Reliability and accuracy of duplex ultrasound vein mapping for dialysis access.

BACKGROUND: Duplex ultrasound vein mapping (DUVM) may increase autogenous dialysis access procedures but has not been universally adopted by surgeons. METHODS: We determined reliability and accuracy of arm vein measurements on physical examination (PE) and DUVM, compared to direct measurements in the operating room (OR, gold standard). Operative plans were developed from each set of measurements and we evaluated which approach identified more options for autogenous procedures. RESULTS: Vein diameters measured on DUVM correlated well with OR measurements but those made on PE did not. Autogenous access options were identified in 34.8% of patients based on PE and in 96.6% based on their DUVM. The 6-month primary-patency was 86.4%; assisted primary-patency was 89.8%. CONCLUSIONS: Duplex ultrasound vein mapping is more reliable and accurate for assessing arm vein anatomy than physical examination. It identifies more autogenous options than physical-examination alone. It is essential for the preoperative evaluation for dialysis access.

Continuous Flow Perfused Cadaver Model for Endovascular Training, Research, and Development.

BACKGROUND: Endovascular simulation employing computer, animal, and static models are common and useful adjuncts for teaching endovascular procedures and developing novel, complex endovascular techniques. Unfortunately, these models lack realistic haptic feedback and thus do not faithfully replicate many of the technical challenges associated with clinical endovascular procedures (e.g., arterial calcification, rigidity, and stenosis). We sought to develop a realistic and reproducible perfused cadaver model for endovascular training, device development, and research. METHODS: Fresh frozen, elderly (age 50-80 years) male cadavers were thawed and prepared for open dissection. The entire arterial tree (ascending aorta to femoral arteries) was dissected free and major branch vessels exposed. Sheaths were placed to allow outflow from selected vessels. A Dacron conduit was sewn to the ascending aorta to generate arterial inflow, which was provided by a centrifugal pump. Aortic aneurysms were created in the descending thoracic and abdominal aorta. Digital subtraction arteriography and various endovascular interventions were performed, including stent grafts and EndoAnchors deployment. RESULTS: Continuous antegrade flow was achieved in the thoracic, abdominal, iliac, and femoral segments. Open and percutaneous access at the femoral region was obtained with realistic back-bleeding and tactile feedback. Adequate, fluoroscopically documented flow was observed in both cannulated major and noncannulated smaller branches. We performed angiography with standard techniques via a pigtail catheter and contrast injector throughout the arterial system. Abdominal and thoracic endografts were deployed with appropriate angiographic guidance and realistic haptic feedback for both guidewire and stent grafts. Additional applications, including selective cannulation, aorto-iliac occlusive disease interventions, and anchor placement, were also successfully simulated. Finally, the model was used as a platform to test investigational devices. CONCLUSIONS: Our pressurized cadaver flow model successfully replicated multiple aspects of advanced endovascular procedures with haptic feedback. This novel human cadaver model allows for training and device development under clinically realistic conditions.

Thoracic Endovascular Repair of Blunt Thoracic Aortic Injury in the Setting of an Aberrant Right Subclavian Artery.

Blunt thoracic aortic injury (BTAI) in a patient with an aberrant right subclavian artery (ARSA) presents unique challenges for patient management and aortic repair. Specific considerations include the need to treat coincidental ARSA, subclavian revascularization, and ARSA exclusion. Despite the rise of endovascular repair as the primary modality for aortic repair for BTAI, reports of this technique in the setting of ARSA are limited. Here we describe 3 patients with ARSA who underwent TEVAR for BTAI, and discuss critical management and technical issues in these patients.

The transient potassium outward current has different roles in modulating the pyloric and gastric mill rhythms in the stomatogastric ganglion.

