Isolated psychosis during exposure to very high and extreme altitude - characterisation of a new medical entity

Psychotomimetic compensation versus sensitization

It is a paradox that psychotomimetic drugs can relieve symptoms that increase risk of and cooccur with psychosis, such as attention and motivational deficits (e.g., amphetamines), pain (e.g., cannabis) and symptoms of depression (e.g., psychedelics, dissociatives). We introduce the ideas of psychotomimetic compensation and psychotomimetic sensitization to explain this paradox. Psychotomimetic compensation refers to a short-term stressor or drug-induced compensation against stress that is facilitated by engagement of neurotransmitter/modulator systems (endocannabinoid, serotonergic, glutamatergic and dopaminergic) that mediate the effects of common psychotomimetic drugs. Psychotomimetic sensitization occurs after repeated exposure to stress and/or drugs and is evidenced by the gradual intensification and increase of psychotic-like experiences over time. Theoretical and practical implications of this model are discussed.

Oxygen and the Spark of Human Brain Evolution: Complex Interactions of Metabolism and Cortical Expansion across Development and Evolution

Scientific theories on the functioning and dysfunction of the human brain require an understanding of its development-before and after birth and through maturation to adulthood-and its evolution. Here we bring together several accounts of human brain evolution by focusing on the central role of oxygen and brain metabolism. We argue that evolutionary expansion of human transmodal association cortices exceeded the capacity of oxygen delivery by the vascular system, which led these brain tissues to rely on nonoxidative glycolysis for additional energy supply. We draw a link between the resulting lower oxygen tension and its effect on cytoarchitecture, which we posit as a key driver of genetic developmental programs for the human brain-favoring lower intracortical myelination and the presence of biosynthetic materials for synapse turnover. Across biological and temporal scales, this protracted capacity for neural plasticity sets the conditions for cognitive flexibility and ongoing learning, supporting complex group dynamics and intergenerational learning that in turn enabled improved nutrition to fuel the metabolic costs of further cortical expansion. Our proposed model delineates explicit mechanistic links among metabolism, molecular and cellular brain heterogeneity, and behavior, which may lead toward a clearer understanding of brain development and its disorders.

The Effect of High-Altitude Hypoxia on Neuropsychiatric Functions

Liu, Bo, Minlan Yuan, Mei Yang, Hongru Zhu, and Wei Zhang. The effect of high-altitude hypoxia on neuropsychiatric functions. High Alt Med Biol. 25:26-41, 2024. Background: In recent years, there has been a growing popularity in engaging in activities at high altitudes, such as hiking and work. However, these high-altitude environments pose risks of hypoxia, which can lead to various acute or chronic cerebral diseases. These conditions include common neurological diseases such as acute mountain sickness (AMS), high-altitude cerebral edema, and altitude-related cerebrovascular diseases, as well as psychiatric disorders such as anxiety, depression, and psychosis. However, reviews of altitude-related neuropsychiatric conditions and their potential mechanisms are rare. Methods: We conducted searches on PubMed and Google Scholar, exploring existing literature encompassing preclinical and clinical studies. Our aim was to summarize the prevalent neuropsychiatric diseases induced by altitude hypoxia, the potential pathophysiological mechanisms, as well as the available pharmacological and nonpharmacological strategies for prevention and intervention. Results: The development of altitude-related cerebral diseases may arise from various pathogenic processes, including neurovascular alterations associated with hypoxia, cytotoxic responses, activation of reactive oxygen species, and dysregulation of the expression of hypoxia inducible factor-1 and nuclear factor erythroid 2-related factor 2. Furthermore, the interplay between hypoxia-induced neurological and psychiatric changes is believed to play a role in the progression of brain damage. Conclusions: While there is some evidence pointing to pathophysiological changes in hypoxia-induced brain damage, the precise mechanisms responsible for neuropsychiatric alterations remain elusive. Currently, the range of prevention and intervention strategies available is primarily focused on addressing AMS, with a preference for prevention rather than treatment.

