High altitude headache: efficacy of acetaminophen vs. ibuprofen in a randomized, controlled trial

Global research trends and emerging hotspots in acute high altitude illness: a bibliometric analysis and review (1937-2024)

INTRODUCTION

Acute High Altitude Illness (AHAI) includes conditions such as Acute Mountain Sickness (AMS), High Altitude Cerebral Edema (HACE), and High Altitude Pulmonary Edema (HAPE), which result from rapid ascent to altitudes exceeding 2,500 m. Although interest in AHAI research has been growing, a systematic and comprehensive analysis of global research trends remains lacking.

CONTENT

A total of 3,214 articles and reviews published from 1937 to 2024 were retrieved from the Web of Science Core Collection. Bibliometric tools, including CiteSpace and VOSviewer, were applied to thoroughly assess publication trends, collaborative networks among authors, institutional contributions, and keyword co-occurrence patterns. The dataset represents the contributions of over 11,758 authors across 86 countries and 3,378 institutions, reflecting the significant growth of this research domain.

SUMMARY AND OUTLOOK

Our findings highlight the increasing scholarly attention to AHAI research, with the United States leading in publication numbers. Emerging research themes include cellular activation, oxidative stress, risk factors, and hypobaric hypoxia. This is the first systematic bibliometric review of AHAI literature, offering a detailed roadmap of research hotspots, potential collaborations, and key future directions. These findings provide a valuable reference for researchers aiming to explore gaps and build on the existing knowledge in high-altitude medicine.

Intranasal Administration of Acetaminophen-Loaded Poly(lactic-co-glycolic acid) Nanoparticles Increases Pain Threshold in Mice Rapidly Entering High Altitudes

Background/Objectives: Orally or intravenously administered acetaminophen experiences considerable liver first-pass elimination and may cause liver/kidney damage. This work examined the pharmacological effects of acetaminophen-loaded poly(lactic-co-glycolic acid) nanoparticles (AAP PLGA NPs) intranasally administered to mice rapidly entering high altitudes. Methods: AAP PLGA NPs were prepared using ultrasonication-assisted emulsification and solvent evaporation and characterized in terms of drug encapsulation efficiency and loading, in vitro and in vivo release behaviors, and toxicity to hippocampal neurons. In vivo fluorescence imaging was used to monitor the concentrations of AAP PLGA NPs (labeled with indocyanine green) in the brain and blood of the mice after intranasal administration. The effects of these NPs on the pain threshold in mice rapidly entering high altitudes were evaluated through hot plate and tail flick experiments. Results: The AAP PLGA NPs were found to be noncytotoxic, highly biocompatible and stable, with a drug encapsulation efficiency and loading capacity of 42.53% and 3.87%, respectively. The in vitro release of acetaminophen lasted for up to 72 h, and the release rate was ~82%. After intranasal administration in vivo, the drug release occurred slowly, and the drug was mainly concentrated in the brain. Compared with nonencapsulated acetaminophen, the intranasal administration of AAP PLGA NPs resulted in higher brain levels of the drug and delayed its elimination, thus increasing the pain threshold in mice rapidly entering high altitudes. Conclusions: The proposed strategy addresses the common problems of intranasal drug administration (low retention time and bioavailability) and paves the way for effective pain management in high-altitude environments.

What Is New in Altitude- and Cold-Related Illnesses of Travel: Appraisal and Summary of the Updated Guidelines from the Wilderness Medical Society

Wilderness medicine is a rapidly evolving field and has benefited from expanded research efforts. Moreover, with an escalating occurrence of severe and cataclysmic global climatologic events, human illness arising from interaction with wilderness and recreational environments warrants increasing consideration. Within the last decade, the Wilderness Medical Society (WMS) has aggregated research findings and created guidelines on prevention measures and therapeutic options for acute altitude illness, frostbite injuries, and avalanche and non-avalanche snow burials. As new research emerges, some guidelines have been updated to reflect the most current and sound scientific conclusions. In this review, we have synthesized the evidence-based guidelines and have reviewed the quality of the guidelines according to the Appraisal of Guidelines for Research and Evaluation (AGREE) II framework. Further research efforts can expand the scope of evidence-based practice in travel medicine and ideally standardize the implementation of recommendations within both pre-travel and post-travel medical practices.

Wilderness Medical Society Clinical Practice Guidelines for the Prevention, Diagnosis, and Treatment of Acute Altitude Illness: 2024 Update

To provide guidance to clinicians about best practices, the Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for prevention, diagnosis, and treatment of acute mountain sickness, high altitude cerebral edema, and high altitude pulmonary edema. Recommendations are graded based on the quality of supporting evidence and the balance between the benefits and risks/burdens according to criteria put forth by the American College of Chest Physicians. The guidelines also provide suggested approaches for managing each form of acute altitude illness that incorporate these recommendations as well as recommendations on how to approach high altitude travel following COVID-19 infection. This is an updated version of the original WMS Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness published in Wilderness & Environmental Medicine in 2010 and the subsequently updated WMS Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness published in 2014 and 2019.

