Acute High-Altitude Illnesses
ABSTRACT A 45-year-old healthy man wishes to climb Mount Kilimanjaro (5895 m) in a 5-day period, starting at 1800 m. The results of a recent exercise stress test were normal; he runs 10 km 4 or 5 times per week and finished a marathon in less than 4 hours last year. He wants to know how he can prevent becoming ill at high altitude and whether training or sleeping under normobaric hypoxic conditions in the weeks before the ascent would be helpful. What would you advise?
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- "In-field diagnosis of AMS is based exclusively on an international consensus of subjective, nonspecific, equallyweighted symptoms (i.e., headache, sleep disturbance, fatigue , and dizziness) (Bartsch and Swenson, 2013). Three distinct patterns of symptoms were consistently identified in a recent study (Hall et al., 2014), supporting different pathophysiological mechanisms of AMS following acute ascent to high altitude. "
ABSTRACT: Lochner, Piergiorgio, Marika Falla, Francesco Brigo, Michael Pohl, and Giacomo Strapazzon. Ultrasonography of the optic nerve sheath diameter for diagnosis and monitoring of acute mountain sickness: A systematic review. High Alt Med Biol. 16:195-203, 2015.- Despite extensive research on acute mountain sickness (AMS), the underlying pathophysiology remains unclear. Ultrasonography studies have shown that optic nerve sheath diameter (ONSD) correlates with intracranial pressure (ICP) in critical care patients, and recent studies report elevated ONSD values at high altitude. The aim of this review was to elucidate whether 1. measurement of ONSD could shed light on the pathophysiology of AMS, and 2. ultrasonography of the ONSD could support the diagnosis of AMS. Systematic search of MEDLINE (through Pubmed; from 1966 to 14 October 2014), Cochrane Central Register of Controlled Trials (CENTRAL), and EMBASE databases. Six studies with 436 subjects (139 women, 297 men; 406 mostly Caucasian; 30 Nepalese) were included. A marked variability in ONSD was found across studies both at baseline and at high altitude. The variability in ONSD across the included studies and within each study limit the utility of ONSD measurement in the diagnosis of AMS. ONSD measurements might be useful from a population perspective, but the accuracy of optic nerve ultrasonography for single subjects and single point-in-time assessment for diagnosing AMS is questionable due to high individual variability in ONSD.High altitude medicine & biology 09/2015; 16(3):195-203. DOI:10.1089/ham.2014.1127 · 1.28 Impact Factor
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- "Reported incidences of AMS in published studies vary widely and the reasons for this variability remain poorly understood. It is generally believed that, for instance, a fast rate of ascent increases, and pre-acclimatization decreases, the risk of AMS (Bärtsch and Swenson, 2013). But for other potentially predictive factors, contradictory data have been reported. "
ABSTRACT: Waeber, Baptiste, Bengt Kayser, Lionel Dumont, Christopher Lysakowski, Martin R. Tramèr, and Nadia Elia. Impact of study design on reported incidences of acute mountain sickness: A systematic review. High Alt Med Biol. 16:000-000, 2015-Aims: Published incidences of acute mountain sickness (AMS) vary widely. Reasons for this variation, and predictive factors of AMS, are not well understood. We aimed to identify predictive factors that are associated with the occurrence of AMS, and to test the hypothesis that study design is an independent predictive factor of AMS incidence. We did a systematic search (Medline, bibliographies) for relevant articles in English or French, up to April 28, 2013. Studies of any design reporting on AMS incidence in humans without prophylaxis were selected. Data on incidence and potential predictive factors were extracted by two reviewers and crosschecked by four reviewers. Associations between predictive factors and AMS incidence were sought through bivariate and multivariate analyses for different study designs separately. Association between AMS incidence and study design was assessed using multiple linear regression. We extracted data from 53,603 subjects from 34 randomized controlled trials, 44 cohort studies, and 33 cross-sectional studies. In randomized trials, the median of AMS incidences without prophylaxis was 60% (range, 16%-100%); mode of ascent and population were significantly associated with AMS incidence. In cohort studies, the median of AMS incidences was 51% (0%-100%); geographical location was significantly associated with AMS incidence. In cross-sectional studies, the median of AMS incidences was 32% (0%-68%); mode of ascent and maximum altitude were significantly associated with AMS incidence. In a multivariate analysis, study design (p=0.012), mode of ascent (p=0.003), maximum altitude (p<0.001), population (p=0.002), and geographical location (p<0.001) were significantly associated with AMS incidence. Age, sex, speed of ascent, duration of exposure, or history of AMS were inconsistently reported and therefore not further analyzed. Reported incidences and identifiable predictive factors of AMS depend on study design.High altitude medicine & biology 07/2015; 16(3). DOI:10.1089/ham.2015.0022 · 1.28 Impact Factor
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- "Please cite this article as: Iglesias D, et al, Vascular reactivity and biomarkers of endothelial function in healthy subjects exposed to acute hypobaric hypoxia, Clin Biochem (2015), http://dx.doi.org/10.1016/j.clinbiochem.2015.06.007 consideration that high TNF-α and IL-6, and low adiponectin concentration were associated with an altered vascular reactivity, the circulating levels of these molecules have been proposed as biomarkers of endothelial function. Evaluation of vascular reactivity could be of relevance when counseling mountaineering activities and especially in individuals who will perform mountaineering activities for the first time . As history of acute mountain sickness is not known in these cases, the assessment of vascular and cardio-respiratory responses to hypoxia could help to identify subjects at risk of high altitude related illnesses. "
ABSTRACT: The aim of this study was to evaluate the effects of acute hypobaric hypoxia (HH) on vascular reactivity and biochemical markers associated with endothelial function (EF). Ten healthy subjects were exposed to a simulated altitude of 4,000 meters above sea level for 4hours in a hypobaric chamber. Vascular reactivity was measured by the flow-mediated vasodilatation (FMVD) test. Endothelin-1, high sensitive-C reactive protein (hsCRP), vascular cell adhesion molecule 1, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), paraoxonase and adiponectin levels and FMVD were evaluated before and after the exposure. Subjects were young (Age: 32±6years), lean [Body mass index: 23.9±2.0kg/m(2), waist circumference: 77(IQR: 72-80) cm] and presented normal clinical and biochemical parameters. No significant changes were evidenced in FMVD in response to HH (pre: 0.45 (0.20-0.70) vs. during: 0.50 (0.20-1.22) mm; p=0.594) On the other hand, endothelin-1 (+54%, p<0.05), hsCRP (+37%, p<0.001), IL-6 (+75%,p<0.05), TNF-α (+75%,p<0.05) and adiponectin (-39%, p<0.01) levels were significantly altered post-HH. FMVD was increased in 7 subjects and it was decreased in 3 individuals during HH exposure. Interestingly, when EF biomarkers were compared between these two subgroups of subjects, only post exposure-adiponectin levels were significantly different (49±5 vs. 38±6μg/ml, respectively, p<0.05). HH exposure had an effect on endothelin-1, adiponectin, hsCRP, IL-6 and TNF-α concentration. However, adiponectin was the only biomarker associated with an altered vascular reactivity. Copyright © 2015. Published by Elsevier Inc.Clinical biochemistry 06/2015; DOI:10.1016/j.clinbiochem.2015.06.007 · 2.28 Impact Factor