The crustacean stomatogastric nervous system is a classic model for understanding the effects of modulating ionic currents and synapses at both the cell and network levels. The stomatogastric ganglion in this system contains two distinct central pattern generators: a slow gastric mill network that generates flexible rhythmic outputs (8-20 s) and is often silent, and a fast pyloric network that generates more consistent rhythmic outputs (0.5-2 s) and is always active in vitro. Different ionic conductances contribute to the properties of individual neurons and therefore to the overall dynamics of the pyloric and gastric mill networks. However, the contributions of ionic currents to different dynamics between the pyloric and gastric mill networks are not well understood. The goal of this study is to evaluate how changes in outward potassium current (I A) in the stomatogastric ganglion affect the dynamics of the pyloric and gastric mill rhythms by interfering with normal I A activity. We bath-applied the specific I A blocker 4-aminopyridine to reduce I A's effect in the stomatogastric ganglion in vitro and evaluated quantitatively the changes in both rhythms. We found that blocking I A in the stomatogastric ganglion alters the synchronization between pyloric neurons, and consistently activates the gastric mill rhythm in quiescent preparations.

A decade of pelvic vascular injuries during the Global War on Terror.

BACKGROUND: Pelvic vascular injuries (PVIs) rarely occur in isolation and are often associated with significant morbidity. The purpose of this study was to examine the incidence, trends, and early outcomes of PVIs sustained in combat. METHODS: The Department of Defense Trauma Registry was queried to identify all patients treated with PVIs during the first 10 years of Operation Enduring Freedom. Patient demographics, mechanism of injury, type of vascular injury, in-theater complications, and early clinical outcomes were examined. RESULTS: From 2003 to 2012, 143 patients (99% male) sustained a PVI in Afghanistan. During this period, there was a persistent increase in the percentage of patient visits (0.4% in 2003 to 2.0% in 2012). The mean Injury Severity Score (ISS) was 24. Sixty-six percent of patient injuries were secondary to explosions. Improvised explosive devices (IEDs) encountered by dismounted personnel accounted for 47% of all injuries and were associated with a significantly higher ISS (28) compared with all other mechanisms of injury (P < .01). There were 85 (43%) arterial and 112 (57%) venous PVIs. The most frequent arterial injury was the common iliac artery. Injury to the femoral vein was associated with a higher median transfusion requirement. One patient died in combat theater. Injuries from IEDs had higher rates of coagulopathy, acidosis, and hypothermia compared with other mechanisms of injury (P = .03). Forty-two patients (29%) sustained early infectious complications. Injuries from explosions were also associated with a significantly higher rate of infectious complications compared with other mechanisms of injury (P < .01). CONCLUSIONS: PVIs have occurred with increasing frequency during Operation Enduring Freedom. Despite a persistently low mortality, complication and infection rates remain high, particularly when injuries are secondary to explosions. IEDs are associated with higher ISS and complication rates. Future studies must continue to focus on the prevention and treatment of PVIs sustained in combat, particularly those caused by explosions.

Role of Ih in differentiating the dynamics of the gastric and pyloric neurons in the stomatogastric ganglion of the lobster, Homarus americanus.

The hyperpolarization-activated inward cationic current (Ih) is known to regulate the rhythmicity, excitability, and synaptic transmission in heart cells and many types of neurons across a variety of species, including some pyloric and gastric mill neurons in the stomatogastric ganglion (STG) in Cancer borealis and Panulirus interruptus However, little is known about the role of Ih in regulating the gastric mill dynamics and its contribution to the dynamical bifurcation of the gastric mill and pyloric networks. We investigated the role of Ih in the rhythmic activity and cellular excitability of both the gastric mill neurons (medial gastric, gastric mill) and pyloric neurons (pyloric dilator, lateral pyloric) in Homarus americanus Through testing the burst period between 5 and 50 mM CsCl, and elimination of postinhibitory rebound and voltage sag, we found that 30 mM CsCl can sufficiently block Ih in both the pyloric and gastric mill neurons. Our results show that Ih maintains the excitability of both the pyloric and gastric mill neurons. However, Ih regulates slow oscillations of the pyloric and gastric mill neurons differently. Specifically, blocking Ih diminishes the difference between the pyloric and gastric mill burst periods by increasing the pyloric burst period and decreasing the gastric mill burst period. Moreover, the phase-plane analysis shows that blocking Ih causes the trajectory of slow oscillations of the gastric mill neurons to change toward the pyloric sinusoidal-like trajectories. In addition to regulating the pyloric rhythm, we found that Ih is also essential for the gastric mill rhythms and differentially regulates these two dynamics.