Prospective Double-Blinded Randomized Field-Based Clinical Trial of Metoclopramide and Ibuprofen for the Treatment of High Altitude Headache and Acute Mountain Sickness

INTRODUCTION

High altitude headache (HAH) and acute mountain sickness (AMS) are common pathologies at high altitudes. There are similarities between AMS and migraine headaches, with nausea being a common symptom. Several studies have shown ibuprofen can be effective for AMS prophylaxis, but few have addressed treatment. Metoclopramide is commonly administered for migraine headaches but has not been evaluated for HAH or AMS. We aimed to evaluate metoclopramide and ibuprofen for treatment of HAH and AMS.

METHODS

We performed a prospective, double-blinded, randomized, field-based clinical trial of metoclopramide and ibuprofen for the treatment of HAH and AMS in 47 adult subjects in the Mount Everest region of Nepal. Subjects received either 400 mg ibuprofen or 10 mg metoclopramide in a 1-time dose. Lake Louise Score (LLS) and visual analog scale of symptoms were measured before and at 30, 60, and 120 min after treatment.

RESULTS

Subjects in both the metoclopramide and ibuprofen arms reported reduced headache severity and nausea compared to pretreatment values at 120 min. The ibuprofen group reported 22 mm reduction in headache and 6 mm reduction in nausea on a 100 mm visual analog scale at 120 min. The metoclopramide group reported 23 mm reduction in headache and 14 mm reduction in nausea. The ibuprofen group reported an average 3.5-point decrease on LLS, whereas the metoclopramide group reported an average 2.0-point decrease on LLS at 120 min.

CONCLUSIONS

Metoclopramide and ibuprofen may be effective alternative treatment options in HAH and AMS, especially for those patients who additionally report nausea.

High-altitude illness: Management approach

In high altitudes, usually above 2500 m, travelers are faced with decreased partial pressure of oxygen along with decreased barometric pressure. High-altitude illness, a syndrome of acute mountain sickness, high-altitude cerebral edema and high-altitude pulmonary edema, occurs due to the hypobaric hypoxia when there is inadequate acclimatization. This review provides detailed information about pathophysiology, clinical features, prevention and treatment strategies for high-altitude illness according to the current literature.

Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness: 2019 Update

To provide guidance to clinicians about best preventive and therapeutic practices, the Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for prevention and treatment of acute mountain sickness, high altitude cerebral edema, and high altitude pulmonary edema. Recommendations are graded based on the quality of supporting evidence and the balance between the benefits and risks/burdens according to criteria put forth by the American College of Chest Physicians. The guidelines also provide suggested approaches to prevention and management of each form of acute altitude illness that incorporate these recommendations. This is an updated version of the original WMS Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness published in 2010 and subsequently updated as the WMS Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness in 2014.

Interventions for preventing high altitude illness: Part 3. Miscellaneous and non-pharmacological interventions

BACKGROUND

High altitude illness (HAI) is a term used to describe a group of mainly cerebral and pulmonary syndromes that can occur during travel to elevations above 2500 metres (˜ 8200 feet). Acute mountain sickness (AMS), high altitude cerebral oedema (HACE), and high altitude pulmonary oedema (HAPE) are reported as potential medical problems associated with high altitude ascent. In this, the third of a series of three reviews about preventive strategies for HAI, we assessed the effectiveness of miscellaneous and non-pharmacological interventions.

OBJECTIVES

To assess the clinical effectiveness and adverse events of miscellaneous and non-pharmacological interventions for preventing acute HAI in people who are at risk of developing high altitude illness in any setting.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, LILACS and the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) in January 2019. We adapted the MEDLINE strategy for searching the other databases. We used a combination of thesaurus-based and free-text search terms. We scanned the reference lists and citations of included trials and any relevant systematic reviews that we identified for further references to additional trials.

SELECTION CRITERIA

We included randomized controlled trials conducted in any setting where non-pharmacological and miscellaneous interventions were employed to prevent acute HAI, including preacclimatization measures and the administration of non-pharmacological supplements. We included trials involving participants who are at risk of developing high altitude illness (AMS or HACE, or HAPE, or both). We included participants with, and without, a history of high altitude illness. We applied no age or gender restrictions. We included trials where the relevant intervention was administered before the beginning of ascent.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures employed by Cochrane.

