Decade-long monitoring of seismic velocity changes at the Irpinia fault system (southern Italy) reveals pore pressure pulsations.

Several studies have monitored crustal seismic velocity changes and attempted to relate them to the stress state and physical properties in volume embedding fault systems. The aim is to provide constraints on fault system dynamics and earthquake triggering mechanisms. Here, we reconstruct the spatiotemporal (4D) seismic velocity images of volume embedding the Irpinia fault system (IFS, South Italy), which originated the 1980 Ms 6.9 multi-segmented ruptures. By inverting data from more than ten years of continuous seismicity monitoring, we retrieved time-constant velocity anomalies, whose shapes correlate well with crustal lithology, while time-changing (up to 20%) velocity anomalies are mapped in the central region. Here, the Vp-to-Vs changes at depths of 1-5 km and 8-12 km correlate well with groundwater recharge and geodetic displacement during the same time interval. This correlation provides evidence for the existence of pulsating, pore pressure changes induced by groundwater recharge processes in a deep volume (8-12 km of depth), fractured and saturated with a predominant gas phase (likely CO2). We suggest that tomographic measurements of the Vp-to-Vs spatiotemporal changes are a suitable proxy to track the pore pressure evolution at depth in highly sensitive regions of fault systems.

A rapid response magnitude scale for timely assessment of the high frequency seismic radiation.

In this work the scaling of seismic moment (M0) and radiated energy (Er) is investigated for almost 800 earthquakes of the 2016-17 Amatrice-Norcia sequences in Italy, ranging in moment magnitude (Mw) from 2.5 to 6.5. The analysis of the M0-to-Er scaling highlights a breaking of the source self-similarity, with higher stress drops for larger events. Our results show the limitation of using M0, and in turn Mw, to capture the variability of the high frequency ground motion. Since the observed seismicity does not agree with the assumptions on stress drop in the definition of Mw, we exploit the availability of both Er and M0 to modify the definition of Mw and introduce a rapid response magnitude (Mr), which accounts for the dynamic properties of rupture. The new Mr scale allows us to improve the prediction of the earthquake shaking potential, as shown by the reduction of the between-event residuals computed for the peak ground velocity. The procedure we propose is therefore a significant step towards a quick assessment of earthquakes damage potential and timely implementation of emergency plans.

Temporal evolution of a seismic sequence induced by a gas injection in the Eastern coast of Spain.

Induced seismicity associated with energy production is becoming an increasingly important issue worldwide for the hazard it poses to the exposed population and structures. We analyze one of the rare cases of induced seismicity associated with the underwater gas storage operations observed in the Castor platform, located in the Valencia gulf, east Spain, near a complex and important geological structure. In September 2013, some gas injection operations started at Castor, producing a series of seismic events around the reservoir area. The larger magnitude events (up to 4.2) took place some days after the end of the injection, with EMS intensities in coastal towns up to degree III. In this work, the seismic sequence is analyzed with the aim of detecting changes in statistical parameters describing the earthquake occurrence before and after the injection and identifying possible proxies to be used for monitoring the sequence evolution. Moreover, we explore the potential predictability of these statistical parameters which can be used to control the field operations in injection/storage fluid reservoirs. We firstly perform a retrospective approach and next a perspective analysis. We use different techniques for estimating the value of the expected maximum magnitude that can occur due to antropogenic activities in Castor.

Hydrological simulation of Po River (North Italy) discharge under climate change scenarios using the RCM COSMO-CLM.

The impacts of climate change on Po River discharges are investigated through a set of climate, hydrological, water-balance simulations continuous in space and time. Precipitation and 2m mean temperature fields from climate projections under two different representative concentration pathways, RCP4.5 and RCP8.5, have been used to drive the hydrological model. Climate projections are obtained nesting the regional climate model COSMO-CLM into the global climate model CMCC-CM. The bias in climate projections is corrected applying the distribution derived quantile mapping. The persistence of climate signal in precipitation and temperature after the bias correction is assessed in terms of climate anomaly for 2041-2070 and 2071-2100 periods versus 1982-2011. To account for the overall uncertainty of emission scenarios, climate models and bias correction, the hydrological/water balance simulations are carried out using both raw and bias corrected climate datasets. Results show that under both RCPs, either considering raw and bias corrected climate datasets, temperature is expected to increase on the whole Po River basin and in all the seasons; the most significant changes in precipitation and discharges occur in summer, when the reduction of precipitation leads to an increase in low flow duration and occurrence likelihood, and in autumn and winter where precipitation shows a positive variation increasing the high flows frequency.

