Composite Sulfonated Polyether-Ether Ketone Membranes with SBA-15 for Electrochemical Energy Systems

The aim of this work is the evaluation of a Sulfonated Poly Ether-Ether Ketone (S-PEEK) polymer modified by the addition of pure Santa Barbara Amorphous-15 (SBA-15, mesoporous silica) and SBA-15 previously impregnated with phosphotungstic acid (PWA) fillers (PWA/SBA-15) in order to prepare composite membranes as an alternative to conventional Nafion^® membranes. This component is intended to be used as an electrolyte in electrochemical energy systems such as hydrogen and methanol Proton Exchange Membrane Fuel Cell (PEMFC) and Electrochemical Hydrogen Pumping (EHP). The common requirements for all the applications are high proton conductivity, thermomechanical stability, and fuel and oxidant impermeability. The morphology of the composite membranes was investigated by Scanning Electron Microscopy- Energy Dispersive X-ray Spectroscopy (SEM-EDS) analysis. Water Uptake (Wup), Ion Exchange Capacity (IEC), proton conductivity, methanol permeability and other physicochemical properties were evaluated. In PEMFC tests, the S-PEEK membrane with a 10 wt.% SBA-15 loading showed the highest performance. For EHP, the inclusion of inorganic materials led to a back-diffusion, limiting the compression capacity. Concerning methanol permeability, the lowest methanol crossover corresponded to the composites containing 5 wt.% and 10 wt.% SBA-15.

Endovascular Repair as First-Choice Treatment for Anastomotic and True Iliac Aneurysms

Purpose:

To report our experience with the endovascular repair of iliac aneurysms secondary to aortoiliac bypass grafting.

Methods:

Thirteen patients (12 men; age range 62–86 years) with histories of aortoiliac reconstructions were treated with endovascular stent-grafts for 11 false and 2 true iliac aneurysms that averaged 5.2 cm in diameter (range 3.0–7.0). Via a percutaneous access and 9-F or 12-F sheaths, Passager or Wallgraft stent-grafts were delivered to exclude the aneurysms.

Results:

Twelve (92%) of 13 interventions were completed satisfactorily; 1 procedure for a true iliac aneurysm was converted to traditional bypass grafting. Two patients underwent additional surgical procedures. The average hospital stay for the patients with endovascular repairs only was 3 days (range 2–5). After a mean follow-up of 28 months (range 17–40), no complication or endoleak has been detected in any patient, and all endografts are patent.

Conclusions:

Endovascular repair is an effective treatment for secondary aneurysms arising after aortoiliac surgery. It is less invasive and involves a shorter hospital stay. Endovascular repair should be the first choice treatment for iliac aneurysms.

Straightforward relative quantitation and age-related human standards of N-acetylaspartate at the centrum semiovale level by CSI (1)H-MRS

1H-MRS was aimed to monitor metabolite concentrations in homogeneous interaxial slices of cerebral matter at the centrum semiovale level in healthy volunteers. NAA (N-acetylaspartate + N-acetylglutamate), Cr (creatine + phosphocreatine), and Cho (choline + acetylcholine) were evaluated by resonance integrations. Using Cr as an internal standard, NAA/Cr ratio was considered as a relative measure of concentration. CSI sequence explored volunteer's interaxial slices of white and gray matter by means of 8 x 8 matrices of (1)H-NMR spectra. NAA/Cr integral ratios were averaged over the whole spectral matrix to obtain the Index of NAA at Centrum Semiovale (INACS) of each individual. Indexes of the sixty-eight healthy volunteers, divided into three groups by age, showed good intraindividual reproducibility, and were virtually unaffected by small shifts or bendings of the interaxial slice analyzed. The INACSs were used to estimate Age-Sectorial INACS Ranges (ASIR), the intervals that, on the basis of a normal statistical distribution, should comprise 95% of the age-matched healthy population. Individual INACSs, compared to accurately defined ASIRs taken as standards, could early detect subtle, diffuse neuronal or axonal damage within centrum semiovale interaxial slices. Periodic inspection of INACS could also allow monitoring of progressive neuronal or axonal degeneration.

Ischemia-reperfusion syndrome: an alternative experimental model

OBJECTIVE

To design an alternative experimental model of ischemia-reperfusion syndrome. Our model mimics the clinical pattern of the syndrome and also assesses the efficacy of therapeutical protocols.

EXPERIMENTAL DESIGN

Ischemia was induced under general anaesthesia in the posterior limbs of 10 sheep by occluding the aorta and vena cava by means of two-way balloon catheters. Ischemia was stopped after 4 hours and blood and histologic parameters determined in the first three hours of revascularization. The animals were divided into three groups: a group of 3 sheep in which a sham operation was performed; a control group (5) to assess the efficacy of induced ischemia; the third group (5) to determine the effect of antioxidant and membrane protective drugs to assess the reliability of the model to study the ischemia-reperfusion syndrome.

RESULTS

At the end of ischemia, skin temperature was decreased (p < 0.04) both in control and treated groups, pH decreased significantly soon after reperfusion in the control group (p < 0.04). Reperfusion in control sheep, compared with treated animals, was followed by a significant increase in CPK blood levels (p < 0.009), related to marked muscle damage, in particular after reperfusion. Tissue damage detected at TEM was less severe in treated animals.