De novo transcriptome assembly for the lobster Homarus americanus and characterization of differential gene expression across nervous system tissues.

BACKGROUND: The American lobster, Homarus americanus, is an important species as an economically valuable fishery, a key member in marine ecosystems, and a well-studied model for central pattern generation, the neural networks that control rhythmic motor patterns. Despite multi-faceted scientific interest in this species, currently our genetic resources for the lobster are limited. In this study, we de novo assemble a transcriptome for Homarus americanus using central nervous system (CNS), muscle, and hybrid neurosecretory tissues and compare gene expression across these tissue types. In particular, we focus our analysis on genes relevant to central pattern generation and the identity of the neurons in a neural network, which is defined by combinations of genes distinguishing the neuronal behavior and phenotype, including ion channels, neurotransmitters, neuromodulators, receptors, transcription factors, and other gene products. RESULTS: Using samples from the central nervous system (brain, abdominal ganglia), abdominal muscle, and heart (cardiac ganglia, pericardial organs, muscle), we used RNA-Seq to characterize gene expression patterns across tissues types. We also compared control tissues with those challenged with the neuropeptide proctolin in vivo. Our transcriptome generated 34,813 transcripts with known protein annotations. Of these, 5,000-10,000 of annotated transcripts were significantly differentially expressed (DE) across tissue types. We found 421 transcripts for ion channels and identified receptors and/or proteins for over 20 different neurotransmitters and neuromodulators. Results indicated tissue-specific expression of select neuromodulator (allostatin, myomodulin, octopamine, nitric oxide) and neurotransmitter (glutamate, acetylcholine) pathways. We also identify differential expression of ion channel families, including kainite family glutamate receptors, inward-rectifying K(+) (IRK) channels, and transient receptor potential (TRP) A family channels, across central pattern generating tissues. CONCLUSIONS: Our transcriptome-wide profiles of the rhythmic pattern generating abdominal and cardiac nervous systems in Homarus americanus reveal candidates for neuronal features that drive the production of motor output in these systems.

Designing and implementing nervous system simulations on LEGO robots.

We present a method to use the commercially available LEGO Mindstorms NXT robotics platform to test systems level neuroscience hypotheses. The first step of the method is to develop a nervous system simulation of specific reflexive behaviors of an appropriate model organism; here we use the American Lobster. Exteroceptive reflexes mediated by decussating (crossing) neural connections can explain an animal's taxis towards or away from a stimulus as described by Braitenberg and are particularly well suited for investigation using the NXT platform.(1) The nervous system simulation is programmed using LabVIEW software on the LEGO Mindstorms platform. Once the nervous system is tuned properly, behavioral experiments are run on the robot and on the animal under identical environmental conditions. By controlling the sensory milieu experienced by the specimens, differences in behavioral outputs can be observed. These differences may point to specific deficiencies in the nervous system model and serve to inform the iteration of the model for the particular behavior under study. This method allows for the experimental manipulation of electronic nervous systems and serves as a way to explore neuroscience hypotheses specifically regarding the neurophysiological basis of simple innate reflexive behaviors. The LEGO Mindstorms NXT kit provides an affordable and efficient platform on which to test preliminary biomimetic robot control schemes. The approach is also well suited for the high school classroom to serve as the foundation for a hands-on inquiry-based biorobotics curriculum.

A large outbreak of typhoid fever associated with a high rate of intestinal perforation in Kasese District, Uganda, 2008-2009.

