New genetic and physiological factors for excessive erythrocytosis and Chronic Mountain Sickness

In the last few years, genetic and functional studies have provided important insight on the pathophysiology of excessive erythrocytosis (EE), the main sign of Chronic Mountain Sickness (CMS). The recent finding of the association of the CMS phenotype with a single-nucleotide polymorphism (SNP) in the Sentrin-specific Protease 1 (SENP1) gene, and its differential expression pattern in Andean highlanders with and without CMS, has triggered large interest in high-altitude studies because of the potential role of its gene product in the control of erythropoiesis. The SENP1 gene encodes for a protease that regulates the function of hypoxia-relevant transcription factors such as Hypoxia-Inducible Factor (HIF) and GATA, and thus might have an erythropoietic regulatory role in CMS through the modulation of the expression of erythropoietin (Epo) or Epo receptors. The different physiological patterns in the Epo-EpoR system found among Andeans, even among highlanders with CMS, together with their different degrees of erythropoietic response, might indicate specific underlying genetic backgrounds, which in turn might reflect different levels of adaptation to lifelong high-altitude hypoxia. This minireview discusses recent genetic findings potentially underlying EE and CMS, and their possible physiological mechanisms in Andean highlanders.

Diabetes, trekking and high altitude: recognizing and preparing for the risks

Although regular physical activity is encouraged for individuals with diabetes, exercise at high altitude increases risk for a number of potential complications. This review highlights our current understanding of the key physiological and clinical issues that accompany high-altitude travel and proposes basic clinical strategies to help overcome obstacles faced by trekkers with Type 1 or Type 2 diabetes. Although individuals with diabetes have adaptations to the hypoxia of high altitude (increased ventilation, heart rate, blood pressure and hormonal responses), elevated counter-regulatory hormones can impair glycaemic control, particularly if mountain sickness occurs. Moreover, high-altitude-induced anorexia and increased energy expenditure can predispose individuals to dysglycaemia unless careful adjustments in medication are performed. Frequent blood glucose monitoring is imperative, and results must be interpreted with caution because capillary blood glucose meter results may be less accurate at high elevations and low temperatures. It is also important to undergo pre-travel screening to rule out possible contraindications owing to chronic diabetes complications and make well-informed decisions about risks. Despite the risks, healthy, physically fit and well-prepared individuals with Type 1 or Type 2 diabetes who are capable of advanced self-management can be encouraged to participate in these activities and attain their summit goals. Moreover, trekking at high altitude can serve as an effective means to engage in physical activity and to increase confidence with fundamental diabetes self-management skills.

Research on rat models of hypobaric hypoxia-induced pulmonary hypertension

OBJECTIVE

Rat models of hypobaric hypoxia-induced pulmonary hypertension are commonly used in studies of chronic mountain sickness, while there are few researches specially focusing on these rats model. This study aims to exploring possible pathogenesis of hypobaric hypoxia-induced pulmonary hypertension by experimenting on hypobaric hypoxia-induced PH rat models at different simulate- altitudes.

MATERIALS AND METHODS

32 healthy male SD rats were randomly divided into six groups of different degree and time period of hypobaric hypoxia. The mean pulmonary arterial pressure (m PAP), right ventricular pressure (RVSP), the right ventricle (RV), left ventricular (LV), ventricular septal (S), the right ventricular hypertrophy index (RVHI) [calculated under the formula of RV / (LV + S)], hematoxylin-eosin staining, elastic fibers staining, the ratio of the thickness of vascular wall to its outer diameter (MT%), the ratio of the cross-sectional area of the middle vascular wall to the total vascular cross-sectional area (MA%); the α-SMA, and the Ki6 expressions were detected to evaluated the pulmonary hypertension.

RESULTS

There were significant differences of the mPAP, RVSP and RVHI value between the hypobaric hypoxia groups and the control group (p < 0.05). The mPAP, RVSP, RVHI, MT%, MA%, α-SMA, and Ki6 of rats in model groups at an altitude of 3KM were higher than those of the control group, which raised gradually with the number of weeks increasing. The mPAP, RVSP, RV / (LV + S) value, MT%, MA%, α-SMA, and Ki67 of the 5KM-4W group were significantly higher than those of the control group (p < 0.05).

CONCLUSIONS

Rat models with pulmonary hypertension at different altitudes have been successfully established by automatic adjusting hypobaric hypoxia chamber. Exposure to a low oxygen environment at a simulate-altitude of 3 km for 8 weeks have caused the pathological remodeling of pulmonary vascular walls and pulmonary hypertension, and further led to a series of pathological changes, including right ventricular hypertrophy. This model is easy to be replicated with good reproducibility and provides evidence for clinical trial of drugs.

Activation of autophagy in rats with plateau stress-induced intestinal failure

Hypobaric hypoxia may damage the intestinal mucosa, which may induce multiple organ dysfunction. However, little work has been done regarding whether high altitude hypoxia is associated with failure of the intestinal mucosal barrier. The aim of this study was to investigate the change of the autophagy after the intestinal failure in rats acutely exposed to plateau stress. Fifty Wistar rats were randomly divided into five groups: the plain group, plateau for 6 h, 12 h, 24 h, and 48 h (n = 10 in each group). The acute exposure to plateau was established at a simulated altitude of 4767 meters (m) in a decompression chamber. Intestinal injury was verified by light microscopy. The autophagosomes in the intestinal epithelial cells were observed by transmission electron microscopy (TEM). The protein expression of Beclin1 and LC3B in the intestinal epithelial cells were analyzed by immunohistochemistry. Compared with the plain group, acute exposure to plateau led to a time-dependent damage of the intestinal epithelium. The autophagosome was observed after the intestinal failure following acute exposure to high altitude for 6 h. The expression of Beclin1 and LC3B protein in the rats exposed to acute plateau for 6 h, 12 h, 24 h and 48 h were significantly higher than those in the plain group. The expression of autophagy also showed a significant increase in rats with intestinal failure following acute exposure to plateau stress.

