Vascular
Recent Submissions
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Hypothenar Hammer Syndrome Presenting as Critical Limb Ischemia in a 41-year-Old Caucasian Female; A Case Report.Traumatic injuries to the hand are commonly encountered in the adult population. Arterial occlusion from digital emboli due to thrombosis is a less frequently observed etiology. An example is hypothenar hammer syndrome, which usually arises following a mechanical injury. We report a case of hypothenar hammer syndrome in a 41-year-old Caucasian female following a blunt injury from exercise. She presented to our facility with complaints of intermittent severe pain in her left hand with discoloration of her fourth and fifth digits. Her symptoms began following an intense upper body strength exercise session and recurred intermittently over the following four to six weeks. MRI of the left hand showed no bony fractures or soft tissue injury. She was commenced on aspirin and Xarelto and subsequently had an arteriogram revealing thrombosis in the distal left ulnar artery. She ultimately had surgical resection of the thrombosed artery with repair using a venous graft which led to the resolution of her symptoms. Xarelto was discontinued after surgery, but she remains on Aspirin.
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Visual analogue self-assessment of acute mountain sickness in adolescents: experience from two Himalayan expeditions.Objective: Recent studies have investigated visual analogue scales (VAS) as an alternative to the Lake Louise AMS Self-Report Score (LLS) for the self-assessment of acute mountain sickness (AMS). We investigated their use in adolescents.
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Acetazolamide for the prophylaxis of acute mountain sickness.No abstract available. Comment on Identifying the lowest effective dose of acetazolamide for the prophylaxis of acute mountain sickness: systematic review and meta-analysis. Low EV, Avery AJ, Gupta V, Schedlbauer A, Grocott MP. BMJ. 2012 Oct 18;345:e6779. doi: 10.1136/bmj.e6779. PMID: 23081689
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Cerebral venous system and anatomical predisposition to high-altitude headache.Objective: As inspired oxygen availability falls with ascent to altitude, some individuals develop high-altitude headache (HAH). We postulated that HAH results when hypoxia-associated increases in cerebral blood flow occur in the context of restricted venous drainage, and is worsened when cerebral compliance is reduced. We explored this hypothesis in 3 studies.
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Has anyone seen my executive function recently?No abstract available
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Kite skier's toe: an unusual case of frostbite.Frostbite is a well-known occurrence in outdoor winter activity and exploration. We report the first documented case of frostbite associated with kite skiing. Kite skiing is an emerging sport that uses a kite to harness wind power for recreation and to travel long distances on skis. Certain characteristics of this sport may predispose athletes to frostbite injury. The stance required to resist and redirect the force created by the wind and kite puts constant pressure and repetitive trauma on the downwind great toe. This can compromise blood flow and increase risk of cold injury. Future kite skier expeditions should focus on specific prevention methods including properly fitting boots, adequate boot insulation, and frequent rest periods to inspect and warm toes.
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Surviving in a crevasse.No abstract available
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Exercise limitation of acetazolamide at altitude (3459 m).Objective: To assess the effect of acetazolamide (Az) on exercise performance during early acclimatization to altitude.
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High-intensity intermittent exercise increases pulmonary interstitial edema at altitude but not at simulated altitude.Objective: Ascent to high altitude leads to a reduction in ambient pressure and a subsequent fall in available oxygen. The resulting hypoxia can lead to elevated pulmonary artery (PA) pressure, capillary stress, and an increase in interstitial fluid. This fluid can be assessed on lung ultrasound (LUS) by the presence of B-lines. We undertook a chamber and field study to assess the impact of high-intensity exercise in hypoxia on the development of pulmonary interstitial edema in healthy lowlanders.
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Cerebral hemodynamics at altitude: effects of hyperventilation and acclimatization on cerebral blood flow and oxygenation.Objective: Alterations in cerebral blood flow (CBF) and cerebral oxygenation are implicated in altitude-associated diseases. We assessed the dynamic changes in CBF and peripheral and cerebral oxygenation engendered by ascent to altitude with partial acclimatization and hyperventilation using a combination of near-infrared spectroscopy, transcranial Doppler ultrasound, and diffuse correlation spectroscopy.
