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M Mehta

Publications and source records attributed to M Mehta.

At least 19 recordsLinked to original sources
PubMed2006

A clinical and optical evaluation of a modified lens for irregular corneae.

BACKGROUND: Correction of high regular and irregular astigmatism with rigid gas-permeable contact lenses can result in discomfort, compromised corneal physiology and fluctuations in visual acuity due to excessive lens movement. Using a non-probability sample, this study explored the optical, clinical and subjective performance of a modified countersunk piggyback lens (MCL) for the management of high regular and irregular corneal astigmatic refractive conditions, as the first phase for a larger randomised control study of the efficacy of the custom piggyback MCL system. METHOD: The sample was a single group of 10 patients (n = 17 eyes) selected primarily on the basis of a history of failure with conventional management regimes. The objective clinical and optical performance of the MCL used in the management of high degrees of regular and irregular corneal astigmatic conditions was assessed, including measures of visual performance and ocular health. Subjective performance of the MCL was evaluated by patient feedback. RESULTS: Objective and subjective measures were analysed using appropriate statistical analyses. There was a significant improvement in the uncorrected vision and visual acuity (VA) with the MCL, as well as a significant improvement in refractive status. There was no statistically significant increase in adverse ocular responses with the MCL. Statistical analysis of the subjective responses indicated a strong acceptance of the MCL by all subjects, thus supporting the objective analysis indicating the superior performance of the MCL over prior conventional treatment regimens. DISCUSSION: The custom piggyback MCL performed successfully in the management of a range of high regular and irregular astigmatic conditions, which have been unsuccessfully managed with a range of conventional optical corrections. Despite the additional cost and handling implications of the two-lens system, the MCL was well accepted by all subjects due to its superior optical and clinical performance.

Astigmatism↗
PubMed2005

Secondary analysis of Radiation Therapy Oncology Group study (RTOG) 9310: an intergroup phase II combined modality treatment of primary central nervous system lymphoma.

PURPOSE: To determine whether a lower dose of hyperfractionated whole brain radiation reduces central nervous system morbidity without compromising survival for primary CNS lymphoma (PCNSL) patients receiving combined modality treatment. MATERIALS AND METHODS: One hundred and two patients received a course of pre-radiation chemotherapy, followed by whole brain radiation, followed by cytosine-arabinoside. Initial radiation dose was 45 Gy/25 fractions (RT) then the study was amended to reduce this dose for complete responders to induction chemotherapy to 36 Gy/30 fractions/3 weeks (HFX). Eighty-two patients received radiotherapy and were evaluable for toxicity analysis (66 RT patients and 16 HFX patients). MMSE scores and survival for the 40 patients who received radiotherapy after complete response to chemotherapy (27 RT and 13 HFX) were compared. There were no notable differences in pre-treatment patient characteristics between the RT and HFX groups. RESULTS: Neurotoxicity: By 4 years, there were 8/82 (10%) grade 5 neurotoxicities which included 2/16 (13%) grade 5 encephalopathies and 0/27 in the RT group of complete responders to chemotherapy. Survival: There was no statistically significant difference in overall or progression-free survival (PFS) between the chemotherapy-complete responders who received RT and HFX. Cognitive function testing: MMSE scores improved at 8 months across both treatment groups. Analysis of the area under the MMSE curve at 8 months showed no statistically significant difference between RT and HFX groups (P=0.81). Leukoencephalopathy occurred later in the HFX group than in the RT patients. CONCLUSION: Although the HFX schedule represented a 25% reduction in biologically effective tumor dose in comparison, PFS and overall survival were not significantly affected. The HFX regimen delayed but did not eliminate severe neurotoxicity from chemoradiation in PCNSL patients.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2004

Relationship of proximal fixation to renal dysfunction in patients undergoing endovascular aneurysm repair.