MAIN RESULTS

We included 20 studies (1406 participants, 21 references) in this review. Thirty studies (14 ongoing, and 16 pending classification (awaiting)) will be considered in future versions of this suite of three reviews as appropriate. We report the results for the primary outcome of this review (risk of AMS) by each group of assessed interventions.Group 1. Preacclimatization and other measures based on pressureUse of simulated altitude or remote ischaemic preconditioning (RIPC) might not improve the risk of AMS on subsequent exposure to altitude, but this effect is uncertain (simulated altitude: risk ratio (RR) 1.18, 95% confidence interval (CI) 0.82 to 1.71; I² = 0%; 3 trials, 140 participants; low-quality evidence. RIPC: RR 3.0, 95% CI 0.69 to 13.12; 1 trial, 40 participants; low-quality evidence). We found evidence of improvement of this risk using positive end-expiratory pressure (PEEP), but this information was derived from a cross-over trial with a limited number of participants (OR 3.67, 95% CI 1.38 to 9.76; 1 trial, 8 participants; low-quality evidence). We found scarcity of evidence about the risk of adverse events for these interventions.Group 2. Supplements and vitaminsSupplementation of antioxidants, medroxyprogesterone, iron or Rhodiola crenulata might not improve the risk of AMS on exposure to high altitude, but this effect is uncertain (antioxidants: RR 0.58, 95% CI 0.32 to 1.03; 1 trial, 18 participants; low-quality evidence. Medroxyprogesterone: RR 0.71, 95% CI 0.48 to 1.05; I² = 0%; 2 trials, 32 participants; low-quality evidence. Iron: RR 0.65, 95% CI 0.38 to 1.11; I² = 0%; 2 trials, 65 participants; low-quality evidence. R crenulata: RR 1.00, 95% CI 0.78 to 1.29; 1 trial, 125 participants; low-quality evidence). We found evidence of improvement of this risk with the administration of erythropoietin, but this information was extracted from a trial with issues related to risk of bias and imprecision (RR 0.41, 95% CI 0.20 to 0.84; 1 trial, 39 participants; very low-quality evidence). Regarding administration of ginkgo biloba, we did not perform a pooled estimation of RR for AMS due to considerable heterogeneity between the included studies (I² = 65%). RR estimates from the individual studies were conflicting (from 0.05 to 1.03; low-quality evidence). We found scarcity of evidence about the risk of adverse events for these interventions.Group 3. Other comparisonsWe found heterogeneous evidence regarding the risk of AMS when ginkgo biloba was compared with acetazolamide (I² = 63%). RR estimates from the individual studies were conflicting (estimations from 0.11 (95% CI 0.01 to 1.86) to 2.97 (95% CI 1.70 to 5.21); low-quality evidence). We found evidence of improvement when ginkgo biloba was administered along with acetazolamide, but this information was derived from a single trial with issues associated to risk of bias (compared to ginkgo biloba alone: RR 0.43, 95% CI 0.26 to 0.71; 1 trial, 311 participants; low-quality evidence). Administration of medroxyprogesterone plus acetazolamide did not improve the risk of AMS when compared to administration of medroxyprogesterone or acetazolamide alone (RR 1.33, 95% CI 0.50 to 3.55; 1 trial, 12 participants; low-quality evidence). We found scarcity of evidence about the risk of adverse events for these interventions.

AUTHORS' CONCLUSIONS

This Cochrane Review is the final in a series of three providing relevant information to clinicians, and other interested parties, on how to prevent high altitude illness. The assessment of non-pharmacological and miscellaneous interventions suggests that there is heterogeneous and even contradictory evidence related to the effectiveness of these prophylactic strategies. Safety of these interventions remains as an unclear issue due to lack of assessment. Overall, the evidence is limited due to its quality (low to very low), the relative paucity of that evidence and the number of studies pending classification for the three reviews belonging to this series (30 studies either awaiting classification or ongoing). Additional studies, especially those comparing with pharmacological alternatives (such as acetazolamide) are required, in order to establish or refute the strategies evaluated in this review.

Physiological, hematological and biochemical factors associated with high-altitude headache in young Chinese males following acute exposure at 3700 m

BACKGROUND

High-altitude headache (HAH) is the most common sickness occurred in healthy people after rapid ascending to high altitude, and its risk factors were still not well understood. To investigate physiological, hematological and biochemical risk factors associated with high-altitude headache (HAH) after acute exposure to 3700 m, we conducted a two-stage, perspective observational study. In 72 h, total 318 young Han Chinese males ascended from sea level (altitude of 50 m) to altitude of 3700 m by train. Demographic data, physiological, hematological and biochemical parameters of all participants were collected within one week prior to the departure, and within 24 h after arrival.

RESULTS

The incidence of HAH was 74.84%. For parameters measured at sea level, participants with HAH exhibited significantly higher age and lower BUN (p < 0.05). For parameters measured at 3700 m, participants with HAH exhibited significantly lower blood oxygen saturation (SpO2), higher resting heart rate (HR), higher systolic blood pressure at resting (SBP) and lower blood urea nitrogen (BUN) (all p < 0.05). At 3700 m, the severity of HAH associated with SpO2, HR and BUN significantly (all p < 0.05). Multivariate logistic regression revealed that for parameters at sea level, BUN was associated with HAH [BUN (OR:0.77, 95% CI:0.60-0.99)] and for parameters at 3700 m, SpO2, HR and BUN were associated with HAH independently [SpO2 (OR:0.84, 95% CI:0.76-0.93); HR (OR:1.03, 95% CI:1.00-1.07); BUN (OR:0.64, 95% CI:0.46-0.88)]. No association between hematological parameters and HAH was observed.