BACKGROUND: Salmonella enterica serovar Typhi (Salmonella Typhi) causes an estimated 22 million typhoid fever cases and 216 000 deaths annually worldwide. In Africa, the lack of laboratory diagnostic capacity limits the ability to recognize endemic typhoid fever and to detect outbreaks. We report a large laboratory-confirmed outbreak of typhoid fever in Uganda with a high proportion of intestinal perforations (IPs). METHODS: A suspected case of typhoid fever was defined as fever and abdominal pain in a person with either vomiting, diarrhea, constipation, headache, weakness, arthralgia, poor response to antimalarial medications, or IP. From March 4, 2009 to April 17, 2009, specimens for blood and stool cultures and serology were collected from suspected cases. Antimicrobial susceptibility testing and pulsed-field gel electrophoresis (PFGE) were performed on Salmonella Typhi isolates. Surgical specimens from patients with IP were examined. A community survey was conducted to characterize the extent of the outbreak. RESULTS: From December 27, 2007 to July 30, 2009, 577 cases, 289 hospitalizations, 249 IPs, and 47 deaths from typhoid fever occurred; Salmonella Typhi was isolated from 27 (33%) of 81 patients. Isolates demonstrated multiple PFGE patterns and uniform susceptibility to ciprofloxacin. Surgical specimens from 30 patients were consistent with typhoid fever. Estimated typhoid fever incidence in the community survey was 8092 cases per 100 000 persons. CONCLUSIONS: This typhoid fever outbreak was detected because of an elevated number of IPs. Underreporting of milder illnesses and delayed and inadequate antimicrobial treatment contributed to the high perforation rate. Enhancing laboratory capacity for detection is critical to improving typhoid fever control.

Successful revascularization for delayed presentation of radiation-induced distal upper extremity ischemia.

Despite several reports of proximal arm ischemia due to radiation therapy, there are no reports of hand ischemia, presumably due to the rarity of radiation treatment of the distal upper extremity. We present a case of a 42-year-old male presenting with acute hand ischemia 36 years after being treated with forearm radiation for Ewing's sarcoma. Angiography demonstrated a patent brachial artery, occluded radial and ulnar arteries in the forearm, and a normal-caliber reconstituted radial artery at the anatomical snuffbox feeding a patent palmar arch. Transluminal balloon angioplasty was attempted initially without improvement. The patient was successfully revascularized with a reversed saphenous vein graft bypass from the distal brachial artery to the distal radial artery. At 22 months of follow-up, the graft remains patent with a palpable distal pulse. The patient continues to report acceptable function and range of motion.

Biomimetic approaches to the control of underwater walking machines.

We have developed a biomimetic robot based on the American lobster. The robot is designed to achieve the performance advantages of the animal model by adopting biomechanical features and neurobiological control principles. Three types of controllers are described. The first is a state machine based on the connectivity and dynamics of the lobster central pattern generator (CPG). The state machine controls myomorphic actuators based on shape memory alloys (SMAs) and responds to environmental perturbation through sensors that employ a labelled-line code. The controller supports a library of action patterns and exteroceptive reflexes to mediate tactile navigation, obstacle negotiation and adaptation to surge. We are extending this controller to neuronal network-based models. A second type of leg CPG is based on synaptic networks of electronic neurons and has been adapted to control the SMA actuated leg. A brain is being developed using layered reflexes based on discrete time map-based neurons.

Oscillations and oscillatory behavior in small neural circuits.

In order to determine the dynamical properties of central pattern generators (CPGs), we have examined the lobster stomatogastric ganglion using the tools of nonlinear dynamics. The lobster pyloric and gastric mill central pattern generators can be analyzed at both the cellular and network levels because they are small, i.e., contain only 25 neurons between them and each neuron and synapse are repeatedly identifiable from animal to animal. We discuss how the biophysical properties of each neuron and synapse in the two circuits act cooperatively to generate two different patterns of sequential activity, how these patterns are altered by neuromodulators and perturbed by noise and sensory inputs. Finally, we show how simplified Hindmarsh-Rose models can be made into analog electronic neurons that mimic the lobster neurons and in addition be incorporated into artificial CPGs with robotic applications.

Underwater walking.

Lobsters are generalist decapods that evolved in a broad variety of niches in the Northwestern Atlantic. Due to their inherent buoyancy they have acquired adaptations to reduced traction and surge. We have developed a biomimetic robot based on the lobster that features artificial muscle actuators and sensors employing labeled-line codes. The central controller for this robot is based on the command neuron, coordinating neuron central pattern generator model. A library of commands is released by sensor feedback to mediate adaptive sequences and goal achieving behavior. Rheotaxic behaviors can mediate adaptations to achieve some of the advantages of the biological models.