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1.
Am J Obstet Gynecol MFM ; 6(1): 101229, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37984691

RESUMO

The incidence of placenta accreta spectrum, the deeply adherent placenta with associated increased risk of maternal morbidity and mortality, has seen a significant rise in recent years. Therefore, there has been a rise in clinical and research focus on this complex diagnosis. There is international consensus that a multidisciplinary coordinated approach optimizes outcomes. The composition of the team will vary from center to center; however, central themes of complex surgical experts, specialists in prenatal diagnosis, critical care specialists, neonatology specialists, obstetrics anesthesiology specialists, blood bank specialists, and dedicated mental health experts are universal throughout. Regionalization of care is a growing trend for complex medical needs, but the location of care alone is just a starting point. The goal of this article is to provide an evidence-based framework for the crucial infrastructure needed to address the unique antepartum, delivery, and postpartum needs of the patient with placenta accreta spectrum. Rather than a clinical checklist, we describe the personnel, clinical unit characteristics, and breadth of contributing clinical roles that make up a team. Screening protocols, diagnostic imaging, surgical and potential need for critical care, and trauma-informed interaction are the basis for comprehensive care. The vision from the author group is that this publication provides a semblance of infrastructure standardization as a means to ensure proper preparation and readiness.


Assuntos
Obstetrícia , Placenta Acreta , Hemorragia Pós-Parto , Gravidez , Feminino , Humanos , Placenta Acreta/diagnóstico , Placenta Acreta/epidemiologia , Placenta Acreta/terapia , Cesárea/métodos
2.
Am J Obstet Gynecol ; 2023 Nov 02.
Artigo em Inglês | MEDLINE | ID: mdl-37918506

RESUMO

OBJECTIVE: Cesarean hysterectomy is generally presumed to decrease maternal morbidity and mortality secondary to placenta accreta spectrum disorder. Recently, uterine-sparing techniques have been introduced in conservative management of placenta accreta spectrum disorder to preserve fertility and potentially reduce surgical complications. However, despite patients often expressing the intention for future conception, few data are available regarding the subsequent pregnancy outcomes after conservative management of placenta accreta spectrum disorder. Thus, we aimed to perform a systematic review and meta-analysis to assess these outcomes. DATA SOURCES: PubMed, Scopus, and Web of Science databases were searched from inception to September 2022. STUDY ELIGIBILITY CRITERIA: We included all studies, with the exception of case studies, that reported the first subsequent pregnancy outcomes in individuals with a history of placenta accreta spectrum disorder who underwent any type of conservative management. METHODS: The R programming language with the "meta" package was used. The random-effects model and inverse variance method were used to pool the proportion of pregnancy outcomes. RESULTS: We identified 5 studies involving 1458 participants that were eligible for quantitative synthesis. The type of conservative management included placenta left in situ (n=1) and resection surgery (n=1), and was not reported in 3 studies. The rate of placenta accreta spectrum disorder recurrence in the subsequent pregnancy was 11.8% (95% confidence interval, 1.1-60.3; I2=86.4%), and 1.9% (95% confidence interval, 0.0-34.1; I2=82.4%) of participants underwent cesarean hysterectomy. Postpartum hemorrhage occurred in 10.3% (95% confidence interval, 0.3-81.4; I2=96.7%). A composite adverse maternal outcome was reported in 22.7% of participants (95% confidence interval, 0.0-99.4; I2=56.3%). CONCLUSION: Favorable pregnancy outcome is possible following successful conservation of the uterus in a placenta accreta spectrum disorder pregnancy. Approximately 1 out of 4 subsequent pregnancies following conservative management of placenta accreta spectrum disorder had considerable adverse maternal outcomes. Given such high incidence of adverse outcomes and morbidity, patient and provider preparation is vital when managing this population.

