Pre-operative Functional Cardiovascular Reserve Is Associated with Acute Kidney Injury after Intervention.

BACKGROUND: Acute kidney injury (AKI) is a common complication after endovascular intervention, associated with poor short and long-term outcomes. However, the mechanisms underlying AKI development remain poorly understood. The impact of pre-existing cardiovascular disease and low cardiovascular reserve (CVR) in AKI is unclear; it remains unknown whether AKI is primarily related to pre-existing comorbidity or to procedural parameters. The association between CVR and AKI after EVAR was therefore assessed. METHODS: This is a case control study. From a database of 484 patients, 292 undergoing elective endovascular aneurysm repair (EVAR) of an infrarenal abdominal aortic aneurysm (AAA) in two tertiary centres were included. Of these, 73 patients who had developed AKI after EVAR were case matched, based on pre-operative estimated glomerular filtration rate (eGFR; within 5 mL/min/1.73 m2) and age, with patients who had not developed AKI. Cardiopulmonary exercise testing (CPET) was used to assess CVR using the anaerobic threshold (AT). Development of AKI was defined using the Kidney Disease Improving Outcomes (KDIGO) guidance. Associations between CVR (based on AT levels) and AKI development were then analysed. RESULTS: Pre-operative AT levels were significantly different between those who did and did not develop AKI (12.1±2.9 SD vs. 14.8±3.0 mL/min/kg, p < .001). In multivariate analysis, a higher level of AT (per 1 mL/min/kg) was associated with a lower odds ratio (OR) of 0.72 (95% CI, 0.63-0.82, p < .001), relative to AKI development. A pre-operative AT level of < 11 mL/min/kg was associated with post-operative AKI development in adjusted analysis, with an OR of 7.8 (95% CI, 3.75-16.51, p < .001). The area under the curve (receiver operating characteristic) for AT as a predictor of post-operative AKI was 0.81 (standard error, 0.06, 95% CI, 0.69-0.93, p < .001). CONCLUSIONS: Poor CVR was strongly associated with the development of AKI. This provides pathophysiological insights into the mechanisms underlying AKI.

Prospective validation study of transorbital Doppler ultrasound imaging for the detection of transient cerebral microemboli.

BACKGROUND: Transient cerebral microemboli are independent biomarkers of early risk of ischaemic stroke in acute carotid syndromes. Transcranial Doppler imaging (TCD) through the temporal bone is the standard method for detection of cerebral microemboli, but an acoustic temporal bone window for TCD is not available in around one in seven patients. Transorbital Doppler imaging (TOD) has been used when TCD is not possible. The aim of this study was to validate the use of TOD against TCD for detecting cerebral microemboli. METHODS: The study included patients undergoing elective carotid endarterectomy; all had confirmed temporal and orbital acoustic windows. Subjects gave written informed consent to postoperative TCD and TOD monitoring, which was performed simultaneously for 30 min by two vascular scientists. RESULTS: The study included 100 patients (mean(s.e.m.) age 72(1) years; 65 men). Microemboli were detected by one or both methods in 40·0 per cent of patients: by TOD and TCD in 24 patients, by TOD alone in ten and by TCD alone in six. For detecting microemboli, TOD had a sensitivity of 80·0 per cent, specificity of 86·1 per cent, positive predictive value of 71·6 per cent and negative predictive value of 91·2 per cent. Bland-Altman analysis revealed no significant bias (bias 0·11 (95 per cent c.i. -0·52 to 0·74) microemboli; P = 0·810) with upper and lower limits of agreement of +6 and -6 microemboli. CONCLUSION: TOD appears a valid alternative to TCD for detecting microembolic signals in patients with no suitable temporal acoustic window.

Nonfreezing cold-induced injuries.