Technological advancements have lead to dramatic improvements in stentgraft device design resulting in more trackable delivery systems and transrenal uncovered stents and barbs for better fixation. Transrenal bare-stents may limit stentgraft migration, particularly in patients with short or flared proximal aortic necks. However, potential disadvantages might be in worsening renal function, particularly in patients with preexisting renal insufficiency. We retrospectively analyzed our recent 7 year experience of patients undergoing endovascular aneurysm repair (EVAR) using a variety of stentgrafts with and without transrenal bare-stent fixation. Patients were divided into 2 groups; infrarenal fixation (IRF) vs transrenal fixation (TRF), or patients with preoperative serum Cr values that were normal (= or <1.5 mg/dl) vs slightly elevated (1.6-2 mg/dl), vs markedly elevated (2.1- 3.5 mg/dl). The exclusion criteria included patients with chronic renal insufficiency (CRI) on hemodialysis, and preoperative high-grade renal artery stenoses requiring angioplasty and stenting. Of 705 patients that underwent EVAR, 496 (IRF: 385 [78%], and TRF: 111 [22%]) were available with routine evaluations of serum Cr and CT scans. Preexisting comorbidities, mean procedure contrast volume, and postprocedure follow-up were similar in both groups. In the immediate postoperative period, mean serum Cr did not change significantly in either the IRF group (1.3+/-0.7 mg/dl to 1.2+/-0.9 mg/dl) or the TRF group (1.3+/-0.5 mg/dl to 1.3+/-0.6 mg/dl). Mean serum Cr did, however, significantly increase over longer follow-up in both groups: 1.4+/-0.8 mg/dl for IRF (P<0.03), and 1.5 +/- 0.8 mg/dl for TRF (P<0.01). Cr clearance was similarly unchanged in the immediate postoperative period (58+/-23 to 61+/-25 ml/min/1.73 m2 for IRF group, 53+/-17 to 55+/-17 ml/min/1.73 m2 for TRF group), but was significantly decreased in longer follow-up (53+/-23 ml/min/1.73 m2 for IRF, p<0.02: and 48+/-16 ml/min/1.73 m2 for TRF, P<0.01). There were no significant differences in serum Cr increase (p=0.19) or Cr clearance decrease (p=0.68) between the IRF and TRF groups. Small renal infarcts were noted in 6 patients (1.6%) in the IRF group, and in 8 patients (7%) in the TRF group (p=0.37). Of patients with normal preoperative renal function, renal dysfunction developed in 7.7% of IRF group and 6.1% of TRF group (p=0.76). In patients with preexisting CRI, renal dysfunction developed in 18.2% of IRF group, and 17.1% of TRF group (p=0.95). Eight patients with postoperative renal dysfunction, 5 (1.3%) from IRF group and 3 (2.7%) from TRF group subsequently required hemodialysis, and this difference was not statistically significant (p=0.91). We also analyzed 200 consecutive patients undergoing EVAR with intra-arterial contrast agents with and without preexisting CRI not on dialysis. The groups were identified on the basis of preprocedure serum Cr: group 1 (n=108), Cr less than 1.5 mg/dL (normal range); group 2 (n=65), Cr 1.5 to 2.0 mg/dL; group 3 (n=27), Cr 2.1 to 3.5 mg/dL. Routine precautions in patients with CRI included preoperative intravenous hydration with 2 L of normal saline solution, discontinuation of all nephrotoxic drugs, intraoperative administration of mannitol (0.5 g/kg intravenously), and use of nonionic, low osmolar intra-arterial contrast agent (Omnipaque 350). One-hundred and eight patients had normal renal function (group 1), and 92 patients had preexisting CRI with baseline Cr 1.5 to 2.0 mg/dL (group 2, n=65) or 2.1 to 3.5 mg/dL (group 3, n=27). Comorbid conditions included coronary artery disease (group 1, 51%; group 2, 49%; group 3, 59%), hypertension (group 1, 39%; group 2, 46%; group 3, 52%), and diabetes mellitus (group 1, 25%; group 2, 35%; group 3, 48%). In groups 1, 2, and 3, the mean volume of low osmolar contrast agent used was 210 cc, 160 cc, 130 cc, respectively; hemodynamic instability developed in 3, 1, and 1 patient, respectively. The incidence of postoperative complications between the 3 study groups was not statistically different. In grications between the 3 study groups was not statistically different. In group 1 a transient increase in serum Cr (>30% over baseline and >1.4 mg/dL) was noted in 3 patients (2.7%), 2 of whom (1.9%) required temporary hemodialysis and 1 (0.9%) who died of renal failure. In group 2 a transient increase in serum Cr was noted in 2 patients (3.1%); both patients (3.1%) required temporary hemodialysis, and 1 patient (1.5%) died of renal failure. In group 3 a transient increase in serum Cr was noted in 2 patients (7.4%); 1 patient (3.7%) required temporary hemodialysis, and 1 patient (3.7%) died of renal failure. Perioperative hypotension significantly increased the risk for elevated serum Cr and death (p<0.05), and larger contrast volume was associated with an increase in serum Cr (p<0.05) during the postoperative period. Following EVAR renal function declines slightly with both IRF and TRF. Our data show no overall difference between patients with IRF and TRF with respect to infarcts, decline in renal function, or onset of dialysis. There were a slightly greater number of renal infarcts in the TRF group, but these infarcts were clinically inconsequential. In patients with CRI, EVAR with intra-arterial radiographic contrast agents is believed to impair renal function, and CRI is considered a relative contraindication to the procedure. Results of our investigation indicate that risk for worsening renal insufficiency, dialysis, and death is only slightly and not significantly greater in patients with CRI compared with patients with normal renal function. With appropriate precautions of avoiding perioperative hypotension and limiting the volume of nonionic contrast agents, CRI need not be a contraindication for EVAR with intra-arterial contrast agents.