Acute mountain sickness predicts the emotional state of amateur mountaineers

Research on amateur mountaineers is scarce, and this study aims to delve into the emotional experiences of ten amateur mountaineers during their ascent using the "Befindlichkeitsskala" (BFS) and Lake Louise Acute Mountain Sickness scoring system (LLS). These subjects were exposed to altitudes of 3140 m, 4300 m, and 5276 m, respectively. We found that LLS scores were negatively correlated with positive emotions (β = -27.54, p < 0.05) and positively correlated with negative emotions (β = 21.97, p < 0.05). At an altitude of 4300 m, individuals with AMS exhibited significant differences in depression, anger, excitement, and inactivity compared to climbers without AMS. Upon returning to 3140 m after completing the climb, significant differences were observed in emotions such as happiness, calmness, anger, excitement, and depression. Throughout the three-day climb, noteworthy differences emerged in activity, happiness, calmness, inactivity, positive emotions (p < 0.01), negative emotions, and overall emotional scores (p < 0.05). Our study suggests a decline in the emotional well-being of amateur climbers with increasing altitude, highlighting AMS as a pivotal predictive factor for emotional experiences while climbing.

An Episode of "Third Person" Phenomenon Involving Somesthetic and Visual Hallucinations in a World-Class Extreme Altitude Climber

Psychotic symptoms can occur at high altitude. However, most reports are in the mountaineering literature and lack a clear medical assessment and interpretation. Here we report an episode of isolated high-altitude psychosis. It consisted of a "third person" phenomenon involving 2 sensory modalities: somesthetic (felt presence) and visual (the light of 2 flashlights) hallucinations. This episode occurred in a highly experienced climber when he was at an altitude of approximately 7500 m while descending at dusk from the summit of Gasherbrum I (8068 m). The symptoms lasted approximately 3 h and had fully resolved on reaching high camp (7150 m). No other physical or mental symptoms were reported. In addition to hypoxia, a number of other risk factors could have contributed to the occurrence of psychosis in this climber. These included sleep deprivation, exhaustion, dehydration, electrolyte disturbance, reduced visibility, feeling of isolation, and perceived danger. The climber has participated in many extreme altitude expeditions, and neither before nor since this episode has the climber experienced psychotic symptoms.

Isolated high altitude psychosis, delirium at high altitude, and high altitude cerebral edema: are these diagnoses valid?

Psychosis is a psychopathological syndrome that can be triggered or caused by exposure to high altitude (HA). Psychosis can occur alone as isolated HA psychosis or can be associated with other mental and often also somatic symptoms as a feature of delirium. Psychosis can also occur as a symptom of high altitude cerebral edema (HACE), a life-threatening condition. It is unclear how psychotic symptoms at HA should be classified into existing diagnostic categories of the most widely used classification systems of mental disorders, including the Diagnostic and Statistical Manual of Mental Disorders (DSM-V) and the International Statistical Classification of Diseases and Related Health Problems (ICD-11). We provide a diagnostic framework for classifying symptoms using the existing diagnostic categories: psychotic condition due to a general medical condition, brief psychotic disorder, delirium, and HACE. We also discuss the potential classification of isolated HA psychosis into those categories. A valid and reproducible classification of symptoms is essential for communication among professionals, ensuring that patients receive optimal treatment, planning further trips to HA for individuals who have experienced psychosis at HA, and advancing research in the field.

AZU1 (HBP/CAP37) and PRKCG (PKC-gamma) may be candidate genes affecting the severity of acute mountain sickness

BACKGROUND

Acute Mountain Sickness (AMS) is one of the diseases that predispose to sudden ascent to high altitudes above 2500 m. Among the many studies on the occurrence and development of AMS, there are few studies on the severity of AMS. Some unidentified phenotypes or genes that determine the severity of AMS may be vital to elucidating the mechanisms of AMS. This study aims to explore the underlying genes or phenotypes associated with AMS severity and to provide evidence for a better understanding of the mechanisms of AMS.