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Lessons from altitude: cerebral perfusion insights and their potential translational clinical significance.The long-held assumption that transcranial Doppler middle cerebral artery velocity is a surrogate for cerebral blood flow has been questioned in certain circumstances, particularly where tissue oxygenation changes. What advances does it highlight? Cerebral venous outflow restriction appears to be implicated in the development of high-altitude cerebral oedema. Rapid ascent to high altitude commonly results in acute mountain sickness and, on occasion, potentially fatal high-altitude cerebral oedema. The exact pathophysiological mechanisms behind these syndromes remain to be determined. One of the main theories to explain the development of acute mountain sickness is an increase in intracranial pressure. Vasogenic (extracellular water accumulation attributable to increased permeability of the blood-brain barrier) and cytotoxic (intracellular) oedema have also been postulated as potential mechanisms that underlie high-altitude cerebral oedema. Recently published findings derived from a very challenging field study (obtained at altitudes of up to 7950 m), substantiated by sea-level hypoxic magnetic resonance angiography studies, have given new insights into the maintenance of cerebral blood flow at altitude. This report provides new perspectives and potential mechanisms to account for the maintenance of cerebral oxygen delivery at high and extreme altitude. In particular, the long-held assumption that transcranial Doppler middle cerebral artery velocity is a surrogate for cerebral blood flow has been shown to be incorrect in certain circumstances. The emerging evidence for a potential third mechanism, namely the restrictive venous outflow hypothesis, in the development of high-altitude cerebral oedema, over and above the accepted vasogenic and cytotoxic hypotheses, is also appraised.
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High Altitude Pulmonary Edema Without Appropriate Action Progresses to Right Ventricular Strain: A Case Study.A 24-year-old male developed high altitude pulmonary edema (HAPE) after three ascents to 4061 m over 3 days, sleeping each night at 2735 m. He complained of exertional dyspnea, dry cough, chest pain, fever, nausea, vertigo, and a severe frontal headache. Inappropriate continuation of ascent despite symptoms led to functional impairment and forced a return to the valley, but dyspnea persisted in addition to new orthopnea. Hospital admission showed hypoxemia, resting tachycardia, and systemic hypertension. ECG revealed right ventricular strain and a chest X-ray revealed right lower zone infiltrates. This case demonstrates that HAPE can develop in previously unaffected individuals given certain precipitating factors, and that in the presence of HAPE, prolonged exposure to altitude with exercise (or exertion) does not confer acclimatization with protective adaptations and that rest and descent are the appropriate actions. The case additionally demonstrates well-characterized right ventricular involvement.
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Caudwell Xtreme Everest: A prospective study of the effects of environmental hypoxia on cognitive functioning.Background: The neuropsychological consequences of exposure to environmental hypobaric hypoxia (EHH) remain unclear. We thus investigated them in a large group of healthy volunteers who trekked to Mount Everest base camp (5,300 m).
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SMYD2 promoter DNA methylation is associated with abdominal aortic aneurysm (AAA) and expression in vascular smooth muscle cells.We assessed global methylation in peripheral blood mononuclear cell DNA from 92 individuals with AAA and 93 controls using enzyme-linked immunosorbent assays, identifying hyper-methylation in those with large AAA and a positive linear association with AAA diameter (P < 0.0001, R2 = 0.3175).We then determined CpG methylation status of regulatory regions in genes located at AAA risk loci identified in genome-wide association studies, using bisulphite next-generation sequencing (NGS) in vascular smooth muscle cells (VSMCs) taken from aortic tissues of 44 individuals (24 AAAs and 20 controls). In IL6R, 2 CpGs were hyper-methylated (P = 0.0145); in ERG, 13 CpGs were hyper-methylated (P = 0.0005); in SERPINB9, 6 CpGs were hypo-methylated (P = 0.0037) and 1 CpG was hyper-methylated (P = 0.0098); and in SMYD2, 4 CpGs were hypo-methylated (P = 0.0012).RT-qPCR was performed for each differentially methylated gene on mRNA from the same VSMCs and compared with methylation. This analysis revealed downregulation of SMYD2 and SERPINB9 in AAA, and a direct linear relationship between SMYD2 promoter methylation and SMYD2 expression (P = 0.038). Furthermore, downregulation of SMYD2 at the site of aneurysm in the aortic wall was further corroborated in 6 of the same samples used for methylation and gene expression analysis with immunohistochemistry.