Non-freezing cold injury (NFCI) is the Cinderella of thermal injuries and is a clinical syndrome that occurs when tissues are exposed to cold temperatures close to freezing point for sustained periods. NFCI is insidious in onset, often difficult to recognize and problematic to treat, and yet the condition accounts for significant morbidity in both military and civilians who work in cold conditions. Consequently recognition of those at risk, limiting their exposure and the appropriate and timely use of suitable protective equipment are essential steps in trying to reduce the impact of the condition. This review addresses the issues surrounding NFCI.

A clinical review of the management of frostbite.

Frostbite is a thermal injury that can occur when temperatures drop low enough for tissue to freeze. On rewarming the tissues, an inflammatory process develops which is often associated with tissue loss. The extent of the tissue loss reflects the severity of the cold exposure and includes factors such as temperature, duration, wind chill, altitude, and systemic hypothermia. This review discusses the epidemiology, the pathophysiological processes involved, and the clinical management of frostbite injuries. Practical advice is given on both the field and hospital management and how to seek expert advice from remote situations. The review also discusses newer developments in frostbite treatment such as intra-vascular thrombolysis and adjunctive treatments such as the use of intravenous vasodilators.

Changes to colour vision on exposure to high altitude.

OBJECTIVES: Several studies have shown deterioration in colour vision at altitudes above 3,000m. These studies have been conducted in photopic (bright daylight) conditions, whereas many military operations take place in mesopic (dim light) conditions. Data suggests that the tritan colour vision axis (blue cones, TA) are more susceptible to hypoxic insult than protan axis (red cones, PA). The objective of this study was to examine colour vision at high altitude, in mesopic conditions, and using a novel method of assessment to discriminate between the tritan and protan axis. METHODS: We examined 42 eyes (21 subjects, mean age 44, range 22-71), at sea level and within 12-36 hours of exposure to 3300m. This was done in a darkened room, with refractive error correction. Colour vision was studied using ChromaTest, a software programme that analyzes colour contrast threshold (CCT) of both TA and PA. We planned to repeat CCT measurement at 4,392m, but technology failure prevented this. Non-parametric paired data was examined using the Wilcoxon signed rank test. RESULTS: There was found to be no change to either the PA (p = 0.409) or the TA (p = 0.871) upon ascent. Within the PA 16 eyes had a lower CCT at high altitude, whilst 26 were higher. In the TA 20 eyes had a lower CCT and 22 were higher. At sea level, mean CCT for PA was 4.21 (SD 2.29) TA was 7.06 (SD 1.77). At 3,300m mean CCT for PA was 4.36 (SD 2.86) and TA was 6.93 (SD 2.39). CONCLUSIONS: This experiment revealed no changes to colour vision with exposure to 3,300m. This may be below the threshold altitude for cone dysfunction, alternatively colour vision deterioration may be less significant in mesopic conditions.

Systemic blood pressure, arterial stiffness and pulse waveform analysis at altitude.

OBJECTIVES: Systemic arterial pressure rises on acute exposure to high altitude and changes in blood pressure (BP) and endothelial function may be important in the pathogenesis of clinical syndromes occurring at high altitude. METHODS: Arterial BP, stiffness (SI) and tone (RI) were studied over 11 days in 17 subjects (three having mild hypertension) ascending to 3,450m and 4,770m using a non-invasive, finger photoplethysmography technique. RESULTS: At 3,450m BP rose from mean 131/75 mmHg (SD 23/12) to 145/86 (23/12) and was maintained at this level (p < 0.001). SI did not change significantly from 8.5 m/sec (2.5) to 9.7 (3.2). RI fell during the first day at 3,450m from 74.4% (7.9) to 70.5% (13.8) (NS p > 0.05) and to 69.9% (12.0) (p < 0.02) at 4,770m but then reverted to baseline. Changes in SI and RI did not relate to changes in blood pressure. Changes in both arterial stiffness and tone were similar in those who developed AMS compared with those who did not. Baseline SI tended to be higher in the three subjects with hypertension 11.1m/sec (SD 2.7)) compared with the normotensives 8.3 m/sec (SD 2.7) (NS) and baseline RI lower 74.7% (7.0) compared with the normotensives 76.5% (8.5) (NS). Changes in SI and RI at altitude in the hypertensive subjects were similar to the non-hypertensive subjects. CONCLUSIONS: We conclude that acute exposure temporarily affected endothelial function as measured by a change in vascular tone but this did not predict the development of AMS. The rise in arterial BP was not related to changes in arterial stiffness or tone.

