Infectious Diseases at High Altitude

Emergency Care for High-Altitude Trekking and Climbing

Introduction: High altitude regions are characterized by harsh conditions (environmental, rough terrain, natural hazards, and limited hygiene and health care), which all may contribute to the risk of accidents/emergencies when trekking or climbing. Exposure to hypoxia, cold, wind, and solar radiation are typical features of the high altitude environment. Emergencies in these remote areas place high demands on the diagnostic and treatment skills of doctors and first-aiders. The aim of this review is to give insights on providing the best possible care for victims of emergencies at high altitude. Methods: Authors provide clinical recommendations based on their real-world experience, complemented by appropriate recent studies and internationally reputable guidelines. Results and Discussion: This review covers most of the emergencies/health issues that can occur when trekking or during high altitude climbing, that is, high altitude illnesses and hypothermia, freezing cold injuries, accidents, for example, with severe injuries due to falling, cardiovascular and respiratory illnesses, abdominal, musculoskeletal, eye, dental, and skin issues. We give a summary of current recommendations for emergency care and pain relief in case of these various incidents.

Respiratory tract infection: an unfamiliar risk factor in high-altitude pulmonary edema

The dramatic changes in physiology at high altitude (HA) as a result of the characteristic hypobaric hypoxia condition can modify innate and adaptive defense mechanisms of the body. As a consequence, few sojourners visiting HA with mild or asymptomatic infection may have an enhanced susceptibility to high-altitude pulmonary edema (HAPE), an acute but severe altitude sickness. It develops upon rapid ascent to altitudes above 2500 m, in otherwise healthy individuals. Though HAPE has been studied extensively, an elaborate exploration of the HA disease burden and the potential risk factors associated with its manifestation are poorly described. The present review discusses respiratory tract infection (RTI) as an unfamiliar but important risk factor in enhancing HAPE susceptibility in sojourners for two primary reasons. First, the symptoms of RTI s resemble those of HAPE. Secondly, the imbalanced pathways contributing to vascular dysfunction in HAPE also participate in the pathogenesis of the infectious processes. These pathways have a crucial role in shaping host response against viral and bacterial infections and may further worsen the clinical outcomes at HA. Respiratory tract pathogenic agents, if screened in HAPE patients, can help in ascertaining their role in disease risk and also point toward their association with the disease severity. The microbial screenings and identifications of pathogens with diseases are the foundation for describing potential molecular mechanisms underlying host response to the microbial challenge. The prior knowledge of such infections may predict the manifestation of disease etiology and provide better therapeutic options.

Hypoxia exacerbates intestinal injury and inflammatory response mediated by myeloperoxidase during Salmonella Typhimurium infection in mice

BACKGROUND

High-altitude exposure can cause oxidative stress damage in the intestine, which leads to increased intestinal permeability and bacterial translocation, resulting in local and systemic inflammation. Control of infection is critically dependent on the host's ability to kill pathogens with reactive oxygen species (ROS). Myeloperoxidase (MPO) targets ROS in pathogens. This study aimed to investigate the effects of hypoxia on the colonic mucosal barrier and myeloperoxidase (MPO)-mediated innate immune response in the colon.

METHODS AND RESULTS

Genetically engineered mice were exposed to a hypobaric oxygen chamber for 3 days and an inflammation model was established using Salmonella Typhimurium infection. We found that hypoxic exposure caused the development of exacerbated bacterial colitis and enhanced bacterial dissemination in MPO-deficient mice. Infection and disease severity were associated with significantly increased Ly6G+ neutrophil and F4/80+ macrophage counts in infected tissues, which is consistent with elevated proinflammatory cytokines and chemoattractant molecules. Hypoxia restrained antioxidant ability and MPO deficiency aggravated the respiratory burst in the colon.

CONCLUSION

Hypoxia can damage the colonic mucosa. MPO mediates the innate immune response and regulates the mucosal and systemic inflammatory responses to Salmonella infection during hypoxia.

Pott's Puffy: First Shot is the Best Shot

OBJECTIVE

Low incidence of Pott's Puffy tumor (PPT) has caused studying risk factors and recurrences of the disease to be difficult. We used the comparatively increased incidence at our institution to evaluate potential risk factors for the disease process itself and prognostic factors for recurrence of the disease.

