Rheological characterisation of xanthan gum in brine solutions at high temperature.

Xanthan gum solutions are used in the oil industry for flooding, drilling and completion operations. The stabilization of the structure of xanthan gum solutions in presence of salts increases the value of both the order-disorder transition temperature and the gel strength. This effect is very important in order to design drilling and completion fluids since not only density and viscosity of the fluid can be improved by increasing the concentration of salts but also the range of temperature where the solution shows viscoelastic behaviour can be extended. This paper presents results from a study on the rheological behaviour of xanthan gum solutions in different saturated brines. Chloride and formate potassium brines not only increase the viscosity of the solution but also extend the shear thinning behaviour to temperatures near 200 °C, maintaining a simple relaxation mechanism over the whole range of temperature where the ordered conformation dominates the rheological behaviour.

Silent ischemia after neuroprotected percutaneous carotid stenting: a diffusion-weighted MRI study.

BACKGROUND AND PURPOSE: To assess by diffusion-weighted MR imaging (DWI) the efficacy of cerebral protection devices in avoiding embolization and new ischemic lesions in patients with severe internal carotid artery (ICA) stenosis undergoing carotid artery stent placement (CAS). METHODS: One hundred sixty-two CASs in the extracranial ICA were performed with the use of distal filters. Mean age of the patients was 68.5 years (range, 33-86) and 122 patients (75.3%) were symptomatic. MR imaging was performed in all patients during the 3-day period before CAS, and DWI was obtained within 24 hours after the procedure. Ninety-five patients (58.6%) were monitored by transcranial Doppler ultrasonography for microemboli detection in the territory of the middle cerebral artery (MCA), ipsilateral to the vessel being treated. RESULTS: Twenty-eight patients (17.3%) showed 58 new ischemic foci in DWI, and 13 patients (46.4%) had multiple foci. Location of new lesions was mainly in the vascular territory supplied by the treated vessel (19 patients; 67.9%), but also in the contralateral MCA (1 patient; 3.6%), and the posterior fossa (4 patients; 14.3%). A significant relationship (P < .03) was found between occurrence of transient ischemic attack (TIA) and appearance of new lesions. Microembolic signals (MES) were detected in 88 patients (92.6%), with no relationship between number of MES and the appearance of new ischemic foci. CONCLUSION: New ischemic foci were observed in 17.3% of the patients undergoing neuroprotected CAS. Appearance of new ischemic lesions were only significantly related to the occurrence of TIA but not to the number of MES registered or other variables. Despite the encouraging results, the incidence of new ischemic lesions should promote research for safer techniques and devices.

Angioplasty of symptomatic high-grade internal carotid artery stenosis with intraluminal thrombus: therapeutic approach.

Intraluminal thrombus in the internal carotid artery (ICA) is usually found in patients with severe atheromatous stenosis. Having reviewed 300 carotid angioplasties for symptomatic >70% ICA stenosis, we found three patients (1%) with intraluminal thrombus. Conservative treatment with anticoagulants and double antiplatelet coverage can result in lysis of the thrombus without severe risks. Percutaneous transluminal angioplasty and stenting, preferably with distal protection, can be an excellent alternative to carotid endarterectomy.

Transient topographical disorientation.

Transient topographical disorientation (TTD) is a short-lasting inability to find one's way in a familiar environment, while the patient remains conscious and is able to recall what happened. We report the study of 10 patients with episodes of TTD, studied on the days following the last episode. The episodes of TTD could be separated into two types: the patients either reported difficulties in spatial orientation with preserved abilities to recognize landmarks and objects, or the difficulties appeared with the recognition of landmarks. Tests exploring spatial orientation, as well as higher visuoperceptive capacities were altered in most of the patients and brain SPECT showed hypoperfusion of the right hemisphere in all patients, which could also be demonstrated 2 years later in some cases. Altogether, our findings suggest that TTD is frequently associated with a more persistent right hemisphere dysfunction of unknown cause. This chronic alteration could represent either a sequel of the acute episode or a preexisting right hemisphere deficit, which inclined the acute insult to be manifested as TTD.

Subclinical hepatic encephalopathy predicts the development of overt hepatic encephalopathy.