Healthcare staff perceptions and misconceptions regarding antibody testing in the United Kingdom: implications for the next steps for antibody screening.

BACKGROUND: Healthcare workers have been at increased risk of exposure, infection and serious complications from COVID-19. Antibody testing has been used to identify staff members who have been previously infected by SARS-CoV-2, and has been rolled out rapidly in the United Kingdom. A number of comment and editorial articles have been published that raise concerns about antibody testing in this context. We present perceptions of National Health Service (NHS) healthcare workers in relation to SARS-CoV-2 antibody testing. METHODS: An electronic survey regarding perceptions towards SARS-CoV-2 antibody testing was distributed to all healthcare workers at a major NHS tertiary hospital following implementation of antibody testing. RESULTS: In total, 560 healthcare workers completed the survey (80% female; 25% of Black and Minority Ethnic background; 58% from frontline clinical staff). Exploring whether they previously had COVID-19 was the primary reported reason for choosing to undergo antibody testing (85.2%). In case of a positive antibody test, 72% reported that they would feel relieved, whilst 48% felt that they would be happier to work in a patient-facing area. Moreover, 12% responded that a positive test would mean "social distancing is less important", with 34% of the responders indicating that in this case they would be both less likely to catch COVID-19 and happier to visit friends/relatives. CONCLUSIONS: NHS staff members primarily seek out SARS-CoV-2 antibody testing for an appropriate reason. Based on our findings and given the lack of definite data regarding the extent of immunity protection from a positive SARS-CoV-2 antibody test, significant concerns may be raised regarding the reported interpretation by healthcare workers of positive antibody test results. This needs to be further explored and addressed to protect NHS staff and patients.

Experience from the selection and nutritional preparation for Expedition ICE MAIDEN: the first successful all-female unassisted Antarctic traverse.

INTRODUCTION: Expedition ICE MAIDEN (Ex IM) was the first all-female unsupported crossing of Antarctica. We describe the prerequisite selection and training, comparing those who formed the final team with other participants, and discuss how the expedition diet was established. METHODS: All women serving in the British Army were invited to participate. Following initial assessments, successful women completed three training/selection ski expeditions. Between expeditions 1 and 2, participants completed 6 months rigorous UK-based training. Weight was measured before and after the 6 months UK-based training, expeditions 2 and 3, and body composition by skinfold before and after expedition 2. Participant feedback, body composition and weight changes were applied to modify the expedition diet and provide weight gain targets prior to Ex IM. RESULTS: Following 250 applications, 50 women were assessed and 22, 12 and seven women attended training expeditions 1, 2 and 3, respectively. The final team of six women lost more weight than other participants during UK-based training (mean (SD) change -1.3 (1.5) kg vs -0.5 (1.6) kg, respectively, p=0.046) and during training expedition 2 (-2.8 (0.8) kg vs -1.7 (0.4) kg, respectively, p=0.048), when they also gained more lean mass (+2.1 (0.8) kg vs +0.4 (0.7) kg, respectively, p=0.004). The Ex IM diet provided 5000 kCal/day, comprising approximately 45% carbohydrate, 45% fat and 10% protein. Median (range) weight change between expedition 3 and Ex IM was +8.7 (-1.9 to +14.3) kg. CONCLUSIONS: The selected Ex IM team demonstrated favourable training-associated body composition changes. Training-associated weight loss informed the expeditionary diet design.

Systemic capillary leak syndrome resulting in compartment syndrome and the requirement for a surgical airway.