METHODS

Single institutional retrospective chart review identified 31 patients from 2010 to 2022 with PPT compared with a control group of 20 patients with either chronic rhinosinusitis or recurrent sinusitis. Patient mean age of PPT was 42 (range of 5 to 90) with the majority of the patient population as male (74%) and Caucasian (68%) in the setting of rural West Texas. Patient mean age of the control group was 50.7 (range of 30-78) with majority of patient population as male (55%) and Caucasian (70%). Interventions studied were functional endoscopic sinus surgery (FESS), FESS with trephination, and cranialization with or without FESS to compare prognostic factors for recurrence rates of PPT. These patients' prognostic risk factors for recurrence and risk factors to develop PPT were analyzed using Analysis of Variance (ANOVA) χ2 statistical analysis with Fischer exact testing.

RESULTS

Mean age was 42 years (range of 5-90) with the majority of the PPT patient population as male (74%) and Caucasian (68%) with an overall incidence of about 1 in 300,000. Pott's Puffy tumor patients were significantly favored in the younger and male population compared with the control patients. Risk factors of no prior allergy diagnosis, previous trauma, medication allergy to penicillin class or cephalosporin class, and lower body mass index were significant in the PPT population compared with the control group. Significant prognostic factors for recurrence of PPT were prior history of sinus surgery and operative treatment choice. Fifty percent (3/6) of patients with prior sinus surgery had recurrence of PPT. Of our 4 treatment options (FESS, FESS with trephination, FESS with cranialization, or cranialization alone), ;FESS had a recurrence of PPT of 0% (0/13), FESS with trephination had a recurrence of PPT of 50% (3/6), FESS with cranialization had a recurrence of PPT of 11% (1/9), and cranizalization alone had a recurrence of PPT of 0% (0/3). Of note, postop chronic rhinosinusitis was seen in 46% (6/13) of FESS alone, 17% (1/6) with FESS with trephination, 0% (0/9) with FESS with cranialization, and 33% (1/3) with just cranialization alone.

CONCLUSIONS

Pott's Puffy tumor patients were younger and predominately male when compared to the control patients. No prior allergy diagnosis, previous trauma history, medication allergy to penicillin class or cephalosporin class, and lower body mass index are risk factors for PPT. There are 2 prognostic factors that predict recurrence of PPT: first operative treatment choice and prior sinus surgery. History of prior sinus surgery tends to increase the recurrence of PPT. The first operative treatment plan is the best shot at definitively treating PPT. Correct management surgically can prevent recurrence of PPT as well as long-term recurrence of chronic rhinosinusitis. With early diagnosis and mild disease, FESS is sufficient to prevent recurrence of PPT but chronic sinusitis may continue to occur if frontal sinus outflow track is not well opened. If considering trephination, a definitive cranialization may be more suited for more advanced disease since our study showed 50% of recurrence of PPT with trephination and FESS along with 17% chronic sinusitis long term. More advanced diseases with higher WBCs and intracranial extension do better with more aggressive surgical management with a cranialization with or without FESS which shows to reduce rates of PPT recurrence significantly.

Exploring the links between gut microbiome changes and irritable bowel syndrome in Han populations in the Tibetan Plateau

The gut microbiome shows changes under a plateau environment, while the disbalance of intestinal microbiota plays an important role in the pathogenesis of irritable bowel syndrome (IBS); however, the relationship between the two remains unexplored. In this work, we followed up a healthy cohort for up to a year before and after living in a plateau environment and performed 16S ribosomal RNA (rRNA) sequencing analysis of their fecal samples. Through evaluating the participants' clinical symptoms, combined with an IBS questionnaire, we screened the IBS sub-population in our cohort. The sequencing results showed that a high-altitude environment could lead to changes in the diversity and composition of gut flora. In addition, we found that the longer the time volunteers spent in the plateau environment, the more similar their gut microbiota composition and abundance became compared to those before entering the plateau, and IBS symptoms were significantly alleviated. Therefore, we speculated that the plateau may be a special environment that induces IBS. The taxonomic units g_Alistipes, g_Oscillospira, and s_Ruminococcus_torques, which had been proved to play important roles in IBS pathogenesis, were also abundant in the IBS cohort at high altitudes. Overall, the disbalance of gut microbiota induced by the plateau environment contributed to the high frequency of IBS and the psychosocial abnormalities associated with IBS. Our results prompt further research to elucidate the relevant mechanism.

