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Biomedical subjects

Alok Tiwari

Publications and source records attributed to Alok Tiwari.

At least 19 recordsLinked to original sources
PubMed2006

Recognition and management of abdominal compartment syndrome in the United Kingdom.

OBJECTIVE: Abdominal compartment syndrome(ACS) is a condition associated with high mortality if undiagnosed and untreated. ACS is seen in patients managed in intensive care units. Very little is known on the causes, diagnosis and treatment of this condition in the United Kingdom. DESIGN: Questionnaire study. SETTINGS: 222 intensive care units in the UK dealing with acute abdominal condition. RESULTS: 127 (57.2%) questionnaires were returned (32 from teaching hospitals and 95 from district general hospitals. Among these, 96.9% of teaching hospitals and 72.6% of district general hospitals had seen cases of ACS. The conditions most frequently associated with ACS were small and large bowel surgery (67%), vascular surgery (62%) and trauma (60%). ACS was suspected mainly when there was a distended abdomen (98.6%), oliguria (94.5%) and increased ventilatory support (72.2%). The diagnosis was confirmed either clinically (68.4%) or by measuring intra-abdominal pressure (83.7%). The commonest method for measuring intra-abdominal pressure was the intra-vesical route. The pressure threshold for diagnosing the condition was variable, with a range of 11-50 mmHg. There was a large variation in the number of patients who were decompressed. CONCLUSION: Fewer patients are diagnosed with ACS in district general hospitals compared with teaching hospitals. The threshold for the diagnosis of ACS is variable in the UK, as were the numbers of patients who were decompressed, suggesting that many doctors are still reluctant to accept this condition. This study would suggest that there is a need for standardisation of diagnostic threshold and protocols regarding decompression in ACS.

Compartment Syndromes↗
PubMed2003

Differential diagnosis, investigation, and current treatment of lower limb lymphedema.

HYPOTHESIS: The causes and management of lower limb lymphedema in the Western population are different from those in the developing world. OBJECTIVE: To look at the differential diagnosis, methods of investigation, and available treatments for lower limb lymphedema in the West. DATA SOURCE: A PubMed search was conducted for the years 1980-2002 with the keyword "lymphedema." English language and human subject abstracts only were analyzed, and only those articles dealing with lower limb lymphedema were further reviewed. Other articles were extracted from cross-referencing. RESULTS: Four hundred twenty-five review articles pertaining to lymphedema were initially examined. This review summarizes the findings of relevant articles along with our own practice regarding the management of lymphedema. CONCLUSIONS: The common differential diagnosis in Western patients with lower limb swelling is secondary lymphedema, venous disease, lipedema, and adverse reaction to ipsilateral limb surgery. Lymphedema can be confirmed by a lymphoscintigram, computed tomography, magnetic resonance imaging, or ultrasound. The lymphatic anatomy is demonstrated with lymphoscintigraphy, which is particularly indicated if surgical intervention is being considered. The treatment of choice for lymphedema is multidisciplinary. In the first instance, combined physical therapy should be commenced (complete decongestive therapy), with surgery reserved for a small number of cases.

Diagnosis, Differential↗
PubMed2003

In vivo biostability of a poly(carbonate-urea)urethane graft.

In peripheral and coronary bypass surgery, the patency of prosthetic grafts is inferior to autologous vein, mainly due to intimal hyperplasia caused in part by compliance mismatch between rigid graft and elastic host artery. We have developed a compliant poly(carbonate-urea)urethane vascular graft "MyoLink" which was biostable in vitro degradation studies. To further investigate the biostability of this material, we report a long-term in vivo study on 8 beagle dogs (15+/-3 kg) implanted with this graft (ID 5mm) in the aorta-iliac position; three grafts were harvested at 18 months to assess short-term biodegradation, with one animal having died from an unrelated infection. The 4 remaining grafts were harvested at 36 months for analysis by: (1) histology, (2) compliance measurements and (3) environmental scanning electron microscopy (ESEM); gel permeation chromatography (GPC); attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and radial tensile strength analysis. There was no infection or inflammation of the grafts or surrounding tissues. Histological analysis showed a well-developed neointima but only at the distal anastomosis. There were no significant differences in compliance pre- and post-implantation and no evidence of material curvature, radial expansion or chemical breakdown, ESEM and GPC showed no signs of degradation. Peak height analysis with ATR-FTIR of the 1740 cm(-1) (C=O of carbonate) and 1253 cm(-1) bands (C-O-C of CO-O-C) showed a loss of carbonate carbonyl but was not statistically significant. Radial tensile strength remained within batch release specifications.This polyurethane graft retains its compliance post-implantation, whilst exhibiting only a minor hydrolysis of the amorphous segment, confirming its biostability in vivo up to 3 years.

Anastomosis, Surgical↗
PubMed2003

The influence of peripheral vascular disease on the carotid and femoral wall mechanics in subjects with abdominal aortic aneurysm.