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Point-of-care measurements reveal release of purines into venous blood of stroke patients.Stroke is a leading cause of death and disability. Here, we examine whether point-of-care measurement of the purines, adenosine, inosine and hypoxanthine, which are downstream metabolites of ATP, has potential to assist the diagnosis of stroke. In a prospective observational study, patients who were suspected of having had a stroke, within 4.5 h of symptom onset and still displaying focal neurological symptoms at admission, were recruited. Clinical research staff in the Emergency Departments of two hospitals used a prototype biosensor array, SMARTCap, to measure the purines in the venous blood of stroke patients and healthy controls. In controls, the baseline purines were 7.1 ± (SD) 4.2 μM (n = 52), while in stroke patients, they were 11.6 ± 8.9 μM (n = 76). Using the National Institutes for Stoke Scale (NIHSS) to band the severity of stroke, we found that minor, moderate and severe strokes all gave significant elevation of blood purines above the controls. The purine levels fall over 24 h. This was most marked for patients with haemorrhagic strokes (5.1 ± 3.6 μM, n = 9 after 24 h). The purine levels measured on admission show a significant correlation with the volume of affected brain tissue determined by medical imaging in patients who had not received thrombolysis or mechanical thrombectomy. ClinicalTrials.gov Identifier: NCT02308605.
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Metabolic rate and substrate utilisation resilience in men undertaking polar expeditionary travel.The energy expenditure and substrate utilisation were measured in 5 men pre- and post- a 67 day, 1750km unassisted Antarctic traverse from the Hercules Inlet to the Ross Sea Ice via the South pole pulling sledges weighing 120kg whilst experiencing temperatures as low as -57°C. A 36-hours protocol in a whole body calorimeter was employed to measure periods of rest, sleep and three periods of standardised stepping exercises at 80, 100 and 120 steps min-1; participants were fed isocalorically. Unlike previous expeditions where large weight loss was reported, only a modest loss of body weight (7%, P = 0.03) was found; fat tissue was reduced by 53% (P = 0.03) together with a small, but not statistically significant, increase in lean tissue weight (P = 0.18). This loss occurred despite a high-energy intake (6500 kcal/day) designed to match energy expenditure. An energy balance analysis suggested the loss in body weight could be due to the energy requirements of thermoregulation. Differences in energy expenditure [4.9 (0.1) vs 4.5 (0.1) kcal/min. P = 0.03], carbohydrate utilisation [450 (180) vs 569 (195) g/day; P = 0.03] and lipid utilisation [450 (61) vs 388 (127) g/day, P = 0.03] at low levels of exertion were different from pre-expedition values. Only carbohydrate utilisation remained statistically significant when normalised to body weight. The differences in energy expenditure and substrate utilisation between the pre- and post-expedition for other physiological states (sleeping, resting, higher levels of exercise, etc) were small and not statistically significant. Whilst inter-subject variability was large, there was a tendency for increased carbohydrate utilisation, post-expedition, when fasted that decreased upon feeding.
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Non-freezing cold injury.No abstract available
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Hypoxia is not the primary mechanism contributing to exercise-induced proteinuria.With placebo, post-exercise α1-AGP levels were similar at sea level and altitude. Odds ratio (OR) for increased resting α1-AGP at altitude versus sea level was greater without losartan (2.16 times greater). At altitude, OR for reduced post-exercise α1-AGP (58% lower) was higher with losartan than placebo (2.25 times greater, p=0.059) despite similar pulse oximetry (SpO2) (p=0.95) between groups. Acetazolamide reduced post-exercise proteinuria by approximately threefold (9.3±9.7 vs 3.6±6.0 μg/min; p=0.025) although changes were not correlated (r=-0.10) with significant improvements in SpO2 (69.1%±4.5% vs 75.8%±3.8%; p=0.001).
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Perioperative Quality Initiative (POQI) consensus statement on fundamental concepts in perioperative fluid management: fluid responsiveness and venous capacitance.Background: Optimal fluid therapy in the perioperative and critical care settings depends on understanding the underlying cardiovascular physiology and individualizing assessment of the dynamic patient state.
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Post-flight confusion: does flying affect the brain?This paper describes a condition termed post-flight confusion using anecdotal and clinical observations. It reviews research from the fields of aviation and altitude medicine and how this could apply to some physiological changes that happen during commercial flights. The collection of symptoms observed is similar to those of delirium. More research is needed to validate these observations, to identify the risks of flying for older people and to consider not only how to minimise these risks but whether this situation contributes to our knowledge about the aetiologies of delirium and dementias.