Electrocardiographic changes during exercise in acute hypoxia and susceptibility to severe high-altitude illnesses

BACKGROUND

The goals of this study were to compare ECG at moderate exercise in normoxia and hypoxia at the same heart rate, to provide evidence of independent predictors of hypoxia-induced ECG changes, and to evaluate ECG risk factors of severe high-altitude illness.

METHODS AND RESULTS

A total of 456 subjects performed a 20-minute hypoxia exercise test with continuous recording of ECG and physiological measurements before a sojourn above 4000 m. Hypoxia did not induce any conduction disorder, arrhythmias, or change in QRS axis. The amplitude of the P wave in V1 was lower in hypoxia than in normoxia. The amplitudes of the R, S, and T waves and the Sokolow index decreased in hypoxia. Under hypoxia, the amplitude of the ST segment decreased in II and V6 and increased in V1, the ST slope rose in V5 and V6, and the J point was lower in II, V5, and V6. Multivariate regression of hypoxic/normoxic ratios of electrophysiological parameters and clinical characteristics showed a correlation between the decrease in Sokolow index and T-wave amplitude in V5 with desaturation at exercise. Trained status and low body mass index were associated with a smaller decrease in T-wave amplitude in V5 and V6. Comparison of ECG between subjects suffering or not suffering from severe high-altitude illness failed to show any difference.

CONCLUSIONS

During a hypoxia exercise test, a dose-dependent hypoxia-induced decrease in the amplitude of the P/QRS/T waves was observed. No standard ECG characteristic predicted the risk of developing severe high-altitude illness. Further studies are required to clarify the cause of these electric changes and their potential predictive role in cardiac events.

Increased systemic low-grade inflammation in high altitude native rats mediated by adrenergic receptors

OBJECTIVE

To compare the serum levels of inflammatory mediators in high altitude (HA) native rats, and to search for the possible underlying mechanism(s).

METHODS

The study was carried out between January and April 2013. Fifty male rats from the same genetic pool were bred at either a HA or low altitude (LA) area. The study was carried out in 2 stages. In the first stage, serum levels of inflammatory markers, adhesive molecules, lipid profiles, catecholamines, magnesium (Mg+2), and lipid peroxidation were compared between theses 2 groups. In the second stages, inflammatory response and lipid peroxidation were analyzed in HA native rats after treatment with either alpha (Prazosin) or beta (propranolol) adrenergic blockage.

RESULTS

The HA native rats showed significant increases in the serum levels of inflammatory cytokines, lipid profiles, as well as a significant increase in the urinary norepinephrine with a concomitant decrease in the serum levels of Mg+2 and increased lipid peroxidation. Blockage of the beta and alpha adrenergic receptors of the HA rats caused partial or complete decreases in both inflammatory and oxidative stress mediators.

CONCLUSION

Living under HA conditions results in an increased systemic inflammatory reaction; an effect that is mediated through the sympathetic nervous system mainly via alpha-adrenergic receptors and could be attributed to low Mg+2 levels.

High-altitude headache

A human being's exposure to altitude, and the consequent hypobarism, entails a complex series of adaptive mechanisms that depend on the rate of ascent and the altitude reached. When these mechanisms fail, so-called acute mountain sickness (AMS) results, with headache as its predominant symptom. It has been observed, nonetheless, that well-acclimated mountaineers may have headache without symptoms of AMS. We consider that high altitude and ensuing hypobarism bring about three possibilities of cephalalgia: the first is covered by the set of AMS clinical manifestations and is undoubtedly the most frequent; the second occurs independently of acute mountain sickness and is probably due exclusively to hypoxia; and the third includes altitude-triggered migraine or migraine-like episodes. These are neurogenic problems secondary to hypoxia caused by hypobarism and, in all events, have a common denominator: hypoxia and a fundamental white organ, the brain.

High-altitude retinopathy--case report

High-altitude retinopathy is one of altitude-related illnesses. Its signs include high-altitude retinal hemorrhages, dilated vessels and peripapillary hyperemia. Increased intracranial pressure seems to be the main cause of all high-altitude diseases including high-altitude retinopathy, cerebral oedema and high-altitude pulmonary oedema. We present the case of high-altitude retinopathy in a 35-year-old woman who reported decreased vision in her right eye, scotomas and high-altitude retinopathy after ascending to more than 7000 meters above sea level. The associated optical coherence tomography findings, fundus photography and literature review are presented. High-altitude retinopathy is an important multifactorial condition of unknown mechanism and etiology, which significantly impacts human vision. Climbing high mountains can cause retinopathy in otherwise healthy people and may lead to permanent sequelae such as retinal nerve fiber layer and optic nerve defects. These symptoms, however, may resolve without causing any permanent damage to the retina. Conservative treatment may help to relieve them. With increasing popularity of mountaineering, ophthalmologists should be prepared to diagnose and treat high-altitude retinopathy.

Clinical practice: Acute high-altitude illnesses

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?

[Effect of high altitude on birth weight and adverse perinatal outcomes in two Argentine populations]

INTRODUCTION

Depending on the geographical altitude the purpose of this work was to analyze in two argentine populations the variation of birth weight (BW) and adverse perinatal outcomes, adjusting for maternal and obstetric factors.

MATERIAL AND METHODS

Data from 4000 births in the provinces of Jujuy and 4000 in Buenos Aires (Sarda Maternity Hospital) (1996-2000) recruited and randomized from the Perinatal Information System was used. The data were grouped according to an altitudinal gradient composed by Sarda Maternity (20 masl) and the geographic regions of Jujuy province: Ramal (500 masl), Valle (1200 masl), Quebrada (2500 masl) and Puna (3500 masl). Outcome variables were BW > 3000 g, BW <2500 g, ponderal index (PI), prematurity, small for gestational age (SGA) and intrauterine growth restriction (FGR), while potentially confounding variables were: age, type of partner, education, overweight, obesity, smoking, hypertension, preeclampsia, urinary infection, growth restriction and cesarean section.

