Wind Generated Rogue Waves in an Annular Wave Flume.

We investigate experimentally the statistical properties of a wind-generated wave field and the spontaneous formation of rogue waves in an annular flume. Unlike many experiments on rogue waves where waves are mechanically generated, here the wave field is forced naturally by wind as it is in the ocean. What is unique about the present experiment is that the annular geometry of the tank makes waves propagating circularly in an unlimited-fetch condition. Within this peculiar framework, we discuss the temporal evolution of the statistical properties of the surface elevation. We show that rogue waves and heavy-tail statistics may develop naturally during the growth of the waves just before the wave height reaches a stationary condition. Our results shed new light on the formation of rogue waves in a natural environment.

[Canaud central venous catheters: 4-year experience]. / Cateteri venosi centrali di canaud: esperienza di oltre quattro anni.

BACKGROUND: The use of central venous catheters for permanent vascular access has become increasingly important because of the characteristics and the clinical problems of incident patients or patients already undergoing chronic hemodialysis. In this study a short and medium term evaluation was made of a double permanent central venous catheter positioned in the right internal jugular vein. The Canaud catheter was evaluated both from the point of view of practical use and for various technical and clinical problems. METHODS: During the observation period, July 1995 - September 1999, these catheters were used in 39 patients (mean age 72 years), 22 females and 17 males; 31% were diabetic patients and 46% were older than 75 years. Forty-five catheters were positioned with an average dwelltime of 347 days. RESULTS: Utilization was almost immediate and the resulting blood flow was suitable for all depurative techniques (blood flow more than 250 ml/min), with an average recirculation of 11.9% and an average resistance index of 0.54. Among the most serious complications during surgery a respiratory block was observed followed by the complete recovery of the patient. Some clinical complications were noted (5 venous thrombosis), as were some technical ones: 12% well as related to problems with the adapter, 24.3% to reversible thrombosis of the catheters occurred in 23 catheters in 22 patients. Infections. CONCLUSIONS: Overall Canaud catheters appear to represent a valid alternative to other more recent catheters for permanent vascular access. If necessary, they can be easily substituted due to the absence of a subcutaneous cuff.

[Permanent central venous catheters for dialysis. The situation in Piedmont-Aosta Valley]. / Cateteri venosi centrali a permanenza per dialisi. Realtà in Piemonte-Valle d'Aosta.

BACKGROUND: Permanent central venous catheters for hemodialysis have become increasingly important as vascular accesses for extracorporeal dialysis. The aim of this study was to evaluate the prevalence and various aspects of these catheters in the chronic dialysis population in Piedmont and Aosta Valley on 30-6-1998 using a multiple-choice questionnaire. METHODS: A total of 2389 patients were receiving chronic hemodialysis. Permanent central venous catheters were present in 6.2% of the population (149 patients), arteriovenous fistulas in 83.1%, vascular prostheses in 9.3% and temporary catheters in 1.4%. The site chosen for permanent catheters was the internal jugular vein in 88.6% of cases, the subclavian vein in 8.7% of cases and the femoral vein in 2.7% of cases. The double catheter is the most frequently used. In 76% of centres catheters are positioned by nephrologists. Thrombosis prophylaxis is performed in 98% of cases with heparin and the most frequently used disinfectant to dress the cutaneous exit is iodopovidone. RESULTS: This study highlights the important role played by permanent catheters. The double catheter was used in 64.4% of the entire population, confirming the greater efficiency of these catheters as reported in the literature. Operating autonomy is relative in 76.2% of centres where catheters are positioned by nephrologists who often use the collaboration of other specialists. CONCLUSIONS: The authors stress the need to reflect on the use of iodopovidone is to dress the cutaneous exit of catheters since this disinfectant is contraindicated by one of the largest manufacturers of silicone catheters owing to its harmful medium long-term effects.