Aged↗
PubMed2002

Semiclassical theory of spin-orbit interactions using spin coherent states.

We formulate a semiclassical theory for systems with spin-orbit interactions. Using spin coherent states, we start from the path integral in an extended phase space, formulate the classical dynamics of the coupled orbital and spin degrees of freedom, and calculate the ingredients of Gutzwiller's trace formula for the density of states. For a two-dimensional quantum dot with a spin-orbit interaction of Rashba type, we obtain satisfactory agreement with fully quantum-mechanical calculations. The mode-conversion problem, which arose in an earlier semiclassical approach, has hereby been overcome.

Journal Article↗
PubMed2002

Structural studies of biomaterials using double-quantum solid-state NMR spectroscopy.

Proteins directly control the nucleation and growth of biominerals, but the details of molecular recognition at the protein-biomineral interface remain poorly understood. The elucidation of recognition mechanisms at this interface may provide design principles for advanced materials development in medical and ceramic composites technologies. Here, we describe both the theory and practice of double-quantum solid-state NMR (ssNMR) structure-determination techniques, as they are used to determine the secondary structures of surface-adsorbed peptides and proteins. In particular, we have used ssNMR dipolar techniques to provide the first high-resolution structural and dynamic characterization of a hydrated biomineralization protein, salivary statherin, adsorbed to its biologically relevant hydroxyapatite (HAP) surface. Here, we also review NMR data on peptides designed to adsorb from aqueous solutions onto highly porous hydrophobic surfaces with specific helical secondary structures. The adsorption or covalent attachment of biological macromolecules onto polymer materials to improve their biocompatibility has been pursued using a variety of approaches, but key to understanding their efficacy is the verification of the structure and dynamics of the immobilized biomolecules using double-quantum ssNMR spectroscopy.

Amino Acid Sequence↗
PubMed2001

A Phase II study of paclitaxel in patients with recurrent malignant glioma using different doses depending upon the concomitant use of anticonvulsants: a North American Brain Tumor Consortium report.

BACKGROUND: The primary objective of the current study was to determine the response rate of paclitaxel in patients with recurrent malignant glioma by using different doses dependent on the concomitant use of anticonvulsants. Secondary objectives were to determine the time period to treatment failure, to evaluate toxicities, and to obtain pharmacokinetic data. METHODS: Adult patients who had recurrent malignant glioma were treated with paclitaxel. Patients were treated at different doses depending on the concomitant use of anticonvulsants known to induce the p450 hepatic enzyme system. Patients on such agents were treated at a dose of 330 mg/m2, whereas those not on these anticonvulsants were treated at a dose of 210 mg/m2. Tumor response was assessed at 6-week intervals. Treatment was continued until documented tumor progression or unacceptable toxicity occurred, or a total of 12 paclitaxel infusions was completed. RESULTS: From January 1997 to June 1997, 23 patients were treated with paclitaxel. Four patients were ineligible for the current study. Of the 19 eligible patients, there were no responses seen. Four (21%) had stabilization of disease. Median time to treatment failure was 1 month (95% confidence interval [CI], 1-2 mos) and median survival was 7 months (95% CI, 6-10 mos). Three patients were removed from the current study because they had toxicity. Pharmacokinetic studies demonstrated that drug levels and clearance values were consistent with previously reported findings. CONCLUSION: Even though higher doses were administered to patients who had recurrent malignant glioma and who were on concomitant anticonvulsants, there were no objective responses to paclitaxel. Time to tumor progression was 1 month. Further testing of paclitaxel at this dose schedule does not appear to be warranted in this patient population.