RESULTS

An increasing altitudinal gradient for adolescent mothers (<19 years) and decreasing for the rest of the maternal obstetric variables was observed. The BW, BW>3000 g, BW<2500 g and PI were negatively associated with altitude (p <0.001). Prematurity, SGA and FGR showed an opposite trend (p <0.001). Adjusted for confounding variables BW <3000 g, SGA, FGR<0.90 and PI <2.53 showed an increased risk with geographical altitude (p <0.05).

CONCLUSIONS

Altitude was independently associated with BW restriction and adverse perinatal outcomes. Given the impact of BW reduction in the risk of chronic no communicable diseases this relationship in other populations, regardless of their location altitude, should be assess.

[Acute mountain sickness and high altitude cerebral and pulmonary edema]

Altitude hypoxia is responsible for acute mountain sickness. It can worsen and generate a high altitude cerebral edema, which can be fatal. After reminding the reader clinical and epidemiological facts, this review aims to present new insights of the physiopathological continuity between these two illnesses and the current preventive and treatment tools. Have new medications, as sumatriptans, kept their promises? Have recent studies provide evidence of empirical use of old drugs as aspirin or ibuprofen? What are acetazolamide and dexamethasone places? This wide range of medication doesn't replace non-pharmacological tools.

[High-altitude retinopathy]

CASE REPORT

This case report presents a 36 year-old male with a sudden loss of vision while taking part in an expedition in the Daulaghiri (8,167 metres high peak located in the Himalayan Mountain Range).

DISCUSSION

High altitude retinal haemorrhage is a common condition in those mountaineers who reach altitudes over 5,500m. Depending on its location it may not present any symptoms and the condition improves with no further complications. However, in case of macular involvement the vision decreases dramatically and the consequences are uncertain.

Protective effect of total flavonoids of seabuckthorn (Hippophae rhamnoides) in simulated high-altitude polycythemia in rats

Seabuckthorn (Hippophae rhamnoides L.) has been used to treat high altitude diseases. The effects of five-week treatment with total flavonoids of seabuckthorn (35, 70, 140 mg/kg, ig) on cobalt chloride (5.5 mg/kg, ip)- and hypobaric chamber (simulating 5,000 m)-induced high-altitude polycythemia in rats were measured. Total flavonoids decreased red blood cell number, hemoglobin, hematocrit, mean corpuscular hemoglobin levels, span of red blood cell electrophoretic mobility, aggregation index of red blood cell, plasma viscosity, whole blood viscosity, and increased deformation index of red blood cell, erythropoietin level in serum. Total flavonoids increased pH, pO₂, Sp_O2, pCO₂ levels in arterial blood, and increased Na⁺, HCO₃⁻, Cl⁻, but decreased K⁺ concentrations. Total flavonoids increased mean arterial pressure, left ventricular systolic pressure, end-diastolic pressure, maximal rate of rise and decrease, decreased heart rate and protected right ventricle morphology. Changes in hemodynamic, hematologic parameters, and erythropoietin content suggest that administration of total flavonoids from seabuckthorn may be useful in the prevention of high altitude polycythaemia in rats.

High altitude-induced pituitary apoplexy

Sudden ascent to high altitudes beyond 2,438 m can cause life-threatening complications such as acute mountain sickness and high altitude cerebral and pulmonary oedema. We present a case of pituitary apoplexy in a young man who ascended to high altitude gradually, after proper acclimatisation. He developed headache, nausea, vomiting and persistent hypotension. Magnetic resonance imaging revealed an enlarged pituitary gland with haemorrhage. His hormonal estimation showed acute adrenal insufficiency due to corticotropin deficiency. The patient responded well to conservative medical management with hormonal replacement therapy. This is most likely the first reported case of high altitude-induced pituitary apoplexy in the literature.

[Pulmonary hypertension and lung edema at high altitude. Role of endothelial dysfunction and fetal programming]

High altitude constitutes an exciting natural laboratory for medical research. While initially, the aim of high-altitude research was to understand the adaptation of the organism to hypoxia and find treatments for altitude-related diseases, over the past decade or so, the scope of this research has broadened considerably. Two important observations led to the foundation for the broadening of the scientific scope of high-altitude research. First, high-altitude pulmonary edema (HAPE) represents a unique model which allows studying fundamental mechanisms of pulmonary hypertension and lung edema in humans. Secondly, the ambient hypoxia associated with high-altitude exposure facilitates the detection of pulmonary and systemic vascular dysfunction at an early stage. Here, we review studies that, by capitalizing on these observations, have led to the description of novel mechanisms underpinning lung edema and pulmonary hypertension and to the first direct demonstration of fetal programming of vascular dysfunction in humans.

High serum zinc and serum testosterone levels were associated with excessive erythrocytosis in men at high altitudes

Chronic mountain sickness (CMS), a lack of adaptation to altitude characterized by excessive erythrocytosis (EE), is a health problem associated with life at high altitude. The erythropoietic process is regulated by both erythropoietin and testosterone. Zinc (Zn) is known to be related with testosterone and hemoglobin levels; meanwhile, nitric oxide was also associated with adaptation to high altitude. The aim of this study was to determine the relationship of hemoglobin and CMS score with serum levels of zinc, total testosterone (TT), calculated free testosterone (cFT), bioavailable testosterone (BAT), hemoglobin, and nitric oxide in men at high altitude with or without EE. Men residing in Lima (150 m) and Cerro de Pasco (4,340 m), Peru, were divided into three groups: (1) low altitude, (2) high altitude without EE (hemoglobin < 21 g/dl), and (3) high altitude with EE (hemoglobin ≥ 21 g/dl). Adjusted multivariable regression models showed that serum testosterone (total or free) and Zn levels were independently correlated with increased hemoglobin levels. Similarly, hemoglobin was positively related with signs/symptoms of CMS; however, both increased the serum Zn and the nitric oxide levels correlated with reduced risk for signs/symptoms of CMS. In conclusion, higher serum testosterone levels and Zn levels were associated with EE, and low scores of signs/symptoms of CMS were associated with higher Zn and nitric oxide levels.