3.
Am J Perinatol ; 40(9): 962-969, 2023 07.
Artigo em Inglês | MEDLINE | ID: mdl-37336213

RESUMO

Since its first description early in the 20th Century, placenta accreta and its variants have changed substantially in incidence, risk factor profile, clinical presentation, diagnosis and management. While systematic use of diagnostic tools and a multidisciplinary team care approach has begun to improve patient outcomes, the condition's pathophysiology, epidemiology, and best practices for diagnosis and management remain poorly understood. The use of large databases with broadly accepted terminology and diagnostic criteria should accelerate research in this area. Future work should focus on non-traditional phenotypes, such as those without placenta previa-preventive strategies, and long term medical and emotional support for patients facing this diagnosis. KEY POINTS: · Placenta accreta spectrum research may be improved with standardized terminology and use of large databases.. · Placenta accreta prediction should move beyond ultrasound with the addition of biomarkers, and needs to extend to those without traditional risk factors.. · Future research should identify practices that can prevent future accreta development..


Assuntos
Placenta Acreta , Placenta Prévia , Gravidez , Feminino , Humanos , Placenta Acreta/diagnóstico por imagem , Placenta Acreta/terapia , Cesárea , Ultrassonografia Pré-Natal , Placenta Prévia/diagnóstico por imagem , Placenta Prévia/terapia , Placenta , Estudos Retrospectivos
4.
Am J Perinatol ; 40(9): 970-979, 2023 07.
Artigo em Inglês | MEDLINE | ID: mdl-37336214

RESUMO

The surgical management of placenta accreta spectrum (PAS) is often challenging. There are a variety of techniques and management options described in the literature ranging from uterine sparing to cesarean hysterectomy. Following the inaugural meeting of the Pan-American Society for Placenta Accreta Spectrum a multidisciplinary group collaborated to describe collective recommendations for the surgical management of PAS. In this manuscript, we outline individual components of the procedure and provide suggested direction at key points of a cesarean hysterectomy in the setting of PAS. KEY POINTS: · The surgical management of PAS requires careful planning and expertise.. · Multidisciplinary team care for pregnancies complicated by PAS can decrease morbidity and mortality.. · Careful surgical techniques can minimize risk of significant hemorrhage by avoiding pitfalls..


Assuntos
Placenta Acreta , Gravidez , Feminino , Humanos , Placenta Acreta/cirurgia , Cesárea/métodos , Morbidade , Histerectomia , Estudos Retrospectivos , Placenta
5.
Am J Perinatol ; 40(9): 1026-1032, 2023 07.
Artigo em Inglês | MEDLINE | ID: mdl-37336221

RESUMO

The ideal management of a patient with placenta accreta spectrum (PAS) includes close antepartum management culminating in a planned and coordinated delivery by an experienced multidisciplinary PAS team. Coordinated team management has been shown to optimize outcomes for mother and infant. This section provides a consensus overview from the Pan-American Society for the Placenta Accreta Spectrum regarding general management of PAS.


Assuntos
Placenta Acreta , Placenta Prévia , Feminino , Humanos , Gravidez , Cesárea , Histerectomia , Mães , Placenta , Placenta Acreta/cirurgia , Estudos Retrospectivos , Fatores de Risco
6.
BMC Med ; 20(1): 333, 2022 09 28.
Artigo em Inglês | MEDLINE | ID: mdl-36167547

RESUMO

BACKGROUND: Identifying pregnancies at risk for preterm birth, one of the leading causes of worldwide infant mortality, has the potential to improve prenatal care. However, we lack broadly applicable methods to accurately predict preterm birth risk. The dense longitudinal information present in electronic health records (EHRs) is enabling scalable and cost-efficient risk modeling of many diseases, but EHR resources have been largely untapped in the study of pregnancy. METHODS: Here, we apply machine learning to diverse data from EHRs with 35,282 deliveries to predict singleton preterm birth. RESULTS: We find that machine learning models based on billing codes alone can predict preterm birth risk at various gestational ages (e.g., ROC-AUC = 0.75, PR-AUC = 0.40 at 28 weeks of gestation) and outperform comparable models trained using known risk factors (e.g., ROC-AUC = 0.65, PR-AUC = 0.25 at 28 weeks). Examining the patterns learned by the model reveals it stratifies deliveries into interpretable groups, including high-risk preterm birth subtypes enriched for distinct comorbidities. Our machine learning approach also predicts preterm birth subtypes (spontaneous vs. indicated), mode of delivery, and recurrent preterm birth. Finally, we demonstrate the portability of our approach by showing that the prediction models maintain their accuracy on a large, independent cohort (5978 deliveries) from a different healthcare system. CONCLUSIONS: By leveraging rich phenotypic and genetic features derived from EHRs, we suggest that machine learning algorithms have great potential to improve medical care during pregnancy. However, further work is needed before these models can be applied in clinical settings.