[Temporary dialysis access in patients with acute renal failure. Protocols of the dialysis centers in the Piedmont and Valled'Aosta]. / Accessi temporanei per dialisi nei pazienti con IRA. Protocolli dei centri dialisi del Piemonte e della Valle d'Aosta.

BACKGROUND: A retrospective study was performed using a multiple-choice questionnaire in order to analyse the normal procedures and trends regarding the insertion and management of emergency dialysis access in patients with acute renal failure in 23 Centres in Piedment and the Aosta Valley, regions in the north of Italy with about 4.5 million inhabitants. METHODS: The observation period ran from January 1996 to July 1997. A questionnaire with 19 main questions and 90 possible multiple answers sent to 22 Centres for adults and the only pediatric centre in both regions. RESULTS: An analysis of the results showed that the most frequently used site in these regions is the subclavian vein (37.8%), followed by the internal jugular vein (32%), the femoral site (28.8%) and peritoneal catheter (1.4%); in pediatric patients, 5% used the femoral site, 10% the subclavian vein, 20% the internal jugular vein and 65% the peritoneal catheter. In 4 centres (18.2%), nephrologists do not position any type ofd access for acute renal failure. In 50% of centres, all doctors insert femoral catheters autonomously. CONCLUSIONS: Some choices, such as the subclavian route, are open to criticism and may perhaps be linked to customary procedures used by anesthetists and intensive care specialists. Some centres only have relative automomy for insertion, and lastly some types of catheters and techniques are not used. The peritoneal catheter has been abandoned by adult centres as an access in acute kidney failure patients.

[Drugs used in the treatment of arterial hypertension in dialysis patients in the Piedmont. What correlations between personal and clinical data can be made from the registry data?]. / I farmaci utilizzati per il trattamento della ipertensione arteriosa nei pazienti in dialisi in Piemonte. Quali correlazioni con i dati anagrafici e clinici sono possibili dai dati del registro?

The therapeutical approach to arterial hypertension in the general population is now relatively well classified, whereas it remains a controversial problem in dialytic patients. The aim of this study was to evaluate the antihypertensive drugs used in dialytic patients in Piedmont and to identify correlations with other personal and clinical data. The authors analysed the data in the Piedmont Dialysis and Transplant Register concerning new patients admitted to dialysis during the period 1990-1995 (2,664 patients at 31/12/1995) and 1,373 patients who began dialysis during the period 1990-1993. A study of the antihypertensive drugs using in single and combined therapy over the five-year period shows major variations in the 45-65 year-old age bracket (increased ACE-inhibitors in single therapy, 15.5-25.6%, increased vasodilators in combined therapy, 15.3-21%). In patients aged > or = 65 years old a slight increase was found in the use of beta-blockers in monotherapy. Antihypertensive drugs at the 1st control (1990-1995 entries) appeared to be stable over the five-year period. From the 1,373 patients who started dialysis in the period 1990-1993, with at least three subsequent controls, the authors selected those hypertensive or normotensive patients receiving ACE-inhibitor therapy (best survival in general population) and compared their survival with that of patients receiving alternative antihypertensive treatment. No significant differences were found. The stability of the antihypertensive drugs taken by these patients over the past 5 years backs the hypothesis of a greater attention paid by nephrologists to the introduction of new drugs, both because of the frequent onset of collateral effects and owing to the special pharmacokinetics present in dialytic patients.

Influence of the hydration state on blood pressure values in a group of patients on regular maintenance hemodialysis.

