Changes in body composition and average daily energy expenditure of men and women during arduous extended polar travel.

Weight and skin-fold measurements were made at five-day intervals during a 47-day expedition by six men and three women from the edge of the sea ice to the South Pole. From these, together with detailed manual records of the nutrition for individual participants, the average daily energy expenditure was determined before and after a resupply at approximately mid-point of the expedition. For all participants body weight fell during the expedition with the overall loss being much smaller for the three female participants (-4.0, -4.0, -4.4kg) than for the male participants, (mean±sd) -8.6±2.0kg. Fat weight fell approximately linearly during the expedition with a total loss of (-4.1, -6.5 and -2.5kg) for the three female participants and -6.8±1.7kg for the male participants. Individual fat-free weight changed by a smaller amount overall: (0.13, 2.5 and -1.8kg) for the three female participants; -1.8±2.0kg for the male participants who, with one exception, lost fat-free tissue All participants showed a substantial variation in fat-free tissue weight during the expedition. Analysis of the daily energy expenditure showed adequate nutrition but the intake fell for the second part of the expedition although the reasons for this are unclear, but adaptation to the cold, altitude and workload are possible explanations. The validity of this time-averaged measurement for individual participants was determined from analysing moments about the mean of time-series actigraphy data from wrist worn devices. The mean and autocorrelation function of the actigraphy data across subjects were analysed to determine whether measures could be compared between participants. The first, second and third moment about the mean of the day-to-day activity was found to be time-invariant for individual subjects (χ2, p>0.05) and the normalized mean and autocorrelation measured over a day for each participant indistinguishable from the mean of the group (χ2, p>0.05) allowing both longitudinal and cross-sectional analysis.

Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Frostbite: 2024 Update.

The Wilderness Medical Society convened an expert panel to develop a set of evidence-based guidelines for the prevention and treatment of frostbite. We present a review of pertinent pathophysiology. We then discuss primary and secondary prevention measures and therapeutic management. Recommendations are made regarding each treatment and its role in management. These recommendations are graded on the basis of the quality of supporting evidence and balance between the benefits and risks or burdens for each modality according to methodology stipulated by the American College of Chest Physicians. This is an updated version of the guidelines published in 2019.

Vascular Surgery Workforce: Evaluation and Estimation of Future Demand in the United Kingdom.

BACKGROUND: Vascular disease is a common cause of death and disability in our growing elderly population and the demand for vascular procedures is increasing worldwide. Workforce planning is essential to meet future demand and provide safe vascular services. Our aim was to evaluate the current workforce in the United Kingdom and estimate future demand for vascular surgeons. METHODS: From November 2020 to January 2021, we surveyed UK vascular surgeons for information on their work patterns. We estimated current vascular surgery (VS) workforce using the National Vascular Registry (NVR) data and population data from the Office for National Statistics. To estimate future demand, we interrogated Hospital Episode Statistic (HES) data using Hospital Admitted Patient Care Activity (HAPCA) and linear trend analysis. RESULTS: NVR data estimate that currently there are 518 consultant VS in the United Kingdom, or 1 per 128,951 population, lower than international comparisons. HAPCA data (2012-2020) suggests VS Finished Consultant Episodes (FCE), admissions, and waiting lists are growing by approximately 2% per year, and we estimate the workforce will need to grow by more than 50% over the next 10 years to meet this demand and Vascular Society of Great Britain and Ireland recommendation. CONCLUSIONS: The UK has a shortage of vascular surgeons at a time when vascular activity is increasing. The VS workforce, both VS consultant and vascular surgeons in training numbers need to expand to address the ongoing shortage and maintain a safe level of service.

Early Use of Iloprost in Nonfreezing Cold Injury.