Assuntos
Nascimento Prematuro , Algoritmos , Registros Eletrônicos de Saúde , Feminino , Idade Gestacional , Humanos , Recém-Nascido , Aprendizado de Máquina , Gravidez , Nascimento Prematuro/diagnóstico , Nascimento Prematuro/epidemiologia
7.
IBRO Neurosci Rep ; 13: 127-135, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-35989697

RESUMO

Stroke is a leading cause of death and disability around the world. To date, the majority of pre-clinical research has been performed using male lab animals and results are commonly generalized to both sexes. In clinical stoke cases females have a higher incidence of ischemic stroke and poorer outcomes, compared to males. Best practices for improving translatability of findings for stroke, encourage the use of both sexes in studies. Since estrogen and progesterone have recognized neuroprotective effects, it is important to compare the size, severity and biochemical composition of the brain tissue following stroke in female and male animal models. In this study a photothrombotic focal stroke was induced in male and female mice. Vaginal secretions were collected twice daily to track the stage of estrous. Mice were euthanized at 24 h post-stroke. Histological staining, Fourier transform infrared imaging and X-ray fluorescence imaging were performed to better define the size and metabolic markers in the infarct core and surrounding penumbra. Our results show while the female mice had a significantly lower body mass than males, the cross-sectional area of the brain and the size of infarct and penumbra were not significantly different between the groups. In addition to the general expected sex-linked differences of altered NADH levels between males and females, estrus females had significantly elevated glycogen in the penumbra compared with males and total phosphorus levels were noted to be higher in the penumbra of estrus females. Elevated glycogen reserves in the tissue bordering the infarct core in females may present alternatives for improved functional recovery in females in the early post-stroke phase.

8.
Metallomics ; 14(4)2022 04 30.
Artigo em Inglês | MEDLINE | ID: mdl-35254441

RESUMO

Hemorrhagic transformation of ischemic stroke has devastating consequences, with high mortality and poor functional outcomes. Animal models of ischemic stroke also demonstrate the potential for hemorrhagic transformation, which complicates biochemical characterization, treatment studies, and hinders poststroke functional outcomes in affected subjects. The incidence of hemorrhagic transformation of ischemic stroke in animal model research is not commonly reported. The postmortem brain of such cases presents a complex milieu of biomarkers due to the presence of healthy cells, regions of varying degrees of ischemia, dead and dying cells, dysregulated metabolites, and blood components (especially reactive Fe species released from lysed erythrocytes). To improve the characterization of hemorrhage biomarkers on an ischemic stroke background, we have employed a combination of histology, X-ray fluorescence imaging (XFI), and Fourier transform infrared (FTIR) spectroscopic imaging to assess 122 photothrombotic (ischemic) stroke brains. Rapid freezing preserves brain biomarkers in situ and minimizes metabolic artifacts due to postmortem ischemia. Analysis revealed that 25% of the photothrombotic models had clear signs of hemorrhagic transformation. The XFI and FTIR metabolites provided a quantitative method to differentiate key metabolic regions in these models. Across all hemorrhage cases, it was possible to consistently differentiate otherwise healthy tissue from other metabolically distinct regions, including the ischemic infarct, the ischemic penumbra, blood vessels, sites of hemorrhage, and a region surrounding the hemorrhage core that contained elevated lipid oxidation. Chemical speciation of deposited Fe demonstrates the presence of heme-Fe and accumulation of ferritin.


Assuntos
Isquemia Encefálica , AVC Isquêmico , Acidente Vascular Cerebral , Animais , Biomarcadores , Isquemia Encefálica/complicações , Isquemia Encefálica/diagnóstico por imagem , Hemorragia/complicações , Humanos , AVC Isquêmico/diagnóstico por imagem , Imagem Multimodal , Acidente Vascular Cerebral/complicações , Acidente Vascular Cerebral/diagnóstico por imagem , Acidente Vascular Cerebral/epidemiologia
9.
Am J Obstet Gynecol ; 223(2): 305, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32247841
10.
Am J Obstet Gynecol ; 222(2): 179.e1-179.e9, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31469990

