Low Flow States Research Articles

1702 Acute Esophageal Necrosis: A Rare Complication of Long-Standing Alcohol Abuse With Severe Hypoperfusion

INTRODUCTION: Acute Esophageal Necrosis, the “black esophagus”, is dark pigmentation of the esophagus with histologic mucosal necrosis that presents with symptoms of bleeding from the upper GI tract. AEN itself is not a poor prognostic factor. AEN in combination with multiple comorbidities raises mortality up to 32%. Risk factors include alcohol abuse, advanced age, male gender, advanced malignancies, hypertension, coronary artery disease, renal disease, and diabetes mellitus. CASE DESCRIPTION/METHODS: A 71 yr old male with medical history of CKD4, CAD, HTN, HLD, Barrett’s esophagus, ulcerative esophagitis, and alcohol use presented with hematemesis, abdominal pain, and melena that began three days prior. Patient was hypotensive and tachycardic with a hemoglobin of 4.8g/dL. Pt was administered multiple unity's of pRBCs, IV PPI, IV Octreotide, and IV fluid resuscitation. Due to hemodynamic compromise, a left IJ CVC was placed and vasopressors started. The GI team was consulted. Emergent EGD revealed circumferential esophagitis with ulcerations, adherent clots, and large areas of black mucosal discoloration. Broad spectrum antimicrobials initiated. A gastrograffin study was obtained without extravasation noted. Patient was diagnosed with pyelonephritis and transitioned to culture sensitive antimicrobial therapy; still requiring vasopressors and blood products due to multifactorial shock. Given severity of illness and grim prognosis, the patient’s family elected for comfort care. DISCUSSION: AEN is a rare condition with an etiology thought to be multifactorial-to a low flow state from watershed distribution and corrosive injury from gastric contents due to esophagogastroparesis and gastric outlet obstruction resulting in decreased function of mucosal barrier systems and impairment of repairing mechanisms. Visualization via EGD of circumferential black mucosal necrosis with an abrupt stop at the GE junction is diagnostic. If circumferential necrosis is seen, immediate withdrawal of the scope should be performed. In patients with patchy necrosis, the clinician may be able to continue with endoscopy. Treatment is supportive with IVFR, IV PPIs, blood transfusions, carafate, and most importantly treatment of the underlying disease state. Complications include esophageal perforation, mediastinal infections with abscesses, esophageal strictures, esophageal stenosis, and death. General Surgery should be consulted for possible intervention. After the patient exhibits improvement, repeat endoscopy should be performed.

3058 An Unusual Case of Ischemic Colitis

INTRODUCTION: 48-year-old obese (BMI: 40) female, G0P0A0 LMP 1 year ago, with hypertension and hypercholesterolemia who presented with sudden left lower abdominal cramping pain associated with bloody diarrhea of one day duration. Denied associated systemic symptoms. She was using aspirin, simvastatin, metoprolol and had a progestin-only intrauterine device (IUD) placed 2 years ago. Physical examination with tenderness at the left lower quadrant. Digital rectal examination unremarkable. Laboratories with leukocytosis, lactatemia and positive fecal leukocytes. Abdominopelvic CT with IV contrast revealed left-sided peri-colonic and colonic inflammatory changes. CASE DESCRIPTION/METHODS: Gastroenterology service consulted due to non-specific colitis and there was concern for ischemic colitis as CT revealed inflammation in a watershed area. Colonoscopy showed edematous mucosa from the splenic flexure to the sigmoid colon associated with multiple large longitudinal ulcers. Biopsies revealed mucosal hemorrhage and neutrophil infiltration, suggestive of ischemic injury. Etiology of ischemia not clear given no obvious risk factors. Cardiovascular, myeloproliferative and prothrombotic workups were negative. The last piece of the puzzle rested on the IUD which was removed by the OBGYN service. A few days later, a follow up CT showed marked inflammation improvement. DISCUSSION: Ischemic colitis is generally considered a disease of the elderly. The most common causes include low-flow states due to cardiac dysfunction and hypovolemia. However, in younger patients, hypercoagulable states and drugs are the most common etiologies. In our patient, it was hard to initially find a reasonable cause of ischemia but, after excluding all etiologies, patient's IUD was the most likely cause of bowel ischemia. Combination contraceptives are a well-known risk factor for venous thromboembolism (VTE). However, few data have been published regarding whether the risk of VTE increases with progestin-only contraceptives (1). Mechanism is unclear, although it is hypothesized that protein concentrations influenced by hormones affect coagulation homeostasis (2). This risk appears to increase if additional VTE risk factors are present such in our patient with an elevated BMI (3). This rare case proves the importance of acquiring a detailed medical history including the use of contraceptives. Moreover, awareness of this diagnosis is essential so that early recognition can lead to individualized treatment decision and better patient's outcome.