OBJECTIVES: In patients with compensated liver cirrhosis the clinical repercussions of detecting subclinical hepatic encephalopathy (SHE) are unclear. We present a long-term follow-up study in cirrhotic patients to examine the relationship between SHE and subsequent episodes of overt hepatic encephalopathy. METHODS: A total of 63 cirrhotic patients were studied by Number Connection Test and auditory evoked potentials. We determined glutamine, ammonia, zinc, glutamate, urea, and ratio of branched chain amino acids to aromatic amino acids, and Child-Pugh classification. RESULTS: Of 63 patients, 34 (53%) exhibited SHE. Nineteen out of 63 (30%) developed overt hepatic encephalopathy during follow-up. Hepatic encephalopathy in follow-up was related to alcoholic etiology, ammonia, glutamine, zinc, ratio of branched chain amino acids to aromatic amino acids, liver function, presence of esophageal varices, and detection of SHE (84% of patients who exhibited hepatic encephalopathy in follow-up showed SHE). In Cox-regression, glutamine levels, SHE, esophageal varices, and Child-Pugh class were the independent variables related to hepatic encephalopathy in follow-up. CONCLUSIONS: SHE (defined on the basis of number connection test or auditory evoked potentials alteration) could predict a subsequent episode of overt hepatic encephalopathy. Lower glutamine levels, presence of esophageal varices, and liver dysfunction were also related to the development of overt hepatic encephalopathy.

[Hyperperfusion syndrome as a complication of percutaneous transluminal angioplasty of the internal carotid artery]. / Síndrome de hiperperfusión como complicación de la angioplastia transluminal percutánea de la arteria carótida interna.

INTRODUCTION: The hyperperfusion syndrome (HS) is described as an infrequent complication of carotid endarterectomy. It may also occur in percutaneous transluminal carotid angioplasty with a similar causal mechanism and clinical features to those seen in HS related to carotid endarterectomy. CLINICAL CASE: We describe the case of a 69 year old man who developed HS at the time of transluminal carotid angioplasty and 'stenting' of symptomatic, pre-occlusive stenosis of the left internal carotid artery. This complication was not detected on the postoperative arteriography. On CT the presence of a hemispheric hematoma was confirmed. It is thought that HS is caused by a fault in autoregulation of the cerebral blood flow following correction of vascular stenosis in previously ischemic territory. CONCLUSIONS: Most of the early complications of transluminal carotid angioplasty are ischemic. HS is rare but is a possible complication of transluminal carotid angioplasty and therefore meticulous control of the blood pressure is necessary. A CT scan after any atypical complication of angioplasty may be considered to be essential.

[Analysis of the changes observed in the sleep EEG recording of patients with juvenile myoclonic epilepsy]. / Análisis de las alteraciones observadas en el registro EEG de sueño de pacientes con epilepsia mioclónica juvenil.

OBJECTIVE: The initial phases and transitional periods of sleep facilitate electroclinical manifestations of juvenile myoclonic epilepsy (JME). The period at the time of waking is identified in the different phases of sleep by cyclic electrophysiological oscillations, which in turn are synchronous with the spike-and-wave or multiple spike-and-wave activity of the electric crises seen in JME and other epileptic syndromes. This observation supports the theory of an alternating cyclical pattern (ACP) as the trigger of these discharges. PATIENTS AND METHODS: Following classical macrostructural and microstructural patterns of EEG sleep analysis, we investigated electrophysiological behavior in 13 patients diagnosed as having JME, and 5 persons of homogeneous epidemiological characteristics as controls. RESULTS: In our study we observed that both groups had similar macrostructural sleep parameters. However, in patients prone to crises, these were concentrated in the first two hours recorded and showed no differences in sleep-waking transition or ACP of phase I sleep. These were significant when both periods were compared with the remaining NREM sleep. CONCLUSION: We conclude from this study that ACP is the microstructural element of sleep which modulates and permits classification of epileptiform anomalies, mainly in studies at the time of wakening.

[Concurrence of short and long lasting episodes of nocturnal paroxysmal dystonia in an epileptic patient]. / Coexistencia de episodios de distonía paroxística nocturna de corta y de larga duración en una paciente epiléptica.

We report the case of a patient with nocturnal paroxysmal dystonia (NPD) meeting not only the diagnostic criteria described by Lugaresi et al. in 1981, but also presenting with features suggestive of underlying epilepsy as well as other differences from the diagnostic criteria originally described for NPD, such as short- and long-lasting episodes and poor response to antiepileptic drugs. The case we describe suggests a different entity, one that is unrelated to epilepsy or true NPD.

