in the surgical procedure of patients with clinical stage I endometrial cancer. Although perioperative outcomes are similar, the involvement of two surgeons increases the length of the procedure as well as the cost of operating room time and physician reimbursement. The efficient use of limited health care resources must be considered as we plan the surgical approach to endometrial cancer.

Adult↗
PubMed2005

[Thyrotoxicosis following the use of ashwagandha].

A 32-year-old healthy woman developed thyrotoxicosis while taking capsules that contained ashwagandha herbal extract for symptoms of chronic fatigue. She was not taking any other remedies or medications. During the first few weeks, she took the capsules only occasionally without any symptoms, but after increasing the dose, she experienced clinical symptoms indicative of thyrotoxicosis. This was confirmed by laboratory assessment. The symptoms resolved spontaneously after discontinuation of the ashwagandha capsules and laboratory values normalised. To our knowledge, this relationship has not been reported previously in humans. Data from animal studies, however, have suggested that ashwagandha can increase serum concentrations of thyroid hormones. This case study suggests that thyrotoxicosis is a potentially serious side effect of ashwagandha.

Adult↗
PubMed2002

Numerical simulation and measurement of liquid hold-up in biporous media containing discrete stagnant zones.

We have studied hydrodynamic dispersion in single-phase incompressible liquid flow through a fixed bed made of spherical, permeable (porous) particles. The observed behaviour was contrasted with the corresponding fluid dynamics in a random packing of impermeable (non-porous) spheres with an interparticle void fraction of 0.37. Experimental data were obtained in the laminar flow regime by pulsed field gradient nuclear magnetic resonance and were complemented by numerical simulations employing a hierarchical transport model with a discrete (lattice Boltzmann) interparticle flow field. Finite-size effects in the simulation associated with the spatial discretization of support particles or dimension and boundaries of the bed were minimized and the simulation results are in reasonable agreement with experiment.

Biological Transport↗
PubMed2002

Intracoronary beta-radiation of de novo coronary lesions using a (186)Re liquid-filled balloon system: six-month results from a clinical feasibility study.

Vascular brachytherapy has shown to be effective for in-stent restenosis, but efficacy in de novo lesions remains uncertain. We evaluated feasibility and outcome of intracoronary beta-radiation therapy in de novo coronary lesions using a (186)Re liquid-filled balloon system. Thirty-three patients received 20 Gy (186)Re beta-radiation immediately after balloon angioplasty. The 6-month restenosis rate was 41% (12/29) and restenosis was located within the target lesion in eight patients and at the edges of the injured and irradiated segment, outside the target lesion, in four patients. At 6 months, four patients (12%), all stented during the initial procedure, had experienced a late (> 30 days) total occlusion. Intracoronary beta-radiation therapy of de novo coronary lesions using (186)Re is technically feasible. No reduction in restenosis was observed. The high incidence of late total occlusions may have been prevented by avoiding new stent implantation and prolonging double antiplatelet therapy.

Aged↗
PubMed2001

Trajectory reconstruction from trace evidence on spent bullets. I. Deposits from intermediate targets.

Contact of a fired bullet with an intermediate target of sufficient resistance commonly causes the bullet to ricochet, fragment or perforate together with a deviation in trajectory. The transfer of intermediate target material to bullets and subsequent detection on the bullet surface after recovery from a bullet collector, were examined using a scanning electron microscope and an energy-dispersive X-ray spectrometer (SEM/EDS). A total of 76 gunshots (9 mm Luger FMJ RN bullets) were fired at various intermediate targets and at combinations of intermediate targets and tissue located in line. Elements already present on unfired bullets and elements from the bullet collector, the jacket, the charge and primer could be consistently detected as a "background". Abundant deposits of "fragile" (brittle) materials such as concrete, flat glass, asphalt and gypsum board could be visualised on every bullet by SEM. The transfer dynamics involved a direct imprint of target material on the bullet surface and thus preferential locations at the tip but also indirect deposition over the entire surface ("powder effect"). X-ray microanalysis demonstrated matching spectra of the elemental composition of these deposits and of the targets contacted. After perforation of "ductile" (flexible) materials such as wood and car body parts, the deposits on the bullets did not show characteristic spectra. If multi-layered car metal targets were hit, few and uncharacteristic fragments were scattered over the bullet surface and titanium indicative of paint-work could be determined on only a minority of bullets. The elemental composition of wood itself was heterogeneous but the fibrous morphology of the deposits was typical. The SEM/EDS findings in gunshots including subsequent perforation of tissue were similar. In particular, the trace evidence primarily transferred to the bullets was not eliminated by secondary contact and the determination of the fragile target materials was not affected. So when a person is killed or injured by a gunshot, the presence of a ricochet and the target material can be determined. This possibility needs to be considered before an evidential bullet is cleaned or contaminated.