Adolescent↗
PubMed2001

A new approach to dose escalation in non-small-cell lung cancer.

PURPOSE: To describe the radiobiological rationale for dose-per-fraction escalation in non-small-cell lung cancer (NSCLC) and to devise a novel Phase I scheme to implement this strategy using advanced radiotherapy delivery technologies. METHODS AND MATERIALS: The data from previous dose escalation trials in NSCLC are reanalyzed to establish a dose-response relationship in this disease. We also use data relating prolongation in treatment time to survival to compute the potential doubling time for lung tumors. On the basis of these results, and using a Bayesian model to determine the probability of pneumonitis as a function of mean normalized lung dose, a dose-per-fraction escalation strategy is developed. RESULTS: Standard approaches to dose escalation using 2 Gy per fraction, five fractions per week, require doses in excess of 85 Gy to achieve 50% long-term control rate. This is partly because NSCLCs repopulate rapidly, with a 1.6% per day loss in survival from prolongation in overall treatment time beyond 6 weeks, and a cell doubling time of only 2.5 to 3.3 days. A dose-per-fraction escalation strategy, with a constant number of fractions, 25, and overall time, 5 weeks, is projected to produce tumor control rates predicted to be 10%-15% better than 2 Gy per fraction dose escalation, with equivalent late effects. This Phase I clinical study is divided into three parts. Step 1 examines the feasibility of the maximum breath-holding technique and junctioning of tomotherapy slices. Step 2 treats 10 patients with 30 fractions of 2 Gy over 6 weeks and then reduces duration to 5 weeks using fewer but larger fractions in 10 patients. Step 3 will consist of a dose-per-fraction escalation study on roughly 50 patients, maintaining 25 fractions in 5 weeks. Bayesian methodology (a modification of the Continual Reassessment Method) will be used in Step 3 to allow consistent and efficient escalation within five volume bins. CONCLUSION: A dose-per-fraction escalation approach in NSCLC should yield superior outcomes, compared to standard dose escalation approaches using a fixed dose per fraction, for a given level of pneumonitis and late toxicity. Highly conformal radiotherapy techniques, such as intensity modulated radiotherapy (IMRT) and helical tomotherapy with its adaptive capabilities, will be necessary to achieve significant dose-per-fraction escalation without unacceptable lung and esophageal morbidity.

Carcinoma, Non-Small-Cell Lung↗
PubMed2001

Optically guided intensity modulated radiotherapy.

BACKGROUND AND PURPOSE: Previously, we reported on development of an optically guided system for 3D conformal intracranial radiotherapy using multiple noncoplanar fixed fields. In this paper we report on the extension of our system for stereotactic fractionated radiotherapy to include intensity modulated static ports. METHODS AND MATERIALS: A 3D treatment plan with maximum beam separation is developed in the stereotactic space established by an optically guided system. Gantry angles are chosen such that each beam has a unique entrance and exit pathway, avoids the critical structures, and has a minimal beam's eye view projection. Once, a satisfactory treatment plan is found using this geometric approach an inverse treatment plan is developed using the beam portals established previously. The purpose of adding inverse planing is two fold, on the one hand it allows further reduction of margins around the PTV, while on the other hand it affords the possibility of conformal avoidance of critical structures that are close to or abut the PTV. RESULTS: The use of the optically guided system in conjunction with intensity modulated noncoplanar radiotherapy treatment planning using fixed fields allows the generation of highly conformal treatment plans that exhibit smaller 90, 70, and 50% of prescription dose isodose volumes, improved PITV ratios, comparable or improved EUD, smaller NTD(mean) for the critical structures, and an inhomogeneity index that is within generally accepted limits. CONCLUSION: Because optically guided technology improves the accuracy of patient localization relative to the linac isocenter and allows real-time monitoring of patient position, the planning target volume needs to be corrected only for the limitations of image resolution. Intensity modulated static beam radiotherapy planning then provides the user the ability to further reduce margins on the PTV and to conform very closely to this smaller target volume, and enhances the normal tissue sparing, and high degree of conformality possible with 3D conformal radiotherapy. In addition, since optically guided technology affords improved patient localization and online monitoring of patient position during treatment delivery it allows for safe and efficient delivery of intensity modulated radiotherapy.