[Changes of VEGF, TNF-alpha, IL-6 and NO in serum of patients with HAPE]

OBJECTIVE

To explore the possible pathophysiological process and mechanisms underlying the development and formation of high altitude pulmonary edema(HAPE) by observing the changes in contents of VEGF, TNF-alpha, IL-6 and NO in serum from the initiated and recovery of HAPE patients.

METHODS

We studied 10 HAPE patients in a Chinese population. The patients were divided into two groups including HAPE initiate group and the recovery group. Contents of VEGF, TNF-alpha, IL-6 and NO in serum of the two groups were determined to study the process of HAPE.

RESULTS

VEGF levels in the HAPE initiate one and the recovery groups were (167.9 +/- 26.5 and 53.1 +/- 17.0 pg/ ml), respectively. There was a significant decrease of VEGF content in recovery one compared to the HAPE group. The same results for TNF-alpha were gained. The levels of TNF-alpha in recovery group was much lower than that in the HAPE initiate one. They were (29.2 +/- 6.8) pg/ml and (86.2 +/- 24.1) pg/ml, respectively. The contents of IL-6 in HAPE initiate group and the recovery group were (32.3 +/- 16.5) pg/ml and (12. 5 +/- 8.0) pg/ml, respectively. But no significance existed. The level of NO in HAPE initiate group was (33.8 +/- 3.3) micromol/L, and it remarkably increased to (74.1 +/- 6.2) micromol/L in recovery one.

CONCLUSION

VEGF, TNF-alpha, IL-6 and NO participated in the different aspects of the pathophysiological process and might have influence on HAPE.

[The study of plasma proteomic changes in a patient with high-altitude cerebral edema]

OBJECTIVE

High-altitude cerebral edema (HACE) is one of the most serious acute mountain sickness and its underlying mechanism is still unknown clearly. The aim of this study was to determine the changes of plasma proteins in high altitude cerebral edema patients for discovering essential biomarkers used for the routine prophylaxis, diagnosis and treatment.

METHODS

Plasma protein profiling two dimensional gel electrophoresis followed by mass spectrometry was used to explore protein alterations in one patient with high-altitude cerebral edema (HACE). Striking differences in two-dimensional gel proteomes of plasma were observed between high-altitude cerebral edema (HACE) and high-altitude pulmonary edema (HAPE) and between high-altitude cerebral edema (HACE) and mild acute mountain sickness (mAMS). Furthermore, apolipoprotein E altered in high-altitude cerebral edema was validated by ELISA.

RESULTS

Different six spots were found in this study from the comparison between HACE and HAPE, and there were different six spots which were detected from the plasma of HACE patient in comparison to mAMS. Apolipoprotein E was identified in the two groups of comparative maps and results of ELISA consisted with the results of 2-DE.

CONCLUSION

In this study, we used proteomic approach to explore HACE firstly and found different proteins that were probably associated with HACE. This would offer a clue to a better understanding of HACE for precaution, diagnosis and treatment.

Delayed appearance of high altitude retinal hemorrhages

BACKGROUND

Retinal hemorrhages have been described as a component of high altitude retinopathy (HAR) in association with altitude illness. In this prospective high altitude study, we aimed to gain new insights into the pathophysiology of HAR and explored whether HAR could be a valid early indicator of altitude illness.

METHODOLOGY/PRINCIPAL FINDINGS

28 mountaineers were randomly assigned to two ascent profiles during a research expedition to Mt. Muztagh Ata (7546 m/24,751 ft). Digital fundus photographs were taken prior to expedition at 490 m (1,607 ft), during expedition at 4497 m (14,750 ft = base camp), 5533 m (18,148 ft), 6265 m (20,549 ft), 6865 m (22,517 ft) and 4.5 months thereafter at 490 m. Number, size and time of occurrence of hemorrhages were recorded. Oxygen saturation (SpO₂) and hematocrit were also assessed. 79% of all climbers exhibited retinal hemorrhages during the expedition. Number and area of retinal bleeding increased moderately to medium altitudes (6265 m). Most retinal hemorrhages were detected after return to base camp from a high altitude. No post-expeditional ophthalmic sequelae were detected. Significant negative (SpO₂ Beta: -0.4, p<0.001) and positive (hematocrit Beta: 0.2, p = 0.002, time at altitude Beta: 0.33, p = 0.003) correlations with hemorrhages were found.

CONCLUSIONS/SIGNIFICANCE

When closely examined, a very large amount of climbers exhibit retinal hemorrhages during exposure to high altitudes. The incidence of retinal hemorrhages may be greater than previously appreciated as a definite time lag was observed between highest altitude reached and development of retinal bleeding. Retinal hemorrhages should not be considered warning signs of impending severe altitude illness due to their delayed appearance.

Effect of chronic high altitude hypoxia on foetal and maternal juxta-alveolar distal pulmonary smooth muscle cells actin and calponin organisation and growth profiles

BACKGROUND

The effect of chronic high altitude hypoxia (CHAH) in the juxta-alveolar region near the air-blood interface is unknown because of the experimental inaccessibility of this region.

OBJECTIVE

To examine primary cultures of digested juxta-alveolar smooth muscle cells for hypoxia-induced changes.