The pathophysiology of hypertension in patients on renal replacement therapy is not yet clear, and the role of extracellular fluid overload is still a matter of debate. The main problem is the lack of techniques to determine the fluid state. Recently new noninvasive techniques have become available which make it possible to accurately determine the hydration state in these patients. We have studied the influence of the hydration state on interdialytic blood pressure in 45 patients: 21 (46.6%) using antihypertensive medication and 24 (53.4%) without antihypertensive medication. Total body water (TBW) was determined by bioelectrical impedance analysis performed just before a hemodialysis session. The TBW was then related to the fat-free mass calculated by the anthropometric method (aFFM) of Durnin. The hydration state was defined using the following formula: TBW/aFFM 100. Furthermore, for each patient the ideal TBW was calculated according to the Watson formula. The difference between TBW and ideal TBW was considered a further index of the hydration state. Ambulatory blood pressure monitoring was performed by using a Takeda 24200 recorder according to the Korotkoff method during the 24 h before the midweek hemodialysis session. Blood pressure monitoring showed a significant correlation with the hydration state of these patients. In conclusion, the hydration state seems to play a major role in interdialytic blood pressure control.

[Epidemiology and clinical course in hepatitis C-positive patients treated with dialysis in Piemonte. Work group of the RPDT]. / Epidemiologia e comportamento clinico nei pazienti epatite C positivi in dialisi in Piemonte. Gruppo di lavoro dell' RPDT.

The high prevalence of HCV positivity in dialysis patients has recently prompted several studies on this controversial subject. The aim of the study was an evaluation of HCV positivity and of influence on clinical outcome in 2,404 patients on dialysis in Piedmont (Northern Italy Region, about 4,400,000 inhab., 20 Dialysis Centers) at December 1993 (32.7% HCV-positive according to the Regional Registry of Dialysis and Transplantation). As expected, a strong correlation was found with time on dialysis (94.4% in patients with treatment follow-up > or = 20 years) and blood transfusions (41.3% HCV positivity in transfused patients versus 22.6% in not transfused ones; p < 0.0001). Dialysis in a hospital setting is confirmed as at high risk of infection, since HCV positivity was 19.6% in patients always treated by bicarbonate dialysis in hospital versus 8.9% in those treated only by CAPD (start of dialysis in 1992-1993). Despite the high prevalence of HCV positivity, however, death rates for liver disease and for all gastrointestinal causes are very low, regardless of HCV antibody status (1.2% in HCV positive versus 2.3% in HCV negative, NS). Whether this depends upon different clinical features of HCV infection in dialysis patients or merely deflects a relatively short follow-up will be matter of discussion in the future.

Recurrent secondary hyperparathyroidism due to parathyroid carcinoma: usefulness of Ki-67 immunostaining in the diagnosis of a malignant parathyroid tumor.

Parathyroid carcinoma is a very rare disease occurring in less than 2-3% of all the cases showing clinical features of primary hyperparathyroidism. Several histological markers have been used for distinguishing between benign and malignant tumors of the parathyroid glands. However, most of these markers are not easily applicable and clinical prognosis cannot be predicted by histopathological criteria alone. A recent study has drawn attention to the role of the cell cycle associated antigen Ki-67 detected by MIB-1 monoclonal immunocytochemistry in parathyroid tumors: in fact, Ki-67 seems to be a valuable marker of malignancy in such tumors since it permits an easy detection of proliferating and dividing cells. Here we report in detail a case of severe recurrent hyperparathyroidism in a 51-year-old female patient undergoing regular hemodialysis treatment. In the surgical specimens of the parathyroid glands, the tumor proliferative fraction of 56, expressed as the number of Ki-67-positive nuclei per thousand cells, and the mean mitosis count of 0.5, expressed as the percentage of the total amount of Ki-67 positive nuclei, support the diagnosis of parathyroid carcinoma despite the scanty amount of microscopical signs considered characteristic of malignancy, i.e. extensive thick fibrous bands or prominent nucleoli. To our knowledge this paper is the first clinical report that supports the diagnostic role of the cell cycle associated antigen Ki-67 in parathyroid carcinoma in a case of secondary hyperparathyroidism in a patient undergoing hemodialysis.

Monitoring of central venous dual-lumen catheter placement in haemodialysis: improvement of a technique for the practising nephrologist.