VAA ECMO: A Hybrid Cannulation Strategy in a Patient with Severe Peripheral Arterial Disease

Introduction Peripheral arterial disease (PAD) can restrict vascular access options for venoarterial extracorporeal membrane oxygenation (VA ECMO). In emergent situations, a comprehensive vascular assessment is impractical, and when severe PAD is encountered, cannulation approaches may be limited. We report a successful cannulation strategy in a patient with severe PAD using bilateral femoral arterial access. Case A 69-year-old White male with ischemic cardiomyopathy with baseline EF 20-25%, coronary bypass grafting (CABG), and peripheral arterial disease (PAD) was admitted to an outside hospital for an elective redo CABG. He had post-cardiotomy shock requiring inotropes and a balloon pump. In 48 hours, he progressed to refractory cardiogenic shock and multiorgan failure with oliguria, coagulopathy, and mild cognitive impairment. VA-ECMO was emergently initiated as a potential bridge to durable ventricular assist device, pending renal recovery.After cut down, heavy circumferential calcification of the left common femoral artery (CFA) was observed, with no palpable pulse. Seldinger technique with incremental dilation was performed. However, a standard 180 cm wire met resistance and could not be advanced beyond 20 cm. Hoping this was extensive plaque, rather than a complete occlusion, a 19-French arterial cannula was placed, with a 6-French antegrade perfusion cannula in the left superficial femoral artery (SFA). ECMO was initiated and only 1 L of flow at 4000 RPM was achieved, indicating the resistance encountered likely implied a complete or critical stenosis of the left iliac artery. A second 19-French arterial cannulation in the right CFA was performed with no resistance this time. The arterial cannulae were connected in a Y configuration and ECMO resumed with roughly 3.5 L at 4000 RPM. The right common femoral vein was accessed with a 21-French venous cannula.He was extubated in less than 48 hours and did well for about 5 days, with evidence of LV recovery on ramp studies. Unfortunately, he then developed hypoxic respiratory failure, hemoptysis, recurrence of multiorgan failure, and hemodynamic instability, suspicious for septic shock. At this point, his family elected to initiate comfort measures, particularly in light of worsening cognitive status. Summary Atherosclerotic vessels pose access difficulties and risk vascular complications. As such, severe PAD often limits patient selection for VA ECMO. To the best of our knowledge, this is the first reported case utilizing a bilateral femoral arterial approach to augment a low flow state in the setting of severe PAD. Various hybrid cannulation strategies may be considered with respect to individual anatomy and broaden the patient pool eligible for VA ECMO.