METHODS

Smooth Muscle Cells (SMCs) obtained by dispase digestion of the extreme lung parenchyma were used to study the effect of CHAH in the juxta-alveolar region and foetal and maternal cells were compared. Pulmonary venous SMCs were also obtained from dissected 5th to 7th generation levels pulmonary veins (<0.5 mm). Fluorescence tagged antibodies against alpha smooth muscle actin (alpha SMA) and calponin respectively were used as markers to identify cellular structural differences by routine immunohistochemistry. Comparison of the functional integrity of the cells was made using their growth profiles obtained by radiolabeled thymidine incorporation and liquid scintillation counting.

RESULTS

Marked differences were seen in juxta-alveolar SMCs obtained by digestion of extreme lung parenchyma of hypoxic sheep. Hypoxic adult sheep cells showed increased filamentation. Hypoxic foetal sheep cells showed internal restructuring and disorganization of both alpha-SMA and calponin filaments. The growth profiles of juxta-alveolar SMCs showed that the hypoxia-affected cells of both the foetus and adult sheep had a fast initial growth rate peaking at 48h while their normoxic equivalents had a steadier growth rate peaking at 72h. Hypoxia-affected cells showed contact inhibition at ~50% subconfluence and apoptosis by 48h.

CONCLUSION

Chronic high altitude hypoxia causes both phenotypical and functional changes in pulmonary smooth muscle cells near the air/blood interface.

[The pathophysiology of acute mountain sickness]

The hypoxia that increases in altitude environment and results from conditions dissimilarity, is the main cause of different forms of the altitude sickness. These range from benign form, called acute mountain sickness (AMS), to the states of direct threat to life, like high altitude pulmonary edema (HAPE) and high altitude cerebral edema (HACE). Each organism demonstrates individual, different sensitivity to the conditions of altitude environment. Prior stays on heights help to develop kind of individual memory, which together with physical preparation meaningly decreases, however does not exclude completely, probability of being taken ill. Growing interest in high-mountaineering makes the altitude sickness one of the challenges of modern medicine.

[High altitude pulmonary edema: the importance of early diagnosis]

In high altitude setting is present a syndrome linked to hypoxia, exercise and low temperatures, causing multiple organ damage, which may also lead to death. The main clinical pictures are represented by acute mountain sickness, high altitude pulmonary edema (HAPE), high altitude cerebral edema. A clinical case with the main determinants of HAPE, during a trek in the Himalayas valley is described.

Sickle cell trait as a cause of splenic infarction while climbing Mt. Fuji

We report a 38-year-old mestizo man with the sudden onset of left upper abdominal pain while climbing Mt. Fuji, which is the highest mountain in Japan. Enhanced computed tomography showed splenic infarction. Although his peripheral blood smear was normal, a hemoglobin S level of 40% established the diagnosis of sickle cell trait (SCT). This trait is common worldwide, but is not well recognized by doctors in Japan because no Japanese patients with SCT have been reported. However, in Japan it is important to consider SCT when assessing foreign patients with splenic infarction.

[Mountain sickness]

Mountain sickness is a common problem upon climbing rapidly to an elevation above 2500 metres. The symptoms are mostly mild, passing within a couple of days. If the symptoms and lack of adaptation to thin air are neglected, the symptoms may quickly become worse, leading to a life-threatening cerebral or pulmonary edema. Every physician providing travel counseling should be aware of this disease and the correct measures for its management.

Efficacy of oxygen inhalation in sumatriptan refractory "high altitude" cluster headache attacks

We describe the case of a 40-year-old woman, affected by episodic cluster headache, who presented with a cluster headache triggered by exposure to high altitude. Her attacks were refractory to sumatriptan, very effective at sea level, but responded to oxygen. A pathophysiological mechanism is proposed.

Emerging concepts in acute mountain sickness and high-altitude cerebral edema: from the molecular to the morphological

Acute mountain sickness (AMS) is a neurological disorder that typically affects mountaineers who ascend to high altitude. The symptoms have traditionally been ascribed to intracranial hypertension caused by extracellular vasogenic edematous brain swelling subsequent to mechanical disruption of the blood-brain barrier in hypoxia. However, recent diffusion-weighted magnetic resonance imaging studies have identified mild astrocytic swelling caused by a net redistribution of fluid from the "hypoxia-primed" extracellular space to the intracellular space without any evidence for further barrier disruption or additional increment in brain edema, swelling or pressure. These findings and the observation of minor vasogenic edema present in individuals with and without AMS suggest that the symptoms are not explained by cerebral edema. This has led to a re-evaluation of the relevant pathogenic events with a specific focus on free radicals and their interaction with the trigeminovascular system.

Effects of iron supplementation and depletion on hypoxic pulmonary hypertension: two randomized controlled trials

CONTEXT

Hypoxia is a major cause of pulmonary hypertension in respiratory disease and at high altitude. Recent work has established that the effect of hypoxia on pulmonary arterial pressure may depend on iron status, possibly acting through the transcription factor hypoxia-inducible factor, but the pathophysiological and clinical importance of this interaction is unknown.

OBJECTIVE

To determine whether increasing or decreasing iron availability modifies altitude-induced hypoxic pulmonary hypertension.

DESIGN, SETTING, AND PARTICIPANTS

Two randomized, double-blind, placebo-controlled protocols conducted in October-November 2008. In the first protocol, 22 healthy sea-level resident men (aged 19-60 years) were studied over 1 week of hypoxia at Cerro de Pasco, Peru (altitude 4340 m). In the second protocol, 11 high-altitude resident men (aged 30-59 years) diagnosed with chronic mountain sickness were studied over 1 month of hypoxia at Cerro de Pasco, Peru.