RESUMO

BACKGROUND: The incidence of placenta accreta spectrum is rising. Management is most commonly with cesarean hysterectomy. These deliveries often are complicated by massive hemorrhage, urinary tract injury, and admission to the intensive care unit. Up to 60% of patients require transfusion of ≥4 units of packed red blood cells. There is also a significant risk of death of up to 7%. OBJECTIVE: The purpose of this study was to assess the outcomes of patients with antenatal diagnosis of placenta percreta that was managed with delayed hysterectomy as compared with those patients who underwent immediate cesarean hysterectomy. STUDY DESIGN: We performed a retrospective study of all patients with an antepartum diagnosis of placenta percreta at our large academic institution from January 1, 2012, to May 30, 2018. Patients were treated according to standard clinical practice that included scheduled cesarean delivery at 34-35 weeks gestation and intraoperative multidisciplinary decision-making regarding immediate vs delayed hysterectomy. In cases of delayed hysterectomy, the hysterotomy for cesarean birth used a fetal surgery technique to minimize blood loss, with a plan for hysterectomy 4-6 weeks after delivery. We collected data regarding demographics, maternal comorbidities, time to interval hysterectomy, blood loss, need for transfusion, occurrence of urinary tract injury and other maternal complications, and maternal and fetal mortality rates. Descriptive statistics were performed, and Wilcoxon rank-sum and chi-square tests were used as appropriate. RESULTS: We identified 49 patients with an antepartum diagnosis of placenta percreta who were treated at Vanderbilt University Medical Center during the specified period. Of these patients, 34 were confirmed to have severe placenta accreta spectrum, defined as increta or percreta at the time of delivery. Delayed hysterectomy was performed in 14 patients: 9 as scheduled and 5 before the scheduled date. Immediate cesarean hysterectomy was completed in 20 patients: 16 because of intraoperative assessment of resectability and 4 because of preoperative or intraoperative bleeding. The median (interquartile range) estimated blood loss at delayed hysterectomy of 750 mL (650-1450 mL) and the sum total for delivery and delayed hysterectomy of 1300 mL (70 -2150 mL) were significantly lower than the estimated blood loss at immediate hysterectomy of 3000 mL (2375-4250 mL; P<.01 and P=.037, respectively). The median (interquartile range) units of packed red blood cells that were transfused at delayed hysterectomy was 0 (0-2 units), which was significantly lower than units transfused at immediate cesarean hysterectomy (4 units [2-8.25 units]; P<.01). Nine of 20 patients (45%) required transfusion of ≥4 units of red blood cells at immediate cesarean hysterectomy, whereas only 2 of 14 patients (14.2%) required transfusion of ≥4 units of red blood cells at the time of delayed hysterectomy (P=.016). There was 1 maternal death in each group, which were incidences of 7% and 5% in the delayed and immediate hysterectomy patients, respectively. CONCLUSION: Delayed hysterectomy may represent a strategy for minimizing the degree of hemorrhage and need for massive blood transfusion in patients with an antenatal diagnosis of placenta percreta by allowing time for uterine blood flow to decrease and for the placenta to regress from surrounding structures.


Assuntos
Cesárea/métodos , Histerectomia/métodos , Histerotomia/métodos , Placenta Acreta/cirurgia , Adulto , Algoritmos , Transfusão de Sangue , Tomada de Decisão Clínica , Gerenciamento Clínico , Feminino , Humanos , Unidades de Terapia Intensiva , Mortalidade Materna , Mortalidade Perinatal , Hemorragia Pós-Parto/prevenção & controle , Hemorragia Pós-Parto/terapia , Gravidez , Índice de Gravidade de Doença , Fatores de Tempo , Sistema Urinário/lesões
11.
J Biophotonics ; 12(2): e201800138, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30259692

RESUMO

Preterm birth (PTB) is the leading cause of neonatal death, however, accurate prediction methods do not exist. Detection of early changes in the cervix, an organ that biochemically remodels to deliver the fetus, has potential to predict PTB risk. Researchers have employed light-based methods to monitor biochemical changes in the cervix during pregnancy, however, these approaches required patients to undergo a speculum examination which many patients find uncomfortable and is not standard practice during prenatal care. Herein, a visually guided optical probe is presented that measures the cervix via introduction by bimanual examination, a procedure that is commonly performed during prenatal visits and labor for tactile monitoring of the cervix. The device incorporates a Raman spectroscopy probe for biochemical monitoring and a camera for visualizing measurement location to ensure it is void of cervical mucus and blood. This probe was tested in 15 patients receiving obstetric and gynecological care, and results acquired with and without a speculum revealed similar spectra, demonstrating that the visually guided probe conserved data quality. Additionally, the majority of patients reported reduced discomfort from the device. In summary, the visual guidance probe successfully measured the cervix while integrating with standard prenatal care, reducing a barrier in clinical translation.