Nonfreezing cold injury (NFCI) is caused by prolonged exposure to cold, usually wet conditions and represents a separate pathological entity from frostbite. The pathophysiology of NFCI is characterized by vasoconstriction and microcirculatory disturbance. Iloprost, a synthetic prostaglandin analogue with vasodilatory properties is a recognized adjuvant treatment in frostbite; however, its role in NFCI is unclear. We present a case of a 29-y-old man with severe NFCI to both forefeet after prolonged immersion in cold seawater. Initial treatment with passive rewarming, analgesia and aspirin was initiated. Infusion of iloprost was used within 24 h from presentation and was well tolerated. This resulted in reduced tissue loss compared to the apparent tissue damage documented during the initial assessment. Delayed surgical intervention allowed minor debridement and minor toe amputations, maintaining the patient's ability to ambulate. This case demonstrates the safe use of iloprost in acute NFCI and highlights the importance of delayed surgical intervention in patients presenting with severe NFCI.

Revacept, an Inhibitor of Platelet Adhesion in Symptomatic Carotid Stenosis: A Multicenter Randomized Phase II Trial.

BACKGROUND: Patients with symptomatic internal carotid artery (ICA) stenosis are at high risk of recurrent ischemic stroke and require early interventional treatment and antiplatelet therapy. Increased bleeding rates might counterbalance the periprocedural efficacy of intensified platelet inhibition. We aim to investigate, whether Revacept, a competitive antagonist of glycoprotein VI, adjunct to standard antiplatelet therapy reduces the occurrence of ischemic lesions in patients with symptomatic ICA stenosis. METHODS: International, multicenter (16 sites), 3-arm, randomized (1:1:1), double-blind, and placebo-controlled study with parallel groups, including patients with symptomatic ICA stenosis. A single infusion over 20 minutes of either placebo, 40 mg or 120 mg Revacept in addition to guideline-conform antiplatelet therapy was evaluated with regard to the exploratory efficacy end point: Number of new ischemic lesions on diffusion-weighted magnetic resonance imaging after treatment initiation. Main clinical outcome was the combined safety and efficacy end point including any stroke or death, transient ischemic attack, myocardial infarction, coronary intervention, and bleeding complications during follow-up. RESULTS: Out of 160 randomized patients, 158 patients (68±10.1 years, 24% female) received study medication (51 patients placebo, 54 patients 40 mg Revacept and 53 patients 120 mg Revacept) and were followed for 11.2±2.3 months. A total of 1.16 (95% CI, 0.88-1.53)/1.05 (95% CI, 0.78-1.42; P=0.629)/0.63 (95% CI, 0.43-0.93) new diffusion-weighted magnetic resonance imaging lesions per patient were detected in the placebo/40 mg/120 mg Revacept groups, without statistical evidence of a difference. A reduction of the combined safety and efficacy end point during the study period was observed in patients who received 120 mg (HR, 0.46 [95% CI, 0.21-0.99]; P=0.047), but not 40 mg Revacept compared with placebo (HR, 0.72 [95% CI, 0.37-1.42]; P=0.343). CONCLUSIONS: Revacept 120 mg reduced the combined safety and efficacy end point in patients with symptomatic ICA stenosis. REGISTRATION: URL: https://www. CLINICALTRIALS: gov; Unique Identifier: NCT01645306.

Vascular Surgeon Burnout and Resilience in the United Kingdom: A Report from the Vascular Society Workforce Committee.

BACKGROUND: Occupational burnout is a growing concern in frontline roles such as vascular surgery, and is associated with medical errors and shortened careers. Our aim is to measure burnout, resilience, and associated risk factors among vascular surgeons (VS) in the United Kingdom (UK). METHODS: We carried out an electronic survey of active VS in the UK using validated self-report questionnaires, including the following: Copenhagen Burnout Inventory (CBI), Brief Resilience Scale (BRS), and information on job characteristics, health, and well-being. Univariate regression analysis looked at potential risk factors. RESULTS: One hundred forty-eight VS responded (49% participation rate), and after excluding retirees and nonconsultants, 133 VS practicing in the UK were analyzed. Mean age was 49.9 ± 7.19 years; the majority (83.5%) were male. In total, 81.3% recorded ethnic identity as White. In addition, 93.2% worked full time; 74.8% were contracted above 10 programmed activities and 87.9% worked more than 40 hr/week. On-call was 1 in 6, or above, for 87.4%. Overall, 38.4% of VS had high burnout on the CBI. Resilience was also high, with BRS mean (standard deviation) of 3.6 (0.69) and median (interquartile range) of 3.7 (3-4). Univariate regression analysis found no significant risk factor associated with high burnout or resilience. CONCLUSIONS: VS in the UK have high levels of burnout and work long hours. Resilience levels were also high, which may offer some protection. However, policymakers and our surgical leaders should address contributing factors and excessive working hours and establish measures to identify and support surgeon well-being for optimal surgeon and patient safety.