AIM: Aortic and carotid stiffness is elevated in patients with abdominal aortic aneurysm (AAA). Peripheral vascular disease (PVD) frequently coexists with AAA and may further impair the arterial wall mechanics and increase the cardiovascular load. We therefore studied the elastic carotid and muscular femoral biomechanical properties and intima-media thickness (IMT) in this group of patients. METHODS: The elastic indices and IMTs of the common carotid and common femoral arteries were determined in 30 patients with AAA (15 with PVD) with a duplex scanner coupled with a wall tracking system. Fasting plasma creatinine level, glucose and lipid concentrations, and their physiologic variables known to influence the arterial wall mechanics were also assessed. RESULTS: Patients with AAA and PVD have significantly stiffer carotid (Petersen's elastic modulus, 2207 +/- 905 mm Hg versus 1268 +/- 432 mm Hg; P =.001; stiffness index, 22.73 +/- 9.63 versus 12.60 +/- 4.24; P =.001] and femoral (Petersen's elastic modulus, 4906 +/- 4057 mm Hg versus 2599 +/- 1169 mm Hg; P =.043; stiffness index, 49.02 +/- 40.04 versus 26.07 +/- 13.22; P =.044) arteries than subjects with AAA alone. Although patients with PVD have thicker carotid and femoral IMTs, no statistical difference was seen between the two groups. The subjects were matched for age, body mass index, heart rate, systolic and diastolic blood pressures, total vascular risk score, plasma creatinine level, and fasting lipid and glucose concentrations. CONCLUSION: Subjects with PVD and AAA have significantly stiffer carotid and femoral arteries, which may indicate increased cardiovascular load and may account for the highest mortality rate seen in these patients in the UK Small Aneurysm Trial. Therefore, treatment of associated cardiovascular risk factors is important and may have to be tailored on an individual basis according to the findings of the arterial wall mechanics.

Aged↗
PubMed2002

Impaired carotid and femoral viscoelastic properties and elevated intima-media thickness in peripheral vascular disease.

BACKGROUND: We undertook a study to determine whether peripheral vascular disease of the lower extremity (PVD) per se affects the arterial viscoelastic properties and intima-media thickness (IMT) of the carotid and femoral arteries. METHODS: Thirty-five patients with PVD, 35 age- and gender-matched control subjects were examined with ultrasound scan wall tracking system, with the simultaneous measurement of blood pressure for carotid and femoral IMT and viscoelastic properties. RESULTS: Subjects with PVD have significantly impaired carotid elastic properties including compliance (mean (SD): 6.50 (2.39) vs 9.93 (4.07) %mmHg(-1)x10(-2), P<0.001), Petersen's elastic modulus (1.77 (0.69) vs 1.19 (0.63) mmHg x 10(3), P=0.001) and stiffness index (17.92 (7.21) vs 12.10 (6.17), P=0.001) when compared to non-PVD controls. They also have significantly altered femoral elastic properties including Petersen's elastic modulus (5.94 (4.98) vs 3.64 (3.27) mmHg x 10(3), P=0.025) and stiffness index (58.42 (47.76) vs 36.96 (33.43), P=0.033). The carotid (0.85 (0.35) vs 0.59 (0.23) mm, P<0.001) and femoral (1.05 (0.39) vs 0.69 (0.31) mm, P<0.001) IMTs are also significantly elevated in PVD patients. After adjustment for the presumed cardiovascular load assessed on the basis of a cumulative total vascular risk score, as well as age, systolic and diastolic pressure, the carotid viscoelastic indices and the carotid and femoral IMTs remained highly significant. However, the difference in femoral elastic variables was no longer evident. CONCLUSION: PVD per se affects the femoral and carotid wall mechanics and morphology similarly to other cardiovascular risk factors and events. These parameters may provide further information for cardiovascular risk assessment in addition to the classical risk factors and the Framingham equation. Indeed, some guidelines have suggested that additional factors such as the carotid scan may influence the clinician's decision to intervene with therapy.

Aged↗
PubMed2002

New prostheses for use in bypass grafts with special emphasis on polyurethanes.

Vascular bypass procedures using traditional prosthetic grafts such as polytetrafluoroethylen (PTFE) and polyethylene tetraphthlate (Dacron) are prone to failure when used in low flow states such as in below knee bypass and when the diameter of the graft is less than 6 mm. A major factor in this is compliance mismatch between the graft and the diseased vessel, which may cause intimal hyperplasia at the distal anastomosis. PTFE and Dacron are rigid grafts with poor compliance. By improving the compliance of the prosthetic graft it is hoped that patency will improve. Recent advances in polyurethane chemistry have developed materials that do not degrade and which allow compliance matching of the graft to the patient's vasculature. It is now possible to manufacture biologically and haemodynamically compatible grafts with small diameter from these polyurethane graft materials. This review will focus on the lack of compliance in current vascular bypass grafts and the promise of the new polyurethane polymers in a new generation of small-bore bypass grafts.

Biocompatible Materials↗