Reprogramming of glucocorticoid receptor function by hypoxia

Here, we investigate the impact of hypoxia on the hepatic response of glucocorticoid receptor (GR) to dexamethasone (DEX) in mice via RNA-sequencing. Hypoxia causes three types of reprogramming of GR: (i) much weaker induction of classical GR-responsive genes by DEX in hypoxia, (ii) a number of genes is induced by DEX specifically in hypoxia, and (iii) hypoxia induces a group of genes via activation of the hypothalamic-pituitary-adrenal (HPA) axis. Transcriptional profiles are reflected by changed GR DNA-binding as measured by ChIP sequencing. The HPA axis is induced by hypothalamic HIF1α and HIF2α activation and leads to GR-dependent lipolysis and ketogenesis. Acute inflammation, induced by lipopolysaccharide, is prevented by DEX in normoxia but not during hypoxia, and this is attributed to HPA axis activation by hypoxia. We unfold new physiological pathways that have consequences for patients suffering from GC resistance.

A Higher Altitude Is Associated with Increased Incidence of Infections following Primary Total Hip Arthroplasty

Purpose

The purpose of this study was to evaluate whether patients undergoing primary total hip arthroplasty (THA) at a higher elevation have higher rates of: 1) in-hospital length of stay (LOS); 2) surgical site infections (SSIs); 3) periprosthetic joint infections (PJIs); and 4) costs.

Materials and Methods

The Medicare claims database was used to identify patients who underwent primary THA at an altitude higher than 4,000 feet (ft). High-altitude patients were matched to patients who underwent primary THA at an altitude less than 100 ft, yielding 24,958 and 124,765 patients respectively. Outcomes that were assessed included in-hospital LOS, SSIs, PJIs, and costs of care. A P-value less than 0.001 was considered statistically significant.

Results

Patients in the study group had significantly longer in-hospital LOS (4 days vs 3 days, P<0.0001). In addition, patients in the study group had a significantly higher incidence and odds of developing SSIs (1.16% vs 0.86%; odds ratio [OR], 1.34; P<0.0001) and PJIs (0.91% vs 0.58%; OR, 1.56; P<0.0001) within 90-days following the index procedure, compared to matched controls. Higher altitude patients incurred higher day of surgery ($16,139.76 vs $15,279.42; P<0.0001) and 90-day costs ($18,647.51 vs $16,401.62; P<0.0001).

Conclusion

This study demonstrated that primary THA procedures performed at an elevation higher than 4,000 ft are associated with longer in-hospital LOS, higher rates of SSIs, PJIs, and costs of care. Orthopedists and other healthcare professionals can use this information to provide adequate education for these patients regarding the potential complications that may occur following their procedure.

Irbesartan ameliorates chronic mountain sickness in a rat model via the cholesterol metabolism: An iTRAQ -based proteomics analysis

OBJECTIVE

To study the effects of irbesartan on pulmonary artery lesions in a rat model with chronic mountain sickness (CMS) and identify the biomarkers involved.

METHODS

In this study, we used a rat model of CMS to evaluate the therapeutic effect of irbesartan by measuring pulmonary artery pressure and evaluating the histopathology of the pulmonary artery. We also used proteomics technology to identify differentially expressed proteins (DEPs) in the serum and performed bioinformatics analysis. Results were then verified by enzyme linked immunosorbent assay (ELISA) and immunohistochemistry (IHC).

RESULTS

Irbesartan treatment induced a significant decrease (P < 0.05) in the pulmonary artery pressure of CMS rats. Histopathological and electron microscope further confirmed that high altitude hypoxia induced changes in the structure of the pulmonary artery tissue and caused ultrastructural lesions. Proteomics analysis identified 40 DEPs; bioinformatics analysis further revealed that the cholesterol metabolism pathway plays a crucial role in the occurrence of CMS. ELISA and IHC verified that several DEPs (Apo-A1, Apo-C1, Apo-E, IGF-1, Profilin1, and Col1a1) represent critical biological markers in pulmonary artery disease caused by CMS.

CONCLUSIONS

Irbesartan significantly improved pulmonary artery damage in a rat model of CMS possibly by impacting on the cholesterol metabolism pathway and by reducing damage to vascular endothelial cells. Irbesartan also inhibited the expression levels of IGF-1, Profilin1 and Col1a1 to relieve pulmonary artery pressure and improve lung function by inhibiting vascular remodeling. Several proteins were identified as potential biomarkers of CMS, including Apo-A1, Apo-C1, Apo-E, IGF-1, Profilin1, and Col1a1.