An Adrenaline Rush: Management of Pheochromocytoma in Advanced Heart Failure

Background Pheochromocytoma is a rare neuroendocrine adrenal tumor characterized by overproduction of catecholamines by chromaffin cells. Clinical manifestations include paroxysms of severe hypertension, palpitations, diaphoresis and headaches. Tumor excision is curative but carries an elevated risk, as removal can lead to sudden fluctuations in catecholamine levels, resulting in life threatening arrhythmias, hemodynamic instability and death. We present a case of perioperative management of a pheochromocytoma in a patient with severe ischemic cardiomyopathy. Case A 47 year old man with hypertension presented with progressive dyspnea on exertion. An echocardiogram revealed a newly depressed ejection fraction of 10-15%. Subsequent coronary angiography demonstrated severe multivessel disease deemed not amenable to percutaneous or surgical intervention. Evaluation of his hemodynamics revealed RA12 RV 59/12 PAP 60/33/44 PCWP 25 MVO2 54% CO/CI 3.2/1.69. Routine CT chest and abdomen demonstrated an incidental 6 cm adrenal mass confirmed to be a pheochromocytoma by metaiodobenzylguanidine scan and urine metanephrines. His perioperative care was managed through a multidisciplinary approach with Advanced Heart Failure, Endocrinology, Oncology, and Surgery. Prior to excision, the patient underwent a 14 day load of phenoxybenzamine. A subclavian intra-aortic balloon pump and Swan Ganz catheter were placed preoperatively for continuous hemodynamic monitoring and support. He subsequently underwent laparoscopic removal without complications. His intra-aortic balloon pump was removed two days postoperatively with slow weaning of inotropic and vasoactive support. Phenoxybenzamine was ultimately discontinued, and he was initiated on goal directed neurohormonal blockade. He was discharged with close outpatient follow up. Discussion This case demonstrates successful management of a pheochromocytoma in a patient with ischemic cardiomyopathy in a decompensated low flow state utilizing preoperative mechanical circulatory support. Successful adrenalectomy was supported by an intra-aortic balloon pump and pre-treatment with alpha-blockade. Pertinent challenges in such cases include timing of surgery and use of temporary support devices. Previous data has been inconclusive regarding timing of excision and perioperative use of percutaneous circulatory support due to risks of anticoagulation. Our case highlights the use of this strategy in select high risk patients.

Regional capnometry to evaluate the adequacy of tissue perfusion.

Tissue hypoperfusion is a major cause of morbidity and mortality in critically ill patients but cannot always be detected by measuring standard whole-body hemodynamic and oxygen-related parameters (e.g., blood pressure, cardiac output, and central venous oxygen saturation). Preclinical and clinical studies have demonstrated that low-flow states are consistently associated with large increases in venous and tissue PCO2. Monitoring regional PCO2 with gastric tonometry (PgCO2) is known to have independent prognostic value for predicting postoperative complications and mortality. The PgCO2 gap might also be of value as a treatment target (endpoint) in critically ill patients. However, this tool has several limitations and has not yet been developed commercially, thus restricting its use. Regional capnography with sublingual and transcutaneous sensors might be an alternative noninvasive option for evaluating the adequacy of tissue perfusion in critically ill patients. However, further studies are needed to determine whether or not this monitoring technique is of value-particularly as an endpoint for guiding resuscitation. Bladder PCO2, has only been evaluated in animal studies, and so remains to be validated in patients.

Real-time Monitoring of Cerebral Blood Flow and Cerebral Oxygenation During Rapid Ventricular Pacing in Neurovascular Surgery: A Pilot Study

Rapid ventricular pacing (RVP) can be used to produce short periods of flow arrest during dissection or rupture of a cerebral aneurysm but carries the risk of inducing cerebral ischemia. This study evaluates the intraoperative effect of RVP on local cerebral blood flow (CBF) and cerebral oxygenation during neurovascular surgery. Five patients undergoing elective cerebrovascular surgery were included in a single-center prospective study. RVP was applied in pacing periods of 40 seconds with 30% and 100% FiO2. Regional cerebral oxygenation was monitored using a Foresight near-infrared spectroscopy sensor. A Clark-type electrode and a thermal diffusion microprobe located in the white matter were used to monitor brain tissue pO2 and CBF, respectively. CBF response to RVP closely followed the blood pressure pattern and resulted in a low-flow state. Unlike CBF, brain tissue pO2 and regional cerebral oxygenation showed a delayed response to RVP, decreasing beyond the pacing period and slowly recovering after RVP cessation. We found a correlation between brain tissue pO2 and regional cerebral oxygenation. Increasing the inspired oxygen concentration had a positive impact on absolute regional cerebral oxygenation and brain tissue pO2 values, but the pattern resulting from applying RVP remained unaltered. RVP reduces CBF and cerebral oxygenation. Brain tissue pO2 and regional cerebral oxygenation are correlated but unlike CBF respond to RVP in a delayed manner. Further research is required to evaluate the impact of longer RVP bursts on brain oxygenation.