Evidence for a difference in rupture initiation between small and large earthquakes.

The process of earthquake rupture nucleation and propagation has been investigated through laboratory experiments and theoretical modelling, but a limited number of observations exist at the scale of earthquake fault zones. Distinct models have been proposed, and whether the magnitude can be predicted while the rupture is ongoing represents an unsolved question. Here we show that the evolution of P-wave peak displacement with time is informative regarding the early stage of the rupture process and can be used as a proxy for the final size of the rupture. For the analysed earthquake set, we found a rapid initial increase of the peak displacement for small events and a slower growth for large earthquakes. Our results indicate that earthquakes occurring in a region with a large critical slip distance have a greater likelihood of growing into a large rupture than those originating in a region with a smaller slip-weakening distance.

Anatomy of a microearthquake sequence on an active normal fault.

The analysis of similar earthquakes, such as events in a seismic sequence, is an effective tool with which to monitor and study source processes and to understand the mechanical and dynamic states of active fault systems. We are observing seismicity that is primarily concentrated in very limited regions along the 1980 Irpinia earthquake fault zone in Southern Italy, which is a complex system characterised by extensional stress regime. These zones of weakness produce repeated earthquakes and swarm-like microearthquake sequences, which are concentrated in a few specific zones of the fault system. In this study, we focused on a sequence that occurred along the main fault segment of the 1980 Irpinia earthquake to understand its characteristics and its relation to the loading-unloading mechanisms of the fault system.

Ulno-basilic arteriovenous fistulae: indications and surgical technique.

Ulnar-basilic fistula is a vascular access option for hemodialysis first reported in 1967. There is no inherent reason why the ulnar artery cannot be used to create a fistula at the wrist; however, a few reports dealing with its complications and survival rates have been published in the literature. In the present work the results of 9 ulnar-basilic fistulae done in 9 adults patients on chronic hemodialysis, are reported. Two fistulae were created as primary access and the remaining 7 fistulae as secondary access after thrombosis of an ipsilateral and controlateral radiocephalic fistula in 6 cases and in a case of high-flux brachiocephalic fistula. No episodes of surgical complications were observed. This fistula is an additional option to create a distal vascular access for hemodialysis before constructing a proximal access.

Seismic evidence of an extended magmatic sill under Mt. Vesuvius.

Mt. Vesuvius is a small volcano associated with an elevated risk. Seismic data were used to better define its magmatic system. We found evidence of an extended (at least 400 square kilometers) low-velocity layer at about 8-kilometer depth. The inferred S-wave (approximately 0.6 to 1.0 kilometer per second) and P-wave velocities (approximately 2.0 kilometer per second) as well as other evidence indicate an extended sill with magma interspersed in a solid matrix.

Properties of multidrug-resistant, ESBL-producing Proteus mirabilis isolates and possible role of beta-lactam/beta-lactamase inhibitor combinations.

At our institution, isolation rates of clinical strains of ESBL-producing Proteus mirabilis increased to 8.8% of all P. mirabilis isolates during the period 1997-1999. To evaluate the susceptibility of ESBL-producing P. mirabilis strains against commonly used drugs, we studied 50 non-duplicated isolates selected on the basis of synergy between clavulanate and beta-lactams (ceftazidime, aztreonam, cefotaxime, and ceftriaxone). The presence of ESBL-coding genes was confirmed by colony hybridization with bla(TEM-1) and bla(SHV-1) probes. Minimum inhibitory concentrations of several antimicrobial agents for each isolate were obtained using the Etest method. All strains were encoding for TEM-derived enzymes. Gene sequencing showed that at least three different genes (TEM-15, TEM-20, and TEM-52) were present. These enzymes have not been previously reported in P. mirabilis. Isolates were characterized by: (a) reduced susceptibility or resistance to third- and fourth-generation cephalosporins (MIC > or = 2 mg/l), (b) resistance to piperacillin that was abolished by tazobactam (MIC > or = 256 vs. < or = 2 mg/l, respectively), (c) multiple antibiotic resistance that included gentamicin, fluoroquinolones and co-trimoxazole. Therapeutic failure and lack of eradication of ESBL-positive P. mirabilis by third-generation cephalosporins has been repeatedly observed both at our Institution and elsewhere. Piperacillin-tazobactam, as well as amikacin and meropenem appear to be important therapeutic options for infections due to multidrug-resistant, ESBL-producing P. mirabilis isolates.

