Ergodic model for the expansion of spherical nanoplasmas.

Recently, the collisionless expansion of spherical nanoplasmas has been analyzed with a new ergodic model, clarifying the transition from hydrodynamiclike to Coulomb-explosion regimes, and providing accurate laws for the relevant features of the phenomenon. A complete derivation of the model is presented here. The important issue of the self-consistent initial conditions is addressed by analyzing the initial charging transient due to the electron expansion, in the approximation of immobile ions. A comparison among different kinetic models for the expansion is presented, showing that the ergodic model provides a simplified description, which retains the essential information on the electron distribution, in particular, the energy spectrum. Results are presented for a wide range of initial conditions (determined from a single dimensionless parameter), in excellent agreement with calculations from the exact Vlasov-Poisson theory, thus providing a complete and detailed characterization of all the stages of the expansion.

Kinetics of the collisionless expansion of spherical nanoplasmas.

The collisionless expansion of spherical plasmas composed of cold ions and hot electrons is analyzed using a novel kinetic model, with special emphasis on the influence of the electron dynamics. Simple, general laws are found, relating the relevant expansion features to the initial conditions of the plasma, determined from a single dimensionless parameter. A transition is identified in the behavior of the ion energy spectrum, which is monotonic only for high electron temperatures, otherwise exhibiting a local peak far from the cutoff energy.

Eversion versus conventional carotid endarterectomy: late results of a prospective multicenter randomized trial.

OBJECTIVE: The durability of carotid endarterectomy (CEA) may be affected by carotid restenosis. The data from randomized trials show that the highest incidence of restenosis after CEA occurs from 12 to 18 months after surgery. The optimal CEA technique to reduce perioperative complications and restenosis rates is still undefined. This study examines the long-term clinical outcome and incidence of recurrent stenosis in patients who undergo eversion CEA. Previously published perioperative results of this study did not show statistically significant differences in study endpoints between the eversion and standard techniques. METHODS: From October 1994 to March 1997, 1353 patients with surgical indications for carotid stenosis were randomly assigned to undergo eversion (n = 678) or standard CEA (n = 675; primary closure, 419; patch, 256). Withdrawal from the assigned treatment occurred in 1.6% of the patients (in 13 assigned to eversion CEA, and in nine assigned to standard CEA). The clinical and duplex scan follow-up examination was 99% complete, and the mean follow-up interval was 33 months (range, 12 to 55 months). The primary outcomes were perioperative and late major stroke and death, carotid restenosis (stenosis >/= 50% of the lumen diameter detected at duplex scanning), and carotid occlusion. The primary evaluation of study outcomes was conducted on the basis of an intention-to-treat analysis. RESULTS: Restenosis was found at duplex scanning in 56 patients (19 in the eversion group, and 37 in the standard group). Within the standard group, the restenosis rates were 7.9% in the primary closure population and 1.5% in the patched population. Of the patients with restenosis, 36% underwent cerebral angiography that confirmed restenosis in all cases. The cumulative restenosis risk at 4 years was significantly lower in the group that underwent treatment with eversion CEA as compared with the standard group (3.6% vs 9.2%; P =.01), with an absolute risk reduction of 5. 6% and a relative risk reduction of 62%. Eighteen patients would have had to undergo treatment with eversion CEA to prevent one restenosis during the 4-year period. The incidence rate of ipsilateral stroke was 3.3% in the eversion population and 2.2% in the standard group. There were no significant differences in the cumulative risks of ipsilateral stroke (3.9% for eversion, and 2.2% for standard; P =.2) and death (13.1% for eversion, and 12.7% for standard; P =.7)) in the two groups. Of the 18 variables that were examined for their influence on restenosis, eversion CEA (hazard ratio, 0.3; 95% confidence interval, 0.2 to 0.6; P =.0004) and patch CEA (hazard ratio, 0.2; 95% confidence interval, 0.07 to 0.6; P =. 002) were negative independent predictors of restenosis with multivariate Cox proportional hazards regression analysis. CONCLUSION: The EVEREST (EVERsion carotid Endarterectomy versus Standard Trial) showed that eversion CEA is safe, effective, and durable. No statistically significant differences were found in late outcome between the eversion and standard techniques at the available follow-up examination.

[Limb salvage in critical ischemia. Our experience]. / Salvataggio d'arto nell'ischemia critica. Nostra esperienza.

The aim of this paper is to present our six-year experience in the treatment of critical limb ischaemia, even if in the period (1987-1993) considered the definition of critical ischaemia had been partly reviewed in the publication of the "European Consensus Document on Critical Limb Ischaemia" (March 1989). Two hundred thirty-nine patients have been treated in our Unit for critical limb ischaemia: reconstructive surgery was used in 34% of cases, lumbar sympathectomy or spinal cord stimulation in 17% of cases and pharmacotherapy in 14% of cases. Taking into account arterial and graft patency as well as the percentage of limb salvage, our results were similar to those presented in the literature.

Cerebral reserve and indications for shunting in carotid surgery.