Effects of Vasopressin and Norepinephrine on Wound Healing of Vascular Smooth Muscle and Endothelium

ObjectivesHemorrhagic shock as a result of trauma or surgical bleeding is frequently temporized with administration of vasopressors in order to augment systemic vascular resistance while resuscitation measures are employed. This mimics the treatment strategy of other forms of shock where systemic vascular resistance is low and vasopressors are heavily relied upon to resuscitate the patient. Blood vessels respond to direct exposure to vasopressin and norepinephrine via receptors on smooth muscle and endothelial cells and ultimately result in vasoconstriction which contributes to a low flow state and increases shear stress within vessels. The effect of vasopressors on vascular cells with regard to direct cellular injury and repair has not been well‐studied. The objective of this study is to examine the in vitro effect of vasopressin and norepinephrine on the rate of healing of vascular cells after wounding.MethodsWounding and measurement of healing rate of cells were performed using Electric Cell‐substrate Impedance Sensing (ECIS) technology. A specified area of a monolayer of cells was wounded via high electrical charge, and healing of the cell layer was assessed via measurement of resistance (ohms) over time. Pig vascular smooth muscle cells (SMCs) and pig vascular endothelial cells (ECs) were seeded in 96‐well plates. Immediately after wounding, cells were treated with either lysine‐vasopressin (LVP; 0, 0.001, 0.01, 0.1, 1, 10, 100, 1000 ηM; n=6/group), or norepinephrine (NE; 0, 0.001, 0.01, 0.1, 1, 10, 100, 1000 μM; n=6/group). Data were recorded continuously for another 18 hours. Statistical comparisons were made using two‐way ANOVA and Tukey HSD post hoc analysis(alpha level = 0.05).ResultsWhen SMCs were injured, NE treatment significantly suppressed healing rate over the course of 10 hours (Time × Dose, F(133,665) = 1.955, p<0.0001), whereas LVP had minimal effect on healing of SMCs (F(133,665) = 0.6346, p=0.999). When ECs were injured, both NE (F(133,665) = 3.716, p<0.0001), and LVP (F(133,665) = 3.058, p<0.0001) significantly suppressed rate of healing.ConclusionsNE significantly suppressed the wound healing response of both SMCs and ECs, whereas LVP suppressed wound healing of ECs only. This strongly suggests that the use of different vasopressors during treatment and resuscitation can elicit unique effects on vascular healing in the body. We plan to further explore the physiological effects of vasopressors on post‐injury healing of blood vessels to aid in optimizing resuscitation strategies that reduce vascular injury and end organ damage in the period after recovery from trauma and shock.Support or Funding InformationThis project was funded by the U.S. Army Medical Command. The views expressed in this abstract are those of the authors and do not reflect the official policy or position of the Department of the Army, Department of Defense, or the U.S. Government.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Propofol-Associated Priapism in a Prepubescent Pediatric Patient.

Introduction. Propofol is a commonly used sedative medication for procedural sedation with a limited side effect profile. Although well tolerated with minimal adverse reactions, uncommon side effects have been reported. Methods. Case report of priapism in a 9-year-old male following the use of propofol for sedation in the pediatric intensive care unit (PICU) setting. The patient was admitted to the PICU for postoperative management following laryngotracheal reconstruction. On postoperative day 2, our patient was initiated on continuous infusion of propofol and he developed priapism. Propofol was then immediately discontinued, and the priapism quickly resolved without any medical or surgical interventions. Results. Priapism is a low-flow state and is considered a urological emergency requiring prompt recognition, withdrawal of suspected offending agents, and possible need for urologic consultation to alleviate complications. Although rare, priapism with propofol has been reported but never in a prepubescent male. The mechanism of propofol-associated priapism is not well understood, but it is thought that it may result from an autonomic system imbalance, leading to an increase in parasympathetic activity. In addition, propofol has been shown to affect nitric oxide–mediated smooth muscle relaxation. In our patient, we suspected propofol to be contributing factor to his priapism based on the temporal relationship between the initiation of the medication and symptoms and resolution of symptoms after propofol discontinuation. Discussion. Given the expansive use of propofol in pediatrics for sedation and anesthesia, pediatric clinicians should be cognizant of this rare adverse effect in pediatric patients with potentially disastrous complications.