DNA-Binding Proteins↗
PubMed2001

An ultrafiltration catheter for monitoring of venous lactate and glucose around myocardial ischemia.

Early detection of myocardial ischemia is of major importance in critical-care medicine. Changes of lactate or glucose levels in the cardial venous efflux may be useful parameters. We succeeded in integrating an ultrafiltration membrane in a cardiac catheter for continuous sampling. The ultrafiltrate was analyzed outside the body, resulting in a lag-time of about 24 min. Biosensors in a flow-injection analysis system were used for minute by minute sample analyses. The coronary sinus of pigs was catheterized to monitor the effects of 5, 15 or 45 min ischemia by coronary artery obstruction or myocardial stress by dobutamine infusion. A total of 27 h was monitored. The intravascular response time was 1.33+/-0.61 min (10-90%). Linear regression in vivo of blood and ultrafiltrate samples was 0.977 for lactate and 0.994 for glucose. Lactate levels rose 0.38+/-0.10 mM above baseline within 5 min after ischemia. Reperfusion was clearly marked by a promptly peaking lactate release (maximum 9.27 mM). Myocardial stress by dobutamine increased glucose but not lactate levels. Once, a wall effect was noted at the catheter tip. In vivo semi-continuous myocardial monitoring of absolute lactate and glucose concentrations was thus achieved by an ultrafiltration catheter. Ischemia and reperfusion can be detected very early by a lactate level rise. Further, development of the ultrafiltration catheter will be focused on the diagnostic potential of lactate monitoring for patients.

Animals↗
PubMed2001

Risk of infection by reprocessed and resterilized virus-contaminated catheters; an in-vitro study.

AIMS: In spite of increasing reuse of disposable catheters, there are few scientific data on potential viral transmission and infection after reuse. To determine the theoretical risk of virus transmission during reuse of catheters an in vitro study was performed using an RNA virus (echovirus-11) and a DNA virus (adenovirus-2). METHODS AND RESULTS: After deliberate contamination of the catheters, reprocessing and reuse of the cleaned and glutaraldehyde sterilized catheters was simulated. The presence of residual virus was determined by cell culture and by polymerase chain reaction (PCR). After the sterilization step, infectious enterovirus was detectable in one (10%) of the samples, whereas two (20%) contained detectable enterovirus RNA. After simulated reuse, enterovirus was cultured from one (10%) of the catheters, but no less than six (60%) of the samples were enterovirus PCR positive and one (10%) contained detectable adenovirus DNA. After sonification of the catheter tips no infectious virus could be detected, but enterovirus RNA was detected in two (20%) and adenovirus DNA in three (30%) of the samples. CONCLUSIONS: It has been clearly demonstrated in this in vitro study that, even after rigorous cleaning and sterilization, virus was still present in the catheter. Reuse of catheters, labelled for single-use only, is dangerous and should be prevented.

Catheterization↗
PubMed2000

Characterization of immortalized human umbilical and iliac vein endothelial cell lines after transfection with SV40 large T-antigen.

Most in vitro studies of human endothelial cells have relied on cells derived from human umbilical veins (HUVEC); however, heterogeneity of primary cultured endothelial cells can make critical interpretation of results difficult. Several endothelial cell lines have been produced to serve as a more constant source of endothelial cells. In this study, we characterized the endothelial cell lines EVLB3 and EVLC2 derived from HUVEC, and EVLK1 and EVLK2 derived from human iliac vein endothelial cells (HIVEC). These cell lines maintained the typical endothelial cell cobblestone morphology and appeared to be growth factor independent. They lost PECAM-1 and von Willebrand factor, GP96 was reduced to the level of vascular smooth muscle cells (SMC), but aSMC-actin was far less than in vascular SMC. Antigen levels of tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor (PAI-1) were comparable with young endothelial cells, and mRNA was present for tPA, PAI-1, tissue factor (TF), tissue factor pathway inhibitor and thrombomodulin. This study revealed that mRNA and protein expression of coagulation and fibrinolytic factors was influenced by the stage of cell confluence. No differences could be detected between the endothelial cell lines derived from HUVEC and HIVEC. These cell lines may be a useful tool for studies on cellular interactions of fibrinolytic components or exploring the regulation of TF expression.

Antigens, Polyomavirus Transforming↗
PubMed1999

The detection of small carcinoma with 18F-FDG using a dual head coincidence camera.