Ultrasound-guided cannulation and endocavitary electrocardiography placement of internal jugular vein catheters in uremic patients: the importance of routine chest X-ray evaluation.

The NKF-DOQI guidelines recommend performing chest-X-ray(CXR) after subclavian and internal jugular vein insertion prior to catheter use. This is to exclude complications such as a pneumothorax before starting hemodialysis. Indication of a central venous dialysis catheter was based on the historic use of the subclavian vein for placement of these catheters and upon the reported incidence of pneumothorax after this approach of between 1% to 12.4%. In contrast, the incidence of these complications using the internal jugular vein (IJV) is much lower (< 1%). We report our experience in ultrasound-guided cannulation of the right IJV for dialysis vascular access in 527 uremic patients and central catheter placement by endocavitary electrocardiography (EC-ECG). Fluoroscopy was not utilized. In the first hundred cases, all patients underwent CXR. Subsequently, because of total absence of complications and catheter tip malpositioning, the CXR control was carried out only in selected cases (repeated cannulation of the jugular vein or absence of P wave). We believe that only in selected cases should a pCXR be performed before starting hemodialysis sessions, and that our method using the right IJV, ultrasound-guided puncture of the vessel, and catheter placement by EC-ECG is a safe and simple technique that avoids the need for CXR control.

Central venous catheter placement in hemodialysis: evaluation of electrocardiography using a guide-wire.

Internal jugular vein cannulation has become a routine and clinically important aspect of medical care in hemodialysis patients. Mismanagement in the location of a central venous catheter may occur in up to 20% of cases. The aim of the study was to evaluate the utility of endocavitary electrocardiography in right internal jugu-lar vein placement of central venous catheters. We examined 327 central venous catheterizations performed in two Dialysis Units; all catheters were positioned using intra-atrial ECG monitoring by guide-wire and after, by catheter filled with NaCl solution. EC-ECG via guide-wire was successful on 321 occasions (98.1%). Correct placement of the catheter was confirmed by EC-ECG via catheter in each case, and by plain chest-X-ray only in the first hundred cases. In 314 patients (98.1%), insertion of the catheter was successful at the first attempt. In 6 catheterizations, no atrial trace was obtained due to atrial fibrillation in 4 cases, and in 2 cases technical error and guide-wire looping into a right jugular vein. Complications as a direct result of guide-wire or catheter placement were not observed. In our opinion this method can be used safely and makes radiological control usually unnecessary. (The Journal of Vascular Access 2001; 2: 45-50).

Experience using a new vascular port access device for hemodialysis: preliminary clinical results.

A new subcutaneous device (Dialock(R), Biolink Corp, Middleboro, MA) provides vascular access to patients who require hemodialysis. The device consists of a port implanted in a subcutaneous pocket in the thoracic area 10 cm below the clavicle. Interdialytic patency is maintained using a priming antithrombotic solution. The device was implanted in 10 outpatients under local anesthesia, and immediately used for he-modialysis. The catheters have been used up to now for a total of 1,480 days ( 24- 248 days), the average being 4.8 months (1-8 months). Survival rate of Dialock (R)was 100% at 8 months. During this period, the device achieved prescription hemodialysis blood flow rates averaging 250-300 ml/min with a venous pressure of 180 +/- 25 mmHg. Malpositioning of the catheters due to their excessive length was observed in the first three patients and led to the repositioning of the catheters' distal tips under local anesthesia. Secondary and delayed hematoma surrounding the Dialock(R)device were observed in 2 patients one or two days after insertion. In one case, a hematoma was surgically removed under local anesthesia. Antibiotic therapy was administered for safety and prophylactic reasons. In one patient spontaneous catheter fracture and distal tip embolization occurred on the 49th day after repositioning. Percutaneous radiological retrieval of the catheter fragment was performed. No infection of the Dialock (R)device occurred and only one episode of bacteremia was observed. Blood cultures were positive for Staphylococcus epidermidis . Infection was cured by appropriate systemic antibiotic therapy combined with gentamicin and sodium citrate lock. The device was well accepted by patients and staff. The Dialock (R)device catheter offers a new vascular alternative for dialysis that deserves further long-term study. In particular, the confidence of structural materials should be tested.