Differential expression of skeletal muscle mitochondrial proteins in yak, dzo, and cattle: a proteomics-based study

Changes in yak mitochondria by natural selection in a hypoxic environment could be utilized to understand adaptation to low-oxygen conditions. Therefore, the differences in proteome profile of skeletal muscle mitochondria from yak, dzo, and cattle were analyzed by mass spectrometry, which were then classified into 3 groups, comparing between yak and dzo, yak and cattle, and dzo and cattle. 376 unique mitochondrial proteins were identified, including 192, 191, and 281 proteins in the yak-dzo, yak-cattle, and dzo-cattle groups, respectively. NRDP1 and COQ8A were expressed at higher levels in yak and dzo compared to those in cattle, indicating higher endurance capacity of yak and dzo in a low-oxygen environment. Gene Ontology (GO) terms of biological processes were significantly enriched in oxidation-reduction process, and that of molecular functions and cellular component were enriched in oxidoreductase activity and the mitochondrion, respectively. The most significantly affected pathways in Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were Parkinson’s disease, Huntington’s disease, and oxidative phosphorylation between the yak-cattle and dzo-cattle groups; while metabolic pathways, citrate cycle, and carbon metabolism were significantly affected pathways in the yak-dzo group. ATP synthases, MTHFD1, MDH2, and SDHB were the most enriched hub proteins in the protein-protein interaction (PPI) network. These results indicated that mammals living at high altitudes could possibly possess better bioenergy metabolism than those living in the plains. The key proteins identified in the present study may be exploited as candidate proteins for understanding and fine-tuning mammalian adaptation to high altitudes.

AMPK and the Need to Breathe and Feed: What's the Matter with Oxygen?

We live and to do so we must breathe and eat, so are we a combination of what we eat and breathe? Here, we will consider this question, and the role in this respect of the AMP-activated protein kinase (AMPK). Emerging evidence suggests that AMPK facilitates central and peripheral reflexes that coordinate breathing and oxygen supply, and contributes to the central regulation of feeding and food choice. We propose, therefore, that oxygen supply to the body is aligned with not only the quantity we eat, but also nutrient-based diet selection, and that the cell-specific expression pattern of AMPK subunit isoforms is critical to appropriate system alignment in this respect. Currently available information on how oxygen supply may be aligned with feeding and food choice, or vice versa, through our motivation to breathe and select particular nutrients is sparse, fragmented and lacks any integrated understanding. By addressing this, we aim to provide the foundations for a clinical perspective that reveals untapped potential, by highlighting how aberrant cell-specific changes in the expression of AMPK subunit isoforms could give rise, in part, to known associations between metabolic disease, such as obesity and type 2 diabetes, sleep-disordered breathing, pulmonary hypertension and acute respiratory distress syndrome.

Inpatient treatment of trekkers and Nepalese workers in the high-altitude environment of Mt. Everest Region 1996-2011: A retrospective analysis

BACKGROUND

The study investigates the diagnoses of inpatients (tourists and Nepali workers) of Kunde Hospital (Mt.Everest region) over 15 years.

METHODS

Records from January 1996 to September 2011 were analyzed concerning date, gender, age group, nationality, purpose of visit, diagnosis, length of treatment, and condition at discharge. Diagnoses were coded according to ICD-10-WHO 2010. Data were analyzed using descriptive statistics and non-parametric tests. P < 0.05 was defined as significant.

RESULTS

479 inpatients were included: 363 (75.8%) males (202 trekkers (42.2%), 277 Nepalese workers (57.8%)). Most suffered from altitude sickness (45.5%), acute gastroenteritis (10.4%) or acute respiratory infection (8.4%). Severe cases of altitude sickness amongst trekkers decreased but increased amongst workers. Severe cases of acute gastroenteritis amongst trekkers increased. Mean length of inpatient treatment was 4.6 days ±2.7 days. 573/2030 days of treatment were caused by altitude sickness. 70 patients were evacuated, 9 died.

CONCLUSION

Altitude illness caused the majority of inpatient treatment and acute gastroenteritis may be an underestimated risk for both groups. Other severe problems were mostly illnesses, not trauma. Improved prevention strategies are needed for both groups. For tourists who often show pre-existing diseases this includes an individual pre-travel expert advice. Nepali workers should be instructed concerning acclimatization.