CONCLUSION

We confirmed that higher HR, lower SpO2 are independent risk factors for HAH. Furthermore, we found that at both 50 m and 3700 m, lower BUN is a novel independent risk factor for HAH, providing new insights for understanding the pathological mechanisms.

Interventions for treating acute high altitude illness

BACKGROUND

Acute high altitude illness is defined as a group of cerebral and pulmonary syndromes that can occur during travel to high altitudes. It is more common above 2500 metres, but can be seen at lower elevations, especially in susceptible people. Acute high altitude illness includes a wide spectrum of syndromes defined under the terms 'acute mountain sickness' (AMS), 'high altitude cerebral oedema' and 'high altitude pulmonary oedema'. There are several interventions available to treat this condition, both pharmacological and non-pharmacological; however, there is a great uncertainty regarding their benefits and harms.

OBJECTIVES

To assess the clinical effectiveness, and safety of interventions (non-pharmacological and pharmacological), as monotherapy or in any combination, for treating acute high altitude illness.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, LILACS, ISI Web of Science, CINAHL, Wanfang database and the World Health Organization International Clinical Trials Registry Platform for ongoing studies on 10 August 2017. We did not apply any language restriction.

SELECTION CRITERIA

We included randomized controlled trials evaluating the effects of pharmacological and non-pharmacological interventions for individuals suffering from acute high altitude illness: acute mountain sickness, high altitude pulmonary oedema or high altitude cerebral oedema.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed the eligibility of study reports, the risk of bias for each and performed the data extraction. We resolved disagreements through discussion with a third author. We assessed the quality of evidence with GRADE.

MAIN RESULTS

We included 13 studies enrolling a total of 468 participants. We identified two ongoing studies. All studies included adults, and two studies included both teenagers and adults. The 13 studies took place in high altitude areas, mostly in the European Alps. Twelve studies included participants with acute mountain sickness, and one study included participants with high altitude pulmonary oedema. Follow-up was usually less than one day. We downgraded the quality of the evidence in most cases due to risk of bias and imprecision. We report results for the main comparisons as follows.Non-pharmacological interventions (3 studies, 124 participants)All-cause mortality and complete relief of AMS symptoms were not reported in the three included trials. One study in 64 participants found that a simulated descent of 193 millibars versus 20 millibars may reduce the average of symptoms to 2.5 vs 3.1 units after 12 hours of treatment (clinical score ranged from 0 to 11 ‒ worse; reduction of 0.6 points on average with the intervention; low quality of evidence). In addition, no complications were found with use of hyperbaric chambers versus supplementary oxygen (one study; 29 participants; low-quality evidence).Pharmacological interventions (11 trials, 375 participants)All-cause mortality was not reported in the 11 included trials. One trial found a greater proportion of participants with complete relief of AMS symptoms after 12 and 16 hours when dexamethasone was administered in comparison with placebo (47.1% versus 0%, respectively; one study; 35 participants; low quality of evidence). Likewise, when acetazolamide was compared with placebo, the effects on symptom severity was uncertain (standardized mean difference (SMD) -1.15, 95% CI -2.56 to 0.27; 2 studies, 25 participants; low-quality evidence). One trial of dexamethasone in comparison with placebo in 35 participants found a reduction in symptom severity (difference on change in the AMS score: 3.7 units reported by authors; moderate quality of evidence). The effects from two additional trials comparing gabapentin with placebo and magnesium with placebo on symptom severity at the end of treatment were uncertain. For gabapentin versus placebo: mean visual analogue scale (VAS) score of 2.92 versus 4.75, respectively; 24 participants; low quality of evidence. For magnesium versus placebo: mean scores of 9 and 10.3 units, respectively; 25 participants; low quality of evidence). The trials did not find adverse events from either treatment (low quality of evidence). One trial comparing magnesium sulphate versus placebo found that flushing was a frequent event in the magnesium sulphate arm (percentage of flushing: 75% versus 7.7%, respectively; one study; 25 participants; low quality of evidence).

AUTHORS' CONCLUSIONS

There is limited available evidence to determine the effects of non-pharmacological and pharmacological interventions in treating acute high altitude illness. Low-quality evidence suggests that dexamethasone and acetazolamide might reduce AMS score compared to placebo. However, the clinical benefits and harms related to these potential interventions remain unclear. Overall, the evidence is of limited practical significance in the clinical field. High-quality research in this field is needed, since most trials were poorly conducted and reported.

Interventions for preventing high altitude illness: Part 2. Less commonly-used drugs

BACKGROUND

High altitude illness (HAI) is a term used to describe a group of mainly cerebral and pulmonary syndromes that can occur during travel to elevations above 2500 metres (˜ 8200 feet). Acute mountain sickness (AMS), high altitude cerebral oedema (HACE) and high altitude pulmonary oedema (HAPE) are reported as potential medical problems associated with high altitude ascent. In this second review, in a series of three about preventive strategies for HAI, we assessed the effectiveness of five of the less commonly used classes of pharmacological interventions.