Ultrasound-guided cannulation of the femoral vein for acute hemodialysis access with silicone catheters.

The percutaneous femoral approach for temporary central venous hemodialysis access is a mandatory part of patient management in many clinical settings. It is usually achieved with a blind, exter-nal landmark-guided technique. The aim of this study is to evaluate whether an ultrasound technique can improve on the external landmark method. From 1990 to January 2000, cannulation of the femoral vein was performed on 230 patients (125 male, 105 female, mean age 72 years, range 52-95 years) for temporary vascular access for hemodialysis (172 patients with acute renal failure and 58 patients in end-stage renal disease), using landmark localization with semi-rigid, uncuffed catheters. Between January 2000 and February 2001, ultrasound-guided can-nulation of the femoral vein was utilized in 38 patients (20 male, 13 female, mean age 71 , range 55-93 years) for temporary vascular access for hemodialysis (28 patients with acute renal failure and 10 patients in end-stage- renal failure). Uncuffed, dual-lumen silicone catheters were used. Cannulation of the femoral vein was achieved in 100% of cases using ultrasound, and in 87% using the landmark-guided technique. Using ultrasound, puncture of the femoral artery occurred in 2.6% of patients, and hematoma in 0%. Using the 'blind' technique, puncture of the femoral artery occurred in 11.2% of patients, and hematoma in 3.9%. The average catheter dwell time, in accordance with NKF-DOQI guidelines, was 5 days (range 2 - 14 days) for semi-rigid catheters and 45 days (range 5-120 days) for silastic catheters. The number of complications rose significantly in the patients with semi-rigid catheters. In this group, local exit infection occurred in 105 persons (45% of cases), total catheter thrombosis in 46 (20%), bacteriemia in 28 (12%), and phlebitis of the leg in 6 (2.6%). In the group with silicone catheters local exit infection occurred in 4 patients (10 % of cas-es), total catheter thrombosis in 1 (2.6%), bacteriemia in 2 (5.2%) and phlebitis in 0 (0%). The result of the study suggests that ultrasound-guided cannulation of the femoral vein is superior to traditional techniques relying on anatomic landmark; it reduces the numbers of unsuccessful attempts and the possible acute complications of the procedure. We believe that femoral cannulation with modern flexible silicone catheters can be considered as a reliable temporary access, even for extended periods.

Real-time ultrasound and endocavitary electrocardiography for venous catheter placement.

The authors report on their experience with internal jugular vein catheterization with temporary and tunnelled cuffed hemodialysis catheters in 527 patients from 1991 to 2001, using ultrasound guidance and monitoring of catheter placement by endocavitary electrocardiography. The incidence of successful puncture and cannulation using ultrasound was 99.62%. The majority of patients had catheters inserted on the first pass (93%) and fewer attempts were required (range, 2 to 5). In the first year of the procedure in 1991, we observed two cases of accidental puncture of the carotid artery because of an error in ultrasound localization of the neck vessel. Arrhythmias were not observed during this procedure. Right atrial electrocardiography was successful on 504 occasions (96.83%), and correct catheter placement was confirmed by plain chest-X-ray in the first 100 patients. The results confirm that real-time ultrasound guidance for catheter insertion is superior to tradi-tional techniques relying on anatomic landmarks and should be adopted as the standard of care. Ultrasound guidance and EC-ECG improves both the success and the safety of internal jugular catheter insertion. The authors propose that EC-ECG be validated as a technique in compliance with recent Food and Drug Ad-ministration guidelines regarding the location of central venous catheter tips.