METHODS

GSE103927 dataset was downloaded from the Gene Expression Omnibus database, and a total of 19 subjects were enrolled in the study. Subjects were divided into a moderate to severe AMS (MS-AMS, 9 subjects) group and a no or mild AMS (NM-AMS, 10 subjects) group based on the Lake Louise score (LLS). Various bioinformatics analyses were used to compare the differences between the two groups. Another dataset, Real-time quantitative PCR (RT-qPCR), and another grouping method were used to validate the analysis results.

RESULT

No statistically significant differences in phenotypic and clinical data existed between the MS-AMS and NM-AMS groups. Eight differential expression genes are associated with LLS, and their biological functions are related regulating of the apoptotic process and programmed cell death. The ROC curves showed that AZU1 and PRKCG had a better predictive performance for MS-AMS. AZU1 and PRKCG were significantly associated with the severity of AMS. The expression of AZU1 and PRKCG were significantly higher in the MS-AMS group compared to the NM-AMS group. The hypoxic environment promotes the expression of AZU1 and PRKCG. The results of these analyses were validated by an alternative grouping method and RT-qPCR results. AZU1 and PRKCG were enriched in the Neutrophil extracellular trap formation pathway, suggesting the importance of this pathway in influencing the severity of AMS.

CONCLUSION

AZU1 and PRKCG may be key genes influencing the severity of acute mountain sickness, and can be used as good diagnostic or predictive indicators of the severity of AMS. Our study provides a new perspective to explore the molecular mechanism of AMS.

Acute Mountain Sickness and the Risk of Subsequent Psychiatric Disorders-A Nationwide Cohort Study in Taiwan

We aim to explore if there is a relationship between acute mountain sickness (AMS) and the risk of psychiatric disorders in Taiwan by using the National Health Insurance Research Database for to the rare studies on this topic. We enrolled 127 patients with AMS, and 1270 controls matched for sex, age, monthly insured premiums, comorbidities, seasons for medical help, residences, urbanization level, levels of care, and index dates were chosen from 1 January 2000 to 31 December 2015. There were 49 patients with AMS and 140 controls developed psychiatric disorders within the 16-year follow-up. The Fine-Gray model analyzed that the patients with AMS were prone to have a greater risk for the development of psychiatric disorders with an adjusted sub-distribution hazard ratio (sHRs) of 10.384 (95% confidence interval [CI]: 7.267-14.838, p < 0.001) for psychiatric disorders. The AMS group was associated with anxiety disorders, depressive disorders, bipolar disorder, sleep disorders, posttraumatic stress disorder/acute stress disorder, psychotic disorder, and substance-related disorder (SRD). The relationship between anxiety, depression, sleep disorders, SRD, and AMS still persisted even after we excluded the psychiatric disorders within the first five years after AMS. There was an association between AMS and the rising risk of psychiatric disorders in the 16 years of long-term follow-up research.

Hiccups and Slurring of Speech: Atypical Presentation of High-Altitude Cerebral Edema

High-altitude cerebral edema (HACE) is one of the rare and severe form of high-altitude mountain sickness. Usually it presents as headache, altered mental status, ataxia in un-acclimatized person with rapid ascent to high altitude. Here we report a case of a 62-year-old male patient who had history of rapid ascent to high altitude and presented to the department of emergency after descent from high altitude with an atypical presentation as hiccups and slurring of speech. Magnetic resonance imaging (MRI) of brain showed white matter edema suggestive of HACE. The patient improved after treatment with supplemental oxygen, dexamethasone, and acetazolamide. He was discharged after three days of hospital stay with complete resolution of symptoms.