OBJECTIVES

To assess the clinical effectiveness and adverse events of five of the less commonly used pharmacological interventions for preventing acute HAI in participants who are at risk of developing high altitude illness in any setting.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, LILACS and the World Health Organization International Clinical Trials Registry Platform (WHO ICTRP) in May 2017. We adapted the MEDLINE strategy for searching the other databases. We used a combination of thesaurus-based and free-text search terms. We scanned the reference lists and citations of included trials and any relevant systematic reviews that we identified for further references to additional trials.

SELECTION CRITERIA

We included randomized controlled trials conducted in any setting where one of five classes of drugs was employed to prevent acute HAI: selective 5-hydroxytryptamine(1) receptor agonists; N-methyl-D-aspartate (NMDA) antagonist; endothelin-1 antagonist; anticonvulsant drugs; and spironolactone. We included trials involving participants who are at risk of developing high altitude illness (AMS or HACE, or HAPE, or both). We included participants with and without a history of high altitude illness. We applied no age or gender restrictions. We included trials where the relevant medication was administered before the beginning of ascent. We excluded trials using these drugs during ascent or after ascent.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures employed by Cochrane.

MAIN RESULTS

We included eight studies (334 participants, 9 references) in this review. Twelve studies are ongoing and will be considered in future versions of this review as appropriate. We have been unable to obtain full-text versions of a further 12 studies and have designated them as 'awaiting classification'. Four studies were at a low risk of bias for randomization; two at a low risk of bias for allocation concealment. Four studies were at a low risk of bias for blinding of participants and personnel. We considered three studies at a low risk of bias for blinding of outcome assessors. We considered most studies at a high risk of selective reporting bias.We report results for the following four main comparisons.Sumatriptan versus placebo (1 parallel study; 102 participants)Data on sumatriptan showed a reduction of the risk of AMS when compared with a placebo (risk ratio (RR) = 0.43, CI 95% 0.21 to 0.84; 1 study, 102 participants; low quality of evidence). The one included study did not report events of HAPE, HACE or adverse events related to administrations of sumatriptan.Magnesium citrate versus placebo (1 parallel study; 70 participants)The estimated RR for AMS, comparing magnesium citrate tablets versus placebo, was 1.09 (95% CI 0.55 to 2.13; 1 study; 70 participants; low quality of evidence). In addition, the estimated RR for loose stools was 3.25 (95% CI 1.17 to 8.99; 1 study; 70 participants; low quality of evidence). The one included study did not report events of HAPE or HACE.Spironolactone versus placebo (2 parallel studies; 205 participants)Pooled estimation of RR for AMS was not performed due to considerable heterogeneity between the included studies (I² = 72%). RR from individual studies was 0.40 (95% CI 0.12 to 1.31) and 1.44 (95% CI 0.79 to 2.01; very low quality of evidence). No events of HAPE or HACE were reported. Adverse events were not evaluated.Acetazolamide versus spironolactone (1 parallel study; 232 participants)Data on acetazolamide compared with spironolactone showed a reduction of the risk of AMS with the administration of acetazolamide (RR = 0.36, 95% CI 0.18 to 0.70; 232 participants; low quality of evidence). No events of HAPE or HACE were reported. Adverse events were not evaluated.

AUTHORS' CONCLUSIONS

This Cochrane Review is the second in a series of three providing relevant information to clinicians and other interested parties on how to prevent high altitude illness. The assessment of five of the less commonly used classes of drugs suggests that there is a scarcity of evidence related to these interventions. Clinical benefits and harms related to potential interventions such as sumatriptan are still unclear. Overall, the evidence is limited due to the low number of studies identified (for most of the comparison only one study was identified); limitations in the quality of the evidence (moderate to low); and the number of studies pending classification (24 studies awaiting classification or ongoing). We lack the large and methodologically sound studies required to establish or refute the efficacy and safety of most of the pharmacological agents evaluated in this review.

Out of air: Is going to high altitude safe for your patient?

As more people travel to high altitudes for recreation or work, more travelers with underlying medical conditions will need advice before traveling or treatment for altitude illness. This article focuses on the two main issues for travelers: whether travel to a high altitude will have a negative effect on their underlying medical condition and whether the medical condition increases the patient's risk of developing altitude illness. Although patients with severe pulmonary or cardiac conditions are most at risk in the hypoxic environment, other conditions such as diabetes and pregnancy warrant attention as well.

Interventions for preventing high altitude illness: Part 1. Commonly-used classes of drugs

BACKGROUND

High altitude illness (HAI) is a term used to describe a group of cerebral and pulmonary syndromes that can occur during travel to elevations above 2500 metres (8202 feet). Acute hypoxia, acute mountain sickness (AMS), high altitude cerebral oedema (HACE) and high altitude pulmonary oedema (HAPE) are reported as potential medical problems associated with high altitude. In this review, the first in a series of three about preventive strategies for HAI, we assess the effectiveness of six of the most recommended classes of pharmacological interventions.