Anatomical variations of the internal jugular vein in non-uremic outpatients.

The internal jugular vein (IJV) should be the preferred form of venous vascular access for the placement of dialysis catheters. 'Blind' puncture or 'skin mark' ultrasound technique puncture present multiple complications due to the significant variations in IJV location in normal subjects and even more so in uremic pa-tients. The aim of this study is to demonstrate the important rate of IJV site variations in a random healthy pop-ulation. We tested 450 subjects (244 male, 206 female) in our hospital Ultrasound Ambulatory using an Ansaldo AUS ul-trasound device with linear 10 MHz probe on both sides at the Sedillot triangle level and noticed the relations between IJV and carotid artery course. The most frequent location of IJV was the anterior lateral (79.3% on the right side, 83.5% on the left). The re-maining options were lateral, anterior, posterior-lateral, anterior-medial. We found no significant difference in IJV diameter on either side of the neck. We therefore consider IJV puncture with ultrasound guidance to be the first choice in central venous cannulation for hemodialysis treatment. This procedure helps avoid incorrect puncture of the carotid artery related to its abnormal location.

Implantation of permanent jugular catheters in patients on regular dialysis treatment: ten years' experience.

Dual-lumen cuffed central venous catheter proved an important alternative vascular access compared to conventional arteriovenous (Cimino-Brescia) shunt in a selected group of patients on regular dialysis treatment. Typically, these catheters are used as bridging access, until fistula or graft is ready for use, or as permanent access when an arteriovenous fistula or graft is not planned (NKF-DOQI). We conducted a prospective study on IJV permanent catheter insertion and its related earlier and long-term complications. From February 1991 to February 2001 we inserted in 124 patients in end stage renal disease 135 cuffed catheters (130 in the right IJV and 5 in the left IJV), 92 of which were Permcath, 27 Vascath, and 16 Ash-Split. We performed the insertion of catheters by puncturing the IJV under ultrasonographic guid-ance in the lower side of the Sedillot triangle and checking the accurate position of the tip by endocavitary electrocardiography (EC-ECG). The duration of catheter use was from 60 to 1460 days, mean 345 days. The actuarial survival rate at 1 year was 82%, at 2 years 56%, at 3 years 42% and at 4 years 20%. The exit site infection and septicemia rates were 5.2 and 2.86 per 1000 catheter days respectively. Catheter sepsis was implicated in the death of three patients, all of whom had multiple medical problems. Several episodes of thrombosis (6% of dialyses) occurred which required urokinase treatment, and catheter replacement in 12 patients (9.6%). In 3 cases the catheters were displaced and correct repositioning was performed. Two catheters (Ash-Split) were replaced due to accidental damage of the external portion of catheters (alcoholic disinfectant). Catheter tip embolism occurred on one occasion during elective catheter exchange over guide-wire. One of the common problems encountered with cuffed tunneled catheters is poor blood flow, most often secondary to the formation of a fibrin sheath around the lumen. Even if we conducted a non-randomized study, in our experience, the higher rate of malfunctioning catheters was in the group with no anticoagulation therapy. Therefore, we suggest anticoagulation treatment in all patients wearing central vascular catheters with no contraindication. Just one year ago, we followed NKF-DOQI clinical practice guidelines for vascular access that indicated that for patients who have a primary AV fistula maturing, but need im-mediate hemodialysis, tunneled cuffed catheters are the access of choice and the preferred insertion site is the right IJV. Considering recent reports of permanent central venous stenosis or occlusion after IJV can-nulation, currently, our first choice is femoral vein cannulation with smooth silicone rubber catheters, tunneled if long-term utilization is needed (more the 3-4 weeks). In our opinion, the right IJV puncture is to be avoided as much as the venipuncture of arm veins suitable for vascular access placement, particularly the cephalic vein of the non-dominant arm. Our data confirm that permanent venous catheters might rep-resent an effective long-term vascular access for chronic hemodialysis, particularly for older patients with cardiovascular disease and for cancer patients.