Tumour imaging with F18-fluorodeoxyglucose (18F-FDG) has yielded promising results for the detection of a variety of tumours. Owing to the high costs and limited availability of dedicated Positron emission tomography (PET) scanners, alternative methods of imaging the 511-KeV photons of positron emitters have been sought. With a dual head coincidence camera PET scanning of FDG is possible. The system parameters, such as sensitivity and spatial resolution, are already measured, but the clinical experience of this alternative imaging method is very limited. Two cases are described in which tumours with a diameter of 4 and 5 mm, respectively, were detected using a dual head coincidence camera. The presented cases support the use of this converted gamma camera in head and neck oncology.

Adult↗
PubMed1999

Community health centers: unrecognized partners in health professions education.

Increasing demand for health professionals with training in ambulatory and primary care practice is placing stress on existing training site capacity. Community health centers can serve as model training sites, offering comprehensive multidisciplinary health care services and teaching clinician role models. In this study, 32 Illinois community and migrant health centers and federally qualified health centers were surveyed to asses their involvement with training in the past three years. Thirty centers had offered training to students from many disciplines, with nursing (27 centers) and medicine (24) the most frequent. Most centers had established formal relationships with training institutions but generally had limited involvement with course planning. Continued participation will likely require adequate funding, with some centers also seeking stronger institutional relationships and better integration of community health issues. Educators and policy makers may need to take a more active role in supporting centers, acquiring funds, and other enabling factors.

Clinical Competence↗
PubMed1998

Percutaneous microcrystalline chitosan application for sealing arterial puncture sites.

Arterial catheterization is one of the most frequently performed inpatient diagnostic and therapeutic procedures in the development countries. Complications may occur after any catheterization from inadequate hemostasis, particularly in the setting of aggressive anticoagulation. This study suggests that microcrystalline chitosan (MCCh) sealant installation via an arterial sheath at the completion of catheterization may improve hemostasis. Results using MCCh in eight heparinized dogs documented significant reductions in manual compression time (P = 0.016) of the artery after withdrawal of both the sheath introducer and catheter. Comparative results were found in rats, wherein a created wound in the aorta could be sealed relatively quickly and easily. The biodegradability, optimalization, and a better pharmaceutical formulation of this potential hemostatic agent require further studies.

Animals↗
PubMed1998

Psychomotor development in children with triphalangeal thumbs. A preliminary study.

In order to explore the influence of an isolated congenital hand malformation on psychomotor development, we performed an exploratory, observational study on 18 children with triphalangeal thumbs. The investigative procedure consisted of a hand function examination, a semi-structured interview with the mother about the development of the child, the so-called "Hand test", and the "Child Behaviour Check List". Our observations suggest specific developmental difficulties in fine motor skills and language development, but the children showed no signs of behavioural psychopathology.

Adolescent↗
PubMed1998

Prediction of lesion size through monitoring the 0 degree C isothermic period following transcatheter cryoablation.

A prototype steerable 8.5 F bipolar catheter fitted with a feedback thermocouple was tested in 7 anaesthetized pigs (30 kg) guided by the electrocardiogram in order to modify the AV nodal and His-Purkinje system conductive properties. Thermal energy was delivered by a pressurized N2O tank (> 650 psi) via a cardiac cryo unit (Spembly, Hampshire, UK) into the catheter wherein gas expands resulting in a tip temperature as low as -70 +/- 2 degrees C within 10 seconds. Cryoablation under fluoroscopic and electrocardiographic guidance was applied at distinct sites in both ventricles for 60 or 120 seconds. After a follow-up period of 6 weeks, the ablation lesions found were well demarcated with small margins of hypertrophy of myocardial cells. With respect to lesion volume variability (8-207 mm3) and geometry, a relationship between the 0 degree C isothermic period and cryolesion volume was found. Results of an in vitro model corroborated this relationship. Therefore, an isothermic period probably can predict the lesion size and its geometry in terms of lesion depth. This potential therapeutic mode of transcatheter cryoablation deserves further investigation.

Animals↗
PubMed1998

Transvenous cold mapping and cryoablation of the AV node in dogs: observations of chronic lesions and comparison to those obtained using radiofrequency ablation.