HLA Antibody Incompatible Renal Transplantation: Long-term Outcomes Similar to Deceased Donor Transplantation.

BACKGROUND: HLA incompatible renal transplantation still remains one of best therapeutic options for a subgroup of patients who are highly sensitized and difficult to match but not much is known about its long-term graft and patient survival. METHODS: One hundred thirty-four HLA incompatible renal transplantation patients from 2003 to 2018 with a median follow of 6.93 y were analyzed retrospectively to estimate patient and graft survivals. Outcomes were compared with groups defined by baseline crossmatch status and the type and timings of rejection episodes. RESULTS: The overall patient survival was 95%, 90%, and 81%; and graft survival was 95%, 85%, and 70% at 1, 5, and 10 y, respectively. This was similar to the first-time deceased donor transplant cohort. The graft survival for pretreatment cytotoxic-dependent crossmatch (CDC) positive crossmatch group was significantly low at 83%, 64%, and 40% at 1, 5, and 10 y, respectively, compared with other groups (Bead/CDC, P = 0.007; CDC/Flow, P = 0.001; and microbead assay/flow cytometry crossmatch, P = 0.837), although those with a low CDC titer (<1 in 2) have comparable outcomes to the CDC negative group. Female patients in general fared worse in both patient and graft survival outcomes in each of the 3 groups based on pretreatment crossmatch, although this did not reach statistical significance. Antibody-mediated rejection was the most frequent type of rejection with significant decline in graft survival by 10 y when compared with no rejection (P < 0.001). Rejection that occurred or continued to occur after the first 2 wk of transplantation caused a significant reduction in graft survivals (P < 0.001), whereas good outcomes were seen in those with a single early rejection episode. CONCLUSIONS: One-, 5-, and 10-y HLA incompatible graft and patient survival is comparable to deceased donor transplantation and can be further improved by excluding high-CDC titer cases. Antibody-positive female patients show worse long-term survival. Resolution of early rejection is associated with good long-term graft survival.

Allograft nephrectomy versus nonallograft nephrectomy after failed renal transplantation: a systematic review by updated meta-analysis.

There is limited evidence regarding the impact of allograft nephrectomy (AN) on the long-term outcome of subsequent kidney re-transplantation compared with no prior allograft nephrectomy. The aim of the present study was to conduct a systematic review and meta-analysis to estimate the accumulation of evidence over time. Primary outcomes were 5-year graft and patient survival. Cochrane library, Google scholar, PubMed, Medline and Embase were systematically searched. Meta-analysis was conducted using both fixed- and random-effects models. Study quality was assessed in duplicate using the Newcastle-Ottawa scale. Sixteen studies were included, with a total of 2256 patients. All included studies were retrospective and comparative. There was no significant difference in 5-year graft survival (GS) [Hazard Ratio (HR) = 1.11, 95% Confidence Intervals (CI): 0.89, 1.38, P = 0.37, I2  = 10%) or in 5-year patient survival (PS; HR = 0.70, 95% CI: 0.45, 1.10, P = 0.12, I2  = 0%]. Patients in the AN cohort were significantly younger than patients in the nonallograft nephrectomy (NAN) cohort by one year. Prior allograft nephrectomy was associated with a significantly higher risk of delayed graft function (DGF), acute rejection, primary nonfunction (PNF), per cent of panel reactive antibodies (% PRA) and allograft loss of the subsequent transplant. Although, DGF, % PRA, acute rejection and primary nonfunction rates were significantly higher in the AN cohort, allograft nephrectomy prior to re-transplantation had no significant association with five-year graft and patient survival.