Effects of Polyethylene Glycol-20k on Postresuscitation Myocardial and Cerebral Function in a Rat Model of Cardiopulmonary Resuscitation.

Polyethylene glycol-20k is a hybrid cell impermeant that reduces ischemia injury and improves microcirculatory flow during and following low flow states through nonenergy-dependent water transfer in the microcirculation. We investigated the effects of polyethylene glycol-20k on postresuscitation microcirculation, myocardial and cerebral function, and duration of survival in a rat model of cardiopulmonary resuscitation. Ventricular fibrillation was induced in 20 male Sprague Dawley rats and untreated for 6 minutes. Animals were randomized into two groups (n = 10 for each group): polyethylene glycol-20k and control. Polyethylene glycol-20k (10% solution in saline, 10% estimated blood volume) and vehicle (saline) were administered at the beginning of cardiopulmonary resuscitation by continuous IV infusion. Resuscitation was attempted after 8 minutes of cardiopulmonary resuscitation. University-Affiliated Research Laboratory. Sprague Dawley Rats. Polyethylene glycol-20k. Buccal microcirculation was measured at baseline, 1, 3, and 6 hours after return of spontaneous circulation using a side-stream dark-field imaging device. Myocardial function was measured by echocardiography at baseline and every hour postresuscitation for 6 hours. The animals were then returned to their cage and observed for an additional 72 hours. Neurologic Deficit Scores were recorded at 24, 48, and 72 hours after resuscitation. Postresuscitation ejection fraction, cardiac output, and myocardial performance index were significantly improved in animals treated with polyethylene glycol-20k (p < 0.05). Perfused buccal vessel density and microcirculatory flow index values were significantly higher at all time points in the polyethylene glycol-20k group compared with the control group. Postresuscitation cerebral function and survival rate were also significantly improved in animals that received polyethylene glycol-20k. Administration of polyethylene glycol-20k following cardiopulmonary resuscitation improves postresuscitation myocardial and cerebral function, buccal microcirculation, and survival in a rat model of cardiopulmonary resuscitation.

Abstract 280: Cerebral Blood Flow and Oxygenation During CPR in Swine

Introduction: Near-infrared spectroscopy (NIRS) has been used during cardiac arrest (CA) to non-invasively measure cerebral oxygenation. Studies have suggested that survival and neurological outcomes can be predicted using cerebral oxygenation, however, the physiology underlying cerebral oxygenation during CA is poorly understood. This exploratory study examined the behavior of cerebral blood flow and oxygenation in response to standard CPR (SCPR) and CPR with Active decompression and lift (ACD) and an impedance threshold device (ITD). Methods: Ventricular fibrillation was electrically induced in eight domestic swine. Following six minutes of untreated VF, SCPR (100 cpm at 20% anterior-posterior distance) was performed for six minutes. ACD+ITD was performed for an additional six minutes at the same rate and depth as SCPR, but with an additional 20% anterior-posterior distance of active lift. Cerebral blood flow was measured via microspheres and cerebral oxygenation was measured using NIRS. Animals were classified as responders if cerebral oxygenation increased within two minutes of initiating SCPR. Cerebral oxygenation did not change or declined during SCPR in non-responders. Results: Six out of eight animals were classified as responders. Cerebral blood flow and oxygenation increased with ACD+ITD compared to SCPR in responders but failed to increase for non-responders. Cerebral blood flow and oxygenation were lower during baseline (BL) in non-responders (Figure). Conclusions: ACD+ITD appears to improve cerebral blood flow and oxygenation. Changes in cerebral oxygenation during CA appear to be associated with measured changes in cerebral blood flow. NIRS may be clinically useful in estimating oxygenation and blood flow during low blood flow states and monitoring physiological responses to different interventions. Failure of improvement in NIRS during CPR may predict poor outcomes and/or the need for additional interventions guided by NIRS.