INTRODUCTION: Radiofrequency (RF) is the most commonly used energy source for the treatment of cardiac arrhythmias. Surgical experience has shown that cryoablation also is effective for ablating arrhythmias. The aims of this study were to (1) investigate the feasibility of inducing permanent complete AV block (CAVB), (2) investigate the value of cold mapping to select the cryoablation site to produce permanent CAVB, (3) study the macro- and microscopic lesion characteristics 6 weeks later, and (4) compare them to those produced with RF energy. METHODS AND RESULTS: A new steerable 8.5-French bipolar electrode catheter having a thermocouple with a 3-mm tip using N2O as the refrigerant controlled by a cryoconsole was used. Six mongrel dogs were anesthetized, and the catheter was positioned via the femoral vein across the tricuspid valve to record a large low right atrial and a small His-bundle potential. After cold mapping (-15 degrees to -20 degrees C tip temperature) resulted in ECG modifications, cryothermia (-70 degrees C) was given twice, lasting 5 minutes each, to create permanent CAVB (Cryo group). Additionally, RF catheter ablation of the AV node was performed in two anesthetized mongrel dogs (RF group). In the Cryo group, a permanent proximal CAVB was created in four dogs (block occurred within 10 to 20 sec of cryothermia). Permanent right bundle branch block was obtained in one dog and transient CAVB in the remaining dog. In both dogs of the RF group, permanent CAVB was obtained. The cryolesions consisted of well-circumscribed, homogeneous areas of fibrotic tissue without viable cardiomyocytes. Lesions produced with RF were less circumscribed and inhomogeneous, with clear evidence of viable cardiomyocytes and cartilage formation (patchy lesions). CONCLUSIONS: (1) Permanent CAVB can be created by using a steerable cryoablation catheter. (2) Histologically, cryoablated sites were homogeneous and showed fibrotic tissue without signs of chronic inflammation and no evidence of viable myocytes. (3) Lesions created with RF were less homogenous and still contained viable myocytes within the lesion and cartilage formation. (4) The arrhythmogenic significance of these differences requires further study. (5) The technology of using reversible cold mapping has the potential to identify the successful ablation site and warrants further clinical study.

Animals↗
PubMed1996

Bone marrow absorbed dose of rhenium-186-HEDP and the relationship with decreased platelet counts.

UNLABELLED: Rhenium-186(Sn)-1,1-hydroxyethylidene diphosphonate (186Re-HEDP) has been used for palliation of metastatic bone pain. The purpose of this study was to find a relationship between the bone marrow absorbed dose and the toxicity, expressed as the percentage decrease in the peripheral blood platelet count. METHODS: The bone marrow absorbed dose was calculated according to the MIRD model using data obtained from ten treatments of patients suffering from metastatic prostate cancer; noninvasive and pharmacokinetic methods were used. The bone marrow doses were related to toxicity using the pharmacodynamic sigmoid Emax model. RESULTS: The mean bone marrow absorbed doses using the noninvasive and pharmacokinetic methods were in a close range to each other (1.07 mGy/MBq and 1.02 mGy/MBq, respectively). There was a good relationship between the toxicity and the bone marrow absorbed dose (r = 0.80). Furthermore, the EDrm50 (i.e., the bone marrow absorbed dose producing a 50% platelet decrease) to bone marrow for 186Re-HEDP was on the order of 2 Gy. CONCLUSION: Although the function of normal bone marrow is affected by metastases in patients with metastatic bone disease, the MIRD model can be used to relate toxicity to the bone marrow absorbed dose after a therapeutic dosage of 186Re-HEDP.

Aged↗
PubMed1995

Ex vivo design evaluation of an implantable blood port system.

A prototype of a totally implantable vascular catheter-port system was evaluated on its design using three animals of different species. The catheter was placed either intravenously or intra-arterially, and connected to the port which was retained outside the body. Parameters used for design evaluation or functionality testing were focused on the use and handling of the port-catheter system such as easiness of flushing, injection, blood sampling, septum stiffness to prevent blood reflux after pushing the septum, and possible diffusion of blood into the saline present in the port-catheter system. This pilot experiment showed that the septum of the prototype port system was too flexible, and that the distance between septum and base of the port was too short. These findings have led to a major improvement of the catheter-port system, currently successfully used in cancer chemotherapy.

Animals↗
PubMed1994

Artificial shunting of cerebrospinal fluid.

A compact three-stage shunt valve system (Orbis Sigma Valve) which operates as a flow regulator within certain differential pressure values has been clinically evaluated in the treatment of hydrocephalus. Clinical trials were performed in 134 cases, covering 128 patients aged from 1 day to 79 years with a mean age at implantation of 11.4 years. One-third of the implants was performed to replace failed DP shunts. Using actuarial statistics, 83.9% of the shunts continued to adequately manage hydrocephalus at three years. Overdrainage occurred in 2 cases (1.5%) and insufficient drainage occurred in four cases (3%). Compared with literature for conventional DP shunts, the incidence of these phenomena is extremely low. Based on the results summarized in this paper and those already reported in the literature, the OSV appears to address the overdrainage limitations of conventional shunts.

Adolescent↗