C3d-positive donor-specific antibodies have a role in pretransplant risk stratification of cross-match-positive HLA-incompatible renal transplantation: United Kingdom multicentre study.

Anti-HLA-antibody characteristics aid to risk-stratify patients and improve long-term renal graft outcomes. Complement activation by donor-specific antibody (DSA) is an important characteristic that may determine renal allograft outcome. There is heterogeneity in graft outcomes within the moderate to high immunological risk cases (cross-match-positive). We explored the role of C3d-positive DSAs in sub-stratification of cross-match-positive cases and relate to the graft outcomes. We investigated 139 cross-match-positive living-donor renal transplant recipients from four transplant centres in the United Kingdom. C3d assay was performed on serum samples obtained at pretreatment (predesensitization) and Day 14 post-transplant. C3d-positive DSAs were found in 52 (37%) patients at pretreatment and in 37 (27%) patients at Day 14 post-transplant. Median follow-up of patients was 48 months (IQR 20.47-77.57). In the multivariable analysis, pretreatment C3d-positive DSA was independently associated with reduced overall graft survival, the hazard ratio of 3.29 (95% CI 1.37-7.86). The relative risk of death-censored five-year graft failure was 2.83 (95% CI 1.56-5.13). Patients with both pretreatment and Day 14 C3d-positive DSAs had the worst five-year graft survival at 45.5% compared with 87.2% in both pretreatment and Day 14 C3d-negative DSA patients with the relative risk of death-censored five-year graft failure was 4.26 (95% CI 1.79, 10.09). In this multicentre study, we have demonstrated for the first time the utility of C3d analysis as a distinctive biomarker to sub-stratify the risk of poor graft outcome in cross-match-positive living-donor renal transplantation.

Nonfreezing Cold Injuries Among Long-Distance Polar Rowers.

INTRODUCTION: Nonfreezing cold injury (NFCI) is a peripheral cold injury that occurs when the extremities are exposed to cold temperatures, at or near the freezing point, for sustained periods of time (48-96 h at temperatures of usually around 0 to 6°C with associated wind chill). Although NFCI often goes unreported and may be underdiagnosed, it is a cause of significant morbidity in those working in cold conditions, particularly those in the military. Thus, further research into the prevention, recognition, and treatment of NFCI is warranted. METHODS: The height, body weight, and body composition of 6 rowers taking part in 1 or 2 legs of the 2017 Polar Row expedition were measured. The weather conditions of the 2 legs of the journey were recorded, and symptoms relating to NFCI were documented. RESULTS: All incidences of NFCI occurred during Leg 2 of the expedition, which was colder and wetter. Of the Leg 2 rowers, those who developed NFCI had a trend toward higher pre-row body weight and body mass index and a trends toward losing more weight and body water relative to those who did not. CONCLUSIONS: The main factor contributing to the incidence of NFCI appeared to be weather; NFCI only occurred during the colder and wetter leg of the expedition. We also tentatively suggest that nutrition and dehydration may be linked to the incidence of NFCI as predisposing factors. More work, with sample sizes greater than those reported here, is required to investigate these associations to further characterize risk factors.

Editor's Choice - Acute Kidney Injury (AKI) in Aortic Intervention: Findings From the Midlands Aortic Renal Injury (MARI) Cohort Study.