We report on a case of systemic capillary leak syndrome associated with a monoclonal band on plasma electrophoresis. In our patient hospital admission was precipitated by ischaemic pain in the left lower limb, associated with polycythaemia, renal failure and hypovolaemic shock. Fluid resuscitation, venesection and renal replacement therapy were instituted but a compartment syndrome developed necessitating surgery. Failure of tracheal intubation resulted in the requirement for a surgical airway. Despite surgical and resuscitative efforts the outcome was fatal from hypovolaemia and hyperkalaemia. We aim to highlight the difficulties in managing this condition and to remind healthcare workers to include it in the differential diagnoses for patients presenting with polycythaemia; in particular polycythaemic patients with a monoclonal band on plasma electrophoresis.

Cold damage to the extremities: frostbite and non-freezing cold injuries.

The treatment of cold injuries to the periphery has advanced substantially in the last 10 years and optimal outcomes are only likely to be achieved if a multidisciplinary team uses the full range of diagnostic and treatment modalities that are now available. The internet and satellite phones with digital images allow immediate access by patients from remote geographical locations to hospital based specialists who can assess cold injuries and advise on early field care. The severity of frostbite injuries can now be assessed with triple phase bone scanning, allowing early prediction of likely subsequent tissue loss. Early hyperbaric oxygen therapy appears to improve outcome and the use of intravenous drugs such as synthetic prostaglandin analogues infusions and tissue plasminogen activator have been shown to reduce amputation rates. In non-freezing cold injuries the early administration of analgesia, the avoidance of secondary exposure, and the use of infrared thermography to assess the injuries are among newer approaches being introduced.

Multimodal analysis of the effects of dexamethasone on high-altitude cerebral oedema: protocol for a pilot study.

BACKGROUND: Acute mountain sickness (AMS) is a cluster of symptoms that commonly occur in those ascending to high altitudes. Symptoms can include headaches, nausea, insomnia and fatigue. Exposure to high altitude can also lead to high-altitude cerebral oedema (HACE), which is a potential cause of death whilst mountaineering. Generally, AMS precedes the development of HACE. Historical studies have demonstrated the effectiveness of regular dexamethasone administration in reducing the symptoms of AMS. However, the mechanism by which dexamethasone works to reduce symptoms AMS remains poorly understood. Further studies, simulating altitude using hypoxic tents, have characterised the effect of prolonged exposure to normobaric hypoxia on cerebral oedema and blood flow using MRI. This randomised trial assesses the effect of dexamethasone on hypoxia-induced cerebral oedema in healthy adult volunteers. METHODS/DESIGN: D4H is a double-blind placebo-controlled randomised trial assessing the effect of dexamethasone on hypoxia-induced cerebral oedema. In total, 20 volunteers were randomised in pairs to receive either 8.25 mg dexamethasone or normal saline placebo intravenously after 8 h of hypoxia with an FiO2 of 12%. Serial MRI images of the brain and spinal cord were obtained at hours 0, 7, 11, 22 and 26 of the study along with serum and urinary markers to correlate with the severity of cerebral oedema and the effect of the intervention. DISCUSSION: MRI has been used to identify changes in cerebral vasculature in the development of AMS and HACE. Dexamethasone is effective at reducing the symptoms of AMS; however, the mechanism of this effect is unknown. If this study demonstrates a clear objective benefit of dexamethasone in this setting, future studies may be able to demonstrate that dexamethasone is an effective therapy for oedema associated with brain and spinal cord ischaemia beyond AMS. TRIAL REGISTRATION: Clinicaltrials.gov, NCT03341676 . Registered on 14 November 2017.

Transcranial Doppler ultrasonography-directed intravenous glycoprotein IIb/IIIa receptor antagonist therapy to control transient cerebral microemboli before and after carotid endarterectomy.