Mismanagement in the placement of central venous catheter (CVC) may occur in up to 20% of cases. The catheter can be inadvertently placed in the contralateral brachiocephalic vein, the ipsi or contralateral internal jugular vein, and usually a thoracic radiograph is necessary to evaluate its location. We propose a technique first described by Serafini et al. to establish the position of a CVC by endocavitary electrocardiography (EC-ECG) and its employment in a large number of uraemic patients requiring haemodialysis. This technique uses the tip of the CVC as reference lead in a standard electrocardiograph. The best employment of this technique has been obtained by echotomographic visualization of the internal jugular vein executed just before transcutaneous puncture of the vessel. For 13 months we have successfully applied this technique in CVC placement in 81 patients requiring haemodialysis. In our opinion this method is a safe and simple technique that avoids the need for thoracic radiographs and time lost waiting for radiographs that prolong the start of the haemodialysis session. According to our experience, we confirm that the EC-ECG technique provides a method for ensuring compliance with Food and Drug Administration guidelines regarding catheter tip location in uraemic patients.

Monitoring of central venous dual-lumen catheter placement in haemodialysis: improvement of a technique for the practising nephrologist.

Mismanagement in the placement of central venous catheter (CVC) may occur in up to 20% of cases. The catheter can be inadvertently placed in the contralateral brachiocephalic vein, the ipsi or contralateral internal jugular vein, and usually a thoracic radiograph is necessary to evaluate its location. We propose a technique first described by Serafini et al. to establish the position of a CVC by endocavitary electrocardiography (EC-ECG) and its employment in a large number of uraemic patients requiring haemodialysis. This technique uses the tip of the CVC as reference lead in a standard electrocardiograph. The best employment of this technique has been obtained by echotomographic visualization of the internal jugular vein executed just before transcutaneous puncture of the vessel. For 13 months we have successfully applied this technique in CVC placement in 81 patients requiring haemodialysis. In our opinion this method is a safe and simple technique that avoids the need for thoracic radiographs and time lost waiting for radiographs that prolong the start of the haemodialysis session. According to our experience, we confirm that the EC-ECG technique provides a method for ensuring compliance with Food and Drug Administration guidelines regarding catheter tip location in uraemic patients.

[Informatics support and teledialysis]. / Supporto informatico e teledialisis.

Computer-assisted medical activity is increasing in several fields, with wide perspectives in nephrology and dialysis accounting for the peculiar characteristics of this population such as number, complexity, follow-up length and economic costs. Since 1980 we have been studying a computerized organization of our Region's departments in order to achieve 3 main results: 1) a registry of all patients undergoing dialysis in the area, with a one- a-year complete clinical update; 2) a computerized medical chart, which could gather all the clinical, technical and managerial aspects of the treatment; 3) a teledialysis program, to follow every session in local and remote stations. The first aim has been reached with useful information for the dialytic policy in the area. The second objective is ongoing with straight evidence of easy, speedy procedures, and accurate data collection. The third goal is on a preliminary phase looking at the safety, reliability and precision of the treatments. Informatic procedures seem to be quite advisable in improving as clinical surveillance of the patients, as technical and managerial aspects of dialysis units.

Small frameshift deletions within the COL4A5 gene in juvenile-onset Alport syndrome.

Small frameshift deletions within the COL4A5 gene were identified in three Alport syndrome Italian families by non-isotopic single-strand conformation polymorphism (SSCP) screening: in family RMA, a 7-bp deletion (GGGTGAA) in exon 39; in family DGR, a 4-bp deletion (TGGA) in exon 41; in family MIB, deletion of a G in exon 50. The phenotype was characterized by juvenile-onset renal failure with sensorineural hearing loss in males, and a milder clinical pattern in heterozygous females.

Death in conditions of cachexia: the price for the dialysis treatment of the elderly?