Red Maca (Lepidium meyenii), a Plant from the Peruvian Highlands, Promotes Skin Wound Healing at Sea Level and at High Altitude in Adult Male Mice

Nuñez, Denisse, Paola Olavegoya, Gustavo F. Gonzales, and Cynthia Gonzales-Castañeda. Red maca (Lepidium meyenii), a plant from the Peruvian highlands, promotes skin wound healing at sea level and at high altitude in adult male mice. High Alt Med Biol 18:373-383, 2017.-Wound healing consists of three simultaneous phases: inflammation, proliferation, and remodeling. Previous studies suggest that there is a delay in the healing process in high altitude, mainly due to alterations in the inflammatory phase. Maca (Lepidium meyenii) is a Peruvian plant with diverse biological properties, such as the ability to protect the skin from inflammatory lesions caused by ultraviolet radiation, as well as its antioxidant and immunomodulatory properties. The aim of this study was to determine the effect of high altitude on tissue repair and the effect of the topical administration of the spray-dried extract of red maca (RM) in tissue repair. Studies were conducted in male Balb/c mice at sea level and high altitude. Lesions were inflicted through a 10 mm-diameter excisional wound in the skin dorsal surface. Treatments consisted of either (1) spray-dried RM extract or (2) vehicle (VH). Animals wounded at high altitude had a delayed healing rate and an increased wound width compared with those at sea level. Moreover, wounding at high altitude was associated with an increase in inflammatory cells. Treatment with RM accelerated wound closure, decreased the level of epidermal hyperplasia, and decreased the number of inflammatory cells at the wound site. In conclusion, RM at high altitude generate a positive effect on wound healing, decreasing the number of neutrophils and increasing the number of macrophages in the wound healing at day 7 postwounding. This phenomenon is not observed at sea level.

Animal, Microbial, and Fungal Borne Skin Pathology in the Mountain Wilderness: A Review

Mountains are home to numerous organisms known to cause skin disease. Bites, stings, poisons, chemicals, toxins, trauma, and infections all contribute to this end. Numerous plants, animals, fungi, bacteria, viruses, and protozoa are responsible. This paper aims to review skin illness and injury sustained from organisms in the mountains of North America. Other factors such as increased ultraviolet radiation, temperature extremes, and decreasing atmospheric pressure along with human physiologic parameters, which contribute to disease severity, will also be discussed. After reading this review, one should feel more comfortable identifying potentially harmful organisms, as well as diagnosing, treating, and preventing organism-inflicted skin pathology sustained in the high country.

Retinal Hemorrhage in a High-Altitude Aid Post Volunteer Doctor: A Case Report

Bhandari, Sanjeeb Sudarshan, Pranawa Koirala, Nirajan Regmi, and Sushil Pant. Retinal hemorrhage in a high-altitude aid post volunteer doctor: a case report. High Alt Med Biol. 18: 285-287, 2017.-High-altitude retinal hemorrhages (HARHs) are seen at altitudes more than 3000 m, are usually multiple, flame shaped, and adjacent to blood vessels. Development near the macula causes blurring of vision, otherwise, they are symptomless and self-limiting. They often develop during the first few days after ascent to high altitude and subjects often suffer from acute mountain sickness (AMS) or high-altitude cerebral edema (HACE). People going to high altitude for the first time are more susceptible to retinal hemorrhages than experienced climbers and high-altitude dwellers. We present a case of a 31-year-old male doctor who developed sudden unilateral blurring of vision without any other symptoms after 6 weeks of volunteering at a high-altitude aid post in Nepal. There were no features suggestive of AMS or HACE. All examinations were normal except for fundoscopic examination in the left eye, which determined macular retinal hemorrhage. Although he was reluctant to descend, he was counseled to descend and refrained from further ascent to higher altitude, which could accentuate hypoxemia and any strenuous activities that increase intraocular pressure. He recovered his vision after few weeks in Kathmandu and his retinal hemorrhages regressed. Hypoxia exacerbated by repeated bouts of rapid ascent to further higher altitudes may have contributed to his HARH. This suggests that unilateral retinal hemorrhages can develop even after several weeks at high altitude without concomitant AMS or HACE. People going to high altitude are reluctant to retreat, before reaching their target, when they suffer from HARH. The same is shown by a physician. So it is very important for healthcare professionals working at high altitudes especially in the Himalayas of Nepal to have a good knowledge about HARH and its proper treatment.