Cognition and Neuropsychological Changes at Altitude-A Systematic Review of Literature

High-altitude (HA) exposure affects cognitive functions, but studies have found inconsistent results. The aim of this systematic review was to evaluate the effects of HA exposure on cognitive functions in healthy subjects. A structural overview of the applied neuropsychological tests was provided with a classification of superordinate cognitive domains. A literature search was performed using PubMed up to October 2021 according to PRISMA guidelines. Eligibility criteria included a healthy human cohort exposed to altitude in the field (at minimum 2440 m [8000 ft]) or in a hypoxic environment in a laboratory, and an assessment of cognitive domains. The literature search identified 52 studies (29 of these were field studies; altitude range: 2440 m-8848 m [8000-29,029 ft]). Researchers applied 112 different neuropsychological tests. Attentional capacity, concentration, and executive functions were the most frequently studied. In the laboratory, the ratio of altitude-induced impairments (64.7%) was twice as high compared to results showing no change or improved results (35.3%), but altitudes studied were similar in the chamber compared to field studies. In the field, the opposite results were found (66.4 % no change or improvements, 33.6% impairments). Since better acclimatization can be assumed in the field studies, the findings support the hypothesis that sufficient acclimatization has beneficial effects on cognitive functions at HA. However, it also becomes apparent that research in this area would benefit most if a consensus could be reached on a standardized framework of freely available neurocognitive tests.

The changes of electroencephalography in mountaineers on Mount Jade, Taiwan: An observational study

BACKGROUND

The diagnosis of acute mountain sickness, which lacks a reliable and objective diagnostic tool, still depends on the clinical symptoms and signs and remains a major threat and unpredictable disease affecting millions of mountaineers.

OBJECTIVES

To record electroencephalography signals with small, convenient, wireless equipment and to test whether electroencephalography parameters, which are more sensitive and reliable markers, could predict the symptoms of acute mountain sickness.

METHODS

Twenty-five participants were enrolled and separated into two groups to climb Mount Jade in Taiwan. We collected electrocardiography signals and arterial oxygen saturation data at ground, moderate (2,400 m), and high altitude (3,400 m). A spectral analysis of the electrocardiography was performed to assess the study subjects' electroencephalography activity at different frequencies (α, β, θ, δ) and the mean power frequency of electrocardiography. The clinical symptoms and Lake Louise Acute Mountain Sickness scores of the subjects were recorded for comparison.

RESULTS

A significant change in the δ power of electroencephalography was recorded in subjects ascending from the ground to a high altitude of 3,400 m in a 4-day itinerary. In addition, between the two groups of subjects with and without acute mountain sickness (Lake Louise Acute Mountain Sickness scores < 3 and ≥ 3), the δ power of electroencephalography at the fronto-parietal 1 and parietal 3 electrodes at moderate altitude as well as the changes of δ power and mean power frequency of electrocardiography over parietal 4 at high altitude showed a significant difference. At moderate altitude, the increasing δ power of electroencephalography at the parietal 4 electrode was related to the headache symptom of acute mountain sickness before ascending to high altitude.

CONCLUSION

At moderate altitude, the δ power increase of electroencephalography at the P4 electrode could be a predictor of acute mountain sickness symptoms before ascending to high altitude. Thus, electroencephalography had the potential to identify the risk of acute mountain sickness.

Optimism and Health Self-Perception-Related Differences in Indigenous Kiwchas of Ecuador at Low and High Altitude: A Cross-Sectional Analysis