OBJECTIVES

To assess the clinical effectiveness and adverse events of commonly-used pharmacological interventions for preventing acute HAI.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (OVID), Embase (OVID), LILACS and trial registries in January 2017. We adapted the MEDLINE strategy for searching the other databases. We used a combination of thesaurus-based and free-text terms to search.

SELECTION CRITERIA

We included randomized-controlled and cross-over trials conducted in any setting where commonly-used classes of drugs were used to prevent acute HAI.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures as expected by Cochrane.

MAIN RESULTS

We included 64 studies (78 references) and 4547 participants in this review, and classified 12 additional studies as ongoing. A further 12 studies await classification, as we were unable to obtain the full texts. Most of the studies were conducted in high altitude mountain areas, while the rest used low pressure (hypobaric) chambers to simulate altitude exposure. Twenty-four trials provided the intervention between three and five days prior to the ascent, and 23 trials, between one and two days beforehand. Most of the included studies reached a final altitude of between 4001 and 5000 metres above sea level. Risks of bias were unclear for several domains, and a considerable number of studies did not report adverse events of the evaluated interventions. We found 26 comparisons, 15 of them comparing commonly-used drugs versus placebo. We report results for the three most important comparisons: Acetazolamide versus placebo (28 parallel studies; 2345 participants)The risk of AMS was reduced with acetazolamide (risk ratio (RR) 0.47, 95% confidence interval (CI) 0.39 to 0.56; I2 = 0%; 16 studies; 2301 participants; moderate quality of evidence). No events of HAPE were reported and only one event of HACE (RR 0.32, 95% CI 0.01 to 7.48; 6 parallel studies; 1126 participants; moderate quality of evidence). Few studies reported side effects for this comparison, and they showed an increase in the risk of paraesthesia with the intake of acetazolamide (RR 5.53, 95% CI 2.81 to 10.88, I2 = 60%; 5 studies, 789 participants; low quality of evidence). Budenoside versus placebo (2 parallel studies; 132 participants)Data on budenoside showed a reduction in the incidence of AMS compared with placebo (RR 0.37, 95% CI 0.23 to 0.61; I2 = 0%; 2 studies, 132 participants; low quality of evidence). Studies included did not report events of HAPE or HACE, and they did not find side effects (low quality of evidence). Dexamethasone versus placebo (7 parallel studies; 205 participants)For dexamethasone, the data did not show benefits at any dosage (RR 0.60, 95% CI 0.36 to 1.00; I2 = 39%; 4 trials, 176 participants; low quality of evidence). Included studies did not report events of HAPE or HACE, and we rated the evidence about adverse events as of very low quality.

AUTHORS' CONCLUSIONS

Our assessment of the most commonly-used pharmacological interventions suggests that acetazolamide is an effective pharmacological agent to prevent acute HAI in dosages of 250 to 750 mg/day. This information is based on evidence of moderate quality. Acetazolamide is associated with an increased risk of paraesthesia, although there are few reports about other adverse events from the available evidence. The clinical benefits and harms of other pharmacological interventions such as ibuprofen, budenoside and dexamethasone are unclear. Large multicentre studies are needed for most of the pharmacological agents evaluated in this review, to evaluate their effectiveness and safety.

Efficacy of ibuprofen on prevention of high altitude headache: A systematic review and meta-analysis

OBJECTIVE

Ibuprofen is used to prevent high altitude headache (HAH) but its efficacy remains controversial. We conducted a systematic review and meta-analysis of randomized, placebo-controlled trials (RCTs) of ibuprofen for the prevention of HAH.

METHODS

Studies reporting efficacy of ibuprofen for prevention of HAH were identified by searching electronic databases (until December 2016). The primary outcome was the difference in incidence of HAH between ibuprofen and placebo groups. Risk ratios (RR) were aggregated using a Mantel-Haenszel random effect model. Heterogeneity of included trials was assessed using the I2 statistics.

RESULTS

In three randomized-controlled clinical trials involving 407 subjects, HAH occurred in 101 of 239 subjects (42%) who received ibuprofen and 96 of 168 (57%) who received placebo (RR = 0.79, 95% CI 0.66 to 0.96, Z = 2.43, P = 0.02, I2 = 0%). The absolute risk reduction (ARR) was 15%. Number needed to treat (NNT) to prevent HAH was 7. Similarly, The incidence of severe HAH was significant in the two groups (RR = 0.40, 95% CI 0.17 to 0.93, Z = 2.14, P = 0.03, I2 = 0%). Severe HAH occurred in 3% treated with ibuprofen and 10% with placebo. The ARR was 8%. NNT to prevent severe HAH was 13. Headache severity using a visual analogue scale was not different between ibuprofen and placebo. Similarly, the difference between the two groups in the change in SpO2 from baseline to altitude was not different. One included RCT reported one participant with black stools and three participants with stomach pain in the ibuprofen group, while seven participants reported stomach pain in the placebo group.