Assuntos
Colo do Útero/citologia , Análise Espectral Raman/instrumentação , Desenho de Equipamento , Feminino , Humanos , Gravidez
12.
Reproduction ; 155(5): 447-456, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29500186

RESUMO

In mouse models used to study parturition or pre-clinical therapeutic testing, measurement of uterine contractions is limited to either ex vivo isometric tension or operative intrauterine pressure (IUP). The goal of this study was to: (1) develop a method for transcervical insertion of a pressure catheter to measure in vivo intrauterine contractile pressure during mouse pregnancy, (2) determine whether this method can be utilized numerous times in a single mouse pregnancy without affecting the timing of delivery or fetal outcome and (3) compare the in vivo contractile activity between mouse models of term and preterm labor (PTL). Visualization of the cervix allowed intrauterine pressure catheter (IUPC) placement into anesthetized pregnant mice (plug = day 1, delivery = day 19.5). The amplitude, frequency, duration and area under the curve (AUC) of IUP was lowest on days 16-18, increased significantly (P < 0.05) on the morning of day 19 and reached maximal levels during by the afternoon of day 19 and into the intrapartum period. An AUC threshold of 2.77 mmHg discriminated between inactive labor (day 19 am) and active labor (day 19 pm and intrapartum period). Mice examined on a single vs every experimental timepoint did not have significantly different IUP, timing of delivery, offspring number or fetal/neonatal weight. The IUP was significantly greater in LPS-treated and RU486-treated mouse models of PTL compared to time-matched vehicle control mice. Intrapartum IUP was not significantly different between term and preterm mice. We conclude that utilization of a transcervical IUPC allows sensitive assessment of in vivo uterine contractile activity and labor progression in mouse models without the need for operative approaches.


Assuntos
Catéteres , Parto/fisiologia , Nascimento Prematuro/fisiopatologia , Contração Uterina/fisiologia , Animais , Modelos Animais de Doenças , Feminino , Lipopolissacarídeos/farmacologia , Camundongos , Mifepristona/farmacologia , Parto/efeitos dos fármacos , Gravidez , Pressão , Contração Uterina/efeitos dos fármacos
13.
Int Nurs Rev ; 61(1): 124-30, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24512262

RESUMO

BACKGROUND: The need to belong has been proposed as the most basic need for human psychological well-being. Lack of belongingness has been associated with stress, anxiety and lack of esteem. Social and psychological functioning in the workplace has been linked to nurses' interconnection with others and their perceptions of belongingness. AIM: To explore factors contributing to Malaysian nurses' sense of belonging in the workplace. METHODS: A descriptive questionnaire survey of registered nurses (n = 437) working in two Malaysian hospitals was conducted in 2011. Previously validated questionnaires translated into the Malay language were used. Data were analysed using SPSS 19.0. RESULTS: Nurses enhanced their sense of belonging through acceptance, 'fitting in', respect and group harmony. There were no specific demographic factors contributing to the nurses' perceptions. The findings suggest that these priorities for belongingness were contextually influenced by factors such as elements of Malaysian culture, the nature of nurses' teamwork and stereotypical values on the nursing profession. LIMITATIONS: Data were collected in only two hospitals. Experiences of nurses in other hospitals and areas of Malaysia may not be similar. The influence of Malaysian culture in this study raises issues about utilization of a measurement scale developed in Western cultures, which may not directly accord with cultural values of an Eastern ethnicity. CONCLUSIONS: Aspects of belongingness in Malaysian nurses reflect those of nurses elsewhere. However, there are specific cultural influences at play. Therefore, development of a measurement scale based on Eastern culture would help in increasing understanding of workplace practices among these groups. IMPLICATIONS FOR NURSING AND HEALTH POLICY: Workplaces that perpetuate an environment that is not conducive to generating a sense of belonging may have an untoward impact on care delivery. Healthcare policies need to ensure patient care has a focus on engaging practitioners within multidisciplinary teams.