The aim of this study was to establish whether a preoperative evaluation of cerebral haemodynamic reserve, carried out by means of transcranial Doppler and single photoemission computed tomography with a provocative test (acetazolamide) is able to select those patients who require carotid shunting to avoid cerebral ischaemia during clamping. All patients were monitored during operation by means of somatosensitive evoked potentials. Those patients who required shunting because of abnormal evoked potentials were also those who had a poor cerebral reserve with a perfusion and velocity increase below 15%. Only one neurological deficit developed in patients who were not shunted.

[Arterial recanalization with the Kensey catheter. Preliminary results]. / Ricanalizzazione arteriosa con catetere di Kensey. Risultati preliminari.

Fifteen patients with chronic obstruction of leg arteries (mean length: 6 cm) were treated with the Kensey catheter and then with PTA. In 11 cases the procedure was successful (74%) and in 2 it was interrupted--in one case for dissection and in the other for vessel perforation. Two maneuvers, after dissection, were ended with PTA and stent placement (overall success rate: 87%). Emergency surgery was never needed. In the cases solved with the Kensey catheter, the cumulative patency rate was 51% at 6, 12 and 24 months. The Kensey catheter did not improve the results of conventional PTA, which means its role is complementary to that of PTA and an alternative to more expensive laser systems, if PTA fails.

[Loco-regional thrombolysis in deep venous thrombosis]. / La thrombolyse loco-régionale dans la thrombose veineuse profonde.

Anticoagulation, by means of heparin and warfarin is, till now, the most common treatment in deep venous thrombosis. Although thrombolytic agents have been available for over 10 years, their use remains quite low, ranging from 15 to 20% of deep venous thromboses. This is due to the relatively high incidence of contraindications as well as to the fact that the potential advantages versus heparin are diminished by the increased bleeding risk and by the potential risk of pulmonary embolism (migration of partially lysed thrombi). Following the example of the "triple armed therapy" proposed by Rosenthal for the treatment of pulmonary embolism, we will evaluate if loco-regional thrombolysis, with the catheter wedged against the thrombus, associated with a temporary vena cava interruption by means of an intraluminal filter, can achieve a better lysis of the thrombus without pulmonary embolism. In our Unit 18 patients affected by proximal deep venous thrombosis were submitted to thrombolytic therapy, 6 to systemic treatment, 3 to local treatment and the last 9 to loco-regional thrombolysis, using recombinant tissue-type Plasminogen Activator. We obtained 10 complete lyses, 1 with systemic and 9 with loco-regional treatment. There were no major complications. Thus, we think that venous loco-regional thrombolysis with rt-PA at lower doses, associated with temporary caval interruption, can probably achieve a better lysis than systemic treatment without risk of pulmonary embolism and with a very low haemorrhagic risk, as in arterial loco-regional thrombolysis. Furthermore, loco-regional thrombolysis, by means of a faster thrombus dissolution, could better prevent post-phlebitic syndrome.

[Hemodynamic reserve in carotid surgery and the use of "superselective" shunt]. / Riserva emodinamica in chirurgia carotidea ed uso "superselettivo" dello shunt.

The aim of this study is to establish whether a preoperative evaluation of the Cerebral Hemodynamic Reserve, carried out by means of transcranial Doppler and SPECT with provocative test (acetazolamide) can single out those patients who, because they are supplied with a poor cerebral reserve, are truly in need of intraoperative shunting after carotid clamping. All patients were intraoperatively monitored by means of Somato Sensitive Evoked Potentials (SSEPs). Those patients who were shunted due to abnormalities in SSEPs were also those who showed a perfusion and velocity increase below 15%, and therefore supplied, in our opinion, with a scanty cerebral reserve. No, but one, neurological deficit appeared on awakening in patients who were not shunted.

[Arterial embolism, venous thrombosis, pulmonary embolism: a suggestive triad]. / Embolia arteriosa, trombosi venosa, embolia polmonare. Una triade suggestiva.

The aim of this study is to present a relatively rare case of paradoxical arterial embolism, found in a patient who was sent to us for serious pulmonary embolism. Taking into account that the foramen ovale, despite being functionally competent, remains anatomically patent in 30% of the adult population, we cannot neglect the possibility of a paradoxical embolism, in the presence of a sudden embolic limb ischemia unless heart pathology or aortic lesions can be held responsible. Furthermore it must not be forgotten that deep venous thrombosis in the lower limbs or in the pelvic plexus may go unobserved on a purely clinical evaluation.

[Deep phlebothrombosis disclosing aortoiliac aneurysms]. / La flebotrombosi profonda quale rivelatrice di aneurismi aorto-iliaci.

The purpose of the present study is to underline the importance of the systematic search for iliocaval venous compression on the part of an aortoiliac aneurysm in the face of a clinical picture of suspected deep venous thrombosis. Early diagnosis of this syndrome, although rare in everyday experience, is of decisive importance, as is every other clinical sign of aneurysmal pathology prior to rupture. Correct, systematic diagnostic exclusion procedure, which is capable of leading to certain diagnosis in all cases is therefore necessary.

Spasm of arm arteries due to ergotamine tartrate. A case report.

Ergotamine tartrate and caffeine has been widely prescribed for the prevention and treatment of migraine headaches. Rarely the ergotamine can cause symptoms of peripheral vascular insufficiency, often concerning the lower extremities. A case report of bilateral severe ischemia to the upper limbs, caused by a chronic assumption of ergotamine tartrate is presented.