Death in conditions of cachexia is increasing in potential dialysis patients, as treated cohorts are aging, the mean age of new patients increased and access to treatment is unlimited. The present study analyzes the clinical features of 417 deaths in conditions of cachexia recorded in 1981 to 1990 in the Dialysis and Transplantation Registry of a northern Italian region, Piedmont (about 4,400,000 inhabitants, 20 dialysis centers; 4,734 patients on file at December 31, 1990; yearly information on 100% of the cases). Death in conditions of cachexia increased from 105 cases in the first four years taken into account (1981 to 1984), to 107 in the last two years (1989 to 1990). Prevalence is higher in the elderly (85% of the death over age 60). Most patients (90.5%) were at high clinical risk. To assess whether the frequency of this diagnosis reflected the wide acceptance of elderly patients for dialysis and was a marked of vascular disease, a specific inquiry was conducted about 107 cachectic deaths recorded from 1989 to 1990: 82.5% of the patients had diffused vascular disease, 11.5% were already cachectic when dialysis was initiated, and 66% were in cachexia at least six months before death. Since mean age of patients dying in condition of cachexia increased from 68.8 in the period of 1981 to 1984 to 70.3 years in 1989 to 1990, and mean time on dialysis from 2.8 years in 1981 to 1984 to 70.3 years in 1989 to 1990, the higher prevalence is not likely to be due to lack of care of elderly patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Diabetic patients on dialysis: a changing picture.

Prevalence of diabetic patients on dialysis is often considered a marker of overall acceptance rate for dialysis; however, even when acceptance policy is open, incidence of diabetic patients varies widely. Epidemiological differences of diabetes incidence all over the world partly explain the discrepancies. Incidence of diabetic patients accepted for dialysis (1981 to 82: 6 p.m.p.; 1989 to 90: 11.5 p.m.p.) differs according to age and sex in the setting analyzed (Piedmont, Northern Italian region, about 4,400,000 inhabitants, 20 dialysis centers, open acceptance since the mid-70s, yearly information on 100% of patients, gathered by a Dialysis and Transplantation Registry). Patterns changed remarkably during the 10 years considered (1981 to 90). Incidence was higher in males (10.4 p.m.p. in the period 1981 to 90), with a peak at ages 60 to 69. Incidence remained relatively stable in the younger patients, but increased in the elderly, mainly in males, rising from 6.23 in 1981 to 82 to 12.88 p.m.p. in 1989 to 90 (males, all ages). In conclusion, the demographic characteristics of diabetic patients with ESRD accepted for dialysis is changing. The stability of incidence of younger patients reassures about the open acceptance policy, at least in these ages. The increase in the elderly probably reflects the longer lifespan of diabetic patients in the overall population. The possibility of a hidden preselection must be further assessed. Future provisions of dialysis needs must take into account the trend towards an increase of this high risk, elderly population.

[Changes in cellular ion transport and arterial pressure in renal transplant recipients undergoing cyclosporin treatment]. / Alterazioni del trasporto ionico cellulare e pressione arteriosa nei portatori di trapianto renale in trattamento con ciclosporina.

Arterial hypertension is a common side effect of cyclosporine A (CyA). Aim of the study was to evaluate the activity of erythrocyte (RBC) Na transport in two groups of patients with a well functioning renal graft (Crs less than 1.7 mg/dl) treated by prednisone+azathioprine (10 pts), or prednisone+CyA (21 pts), in relationship with blood pressure status. Twenty-one age matched healthy subjects were studied as a control group. Na,K pump and Na,K cotransport were significantly lower in CyA than in AZA patients (2,184 +/- 106 vs 3,089 +/- 162 and 58 +/- 8 vs 187 +/- 28 mumol/l RBC/h: p less than 0.01), without differences between normotensive and hypertensive patients. Na,K pump efflux in normal subjects was 2334 +/- 66 mumol/l RBC/h (p less than 0.01 vs AZA), NA,K cotransport was 205 +/- 18 mumol/l RBC/h (p less than 0.01 vs CyA). Significant correlations were found between RBC Na,K pump activity and trough plasma CyA levels (p less than 0.02) and between systolic pressure and plasma creatinine in CyA patients (p less than 0.01). Trough plasma CyA levels were higher in hypertensive than in normotensive CyA patients (64 +/- 5 vs 46 +/- 4 ng/ml; p less than 0.01).