OBJECTIVES: The incidence of acute kidney injury (AKI) after open (OAR) or endovascular (EVAR) aortic repair is unknown. This research assessed the proportion of patients who develop AKI after aortic intervention using validated criteria, and explored AKI risk factors. METHODS: This was a multicentre national prospective cohort study. Eleven centres recruited patients undergoing EVAR or OAR (September 2017-December 2018). Serum creatinine (SCr) and urine outputs were measured over a minimum of 48 h or throughout the index inpatient stay to define post-operative AKI using the Kidney Disease Improving Global Outcomes (KDIGO) criteria. Renal decline at 30 days was calculated using estimated glomerular filtration rate (eGFR) and the Major Adverse Kidney Events (MAKE) 30 day composite endpoint (consisting of: death, new dialysis, > 25% eGFR decline). RESULTS: 300 patients (mean age: 71 years, standard deviation [SD] 4 years; 9% females) were included, who underwent: infrarenal endovascular aneurysm repair (EVAR) 139 patients, fenestrated EVAR (fEVAR) 30, branched EVAR (bEVAR) seven, infrarenal open aneurysm repair (OAR) 98, juxtarenal OAR 26. Overall, 24% of patients developed stage 1 AKI (defined at 48 h as per KDIGO), 2.7% stage 2 AKI and 1% needed renal replacement therapy before discharge. AKI proportions per intervention were: infrarenal EVAR 18%; fEVAR 27%; bEVAR 71%; infrarenal OAR 41%; juxtarenal OAR 63%. Older age (odds ratio [OR] 1.44 for EVAR, 1.58 for OAR), lower baseline eGFR (OR 0.88 EVAR, 0.74 OAR), and ischaemic heart disease (OR 4.42 EVAR, 5.80 OAR) were the main predictors of AKI for infrarenal EVAR and OAR. Overall, 24% developed the MAKE30 endpoint. All patients who died (0.6%) or developed a major cardiac event (5.6%) at one year had developed AKI. CONCLUSION: AKI and short term renal decline after aortic intervention are common. Age, renal function, and cardiovascular disease are the main risk factors. Research should now focus on AKI prevention in this high risk group.

Endovascular Aneurysm Repair May Provide a Survival Advantage in Patients Deemed Physiologically Ineligible for Open Abdominal Aortic Aneurysm Repair.

BACKGROUND: Cardiopulmonary exercise testing (CPET) provides an objective assessment of functional capacity and fitness. It can be used to guide decision making prior to major vascular surgery. The EVAR-2 trial suggested that endovascular aneurysm repair (EVAR) in patients unfit for open repair failed to provide a significant survival advantage over nonsurgical management. The aim of this study is to assess contemporary survival differences between patients with poor CPET measures who underwent EVAR or were not offered surgical intervention. METHODS: A prospectively maintained database of CPET results of patients considered for elective infrarenal aortic aneurysm repair were interrogated. Anaerobic threshold (AT) of <11 mL/min/kg was used to indicate poor physical fitness. Hospital electronic records were then reviewed for perioperative, reintervention, and long-term outcomes. RESULTS: Between November 2007 and October 2017, 532 aortic aneurysm repairs were undertaken, of which 376 underwent preoperative CPET. Seventy patients were identified as having an AT <11 mL/min/kg. Thirty-seven patients underwent EVAR and 33 were managed nonsurgically. All-cause survival at 1, 3, and 5 years for those patients who underwent EVAR was 97%, 92%, and 81%, respectively. For those not offered surgical intervention survival at the same points was 72%, 48%, and 24% [hazard ratio, HR = 5.13 (1.67-15.82), P = 0.004]. Aneurysm-specific survival at 1, 3, and 5 years for those patients who underwent EVAR was 97%, 94%, and 94%, respectively. Survival at the same time points for those not offered surgical intervention was 90%, 69%, and 39%, respectively [HR = 7.48 (1.37-40.82), P = 0.02]. CONCLUSIONS: In this small, retrospective, single-center, nonrandomized cohort, EVAR may provide a survival advantage in patients with poor physical fitness identified via CPET. Randomized studies with current generation EVAR are required to validate the results shown here.

Purine nucleoside use as surrogate markers of cerebral ischaemia during local and general anaesthetic carotid endarterectomy.