INTERVENTION

In the first protocol, participants received intravenous infusions of Fe(III)-hydroxide sucrose (200 mg) or placebo on the third day of hypoxia. In the second protocol, patients underwent staged isovolemic venesection of 2 L of blood. Two weeks later, patients received intravenous infusions of Fe(III)-hydroxide sucrose (400 mg) or placebo, which were subsequently crossed over.

MAIN OUTCOME MEASURE

Effect of varying iron availability on pulmonary artery systolic pressure (PASP) assessed by Doppler echocardiography.

RESULTS

In the sea-level resident protocol, approximately 40% of the pulmonary hypertensive response to hypoxia was reversed by infusion of iron, which reduced PASP by 6 mm Hg (95% confidence interval [CI], 4-8 mm Hg), from 37 mm Hg (95% CI, 34-40 mm Hg) to 31 mm Hg (95% CI, 29-33 mm Hg; P = .01). In the chronic mountain sickness protocol, progressive iron deficiency induced by venesection was associated with an approximately 25% increase in PASP of 9 mm Hg (95% CI, 4-14 mm Hg), from 37 mm Hg (95% CI, 30-44 mm Hg) to 46 mm Hg (95% CI, 40-52 mm Hg; P = .003). During the subsequent crossover period, no acute effect of iron replacement on PASP was detected.

CONCLUSION

Hypoxic pulmonary hypertension may be attenuated by iron supplementation and exacerbated by iron depletion.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00952302.

[Gastrointestinal dysfunction in acute severe mountain sickness and its relation with multiple organ dysfunction syndrome]

OBJECTIVE

To investigate the relationship between gastrointestinal dysfunction (GD) and multiple organ dysfunction syndrome (MODS) in acute severe mountain sickness (ASMS), including high altitude pulmonary edema (HAPE), and high altitude cerebral edema (HACE), by a retrospective study of medical records and prospective study of hospitalized patients.

METHODS

In retrospective study, the clinical data of 3 184 inpatients of General Hospital of Tibetan Military Command suffering from ASMS in the past 50 years (from June, 1958 to June, 2007) were collected. Statistical analysis was performed to study the relationship between GD and MODS in these patients. For the prospective study, 10 admitted patients of ASMS were included. Gastroscopic examination was performed for the ASMS patients, and gastric and duodenal mucosa was scrutinized. At the same time, 30 g of glutamine (Gln) capsule was orally ingested each day for 3 days after the first day of admission. Ten healthy volunteers were included in the control group, and received the same treatment. The levels of serum diamine oxidase (DAO), malonic dialdehyde (MDA), endotoxin and lactulose/mannitol (L/M) ratio were detected before and after treatment in two groups.

RESULTS

First, 49.8% of the patients with ASMS were complicated with GD, with 1.5% of fairy stool, and 1.0% with occult blood in stool. In 83 cases of ASMS complicated with MODS, 21.7% (18 cases) appeared GD, and the score of GD was 5.5 in the total score of all organ injury. Second, endoscopic examination showed extensive edema and localized hemorrhage in gastrointestinal mucous membrane, with dotted and patched erosion in gastric antrum and fundus. The pre-treatment DAO, MDA, and endotoxin were higher in the observation group than those in the control group (all P<0.01). After 3 days of Gln capsule treatment, DAO, MDA, and endotoxin were significantly decreased in the observation group (P<0.05 or P<0.01). The pre-treatment L/M ratio in observation group was significantly higher than that in healthy control group (150.69+/-19.91 vs. 117.91+/-17.78, P<0.01). The L/M ratio was significantly decreased after the treatment, as it decreased to 129.37+/-19.75 (P<0.05). However, no significant change in the healthy control group was observed.

CONCLUSION

GD plays a major role in the pathogenesis of MODS in ASMS patients.

[Serious and sometimes fatal consequences of high-altitude pulmonary oedema]

Three women aged 25, 34 and 22 years respectively, experienced high-altitude pulmonary oedema during a climbing holiday. The first patient presented with complaints arising from a fast ascent to high altitude and was treated with acetazolamide and rapid descent. She recovered without any complications. The second patient developed symptoms during the night, which were not recognised as high-altitude pulmonary oedema. The next morning she died while being transported down on a stretcher without having received any medication or oxygen. The third case was not a specific presentation of high-altitude pulmonary oedema but autopsy revealed pulmonary oedema. This woman had already been higher up on the mountain before she developed complications. The cases illustrate the seriousness of this avoidable form of high altitude illness. The current Dutch national guidelines advise against the use of medication by lay people. A revision is warranted: travellers to high altitude should be encouraged to carry acetazolamide, nifedipine and corticosteroids on the trip. Travel guides ought to be trained to use these drugs. In addition climbing travellers should be encouraged to adopt appropriate preventive behaviour and to start descending as soon as signs of high-altitude pulmonary oedema develop.

A case of hereditary protein S deficiency presenting with cerebral sinus venous thrombosis and deep vein thrombosis at high altitude

A 35-year-old healthy male with no history of any past medical illness developed severe headache, vomiting and drowsiness while at high altitude (4,572 m) in the eastern Himalayan ranges. He was evacuated to a tertiary-care hospital where he was diagnosed to have cerebral sinus venous thrombosis (CSVT) on magnetic resonance imaging, with deep vein thrombosis (DVT) of his right popliteo-femoral vein on color Doppler study. Investigation for thrombophilia revealed protein S (PS) deficiency in this patient. Family screening revealed low levels of PS in two elder brothers. One brother had a history of 'stroke in young' at the age of 20 years with the other being asymptomatic. This established the hereditary nature of PS deficiency. We are not aware of any previously published report on hereditary PS deficiency combined with CSVT and DVT occurring at high altitude. However, 1 case of protein C deficiency with CSVT has been reported previously.