Algorithms↗
PubMed2001

Adolescent girls' life aspirations and reproductive health in Nepal.

The study described in this paper takes a participatory and positive approach to improving adolescent reproductive health in a rural and urban community in Nepal. It shows that adolescent girls in these communities have dreams and aspirations for a better future and that adults acknowledge and support these ideals. However, social norms and institutions are restrictive, especially for girls, who are often unable to realise their hopes for continuing education, finding better-paid work or delaying marriage and childbearing, and this directly impacts reproductive outcomes. Insight into the broader context of adolescent girls' lives provides a valuable framework for designing positive programmatic actions which take as their entry point the disjuncture between girls' aspirations and realities. Interventions begun in these communities include youth clubs for safe social interaction and literacy classes; training of peer educators to teach life-skills, including for married adolescents; forums for parents, teachers and health service providers to discuss their own concerns and those of adolescents; and work with the community to design programmes that will contribute to greater financial independence and employment opportunities for adolescents.

Adolescent↗
PubMed2001

Bioavailability and bioequivalence: an FDA regulatory overview.

Bioavailability and/or bioequivalence studies play a key role in the drug development period for both new drug products and their generic equivalents. For both, these studies are also important in the postapproval period in the presence of certain manufacturing changes. Like many regulatory studies, the assessment of bioavailability and bioequivalence can generally be achieved by considering the following three questions. What is the primary question of the study? What are the tests that can be used to address the question? What degree of confidence is needed for the test outcome? This article reviews the regulatory science of bioavailability and bioequivalence and provides FDA's recommendations for drug sponsors who intend to establish bioavailability and/or demonstrate bioequivalence for their pharmaceutical products during the developmental process or after approval.

Biological Availability↗
PubMed2001

Micromanipulation of chloroplasts using optical tweezers.

This paper describes experiments using optical tweezers to probe chloroplast arrangement, shape and consistency in cells of living leaf tissue and in suspension. Dual optical tweezers provided two-point contact on a single chloroplast or two-point contact on two adhered chloroplasts for manipulation in suspension. Alternatively, a microstirrer consisting of a birefringent particle trapped in an elliptically polarized laser trap was used to induce motion and tumbling of a selected chloroplast suspended in a solution. We demonstrate that displacement of chloroplasts inside the cell is extremely difficult, presumably due to chloroplast adhesion to the cytoskeleton and connections between organelles. The study also confirms that the chloroplasts are very thin and extremely cup-shaped with a concave inner surface and a convex outer surface.

Chloroplasts↗
PubMed2001

All sealed endoleaks are not the same: a treatment strategy based on an ex-vivo analysis.

PURPOSE: factors contributing to pressure transmission through thrombosed or sealed endoleaks have not been elucidated. The purpose of this investigation was to create an ex-vivo model that mimics patent and sealed endoleaks and that can quantitatively analyse the effects of length, diameter and thrombus on pressure transmission to the interior of the aneurysm sac. METHODS: In the ex-vivo model, endoleak channels (ELCs) of various lengths (2 cm, 6 cm, 10 cm) and diameters (0.6 cm, 1.0 cm, 1.4 cm) were constructed using polytetrafluoroethylene (PTFE) grafts and attached to an artificial aneurysm sac. These ELCs were incorporated within a mock circulation made of rubber tubing connected to a pulsatile pump. Peak systolic pressure (PSP) was recorded in the aneurysm sac, distal to each ELC. Subsequently the ELCs were filled with human thrombus, and the pressure measurements repeated (n =5). Data was evaluated by regression analysis. RESULTS: Peak systolic pressure in the artificial circulation was maintained at 150 mmHg. In the absence of thrombus pressure did not change across the ELC, regardless of its length or diameter. In the presence of organised thrombus, the pressure curves distal to the ELC were dampened, and the pressure reduction was directly proportional to the length and inversely proportional to the diameter of the ELC. Regression analysis indicated statistical significance. CONCLUSION: In the absence of thrombosis, pressure transmitted via an ELC to the aneurysm sac is unchanged regardless of its length or diameter. All sealed endoleaks also transmit pressure. However, when an endoleak has thrombosed, pressure reduction is directly proportional to the length and inversely proportional to the diameter of its channel. This ex-vivo model suggests that Type 2 endoleaks with longer channels and smaller diameters would derive a greater benefit from adjunctive manoeuvres (coil embolisation) that hasten thrombosis. On the other hand, thrombosis of endoleaks with short and wide channels (e.g. Type 1) may not result in substantial pressure reduction within the aneurysm sac and a successful outcome.