Bivalirudin and ECLS

Bivalirudin and ECLS

A Rare Case of Severe Ischemic Gastropathy Causing Upper GI Bleed

Ischemic gastropathy is an uncommon diagnosis due to the extensive arterial collaterals that supply the stomach. Hence, its diagnosis is infrequently entertained in patients presenting with upper GI bleed. A 76 year-old woman with hypertension, hyperlipidemia, and chronic kidney disease presented with acute onset shortness of breath. She was tachycardic, tachypneic, and hypotensive. On exam she had rales, expiratory wheezes, and abdominal distention. Labs showed elevated lactate of 3.27 mmol/L, metabolic acidosis, leukocytosis of 22 K/uL, and normal hemoglobin. She was managed for acute hypoxemic respiratory failure and sepsis secondary to pneumonia. Despite treatment of her sepsis, lactic acidosis persisted > 2mmol/L. An abdominal CT was obtained to evaluate distention showed pneumatosis intestinalis. IV metronidazole was started to treat gas forming organisms, with an immediate improvement in WBC from 24 to 8.6 K/uL. There were episodes of melena requiring a total of 9 units of PRBCs. EGD was done and showed extensive shallow ischemic ulcers involving most of the anterior gastric wall and denuded duodenal mucosa. Subsequent CT angiography of the abdomen showed severe atherosclerotic plaques causing focal high grade stenosis at the celiac axis and lesser stenosis of the superior mesenteric artery, and complete resolution of pneumatosis intestinalis. An IR guided stent was placed across the celiac with successful reperfusion confirmed by fluoroscopy. Serum lactate levels rapidly normalized and a repeat EGD three weeks later showed near complete resolution of the gastric ulcers.2679_A Figure 1. Pneumatosis intestinalis.2679_B Figure 2. Large ischemic gastric ulcers.2679_C Figure 3. Healing ischemic gastric ulcers s/p stent placement.Gastric ischemia may be secondary to systemic hypoperfusion in the setting of shock or local splanchnic vessel stenosis or thrombosis. Ischemia leads to gastric mucosal barrier dysfunction, accumulation of gastric acid, and subsequent ulceration. Our patient had episodes of global hypoperfusion as well as local atherosclerosis. She was also on intermittent hemodialysis, which has been shown to cause accelerated rates of atherosclerosis. Ischemic gastropathy is a rare cause of upper GI bleeding. Hence, it is important to consider in patients with persistent lactic acidosis and non-healing gastric ulcers despite proton pump inhibitors. While ischemia secondary to transient low flow states may be managed conservatively with bowel rest and broad spectrum antibiotics, definitive recanalization of the celiac trunk may be required when high grade stenosis is present.

Symmetrical Peripheral Gangrene Associated with Low Output Cardiac Failure

Introduction Symmetrical peripheral gangrene (SPG) is a rare clinical condition with acute, symmetrical ischemia of two or more extremities leading to gangrene in the absence of large vessel obstruction or vasculitis. We present a case of SPG presenting in the setting of severely depressed cardiac ejection fraction. Case Description Patient is a 64-year-old man referred to our emergency department from an outside hospital for management of liver failure and bilateral necrotic toes. His past medical history and surgical history were unremarkable. He drank 3-4 beers and 2-3 glasses of hard liquor daily. He had dry and gangrenous second through fifth toes and densely cyanotic first toes bilaterally. (Figure 1) Dorsalis pedis and posterior tibialis pulses were present bilaterally on palpation. His liver function test (LFT) was deranged (Total bilirubin: 35.0 mg/dL, direct bilirubin: >10.0 mg/dL, AST: 309 IU/L, ALT: 295 IU/L). Echo showed ejection fraction of 10 percent with global hypokinesis and severe left ventricular enlargement but no embolus. His brain natriuretic peptide was 18,984 pg/mL (reference range: Discussion Diagnosis should be suspected in patients with bluish discoloration of extremities and elevated lactate levels. Various infective and noninfective factors are responsible for development of SPG. Among them, cardiac conditions like myocardial infarction, myocardial infarction with coronary artery bypass graft and ventricular septal defect repair, ball-valve thrombus with mitral stenosis, paroxysmal ventricular tachycardia, ventricular pseudoaneurysm and severe heart failure have been associated with SPG. Conclusion SPG is associated with significant mortality and morbidity with an alarmingly high rate of amputation in survivors. Awareness of this condition and association with low flow state can help diagnose this condition early with prompt treatment for early recovery.