CONCLUSIONS

Based on a limited number of studies ibuprofen seems efficacious for the prevention of HAH and may therefore represent an alternative for preventing HAH with acetazolamide or dexamethasone.

Prophylactic Acetaminophen or Ibuprofen Results in Equivalent Acute Mountain Sickness Incidence at High Altitude: A Prospective Randomized Trial

OBJECTIVE

Recent trials have demonstrated the usefulness of ibuprofen in the prevention of acute mountain sickness (AMS), yet the proposed anti-inflammatory mechanism remains unconfirmed. Acetaminophen and ibuprofen were tested for AMS prevention. We hypothesized that a greater clinical effect would be seen from ibuprofen due to its anti-inflammatory effects compared with acetaminophen's mechanism of possible symptom reduction by predominantly mediating nociception in the brain.

METHODS

A double-blind, randomized trial was conducted testing acetaminophen vs ibuprofen for the prevention of AMS. A total of 332 non-Nepali participants were recruited at Pheriche (4371 m) and Dingboche (4410 m) on the Everest Base Camp trek. The participants were randomized to either acetaminophen 1000 mg or ibuprofen 600 mg 3 times a day until they reached Lobuche (4940 m), where they were reassessed. The primary outcome was AMS incidence measured by the Lake Louise Questionnaire score.

RESULTS

Data from 225 participants who met inclusion criteria were analyzed. Twenty-five participants (22.1%) in the acetaminophen group and 18 (16.1%) in the ibuprofen group developed AMS (P = .235). The combined AMS incidence was 19.1% (43 participants), 14 percentage points lower than the expected AMS incidence of untreated trekkers in prior studies at this location, suggesting that both interventions reduced the incidence of AMS.

CONCLUSIONS

We found little evidence of any difference between acetaminophen and ibuprofen groups in AMS incidence. This suggests that AMS prevention may be multifactorial, affected by anti-inflammatory inhibition of the arachidonic-acid pathway as well as other analgesic mechanisms that mediate nociception. Additional study is needed.

Acute high-altitude sickness

At any point 1–5 days following ascent to altitudes ≥2500 m, individuals are at risk of developing one of three forms of acute altitude illness: acute mountain sickness, a syndrome of nonspecific symptoms including headache, lassitude, dizziness and nausea; high-altitude cerebral oedema, a potentially fatal illness characterised by ataxia, decreased consciousness and characteristic changes on magnetic resonance imaging; and high-altitude pulmonary oedema, a noncardiogenic form of pulmonary oedema resulting from excessive hypoxic pulmonary vasoconstriction which can be fatal if not recognised and treated promptly. This review provides detailed information about each of these important clinical entities. After reviewing the clinical features, epidemiology and current understanding of the pathophysiology of each disorder, we describe the current pharmacological and nonpharmacological approaches to the prevention and treatment of these diseases.

Lack of acclimatisation is the main risk factor for acute altitude illness; descent is the optimal treatmenthttp://ow.ly/45d2305JyZ0

Pharmacotherapy of High-Altitude Illness

High-altitude illness (HAI) encompasses an array of conditions that may occur in individuals who travel to high elevations, including acute mountain sickness, high-altitude cerebral edema, and high-altitude pulmonary edema. Individuals with a history of HAI are predisposed to developing HAI; however, other risk factors are not well defined. The primary method of preventing HAI is acclimatization through gradual ascent to high altitude. In addition, many studies have assessed the use of pharmacologic prophylaxis. The most studied and widely recommended prophylactic agent is acetazolamide; additional agents that have been considered include dexamethasone, Gingko biloba, antioxidant vitamins, nifedipine, aspirin, and salmeterol. The treatment of choice for all forms of HAI is descent to lower altitude. The use of additional treatments, including supplemental oxygen, varies depending on the severity of the clinical presentation. Acetazolamide and dexamethasone have been studied as adjunctive treatments for acute mountain sickness, while nitric oxide and nifedipine have been evaluated for the treatment of high-altitude pulmonary edema. Data with analgesics and phosphodiesterase-5 inhibitors, while limited, are promising. This review will present the evidence supporting the use of pharmacotherapy for prevention and treatment of HAI.

Drug Use and Misuse in the Mountains: A UIAA MedCom Consensus Guide for Medical Professionals

Donegani, Enrico, Peter Paal, Thomas Küpper, Urs Hefti, Buddha Basnyat, Anna Carceller, Pierre Bouzat, Rianne van der Spek, and David Hillebrandt. Drug use and misuse in the mountains: a UIAA MedCom consensus guide for medical professionals. High Alt Med Biol. 17:157-184, 2016.-Aims: The aim of this review is to inform mountaineers about drugs commonly used in mountains. For many years, drugs have been used to enhance performance in mountaineering. It is the UIAA (International Climbing and Mountaineering Federation-Union International des Associations d'Alpinisme) Medcom's duty to protect mountaineers from possible harm caused by uninformed drug use. The UIAA Medcom assessed relevant articles in scientific literature and peer-reviewed studies, trials, observational studies, and case series to provide information for physicians on drugs commonly used in the mountain environment. Recommendations were graded according to criteria set by the American College of Chest Physicians.