Assuntos
Recursos Humanos de Enfermagem Hospitalar/psicologia , Distância Psicológica , Percepção Social , Local de Trabalho , Adulto , Feminino , Humanos , Satisfação no Emprego , Malásia , Masculino , Inquéritos e Questionários
14.
RSC Adv ; 4(53): 28036-28040, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-26052433

RESUMO

We demonstrate an enzyme stabilization approach whereby a model enzyme is PEGylated, followed by controlled chemical modification with glutaraldehyde. Using this stabilization strategy, size increases and aggregation due to intermolecular crosslinking are avoided. Immediately following synthesis, the PEGylated enzyme with and without glutaraldehyde modification possessed specific activities of 372.9 ± 20.68 U/mg and 373.9 ± 15.14 U/mg, respectively (vs. 317.7 ± 19.31 U/mg for the native enzyme). The glutaraldehyde-modified PEGylated enzyme retains 73% original activity after 4 weeks at 37 °C (vs. 2% retention for control).

16.
Int J Pharm ; 361(1-2): 33-40, 2008 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-18571347

RESUMO

The aim of the study was to investigate the possibility of incorporating non-ionic surfactants into pellets produced from microcrystalline cellulose by the process of extrusion/spheronization and the properties of the pellets. A hydrophilic surfactant, polysorbate 60 (PS 60), and two hydrophobic surfactants, sorbitan monostearate (S 60) and sorbitan monooleate (S 80), were included in the water used to form the pellets in concentrations ranging from 5 to 95%. The presence of the surfactants influenced the type of the extrusion profile and improved the ability to provide round pellets, and the addition of the surfactants changed the range of liquid levels required to prepare the pellets. At a low level, i.e., 5%, all the surfactants increased the range of water contents possible, compared to the use of water alone. At high surfactant levels, the level of liquid, which could be used, became restricted. The median size of the pellets was dependent on the type of surfactant and the concentration included in the formulation. The range of sizes produced was generally quite narrow and there were many systems with more than 90% of the pellets in the modal fraction. The highest concentration of the surfactant in water that can be used to form pellets ranged from 50% for S 60, to 80% for S 80 and 95% for PS 60. The maximum amount of the surfactant, which could be incorporated into the final pellet, however, was found to be approximately 22.5% for both the hydrophobic surfactants and 32.5% for the hydrophilic surfactant.


Assuntos
Celulose/química , Excipientes/química , Tensoativos/química , Química Farmacêutica/métodos , Formas de Dosagem , Hexoses/química , Interações Hidrofóbicas e Hidrofílicas , Tamanho da Partícula , Polissorbatos/química , Água/química
17.
Int J Pharm ; 350(1-2): 145-54, 2008 Feb 28.
Artigo em Inglês | MEDLINE | ID: mdl-17905548

RESUMO

The performance of microcrystalline cellulose (MCC) which had been modified by the inclusion of various levels of sodium carboxymethylcellulose (SCMC) in the wet cake prior to drying, in terms of their ability to form pellets by a standardised extrusion/spheronization process has been assessed. Initial screening of the ability of the modified MCCs to form pellets with an 80% level of lactose as a model drug identified two potential products containing 6 or 8% of SCMC (B 6 and B 8). These two products were compared with a standard grade of MCC (Avicel PH101) in terms of their ability to produce pellets with 80% of model drugs of low (ibuprofen), intermediate (lactose) and high (ascorbic acid) water solubility when subjected to a standardised extrusion/spheronization process. Also assessed was their ability to retain water with applied pressure using a pressure membrane technique and their ability to restrict water migration during extrusion with a ram extruder. The two new types of MCC (B 6 and B 8) were able to form good quality pellets with all three model drugs, whereas Avicel PH101 could not form pellets with this high level of ibuprofen. This improved performance was related to the ability of the new types of MCC to hold higher levels of water within their structure and restrict the migration of water in the wet mass when subjected to pressure applied during the process of preparing the pellets. There is evidence to show that the two new types of MCC can function over a wider range of water contents than Avicel PH101 and that they have an improved performance if the extrusion process is rapid and if, after incorporation of the water into the powder, the sample is stored for some time before extrusion.