Effects of kinematic parameters on three-dimensional flapping wing at low Reynolds number

In nature, creatures such as birds, insects, and fish have excellent flight and mobility capabilities. The prominent flight performance of many creatures employing flapping wings has attracted researchers to study the aerodynamics of bionic flapping wings, which has potential application in designing micro air vehicles and autonomous underwater vehicles. Bionic movements usually have to adapt to the low Reynolds number environment. It is noteworthy that the flow field of a flapping wing at low Reynolds numbers flow state is closely related to the complex non-linear shedding and viscous phenomenon, especially in a three-dimensional (3D) flapping wing. In order to observe the influence of the viscous phenomenon on flapping wing propulsive performance at low Reynolds numbers, the flow field characteristics of the 3D flapping wing under different Reynolds numbers are discussed using the immersed boundary-lattice Boltzmann method with the Chinese supercomputer TianHe-II in this paper. The influence of kinematic parameters on the flow characteristics at low Reynolds number is particularly emphasized, considering that the biological movement involves many kinematic parameters, the unsteady flow field and vortex structure around the flapping wing are analyzed in detail. This study reports that the law of the flapping wing propulsive performance strongly depends on kinematic parameters that affect the vortex changes. The underlying flow mechanism behind flapping wing performance at low Reynolds numbers has been explored, which will make it possible to apply superior kinematic parameters to improve the propulsive performance of a flapping-like new airplane.

Radiological imaging of acute infectious and non-infectious enterocolitis

Computed tomography (CT) is often used as the initial diagnostic test in patients with inflammatory and infectious types of enterocolitis. The differential diagnosis is broad, including infectious, non-infectious and vascular causes, which have substantially different management strategies. Although a definitive diagnosis often relies on endoscopic biopsy results, stool culture results or other clinical features, radiologists often help to guide the diagnosis. This article reviews the CT appearance of different infectious and inflammatory forms of enterocolitis. General and specific intramural and extramural CT findings in the small bowel and colon are discussed. Added focus is placed on distribution patterns and medication side effects that can act as important diagnostic clues. Infectious enterocolitis is due to bowel inflammation caused by bacteria, viruses, or parasites, which show a preferential localization. Pancolitis can be seen with Clostridium difficile with the relatively specific CT finding of the "giraffe coat" sign. Inflammatory enterocolitis can be primary (inflammatory bowel disease, vasculitis) or secondary (radiation therapy, graft versus host disease etc.). Ischemic colitis and enteritis can result from arterial compromise, low flow states that globally reduce perfusion or venous insufficiency. The CT appearance varies depending on the cause, the time of onset and grade of reperfusion. Knowledge of characteristic mural and extramural CT of MRI findings, geographic distributions and therapy effects help to guide the differential diagnostics in inflammatory and infectious types of enterocolitis.

Mini-Review: Perfluorocarbons, Oxygen Transport, and Microcirculation in Low Flow States: In Vivo and In Vitro Studies: Erratum.

Mini-Review: Perfluorocarbons, Oxygen Transport, and Microcirculation in Low Flow States: In Vivo and In Vitro Studies: Erratum.

Unresponsive Patient with LVAD: A Case Series

Mechanical circulatory support (MCS) for patients with advanced heart failure (HF) is becoming more commonplace as technology has progressed and reliability of these systems has improved. We report our experience with three patients with cardiopulmonary arrest in the hospital and propose a protocol for the prompt assessment and treatment of an unresponsive patient with a LVAD in place. We presented three cases of unresponsive patients on LVAD support with low flow or no flow through the LVAD. Although all three of them were alive after resuscitation, none survived to discharge. In all three cases, there were no flaws in LVAD per se, with power source and controller appropriately attached, and the pump functioning normally. The low flow state was secondary to non-cardiac conditions (respiratory acidosis, dehydration, and stroke). In early 2017 we developed our algorithm for unresponsive LVAD patients. Utilization of LVAD flow, which can be obtained quickly and non-invasively at the bedside of a patient is used to direct resuscitation efforts in this proposed protocol. Rapid and standardized protocol for resuscitation of LVAD patients with in-hospital cardiopulmonary arrest is necessary to decrease morbidity and mortality. Further investigation regarding the best practice in this clinical scenario is evolving and further studies are needed.