BACKGROUND: Patients with a transient focal neurological deficit, critical carotid stenosis and/or microemboli detected by transcranial Doppler ultrasonography (TCD) have a significant risk of stroke. The effect of tirofiban, a selective glycoprotein IIb/IIIa inhibitor, was assessed in patients with microembolic signals on TCD after transient ischaemic attacks or carotid endarterectomy (CEA). METHODS: Thirty-three patients with microemboli on TCD (13 symptomatic preoperative, 19 postoperative, one both) were treated with tirofiban between 2002 and 2007. All patients had carotid stenosis greater than 70 per cent. TCD monitoring was used during and after tirofiban therapy. RESULTS: The median (range) rate of microemboli decreased from 22 (4-260) per h before surgery and 81 (44-216) per h after surgery to 0 (0-9) per h in both groups (P < 0.001, Mann-Whitney U test). This occurred rapidly (preoperative median 30 min; postoperative median 45 min) and was well tolerated in all patients, with no serious adverse effects. CONCLUSION: Cerebral microemboli were controlled by tirofiban both before and after CEA. Further study is required to compare the relative efficacy of tirofiban and dextran.

Advances in the available non-biological pharmacotherapy prevention and treatment of acute mountain sickness and high altitude cerebral and pulmonary oedema.

INTRODUCTION: The physiological responses on exposure to high altitude are relatively well known, but new discoveries are still being made, and novel prevention and treatment strategies may arise. Basic information has changed little since our previous review in this journal 10 years ago, but considerable more detail on standard therapies, and promising new approaches are now available. AREAS COVERED: Herein, the authors review the role of pharmacological agents in preventing and treating high-altitude illnesses. The authors have drawn on their own experience and that of international experts in this field. The literature search was concluded in March 2018. EXPERT OPINION: Slow ascent remains the primary prevention strategy, with rapid descent for the management of serious altitude illnesses. Pharmacological agents are particularly helpful when rapid ascent cannot be avoided or when rapid descent is not possible. Acetazolamide remains the drug of choice for prophylaxis of acute mountain sickness. However, evidence indicates that reduced dosage schemes compared to the current recommendations are warranted. Calcium channel blockers and phosphodiesterase inhibitors remain the drugs of choice for the management of high-altitude pulmonary edema. Dexamethasone should be reserved for the treatment of more severe cases of altitude illnesses such as cerebral edema.

Ethnicity and cardiovascular disease prevention in the United Kingdom: a practical approach to management.

The United Kingdom is a diverse society with 7.9% of the population from black and minority ethnic groups (BMEGs). The causes of the excess cardiovascular disease (CVD) and stroke morbidity and mortality in BMEGs are incompletely understood though socio-economic factors are important. However, the role of classical cardiovascular (CV) risk factors is clearly important despite the patterns of these risk factors varying significantly by ethnic group. Despite the major burden of CVD and stroke among BMEGs in the UK, the majority of the evidence on the management of such conditions has been based on predominantly white European populations. Moreover, the CV epidemiology of African Americans does not represent well the morbidity and mortality experience seen in black Africans and black Caribbeans, both in Britain and in their native African countries. In particular, atherosclerotic disease and coronary heart disease are still relatively rare in the latter groups. This is unlike the South Asian diaspora, who have prevalence rates of CVD in epidemic proportions both in the diaspora and on the subcontinent. As the BMEGs have been under-represented in research, a multitude of guidelines exists for the 'general population.' However, specific reference and recommendation on primary and secondary prevention guidelines in relation to ethnic groups is extremely limited. This document provides an overview of ethnicity and CVD in the United Kingdom, with management recommendations based on a roundtable discussion of a multidisciplinary ethnicity and CVD consensus group, all of whom have an academic interest and clinical practice in a multiethnic community.

Reporting individual surgeon outcomes does not lead to risk aversion in abdominal aortic aneurysm surgery.