[Two years of experience and 119 peritoneal dialysis catheters placed with peritoneoscopy control and Y-TEC system]. / Due anni di esperienza e 119 cateteri per dialisi peritoneale posizionati con controllo peritoneoscopico e sistema Y-TEC.

In this work we report our 24 months experience in the placement of 119 peritoneal catheters in 105 patients (59 males, 46 females, mean age 60.1 years; range 24-90) using the peritoneoscopic insertion technique. After catheter implantation a dialysis solution leak is encountered in 7.5% of cases, tunnel infection in 4 cases (3.3%) and exit site infection in 12.5% of the catheters. Placement by endoscopic control is considered as a technique able to avoid catheter migration; in our series we reported this complication in 15 cases (12.5%). The easy access to the peritoneal cavity and the atraumatic insertion of the catheter obtained with the Y-TEC procedure reduced the hospitalization period from 25 to 5 days on average. In our experience actuarial survival of catheters is 82.5% at 24 months.

[Effects of saline infusion on the activity of erythrocyte sodium-potassium pump in normal subjects and in patients with essential hypertension]. / Effetti dell'infusione salina sull'attività della pompa Na,K eritrocitaria in soggetti normali e in pazienti con ipertensione essenziale.

The effects of a 2 litre isotonic saline infusion on erythrocyte Na,K pump activity and urinary sodium excretion (UNaV) were evaluated in 20 patients with essential hypertension and 15 normotensive subjects. The effect of preincubation of normal erythrocytes in plasma from hypertensive patients on erythrocyte Na,K pump was also studied. Before saline infusion no significant differences were found between normotensive and hypertensive subjects in the mean values of intracellular sodium and potassium concentration, ouabain-sensitive Na efflux in erythrocytes and urinary sodium excretion. Erythrocyte Na,K pump activity decreased significantly (p less than 0.01) after saline infusion in both groups of subjects. The reduction was significantly lower in hypertensives than in normotensive. delta UNaV was significantly higher in hypertensive patients than in normotensive subjects (25 +/- 4 vs 14 +/- 2 mmol/h; p = 0.04). Only in normal subjects a significant correlation was found between the difference in Na,K pump activity pre and post saline infusion and delta UNaV (r = 0.52; p less than 0.05). Plasma from hypertensive patients obtained before saline infusion significantly (p less than 0.01) inhibited Na,K pump of erythrocytes from normal subjects; plasma taken after saline infusion produced a marked increase of this inhibition, significantly (p less than 0.01) higher than serum taken before the infusion.

[Peritoneal complications of continuous ambulatory peritoneal dialysis]. / La complicanza peritonitica in dialisi peritoneale ambulatoriale continua (CAPD).

Aim of this work is an analysis of the clinical and microbiological aspects in 205 peritonitis episodes occurred in 156 patients admitted on peritoneal dialysis from January 1980 to December 1989. The evaluation of causative organisms shows a high prevalence of Gram+ organisms (60% of cases), while Gram- organisms are responsible for 16% of peritonitis episodes and fungi for 4%. No cultural growth was observed in 13% of the cases, while more than one organism occurred in 7%. Peritonitis incidence decreased from one episode every 3.9 patient months during 1980-81 to one every 33.6 patient months during 1988-89. This improvement is especially related to the employment of Y-set connection system and to the sterilization of connection lines by amuchina. From 1984 Y-set was used in each of the new patients admitted on CAPD. After its employment peritonitis incidence decreased from one episode every 6.2 patient months to one every 29 patient months. In our experience vancomycin i.v. proved to be effective and well tolerated. In no case a persistence of infectious disease was observed and no catheter was removed.