OBJECTIVES: In periods of cerebral ischaemia, adenosine triphosphate is metabolised, leading to accumulation of adenosine inosine and hypoxanthine. These can be measured in real time using peripheral blood samples intraoperatively. The primary aim of this study was to describe changes in purine concentrations in a cohort of patients undergoing carotid endarterectomy under general anaesthetic, and to evaluate correlation between changes in values with major perioperative steps. The secondary aim was to compare changes in concentrations with a previous cohort of patients who had undergone carotid endarterectomy under local anaesthetic. METHODS: This was a prospective observational study. Purine concentrations were determined from arterial line samples and measured via an amperometric biosensor at specific time points during carotid endarterectomy. Mean arterial pressure was manipulated to maintain steady cerebral perfusion pressure throughout the procedure. These results were analysed against data from a cohort of patients who underwent carotid endarterectomy under local anaesthetic in previously published work. RESULTS: Valid results were obtained for 37 patients. Purine concentrations at baseline were 3.02 ± 1.11 µM and 3.16 ± 1.85 µM for the unshunted and shunted cohorts, respectively. There was no significant change after 30 min of carotid clamping at 2.07 ± 0.89 and 2.4 ± 3.09 µM, respectively (both p > 0.05). Peak purine during the clamp phase in the loco-regional anaesthetic cohort was 6.70 ± 3.4 µM, which was significantly raised compared to both general anaesthetic cohorts (p = 0.004). There were no perioperative neurological events in either cohort. CONCLUSION: This small study does not demonstrate conclusive evidence that purine nucleosides can be used as a marker of cerebral ischaemia; the comparisons to the loco-regional anaesthetic data offer information about differences in the cerebral adenosine triphosphate metabolism between general anaesthetic and loco-regional anaesthetic. We hypothesise that the lack of a rise in purine nucleosides under general anaesthetic may be caused by a decrease in the cerebral metabolic rate and loss of metabolic rate-blood flow coupling caused by general anaesthetic agents.

Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Frostbite: 2019 Update.

The Wilderness Medical Society convened an expert panel to develop a set of evidence-based guidelines for prevention and treatment of frostbite. We present a review of pertinent pathophysiology. We then discuss primary and secondary prevention measures and therapeutic management. Recommendations are made regarding each treatment and its role in management. These recommendations are graded on the basis of the quality of supporting evidence and balance between the benefits and risks or burdens for each modality according to methodology stipulated by the American College of Chest Physicians. This is an updated version of the guidelines published in 2014.

The clinical application of purine nucleosides as biomarkers of tissue Ischemia and hypoxia in humans in vivo.

During periods of ischemia and hypoxia, intracellular adenosine triphosphate stores are rapidly depleted. Its metabolism results in release of purine nucleosides into the systemic circulation. While the potential of purine nucleosides as a biomarker of ischemia has long been recognized, this has been limited by their complex physiological role and inherent instability leading to problematic sampling and prolonged, complex analysis procedures. Purine release has been demonstrated from cerebral tissue in patients undergoing carotid endarterectomy and patients presenting to hospital with stroke and transient ischemic attack. Rises in purine nucleosides have also been demonstrated in patients with angina and myocardial infarction, during systemic hypoxia, exercise, in patients with peripheral arterial disease and during surgery. This article reviews purine nucleoside production in ischemia, the development of purine analysis technology and details results of the studies investigating purine nucleosides as a biomarker of ischemia with suggestions for areas of future research.

The association between early neurological deterioration and whole blood purine concentration during acute stroke.

BACKGROUND: Early neurological deterioration (END) is common after stroke. Prediction could identify patients requiring additional monitoring and intervention. Purines, breakdown products of adenosine triphosphate which accumulate during acute hypoxia, may reflect the subclinical presence of vulnerable tissue. We considered whether whole blood purine concentration (WBPC) measurements during acute stroke were associated with subsequent END. METHODS: Patients within 4.5 h of stroke onset underwent point-of-care finger-prick measurement of WBPC and blinded assessment of symptom severity using the National Institutes of Health Stroke Scale (NIHSS). END was defined as an NIHSS increase ≥2 points at 24-36 h compared to baseline. RESULTS: 15/152 (9.8%) patients experienced END with a median [IQR] NIHSS increase of 4 [2-7] points. There were no strong associations between END and baseline NIHSS, clinical stroke subtype, thrombolytic therapy, physiological characteristics or time to assay. The median [IQR] WBPC concentration (uM) was higher before the occurrence of END but without statistical significance (7.21 [4.77-10.65] versus 4.83 [3.00-9.02]; p = 0.1). Above a WBPC threshold of 6.05uM, the risk of END was significantly greater (odds ratio 3.7 (95% CI 1.1-12.4); p = 0.03). CONCLUSION: Although the study lacked statistical power, early WBPC measurement could be a convenient biomarker for identifying acute stroke patients at risk of END, but further evaluation is required.