[Cerebral vasoreactivity in high-altitude cerebral edema]

INTRODUCTION

High-altitude cerebral edema is a potentially fatal neurologic syndrome that develops in subjects exposed to high-altitude. It may appear associated to other forms of altitude illnesses as acute mountain sickness or high-altitude pulmonary edema. The exact pathophysiology of high-altitude cerebral edema is still unknown and there is not consensus about the primarily type of edema: vasogenic or cytotoxic. We present a patient who suffered high-altitude cerebral edema and the clinical, neuroimaging and ultrasonographic findings at first and during the follow up.

CLINICAL CASE

A 49 year old man, mountain climber, at altitude of 5,400 m presented altered mental status and ataxia with progressive neurologic deterioration, associated to pulmonary edema. After being introduced at hyperbaric chamber, patient was descended to hospital. The magnetic resonance imaging (MRI) revealed increased T2 signal in the white matter, especially in the splenium of the corpus callosum. Corticosteroids and acetazolamide were administered and patient was transferred to our hospital. Transcranial Doppler sonography (TCD-A) using acetazolamide showed an impaired cerebral vasoreactivity. Clinical improvement of the patient was fast. MRI performed 14 days after clinical onset showed partial resolution of corpus callosum lesion. MRI and TCD-A performed six months after were normal.

CONCLUSIONS

TCD-A in our patient show a diminished cerebral vasoreactivity related to high-altitude cerebral edema. These findings suggest that impairment of cerebral autoregulation might play a role in high-altitude cerebral edema pathogenesis. Reversible clinical and neuroimaging changes indicate a predominant vasogenic edema.

[A case of acute mountain sickness followed by globus pallidus syndrome]

A 71-year-old female was suffered from acute mountain sickness at an altitude of about 3,700 m. and became comatose. Although the patient recovered from the symptom after coming down from the mountain, family members and friends began to notice her personality changes in daily life. She became apathetic, uncommunicative, expressionless, less interested in hobbies and less sociable and was pointed it out by them. In neurological images, MRI revealed localized lesions at the globus pallidus, bilaterally. It was conjectured that pallidal lesions caused by hypobaric hypoxia at high elevation in the case induced neurobehavioral syndrome (globus pallidus syndrome) similar to the frontal lobe syndrome by way of the frontal-subcortical circuits. As, in recent years, the transportation to high ground has become relatively easy for the elderly, it is feared that the incidence of acute mountain sickness may increase. In acute mountain sickness, while neurological symptoms at the acute phase, such as headache, consciousness disturbances and ataxia, are emphasized, it is necessary, in examination of patients who recovered from acute symptoms, to recognize the presence of executive dysfunction as aftereffect, as seen in the present case.

[The clinical significance of leucocytosis and increase in interleukin content in acute mountain sickness complicated with multiple organ dysfunction syndrome]

OBJECTIVE

To study the role of white blood cell (WBC) and interleukins (ILs) in acute mountain sickness (AMS) complicated with multiple organ dysfunction syndrome (MODS).

METHODS

Three thousand one hundred and eighty-four patients suffering from severe AMC in the past 50 years were surveyed with questionnaire. Correlation analysis was done to explore the relationship between differential count of WBC and elevation of ILs contents and MODS.

RESULTS

There was no difference in differential count of WBC between essential high altitude pulmonary edema (HAPE) and secondary HAPE. No difference was also found between simple HAPE and high altitude cerebral edema (HACE). However, obvious difference in WBC was found between HACE accompanied by HAPE and simple HAPE or simple HACE in the differential counts of WBC, counts of WBC and neutrophil were significantly elevated, while lymphocyte was significantly declined (all P < 0.05). The count of WBC in people suffering from AMS accompanied by MODS was higher than patients only suffering from AMS, lymphocyte was significantly decreased, the difference was obviously (both P < 0.01). The content of tumor necrosis factor-alpha (TNF-alpha), IL-1, IL-2, IL-6 and IL-8 of severe AMS patients were obviously higher than that of normal people, therefore the content of IL-4 in severe AMS patients was obviously lower than that normal people the difference were obvious (all P < 0.01).

CONCLUSION

People suffering from AMS also exist systemic inflammatory response syndrome (SIRS). SIRS play an important part in MODS which is a major cause of AMS, and it's a critical factor of high altitude MODS.

Treatment of high altitude pulmonary edema at 4240 m in Nepal

High altitude pulmonary edema (HAPE) is the leading cause of death from altitude illness and rapid descent is often considered a life-saving foundation of therapy. Nevertheless, in the remote settings where HAPE often occurs, immediate descent sometimes places the victim and rescuers at risk. We treated 11 patients (7 Nepalese, 4 foreigners) for HAPE at the Himalayan Rescue Association clinic in Pheriche, Nepal (4240 m), from March 3 to May 14, 2006. Ten were admitted and primarily treated there. Seven of these (6 Nepalese, 1 foreigner) had serious to severe HAPE (Hultgren grades 3 or 4). Bed rest, oxygen, nifedipine, and acetazolamide were used for all patients. Sildenafil and salmeterol were used in most, but not all patients. The duration of stay was 31 +/- 16 h (range 12 to 48 h). Oxygen saturation was improved at discharge (84% +/- 1.7%) compared with admission (59% +/- 11%), as was ultrasound comet-tail score (11 +/- 4 at discharge vs. 33 +/- 8.6 at admission), a measure of pulmonary edema for which admission and discharge values were obtained in 7 patients. We conclude it is possible to treat even serious HAPE at 4240 m and discuss the significance of the predominance of Nepali patients seen in this series.

High-altitude headache

High-altitude headache (HAH) is an important public health problem because many of the millions of visitors to locations high above sea level get significant headaches each year. Headache is the most common symptom of acute exposure to high altitude. It may be a manifestation of acute mountain sickness (AMS), as well as of chronic mountain sickness (CMS). This article describes the clinical picture of AMS and CMS. The clinical characteristics of HAH are presented, its pathophysiology is discussed, and the acute and preventive treatment options are reviewed.