Aortic Aneurysm↗
PubMed2001

Unilateral and bilateral hypogastric artery interruption during aortoiliac aneurysm repair in 154 patients: a relatively innocuous procedure.

OBJECTIVE: Hypogastric artery (HA) occlusion during aortic aneurysm repair has been associated with considerable morbidity. We analyzed the consequences of interrupting one or both HAs in the standard surgical or endovascular treatment of aortoiliac aneurysms (AIAs). METHODS: From 1992 to 2000, 154 patients with abdominal aortic aneurysms (n = 66), iliac aneurysms (n = 28), or AIAs (n = 60) required interruption of one (n = 134) or both (n = 20) HAs as part of their endovascular (n = 107) or open repair (n = 47). Endovascular treatment was performed with a variety of industry- or surgeon-made grafts in combination with coil embolization of the HAs. The standard surgical techniques included oversewing or excluding the origins of the HAs and extending the prosthetic graft to the external iliac or femoral artery. RESULTS: There were no cases of buttock necrosis, ischemic colitis requiring laparotomy, or death when one or both HAs were interrupted. Persistent buttock claudication occurred after 16 (12%) of the unilateral and 2 (11%) of the bilateral HA interruptions. Impotence occurred in 7 (9%) of the unilateral and 2 (13%) of the bilateral HA interruptions. Minor neurologic deficits of the lower extremity were observed in 2 (1.5%) of the patients with unilateral HA interruption. CONCLUSIONS: Although HA flow should be preserved if possible, selective interruption of one or both HAs can usually be accomplished safely during endovascular and open repair of anatomically challenging AIAs. We believe other comorbid factors such as shock, distal embolization, or the failure to preserve collateral branches from the external iliac and femoral arteries may have contributed to the morbidity in other reports of HA interruption.

Aged↗
PubMed2001

Efficacy of a proximal occlusion catheter with reversal of flow in the prevention of embolic events during carotid artery stenting: an experimental analysis.

OBJECTIVE: The role of percutaneous angioplasty and stenting of carotid bifurcation lesions has been limited by its potential for producing embolic debris. We evaluated the efficacy of a proximal occlusion catheter (POC) in the prevention of embolic events during carotid artery stenting. In addition, pressure measurements relevant to the clinical application of this device were obtained from 10 patients undergoing carotid endarterectomy. METHODS: The POC is a guiding catheter with an occlusion balloon attached on the outside of the catheter at its distal end. Occlusion of the common carotid artery (CCA) was achieved by inflating the balloon while access to carotid bifurcation lesions was obtained through the inner lumen. The POC was inserted in the CCA of 10 dogs via the femoral artery. The side port of the POC was connected to a sheath placed in the femoral vein, thereby creating an external arteriovenous shunt. Ten artificial radiopaque particles simulating embolic particles and contrast agent were introduced in the CCA and monitored fluoroscopically. As a control, the same procedure was performed with a standard guiding catheter without an occlusion balloon. In 10 patients undergoing carotid endarterectomy, the internal carotid artery (ICA) and external carotid artery stump pressures and the pressure in the internal jugular vein were measured. RESULTS: Without the external arteriovenous shunt, in all animals there was prograde flow in the distal CCA despite CCA occlusion. This flow was derived from the thyroid artery. However, once the arteriovenous shunt was activated, reversal of flow in the distal CCA was achieved in each animal, and all the artificial particles were recovered from the side port of the POC. In the control group, each particle embolized to the brain (100%, P <.01). In the patients, the mean stump pressures in the ICA and external carotid artery and the jugular vein pressure were 51.8 +/- 14.2, 62.2 +/- 15.1, and 6.5 +/- 3.5 mm Hg, respectively. In each case, the jugular vein pressure was the lowest among the three. CONCLUSIONS: Obtaining proximal CCA control by inflating the POC does not sufficiently prevent embolization. However, reversal of flow in the ICA can always be created with the external shunt, which effectively prevents embolization. Thus, POC may markedly lower procedural stroke rates during carotid artery stenting. The ability of POC to prevent embolization before crossing the lesion with a guidewire may be an important advantage over other distal protection devices.