Ortiz-Prado, Esteban, Katherine Simbaña-Rivera, Diego Duta, Israel Ochoa, Juan S. Izquierdo-Condoy, Eduardo Vasconez, Kathia Carrasco, Manuel Calvopiña, Ginés Viscor, and Clara Paz. Optimism and health self-perception-related differences in indigenous Kiwchas of Ecuador at low and high altitude: a cross-sectional analysis. High Alt Med Biol 00:000-000, 2021. Background: Living at high altitude causes adaptive responses at every physiological and molecular level within the human body. Emotional and psychological short- or long-term consequences, including mood changes, higher mental overload, and depression prevalence, as well as increased risk to commit suicide have been reported among highlanders. The objective of this report is to explore the differences in self-reported dispositional optimism and health perception among sex-, age-, and genotype-controlled indigenous Kiwcha natives living at two different altitudes. Methods: A cross-sectional analysis of the comparison of means of subscales and summary scores of the 36-item short-form health survey (SF-36) self-reported questionnaire and the Life Orientation Test-Revised was conducted among 219 adults Kiwchas living at low (230 m) and high altitude (3,800 m) in Ecuador. Results: High-altitude dwellers presented lower scores in all the studied dimensions of SF-36 and the total score. Differences were found for the role limitation sphere due to vitality (p = 0.005), mental health (p = 0.002), and social functioning (p = 0.005). In all the cases, participants living at low altitudes scored higher than those living at high altitudes. Lowland women were more optimistic than their high-altitude counterparts. Conclusions: We observe that populations located at high altitudes have more unfavorable self-reported health states. Although our results depict the existence of significant differences in the health status of indigenous peoples living at different altitudes, further studies are needed to explain in depth the sociodemographic and/or environmental factors that might underlie these differences.

Recommendations for traveling to altitude with neurological disorders

BACKGROUND

Several neurological conditions might worsen with the exposure to high altitude (HA). The aim of this review was to summarize the available knowledge on the neurological HA illnesses and the risk for people with neurological disorders to attend HA locations.

METHODS

A search of literature was conducted for several neurological disorders in PubMed and other databases since 1970. The neurological conditions searched were migraine, different cerebrovascular disease, intracranial space occupying mass, multiple sclerosis, peripheral neuropathies, neuromuscular disorders, epileptic seizures, delirium, dementia, and Parkinson's disease (PD).

RESULTS

Attempts were made to classify the risk posed by each condition and to provide recommendations regarding medical evaluation and advice for or against traveling to altitude. Individual cases should be advised after careful examination and risk evaluation performed either in an outpatient mountain medicine service or by a physician with knowledge of HA risks. Preliminary diagnostic methods and anticipation of neurological complications are needed.

CONCLUSIONS

Our recommendations suggest absolute contraindications to HA exposure for the following neurological conditions: (1) Unstable conditions-such as recent strokes, (2) Diabetic neuropathy, (3) Transient ischemic attack in the last month, (4) Brain tumors, and 5. Neuromuscular disorders with a decrease of forced vital capacity >60%. We consider the following relative contraindications where decision has to be made case by case: (1) Epilepsy based on recurrence of seizure and stabilization with the therapy, (2) PD (± obstructive sleep apnea syndrome-OSAS), (3) Mild Cognitive Impairment (± OSAS), and (4) Patent foramen ovale and migraine have to be considered risk factors for acute mountain sickness.

Visual hallucinations in 246-km mountain ultra-marathoners: An observational study

Ultra-marathons are typically held over harsh terrains such as mountains, deserts, or other wilderness, and place severe demands on the physical and psychological capabilities of participants. Adventure-race competitors commonly report hallucinations. The goal of this study was to gain insight into visual hallucinations (VHs) during a mountain ultra-marathon. Thirty-one Taiwanese runners who participated in the 2018 Run Across Taiwan Ultra-Marathon, which spans 246 km with an altitude difference of 3266 m and an overall cut-off time of 44 h, volunteered for this study. Self-reported questionnaires on sleep duration, hallucinatory experiences, clinical symptoms of cold- and heat-related illnesses, and the 2018 Lake Louise Acute Mountain Sickness (AMS) Score were recorded prerace, during the summit, immediately postrace, and 3-days postrace. Hematological samples were collected 1 week before, immediately after, and 3 days after the race. Eight ultra-marathoners (six males and two females; seven finishers and one withdrawer) were recruited. Three out of eight (37.5%) subjects (two males and one female) reported experiencing VHs during the last 60 km. Three out of five (60%) lower-ranked subjects experienced VHs. All eight runners slept for <30 min during the race. None of the runners presented with headache either during or after the race to meet the criteria for AMS. None of the runners suffered an abnormal thermoregulatory response or a hypoglycemic episode throughout the ultra-marathon. The changes in blood osmolality immediately postrace were subclinical, despite being statistically significant. Among the three runners with VHs, none presented with severe dehydration or dysnatremia immediately postrace. High-altitude exposure, hyper/hypothermia, dehydration, dysnatermia, or hypoglycemia did not seem to contribute to hallucination onset in our subjects during the event. VHs of ultra-marathoners may be associated with excessive physical exertion and sleep deprivation.