Alternobaric vertigo: prevalence in Portuguese Air Force pilots

CONCLUSION

Having found a prevalence rate of alternobaric vertigo in Portuguese Air Force pilots that is somewhat higher than previously reported, we underline the importance of implementing education on the management of this condition as part of routine Air Force pilot training programs.

OBJECTIVES

Alternobaric vertigo is a condition in which transient vertigo with spatial disorientation occurs suddenly during flying or diving activities, caused by bilateral asymmetrical changes in middle ear pressure. Its prevalence is very likely underestimated and under-reported, with the 10-17% prevalence rate mentioned in early literature not being challenged by recent data.

SUBJECTS AND METHODS

To assess its actual prevalence, the authors requested all high performance aircraft pilots presently on active duty in the Portuguese Air Force to anonymously answer a questionnaire on alternobaric vertigo symptoms, after a short briefing on the subject.

RESULTS

A 29% prevalence rate of in-flight episodes consistent with alternobaric vertigo was obtained.

High altitude pulmonary edema in a patient with previous pneumonectomy

High altitude pulmonary edema (HAPE) is a life-threatening illness that can occur in individuals ascending to altitudes exceeding 2400 m. The risk factors are rapid ascent, physical exertion and a previous history of HAPE. This work presents a case study of a 74-year-old man who underwent left side pneumonectomy 40 years ago and subsequently experienced several instances of HAPE. The well-known risk factors for HAPE were excluded in this patient. We suspect that the post-pneumonectomy condition may be a risk factor for HAPE based on this case.

Acute mountain sickness with reversible vasospasm

A 32-year-old Japanese woman with headache, anorexia and malaise, just after travelling cities of the altitude of over 4,000 m by a long-distance coach is described. Her magnetic resonance imaging (MRI) demonstrated strikingly increased T2 signal in the corpus callosum, particularly in the splenium, and MR angiography (MRA) revealed widespread vasospasm. These abnormalities resolved on subsequent MRI studies. We diagnosed her as high altitude cerebral edema (HACE), considered to be the end stage of acute mountain sickness (AMS).

Reverse association between high-altitude headache and nasal congestion

No evidence is available to show that nasal congestion is a manifestation of exposing an individual to high altitude and hypoxia. Since both nasal congestion and high-altitude headache are vasogenic, we explored whether there is a coincidence between these two symptoms. A prospective observational study was carried out on a cohort of 118 adults (>18 years old) in a mountain clinic at 3450 m. After 24 h of ascent, an interview was held to ask if each individual experienced acute mountain sickness symptoms (headache, etc.) and nasal congestion. Sixty-six (55.9%) individuals mentioned headache within 24 h after ascent and nasal congestion was reported by 34 (28.8%) individuals. There was a reverse association between headache and nasal congestion (P < 0.001). In conclusion, there is a reverse association between altitude headache and nasal congestion, probably as result of contradictory autoregulation effects or exaggerated sympathetic activity.

High altitude pulmonary edema: a pressure-induced leak

High altitude pulmonary edema (HAPE) is a non-cardiogenic pulmonary edema that can occur in healthy individuals who ascend rapidly to altitudes above 3000-4000m. Excessive pulmonary artery pressure (PAP) is crucial for the development of HAPE, since lowering pulmonary artery pressure by nifedipine or tadalafil (phosphodiesterase-5-inhibitor) will in most cases prevent HAPE. Recent studies using microspheres in swine and magnetic resonance imaging in humans strongly support the concept and primacy of nonuniform hypoxic arteriolar vasoconstriction to explain how hypoxic pulmonary vasoconstriction occurring predominantly at the arteriolar level can cause leakage. Evidence is accumulating that the excessive PAP response in HAPE-susceptible individuals is due to a reduced NO bioavailability. HAPE-susceptible individuals show an endothelial dysfunction in the systemic circulation in hypoxia. Lower levels of exhaled NO in hypoxia before and during HAPE suggest that this abnormality also occurs in the lungs and polymorphisms of the eNOS gene are associated with susceptibility to HAPE in the Indian and Japanese population.

Magnetic resonance imaging evidence of cytotoxic cerebral edema in acute mountain sickness

The present study applied T2- and diffusion-weighted magnetic resonance imaging to examine if mild cerebral edema and subsequent brain swelling are implicated in the pathophysiology of acute mountain sickness (AMS). Twenty-two subjects were examined in normoxia (21% O2), after 16 hours passive exposure to normobaric hypoxia (12% O2) corresponding to a simulated altitude of 4,500 m and after 6 hours recovery in normoxia. Clinical AMS was diagnosed in 50% of subjects during hypoxia and corresponding headache scores were markedly elevated (P<0.05 versus non-AMS). Hypoxia was associated with a mild increase in brain volume (+7.0+/-4.8 ml, P<0.05 versus pre-exposure baseline) that resolved during normoxic recovery. Hypoxia was also associated with an increased T2 relaxation time (T2rt) and a general trend toward an increased apparent diffusion coefficient (ADC). During the normoxic recovery, brain volume and T2rt recovered to pre-exposure baseline values, whereas a more marked reduction in ADC in the splenium of the corpus callosum (SCC) was observed (P<0.05). While changes in brain volume and T2rt were not selectively different in AMS, ADC values were consistently lower (P<0.05 versus non-AMS) and associated with the severity of neurologic symptoms. Acute mountain sickness was also characterized by an increased brain to intracranial volume ratio (P<0.05 versus non-AMS). These findings indicate that mild extracellular vasogenic edema contributes to the generalized brain swelling observed at high altitude, independent of AMS. In contrast, intracellular cytotoxic edema combined with an anatomic predisposition to a 'tight-fit' brain may prove of pathophysiologic significance, although the increase in brain volume in hypoxia was only about 0.5% of total brain volume.