Angioplasty, Balloon↗
PubMed2001

Eversion technique increases the risk for post-carotid endarterectomy hypertension.

OBJECTIVE: The incidence of postoperative hypertension (HTN) after eversion carotid endarterectomy (e-CEA) was compared with that after standard carotid endarterectomy (s-CEA). METHODS: In a retrospective analysis from January 1998 to January 2000, 217 patients underwent 219 CEAs for symptomatic (68) or asymptomatic (151) high-grade (>80%) carotid artery stenosis by either standard (137) or eversion (82) techniques. The eversion technique involves an oblique transection of the internal carotid artery at the carotid bulb and a subsequent endarterectomy by everting the internal carotid artery over the atheromatous plaque. All procedures were done under general anesthesia, and somatosensory-evoked potentials were used for cerebral monitoring. Patients with s-CEA were compared with those with e-CEA for postoperative hemodynamic instability, carotid sinus nerve block, requirement for intravenous vasodilators or vasopressors, stroke, and death. RESULTS: Patients who underwent e-CEA had a significantly (P <.005) increased postoperative blood pressure and required more frequent intravenous antihypertensive medication (24%), compared with patients having an s-CEA (6%). Furthermore, postoperative vasopressors were required after 10% of s-CEAs, but after none of the e-CEAs. No statistically significant difference was noted in the morbidity or mortality of patients after s-CEA and e-CEA. CONCLUSION: e-CEA is a substantial risk factor for HTN in the immediate postoperative period, when compared with the s-CEA. This difference would be even more remarkable in the absence of antihypertensive medications in the e-CEA group and vasopressors in the s-CEA group. Therefore, particular attention should be focused on diagnosing and controlling postoperative HTN in patients after e-CEA.

Aged↗
PubMed2001

Overt colon ischemia after endovascular aneurysm repair: the importance of microembolization as an etiology.

OBJECTIVE: The purpose of this study was to analyze the incidence, severity, and etiologic factors of the development of colon ischemia after endovascular aortoiliac aneurysm repair (EVAR). METHODS: During the last 9 years we performed 278 elective EVARs using a variety of grafts. To facilitate these repairs, one hypogastric artery (HA) was coil embolized in 109 patients and both HAs were coil embolized in 13 patients. The preprocedural status of the inferior mesenteric, hypogastric, and iliac arteries as well as anatomical characteristics of the abdominal aortic aneurysm were determined arteriographically and by computerized tomographic scans. Postoperative colon ischemia was documented by colonoscopy or operative findings. RESULTS: Colon ischemia occurred in eight patients (2.9%). Three patients with colon ischemia died and had evidence of widespread (cutaneous, renal, small bowel, and/or lower extremity) microembolization. One of these three had a colectomy and microscopic emboli were present. One other patient who required a colectomy also had pathologic evidence of colonic microembolization but survived. Four other patients with colon ischemia were treated conservatively and survived. In one patient, previous colectomy with interruption of mesenteric collaterals may have been a contributory cause of colon ischemia. Of the eight patients with colon ischemia, only one had unilateral HA occlusion, and none had bilateral HA occlusion. The other 121 patients with unilateral and bilateral HA occlusion had no evidence of colon ischemia. CONCLUSIONS: Colon ischemia occurs after EVAR with an incidence approximating that of open repair. Colon ischemia was unrelated to HA interruption. Embolization appears to be a major cause of colon ischemia, although inadequate mesenteric collateral circulation may also play an etiologic role. Mortality with colon ischemia accompanied by widespread embolization was high, whereas colon ischemia without it was often mild and amenable to nonoperative management.

Aged↗