Evaluation of the Lake Louise Score for Acute Mountain Sickness and Its 2018 Version in a Cohort of 484 Trekkers at High Altitude

Richalet, Jean-Paul, Chantal Julia, and François J. Lhuissier. Evaluation of the Lake Louise Score for acute mountain sickness and its 2018 version in a cohort of 484 trekkers at high altitude. High Alt Med Biol. 22:353-361, 2021. Background: The Lake Louise Score (LLS) is widely used in field studies and chamber studies for the diagnosis of Acute Mountain Sickness (AMS). This score aggregates symptoms that are nonspecific: headache, gastrointestinal symptoms, fatigue, dizziness and sleep disturbance can be due to a variety of causes unrelated to altitude hypoxia. The objectives of this study were to (1) reevaluate the need for a headache score >0 for the diagnosis of AMS, (2) evaluate the role of sleep disturbances, in relation with other symptoms, (3) evaluate the significance of dizziness. Materials and Methods: We analyzed LLS from 484 trekkers at high altitude. Among them, 212 suffered from moderate AMS (mAMS: 3 ≤ LLS < 6) and 115 from severe AMS (sAMS: LLS ≥ 6). Results: Cluster analysis of AMS revealed three main groups presenting the following symptoms: Group 1 includes 254 subjects who had less than 2 symptoms; Group 2 includes 137 subjects who had fatigue, sleep disturbance, and headache, corresponding to mAMS; Group 3 includes 93 subjects who had headache, fatigue, dizziness and sleep disturbance, corresponding to sAMS. A headache score of zero was found in 25% of mAMS and 5% of sAMS subjects. Only the absence of headache associated with the absence of fatigue was specific of absence of sAMS. In subjects with a dizziness score > 1, end-tidal partial pressure of carbon dioxide during a hypoxic exercise test was lower than that in subjects with a dizziness score < 2. Subjects with high ventilatory response to hypoxia may develop dizziness with high altitude exposure. Conclusion: (1) An isolated headache score > 0 should not be mandatory to define AMS, (2) sleep disruption contributes to the diagnosis of AMS, (3) gastrointestinal symptoms and dizziness are weaker contributors to the LLS, (4) dizziness might be linked to a hyperresponsiveness to hypoxia and not to AMS itself.

Assessment of Psychotic Symptoms in Individuals Exposed to Very High or Extreme Altitude: A Field Study