CONCLUSIONS

This model is an effective experimental strategy and a means of assessing preventive treatment.

Prevention of reperfusion syndrome in acute muscular ischaemia with free radical scavengers and membrane-protecting compounds: an experimental study

The prevention of oxidant-induced damage following reperfusion was experimentally evaluated. Two pharmacological regimens containing different combinations of antioxidant factors and membrane-stabilizing compounds, such as alpha-tocopherol (vitamin E), methionine, dexamethasone, mannitol and cysteine, were administered. The reduced/oxidized glutathione (GSH/GSSG) ratio in muscle was used to evaluate oxidative stress. Ischaemia was induced by occluding the aorta and the inferior vena cava with an irrigation-occlusion catheter. After 4 h of ischaemia, five sheep were reperfused without any treatment (control group) and five treated with an endoaortic bolus administered at declamping (treatment 1). In five other sheep, treatment started during ischaemia (treatment 2). Ischaemia and, in particular, reperfusion significantly reduced the muscle GSH content, compared with the basal value in the control group; thus the GSH/GSSG ratio decreased significantly in the control group from 10.5(2.2) (mean(s.e.) basal value) to 0.687(0.3) at reperfusion (P < 0.009). Both treatments 1 and 2 significantly prevented a reduction in GSH content induced by reperfusion following ischaemia; the GSH/GSSG ratio (10.5(2.2) basal value) increased to 19.67(4.6) with reperfusion in the treatment group 1, mainly because of a lower decrease of GSH and a lower level of GSSG while it did not change in treatment group 2 (10.7(5.0)). Levels of creatine phosphokinase did not change in the treated groups, although they increased significantly in the control group (P < 0.006). Although oxidative stress is not the only cause of damage in revascularization, this study confirms the protective ability of treatment with free radical scavengers and membrane-stabilizing compounds.

[The fibrinolytic treatment with urokinase of acute arterial thrombosis]

We present our experiences on 86 patients with acute arterial thrombosis of the legs, undergoing a fibrinolytic treatment with urokinase. Results from the treatment are analyzed according to: the administration way (systemic, locoregional, intrathrombotic), the level of thrombosis (upper or lower legs), the associated morbidity and mortality.

Cerebral SPECT with 99mTc-HMPAO in extracranial carotid pathology: evaluation of changes in the ischemic area after carotid endarterectomy

The authors report their experience in studying patients undergoing carotid endarterectomy with simple photon emission computed tomography (SPECT). This technique made it possible to identify areas of preoperative cerebral hypoperfusion in 54.8% of the patients which had a good correlation with neurological symptoms. To distinguish gradual changes in the ischemic lesions, a method of assessing the surface of the hypoperfused areas was adopted. In addition, SPECT made it possible to detect a greater number of hypoperfused areas even in sites other than those revealed by CT. Moreover, there was good correlations between the SPECT data and the grade and site of the carotid lesion and the data provided by some intraoperative monitoring procedures. The Authors therefore propose the use of SPECT in the evaluation of patients with cerebrovascular insufficiency following a carotid disease.

Morbidity and mortality following carotid surgery

The records of 920 patients who underwent carotid endarterectomy by the same surgeon (M. D'A) between 1976 and 1989 were reviewed. Particular attention was paid to both the neurological and general complications and to how and when the neurological symptoms appeared. Among these patients, a cumulative stroke plus death rate of 3.1% was observed. Complications were classified as clamping ischemia (2.2%), postoperative embolism (1.5%), postoperative thrombosis (2.4%), and cerebral haemorrhage (0.3%). Two patients (0.2%) died from myocardial infarction. In 3.5% of patients, neurological symptoms were transient. The incidence of clamping ischemia was higher when 40 mmHg was considered as the safety limit of the back-pressure; this incidence fell by raising this limit to 50 mmHg, and introducing, in recent years, SEPs monitoring. Intraoperative monitoring of SEPs, in fact, reduced the neurological complications to 1.4%, while intraoperative angiography reduced the need for intraoperative reoperation from 10% to 2%. The use of antiplatelet drugs and an accurate surgical technique are useful steps in the prevention of postoperative embolism or thrombosis.

Carotid endarterectomy in young adults

The results of carotid endarterectomy in 521 patients were analyzed to verify whether the early and late outcome in young patients is worse than in older patients, such as the results observed in peripheral arterial reconstruction in young adults. The patients were subdivided into 3 groups: 105 under 55 years, 397 aged between 56 and 74 years and 19 over 75 years. Young patients presented less risk factors and associated diseases than older ones, with the exception of smoking-habit; on the other hand, they presented a higher incidence of early post-operative thrombosis, myocardial infarction and of recurrent stenosis at follow-up. This trend has already been observed in other series. Young age and smoking habit have also been significantly related with recurrent carotid stenosis. In spite of these complications, carotid endarterectomy is indicated in severe stenosis or complicated carotid plaques, in young adults, because of a low operative mortality and a better trend in the follow-up period; however, the pre-operative evaluation needs a more accurate study and, when possible, the normalization of metabolic risk factors and the elimination of smoking.