Percutaneous transluminal angioplasty of the symptomatic atherosclerotic carotid arteries. Results, complications, and follow-up.

BACKGROUND AND PURPOSE: Carotid endarterectomy reduces stroke risk in patients with > 70% symptomatic stenosis. We present our results of percutaneous transluminal angioplasty (PTA) as an alternative treatment. METHODS: Ninety-eight patients with symptomatic > 70% stenosis of the internal carotid artery were considered for PTA. Details of the procedure, complications, and 4-year follow-up were registered. RESULTS: Eighty-five PTAs were performed in a 4-year period. Transient cardiovascular effects were frequent: hypotension (54.1%), bradycardia (67.1%), asystole (25.9%), and syncope (16.5%). Transient ischemic attack occurred in 3 of 82 patients (3.7%), and disabling stroke occurred in 4 (4.9%); mortality was 0%. After a mean follow-up period of 18.7 months, 4 patients died, 1 due to fatal stroke. The overall probability of surviving any stroke or death was 86.7%. Restenosis (> 70%) was seen in 6 cases (7.4%). CONCLUSIONS: PTA may be a reasonable treatment for symptomatic atherosclerotic stenosis, at least in patients at high risk for carotid endarterectomy.

Evoked potentials in mitochondrial disorders.

Twenty-eight adult patients with mitochondrial disease were evaluated with muitimodal evoked potentials (EPs) to assess a possible CNS involvement The patients were classified into five groups: encephalopathy (two cases), progressive external ophthalmoplegia (PEO; four cases), pure myopatby (15 cases), cardiomyopathy (five cases) and asymptomatic relatives (two cases). EPs showed differences between encephalopathy (all EP modalities affected) and PEO groups (all patients with at least one EP altered), with lesser degrees of affection in pure myopathy and cardiomyopathy groups. The asymptomatics registered normal EPs. In view of these results, progressive CNS damage in mitochondriopathies, expressed by abnormal EPs, can be established as follows (from greatest to minor severity): encephalopathy, PEO, pure myopathy/cardiomyopathy and asymptomatic condition.

[Dr. Jose Gregorio Hernandez, university professor, 1891-1919]. / Doctor Jose Gregorio Hernandez, profesor universitario, 1891-1919.

In remembrance of the First Centennial of the Normal and Pathological Histology, Experimental Physiology and Bacteriology courses foundation, a quantitative analysis of the Dr. José Gregorio Hernández career between 1891 and 1919 is made. He was its Founder Professor and, with that, the Pasteurian and Experimental era initiator in our medicine. His elevated pedagogic quality, as well as his excellent condition as searcher and in the practice of medicine is highlighted.

[Visual evoked potentials in benign intracranial hypertension]. / Potenciales evocados visuales en la hipertensión intracraneal benigna.

In 20 patients with benign intracranial hypertension (BIH) a study of the P100 latency of visual evoked potentials (VEP) was carried out. At admission only 5 patients showed abnormal latencies. The mean of the P100 latencies in patients was significantly increased as compared with controls. Latencies persisted relatively prolonged once the funduscopy had become normal. In the last investigation, one year after BIH had disappeared, the latencies in patients were already similar to those in the control group. On the other hand, no patient with normal latencies had visual sequelae. Sequelae also did not develop in patients in whom initially prolonged latencies progressively returned to normal during the evolution. Sequelae developed in one patient in whom latencies became progressively prolonged. In that case the increased latencies preceded the fall in visual acuity. These data may be useful to evaluate visual function in patients with BIH.

Episodic cluster headache and narcolepsy: a case report.

A patient who first presented with episodic cluster headache later developed narcolepsy. In spite of REM sleep alterations associated with narcolepsy, the frequency and distribution of pain attacks did not change when narcolepsy occurred and were similar to those seen in cases of episodic cluster without narcolepsy. The lack of influence of narcolepsy on the pattern of cluster pains questions the role of REM sleep states in triggering pain in episodic cluster.

[A tribute to Jose Maria Benetez on the bicentennial of his birth]. / Homenaje al licenciado Jose Maria Benetez en el bicentenario de su natalicio.

A biographical essay on Dr. José María Benítez to commemorate 200 years of his birthday. His professional practice for 31 years in La Victoria (Aragua State) and his fight against malaria and cholera are highlighted. He was the scientific discoverer of the cinchona (peruvian bark). Dr. Benítez affirmed that "cholera was contagious" when the contrary was believed.