Hüfner, Katharina, Fabio Caramazza, Agnieszka E. Stawinoga, Evelyn R. Pircher Nöckler, Paolo Fusar-Poli, Sanjeeb S. Bhandari, Buddha Basnyat, Monika Brodmann Maeder, Giacomo Strapazzon, Iztok Tomazin, Barbara Sperner-Unterweger, and Hermann Brugger. Assessment of psychotic symptoms in individuals exposed to very high or extreme altitude: A field study. High Alt Med Biol. xx:xxx-xxx, 2021. Background: Symptoms of psychosis such as hallucinations can occur at high or extreme altitude and have been linked to accidents on the mountain. No data are available on how to assess such symptoms in the field and what their prevalence or predisposing factors might be. Methods: In this field study at Everest Base Camp (5,365 m) in Nepal, 99 participants of organized expeditions underwent 279 assessments: The High Altitude Psychosis Questionnaire (HAPSY-Q), the Prodromal Questionnaire, 16-items (PQ-16), and the Mini International Neuropsychiatric Interview (M.I.N.I., psychosis section) were collected together with further clinical data. Statistical analysis was done for each phase, that is, altitude range of the climb, and overall data. Results: One of 97 climbers fulfilled the M.I.N.I. diagnostic criteria for psychosis during one acclimatization climb. At least one endorsed item on the HAPSY-Q and the PQ-16, indicating the presence of symptoms of psychosis in the absence of a psychotic disorders, were identified in 10/97 (10.3%) and 18/87 (20.7%) participants respectively. The scores of the HAPSY-Q and the PQ-16 were correlated (r = 0.268, p < 0.001). Odds ratio analysis identified an increased risk for accidents in individuals with endorsed items on the HAPSY-Q. Conclusions: The diagnosis of high altitude psychosis is rare in climbers during organized expeditions. Nevertheless, subdiagnostic symptoms of psychosis occurred in a significant proportion of climbers. Future research is needed to validate these pilot findings.

High-altitude cerebral edema: its own entity or end-stage acute mountain sickness?

High-altitude cerebral edema (HACE) and acute mountain sickness (AMS) are neuropathologies associated with rapid exposure to hypoxia. However, speculation remains regarding the exact etiology of both HACE and AMS and whether they share a common mechanistic pathology. This review outlines the basic principles of HACE development, highlighting how edema could develop from 1) a progression from cytotoxic swelling to ionic edema or 2) permeation of the blood brain barrier (BBB) with or without ionic edema. Thereafter, discussion turns to the available neuroimaging literature in the context of cytotoxic, ionic, or vasogenic edema in both HACE and AMS. Although HACE is clearly caused by an increase in brain water of ionic and/or vasogenic origin, there is very little evidence that this type of edema is present when AMS develops. However, cerebral vasodilation, increased intracranial blood volume, and concomitant intracranial fluid shifts from the extracellular to the intracellular space, as interpreted from changes in diffusion indices within white matter, are observed consistently in persons acutely exposed to hypoxia and with AMS. Therefore, herein we explore the idea that intracellular swelling occurs alongside AMS, and is a critical precursor to extracellular ionic edema formation. We propose that this process produces a subtle modulation of the BBB, which either together with or independent of vasogenic edema provides a transvascular segue from the end-stage of AMS to HACE. Ultimately, this review seeks to shed light on the possible processes underlying HACE pathophysiology, and thus highlights potential avenues for future prevention and treatment.

Pivotal mental states

This paper introduces a new construct, the 'pivotal mental state', which is defined as a hyper-plastic state aiding rapid and deep learning that can mediate psychological transformation. We believe this new construct bears relevance to a broad range of psychological and psychiatric phenomena. We argue that pivotal mental states serve an important evolutionary function, that is, to aid psychological transformation when actual or perceived environmental pressures demand this. We cite evidence that chronic stress and neurotic traits are primers for a pivotal mental state, whereas acute stress can be a trigger. Inspired by research with serotonin 2A receptor agonist psychedelics, we highlight how activity at this particular receptor can robustly and reliably induce pivotal mental states, but we argue that the capacity for pivotal mental states is an inherent property of the human brain itself. Moreover, we hypothesize that serotonergic psychedelics hijack a system that has evolved to mediate rapid and deep learning when its need is sensed. We cite a breadth of evidences linking stress via a variety of inducers, with an upregulated serotonin 2A receptor system (e.g. upregulated availability of and/or binding to the receptor) and acute stress with 5-HT release, which we argue can activate this primed system to induce a pivotal mental state. The pivotal mental state model is multi-level, linking a specific molecular gateway (increased serotonin 2A receptor signaling) with the inception of a hyper-plastic brain and mind state, enhanced rate of associative learning and the potential mediation of a psychological transformation.