L’ischémie mésentérique à l’ère des structures d’urgences vasculaires intestinales

Mesenteric ischemia is a gut and life-threatening, medical and surgical, digestive and vascular emergency. Mesenteric ischemia is the result of an arterial or venous occlusion, a vasospasm secondary to low-flow states in intensive care patients, aortic clamping during vascular surgery or intestinal transplantation. Progression towards mesenteric infarction and its complications is unpredictable and correlates with high rates of mortality or a high risk of short bowel syndrome in case of survival. Thus, mesenteric ischemia should be diagnosed and treated at an early stage, when gut injury is still reversible. Diagnostic workup lacks sensitive and specific clinical and biological marker. Consequently, diagnosis and effective therapy can be achieved by a high clinical suspicion and a specific multimodal management: the gut and lifesaving strategy. Based on the model of ischemic stroke centers, the need for a multidisciplinary and expert 24/24 emergency care has led, in 2016, to the inauguration of the first Intestinal Stroke Center (Structure d’urgences vasculaires intestinales [SURVI]) in France. This review highlights the pathophysiological features of chronic and acute mesenteric ischemia, as well as the diagnosis workup and the therapeutic management developed in this Intestinal Stroke Center.

Challenges in Aortic Valve Stenosis: Low-Flow States Diagnosis, Management, and a Review of the Current Literature.

We will describe and define the current diagnosis, management, and potential therapy for low-flow aortic stenosis (AS) states, as well as summarize the available evidence underlying these recommendations. Low-flow aortic stenosis syndromes have worse prognoses than traditionally defined normal flow severe aortic stenosis. In this setting, aortic valve replacement is the only therapy that improves outcomes. Transcatheter aortic valve replacement has an ever-expanding role in the treatment of aortic stenosis, and there is growing evidence that TAVR may be a preferred therapy for low-flow AS states. Aortic stenosis remains one of the most common valvular diseases requiring therapy. Low-flow AS represents up to 40% of all patients with AS and is associated with significant mortality. This condition requires further testing for appropriate diagnosis and treatment. Low-flow AS states have poor prognoses, thus AVR and especially TAVR have a growing role in treatment of this challenging subset of AS patients.

Candidiasis in a Patient With Black Esophagus: Cause or Incidental Finding?

Introduction Diagnosed with upper endoscopy with a striking appearance, black esophagus or acute esophageal necrosis (AEN) is a rare diagnosis with only about one hundred cases described in the literature; incidence is 0.01-0.28%[i]. Etiology is unclear and typically associated with low blood flow states, DKA, and sepsis; treatment is primarily supportive, and prognosis is poor due to the advanced age and comorbid conditions in patients that develop AEN[ii]. We describe a case of black esophagus in a patient presenting with melena who was found to have concomitant candidiasis.Figure: Image taken during endoscopy. Upper one third of esophagus.Figure: Image taken during endoscopy. Middle one third of esophagus with necrotic-appearing black tissue.Figure: Image taken during endoscopy. Lower one third of esophagus with necrotic-appearing black.Case A 79 year old female with PMH of hypertension, congestive heart failure, metastatic cancer complicated by malignant ascites with an unknown primary presented to the ED with nausea, vomiting, odynophagia and melena..On admission, her vitals were stable, but physical exam was remarkable for dry mucous membranes, abdominal distention with shifting dullness and black stool on rectal exam. Before endoscopy patient was started on proton pump inhibitor and IV fluids. Upper endoscopy revealed black discoloration of the mid to distal esophagus and diffuse severe inflammation characterized by congestion, erythema, friability and superficial ulcerations. Subsequent pathology findings revealed fibrinopurulent exudate and yeasts consistent with necrosis and candida respectively. Three days later, the patient worsened due to untreated malignancy and decision was made for palliative care after which she expired during the hospitalization. Discussion Although postulated to be a result of an “ischemic insult”, exact mechanism of AEN is unknown. Current case of a female patient is a unique presentation of this rare entity. Esophageal candidiasis associated with AEN is reported in only 4 cases in the literature thus far. Whether, this is an association or causative factor remains to be determined. Thus, increasing awareness of AEN can lead to early recognition and prompt treatment, decreasing the incidence of esophageal complications and mortality.