Analysis of Retinal Segmentation Changes at High Altitude With and Without Acetazolamide.

Purpose: Our aim was to assess retinal venous diameter and segmented retinal layer thickness variation in acute systemic hypoxia with and without acetazolamide and to relate these changes to high altitude headache (HAH), as a proxy for intracerebral pathophysiology. Methods: A total of 20 subjects participated in a 4-day ascent to the Margherita Hut (4,559 m) on Monte Rosa in the Italian Alps. Each participant was randomized to either oral acetazolamide 250 mg twice daily or placebo. A combination of digital imaging and optical coherence tomography was used to measure retinal vessel diameter and retinal layer thickness. Clinically-assessed HAH was recorded. Results: A total of 18 participants had usable digital and OCT images, with 12 developing HAH. Significant thickening was seen only in the two inner layers of the retina, the retinal nerve fiber layer (RNFL) and ganglion cell layer (GCL) at P = 0.012 and P = 0.010, respectively, independent of acetazolamide. There was a significant positive correlation between HAH and both retinal venous diameter (T = 4.953, P = 0.001) and retinal artery diameter (T = 2.865, P = 0.015), with both unaffected by acetazolamide (F = 0.439, P = 0.518). Conclusions: Retinal venous diameter correlates positively with HAH, adding further evidence for the proposed venous outflow limitation mechanism. The inner layers of the retina swelled disproportionately when compared to the outer layers under conditions of systemic hypoxia. Acetazolamide does not appear to influence altitudinal changes of retinal layers and vasculature.

Female Reproductive, Adrenal, and Metabolic Changes during an Antarctic Traverse.

PURPOSE: To explore the effects of the first all-female transantarctic expedition on hormonal axes pertinent to reproductive and metabolic function. METHODS: Six females (age, 28-36 yr; body mass index, 24.2 ± 0.97 kg·m) hauled 80-kg sledges 1700 km in 61 d. Estimated average energy intake was 20.8 ± 0.1 MJ·d (4970 ± 25 kcal·d). Whole and regional body composition was measured by dual-energy x-ray absorptiometry 1 and 2 months before and 15 d after, the expedition. Body fat was also estimated by skinfold and bioimpedance immediately before and after the expedition. Basal metabolic and endocrine blood markers and, after 0.25 mg dexamethasone suppression, 1-h 10-µg gonadorelin and 1.0 µg adrenocortiocotrophin-(1-24) tests were completed, 39-38 d preexpedition and 4 to 5 d and 15 to 16 d postexpedition. Cortisol was assessed in hair (monthly average concentrations) and saliva (five-point day curves and two-point diurnal sampling). RESULTS: Average body mass loss was 9.37 ± 2.31 kg (P < 0.0001), comprising fat mass only; total lean mass was maintained. Basal sex steroids, corticosteroids, and metabolic markers were largely unaffected by the expedition except leptin, which decreased during the expedition and recovered after 15 d, a proportionately greater change than body fat. Luteinizing hormone reactivity was suppressed before and during the expedition, but recovered after 15 d, whereas follicle-stimulating hormone did not change during or after the expedition. Cortisol reactivity did not change during or after the expedition. Basal (suppressed) cortisol was 73.25 ± 45.23 mmol·L before, 61.66 ± 33.11 mmol·L 5 d postexpedition and 54.43 ± 28.60 mmol·L 16 d postexpedition (P = 0.7). Hair cortisol was elevated during the expedition. CONCLUSIONS: Maintenance of reproductive and hypothalamic-pituitary-adrenal axis function in women after an extreme physical endeavor, despite energy deficiency, suggests high female biological capacity for extreme endurance exercise.