Assuntos
Celulose/química , Química Farmacêutica/métodos , Tecnologia Farmacêutica/métodos
18.
J Pharm Pharmacol ; 59(7): 941-5, 2007 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-17637188

RESUMO

The aim of this study was to compare the gastrointestinal transit of multiple unit, small diameter (3.2 mm), non-disintegrating tablets of differing densities with results previously reported in the same volunteers in the fasted state for larger diameter (6.6 and 12.2 mm) tablets. The gastrointestinal transit was observed with gamma-scintigraphy at various intervals over a 9-h period to give an accurate assessment of the transit characteristics. The value for the median emptying time of the first light tablet was significantly shorter than that for the dense tablet, but the total emptying time and the time for the last tablet to empty for both sets of tablets were not statistically different. The value of the median time for initial and final emptying of the small tablets from the stomach was significantly longer than that for the larger diameter tablets. The 9-h time limit of the observations limited the estimation of the time taken to enter the caecum and consequently the small intestine transit times. There was clear evidence that for the dense tablets of all sizes, the value for the small intestine transit time was longer than the 3-4 h reported in the literature. The only tablet system to enter the caecum within the time limit of the study was the normal density 12.2-mm tablets.


Assuntos
Preparações de Ação Retardada , Jejum , Trânsito Gastrointestinal , Comprimidos , Adulto , Química Farmacêutica , Esvaziamento Gástrico , Mucosa Gástrica/metabolismo , Humanos , Radioisótopos de Índio , Masculino , Pessoa de Meia-Idade , Cintilografia , Gravidade Específica , Estômago/diagnóstico por imagem , Tecnécio
19.
Neuroimage ; 36(4): 1159-70, 2007 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-17524673

RESUMO

We evaluate and discuss the relevance of fiber anisotropy in estimating the effect of transcranial magnetic stimulation (TMS) on the human brain. Finite element simulations were carried out on a three-dimensional model of the head that included anisotropic conductivity information derived from diffusion tensor imaging (DTI). The results show that anisotropy has minor effects both on the position of the main locus of activation and on its intensity. It has considerably more effect on the spatial distribution of the induced electric field, yielding differences of the order of 10% of the maximum induced field. Moreover the area affected by magnetic stimulation is slightly larger when we include fiber anisotropy in the calculations than in an isotropic model. We also show that the induced field observed in the anisotropic model does not always align with the local fiber orientation but rather follows specific patterns of parallelity. These findings will help to improve the estimation of the areas involved in magnetic stimulation.


Assuntos
Córtex Cerebral/fisiologia , Imagem de Difusão por Ressonância Magnética , Processamento de Imagem Assistida por Computador , Fibras Nervosas/fisiologia , Estimulação Magnética Transcraniana , Anisotropia , Simulação por Computador , Análise de Elementos Finitos , Humanos , Software
20.
J Pharm Pharmacol ; 59(1): 23-7, 2007 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17227617

RESUMO

The aim of this work was to identify the influence of tablet density on their gastric emptying in fasted subjects and to compare the findings with those of a previous study using the same subjects with tablets of a larger diameter. Tablets of 6.6 mm diameter and densities of 1.41 and 2.85 g cm-3 were labelled with 99mTc and 111In. They were coated with ethyl cellulose to ensure that they remained intact within the gastrointestinal tract. Their position within the gastrointestinal tract of fasted healthy subjects was monitored with a double-headed gamma camera at 1-min time intervals. The median gastric emptying time and the interquartile range were derived from the Bernoulli random event distribution. It was found that the dense tablets had a significantly longer gastric emptying time than the light tablets. Comparison with the results from the previous study gave a clear indication that irrespective of tablet density, the 6.6-mm tablets had longer gastric emptying times than the 12.0-mm tablets.


Assuntos
Esvaziamento Gástrico/fisiologia , Comprimidos com Revestimento Entérico/química , Adulto , Química Farmacêutica , Jejum/fisiologia , Mucosa Gástrica/metabolismo , Humanos , Índio , Masculino , Pessoa de Meia-Idade , Cintilografia , Estômago/diagnóstico por imagem , Tecnécio
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