INTRODUCTION Reporting surgeons' outcomes has recently been introduced in the UK. This has the potential to result in surgeons becoming risk averse. The aim of this study was to investigate whether reporting outcomes for abdominal aortic aneurysm (AAA) surgery impacts on the number and risk profile (level of fitness) of patients offered elective treatment. METHODS Publically available National Vascular Registry data were used to compare the number of AAAs treated in those centres across the UK that reported outcomes for the periods 2008-2012, 2009-2013 and 2010-2014. Furthermore, the number and characteristics of patients referred for consideration of elective AAA repair at a single tertiary unit were analysed yearly between 2010 and 2014. Clinic, casualty and theatre event codes were searched to obtain all AAAs treated. The results of cardiopulmonary exercise testing (CPET) were assessed. RESULTS For the 85 centres that reported outcomes in all three five-year periods, the median number of AAAs treated per unit increased between the periods 2008-2012 and 2010-2014 from 192 to 214 per year (p=0.006). In the single centre cohort study, the proportion of patients offered elective AAA repair increased from 74% in 2009-2010 to 81% in 2013-2014, with a maximum of 84% in 2012-2013. The age, aneurysm size and CPET results (anaerobic threshold levels) for those eventually offered elective treatment did not differ significantly between 2010 and 2014. CONCLUSIONS The results do not support the assumption that reporting individual surgeon outcomes is associated with a risk averse strategy regarding patient selection in aneurysm surgery at present.

Effect of exercise on cerebral perfusion in humans at high altitude.

The effects of submaximal and maximal exercise on cerebral perfusion were assessed using a portable, recumbent cycle ergometer in nine unacclimatized subjects ascending to 5,260 m. At 150 m, mean (SD) cerebral oxygenation (rSO2%) increased during submaximal exercise from 68.4 (SD 2.1) to 70.9 (SD 3.8) (P < 0.0001) and at maximal oxygen uptake (.VO2(max)) to 69.8 (SD 3.1) (P < 0.02). In contrast, at each of the high altitudes studied, rSO2 was reduced during submaximal exercise from 66.2 (SD 2.5) to 62.6 (SD 2.1) at 3,610 m (P < 0.0001), 63.0 (SD 2.1) to 58.9 (SD 2.1) at 4,750 m (P < 0.0001), and 62.4 (SD 3.6) to 61.2 (SD 3.9) at 5,260 m (P < 0.01), and at .VO2(max) to 61.2 (SD 3.3) at 3,610 m (P < 0.0001), to 59.4 (SD 2.6) at 4,750 m (P < 0.0001), and to 58.0 (SD 3.0) at 5,260 m (P < 0.0001). Cerebrovascular resistance tended to fall during submaximal exercise (P = not significant) and rise at .VO2(max), following the changes in arterial oxygen saturation and end-tidal CO(2). Cerebral oxygen delivery was maintained during submaximal exercise at 150 m with a nonsignificant fall at .VO2(max), but at high altitude peaked at 30% of .VO2(max) and then fell progressively at higher levels of exercise. The fall in rSO2 and oxygen delivery during exercise may limit exercise at altitude and is likely to contribute to the problems of acute mountain sickness and high-altitude cerebral edema.

Vascular surgical society of great britain and ireland: near-infrared spectroscopic monitoring of patients undergoing carotid endarterectomy under locoregional anaesthesia

BACKGROUND: The level of cerebral desaturation, which is associated with a change in level of consciousness during carotid endarterectomy, was measured by near-infrared spectroscopy. METHODS: Patients were recruited in two centres over 24 months. Surgery was performed under deep and superficial cervical block using 0.5 per cent bupivacaine, with temazepam as a premedication. Cerebral oxygenation was measured by Critikon 2020 near-infrared spectrophotometers (Johnson and Johnson Medical, Newport, UK). RESULTS: Forty-nine procedures were performed on 45 patients (39 men; age range 52-84 (mean 68) years). Recordings were made from the ipsilateral frontal site in 38 patients, from the ipsilateral temporal site in 23 and bifrontally in eight patients. Monitoring failed in three subjects. Percentage changes in regional cerebral oxygen saturation are detailed below. CONCLUSION: Significantly different levels of cerebral desaturation occur in patients with neurological compromise during carotid endarterectomy compared with those who are unaffected.