Global REACH 2018: The influence of acute and chronic hypoxia on cerebral haemodynamics and related functional outcomes during cold and heat stress

KEY POINTS

Thermal and hypoxic stress commonly coexist in environmental, occupational and clinical settings, yet how the brain tolerates these multi-stressor environments is unknown Core cooling by 1.0°C reduced cerebral blood flow (CBF) by 20-30% and cerebral oxygen delivery (CDO₂ ) by 12-19% at sea level and high altitude, whereas core heating by 1.5°C did not reliably reduce CBF or CDO₂ Oxygen content in arterial blood was fully restored with acclimatisation to 4330 m, but concurrent cold stress reduced CBF and CDO₂ Gross indices of cognition were not impaired by any combination of thermal and hypoxic stress despite large reductions in CDO₂ Chronic hypoxia renders the brain susceptible to large reductions in oxygen delivery with concurrent cold stress, which might make monitoring core temperature more important in this context ABSTRACT: Real-world settings are composed of multiple environmental stressors, yet the majority of research in environmental physiology investigates these stressors in isolation. The brain is central in both behavioural and physiological responses to threatening stimuli and, given its tight metabolic and haemodynamic requirements, is particularly susceptible to environmental stress. We measured cerebral blood flow (CBF, duplex ultrasound), cerebral oxygen delivery (CDO₂ ), oesophageal temperature, and arterial blood gases during exposure to three commonly experienced environmental stressors - heat, cold and hypoxia - in isolation, and in combination. Twelve healthy male subjects (27 ± 11 years) underwent core cooling by 1.0°C and core heating by 1.5°C in randomised order at sea level; acute hypoxia ( P ET , O 2  = 50 mm Hg) was imposed at baseline and at each thermal extreme. Core cooling and heating protocols were repeated after 16 ± 4 days residing at 4330 m to investigate any interactions with high altitude acclimatisation. Cold stress decreased CBF by 20-30% and CDO₂ by 12-19% (both P < 0.01) irrespective of altitude, whereas heating did not reliably change either CBF or CDO₂ (both P > 0.08). The increases in CBF with acute hypoxia during thermal stress were appropriate to maintain CDO₂ at normothermic, normoxic values. Reaction time was faster and slower by 6-9% with heating and cooling, respectively (both P < 0.01), but central (brain) processes were not impaired by any combination of environmental stressors. These findings highlight the powerful influence of core cooling in reducing CDO₂ . Despite these large reductions in CDO₂ with cold stress, gross indices of cognition remained stable.

Going to Altitude with a Preexisting Psychiatric Condition

Psychiatric disorders have a high lifetime prevalence affecting about 30% of the global population. Not much is known about high altitude (HA) sojourns in individuals living with a psychiatric condition. This lack of scientific evidence contrasts with the anticipated increase in numbers of individuals with preexisting psychiatric conditions seeking medical advice on HA exposure. Not only are there risks associated with a HA climb, but physical activity in general is known to improve symptoms of many psychiatric disorder and enhance measures of mental well-being like quality of life and resilience. There are additional positive effects of alpine environments on mental health beyond those of physical activity. All individuals going to HA with a preexisting psychiatric condition should be in a state of stable disease with no recent change in medication. Specific considerations and recommendations apply to individual psychiatric disorders. During the HA sojourn the challenge is to separate altitude-related symptoms such as insomnia from prodromal symptoms of the underlying disorder (e.g., depressive episode) or altitude-related hyperventilation from panic attacks. In case an individual with preexisting anxiety disorder decides to go to HA there might be a predisposition toward acute mountain sickness (AMS), but it should always be considered that many symptoms of anxiety and AMS overlap. Any medication that is anticipated to be taken during ascent or at HA should be tested for compatibility with the psychiatric condition and medication before the trip.