RESULTS

Prophylactic, therapeutic, and recreational uses of drugs relevant to mountaineering are presented with an assessment of their risks and benefits.

CONCLUSIONS

If using drugs not regulated by the World Anti-Doping Agency (WADA), individuals have to determine their own personal standards for enjoyment, challenge, acceptable risk, and ethics. No system of drug testing could ever, or should ever, be policed for recreational climbers. Sponsored climbers or those who climb for status need to carefully consider both the medical and ethical implications if using drugs to aid performance. In some countries (e.g., Switzerland and Germany), administrative systems for mountaineering or medication control dictate a specific stance, but for most recreational mountaineers, any rules would be unenforceable and have to be a personal decision, but should take into account the current best evidence for risk, benefit, and sporting ethics.

Hemodynamic characteristics of high-altitude headache following acute high altitude exposure at 3700 m in young Chinese men

Background

This study aimed to identify the systemic and cerebral hemodynamic characteristics and their roles in high-altitude headache (HAH) among young Chinese men following acute exposure.

Methods

The subjects (n = 385) were recruited in June and July of 2012. They completed case report form questionnaires, as well as heart rate (HR), blood pressure, echocardiogram and transcranial Doppler examinations at 3700 m following a two-hour plane flight. A subgroup of 129 participants was examined at two altitudes (500 and 3700 m).

Results

HAH was characterized by increased HR and cardiac output (CO) and lower saturation pulse oxygen (SpO₂) (all p < 0.05). The change in tricuspid regurgitation was also different between the HAH positive (HAH+) and HAH negative (HAH-) subjects. Furthermore, the HAH+ subjects exhibited faster mean (V_m), systolic (V_s) and diastolic (V_d) velocities in the basilar artery (BA; all p < 0.05) and a faster V_d ( 25.96 ± 4.97 cm/s vs. 24.76 ± 4.76 cm/s, p = 0.045) in the left vertebral artery (VA). The bilateral VA asymmetry was also significantly different between the two groups. The pulsatility index (PI) and resistance index (RI) of left VA were lower in the HAH subjects (p < 0.05) and were negatively correlated with HAH (p < 0.05). Baseline CO and V_m in left VA (or right MCA in different regressions) were independent predictors for HAH, whereas CO/HR and ΔV_d (V_d difference between bilateral VAs) were independent risk factors for HAH at 3700 m.

Conclusions

HAH was characterized, in part, by increased systemic hemodynamics and posterior cerebral circulation, which was reflected by the BA and left VA velocities, and lower arterial resistance and compliance. Furthermore, baseline CO and V_m in left VA or right MCA at sea level were independent predictors for HAH, whilst bilateral VA asymmetry may contribute to the development of HAH at high altitude.

Electronic supplementary material

The online version of this article (doi:10.1186/s10194-015-0527-3) contains supplementary material, which is available to authorized users.

Evaluating the Risks of High Altitude Travel in Chronic Liver Disease Patients

Luks, Andrew M., and Erik R. Swenson. Clinician's Corner: Evaluating the risks of high altitude travel in chronic liver disease patients. High Alt Med Biol 16:80-88, 2015.--With improvements in the quality of health care, people with chronic medical conditions are experiencing better quality of life and increasingly participating in a wider array of activities, including travel to high altitude. Whenever people with chronic diseases travel to this environment, it is important to consider whether the physiologic responses to hypobaric hypoxia will interact with the underlying medical condition such that the risk of acute altitude illness is increased or the medical condition itself may worsen. This review considers these questions as they pertain to patients with chronic liver disease. While the limited available evidence suggests there is no evidence of liver injury or dysfunction in normal individuals traveling as high as 5000 m, there is reason to suspect that two groups of cirrhosis patients are at increased risk for problems, hepatopulmonary syndrome patients, who are at risk for severe hypoxemia following ascent, and portopulmonary hypertension patients who may be at risk for high altitude pulmonary edema and acute right ventricular dysfunction. While liver transplant patients may tolerate high altitude exposure without difficulty, no information is available regarding the risks of long-term residence at altitude with chronic liver disease. All travelers with cirrhosis require careful pre-travel evaluation to identify conditions that might predispose to problems at altitude and develop risk mitigation strategies for these issues. Patients also require detailed counseling about recognition, prevention, and treatment of acute altitude illness and may require different medication regimens to prevent or treat altitude illness than used in healthy individuals.

Network analysis reveals distinct clinical syndromes underlying acute mountain sickness

Acute mountain sickness (AMS) is a common problem among visitors at high altitude, and may progress to life-threatening pulmonary and cerebral oedema in a minority of cases. International consensus defines AMS as a constellation of subjective, non-specific symptoms. Specifically, headache, sleep disturbance, fatigue and dizziness are given equal diagnostic weighting. Different pathophysiological mechanisms are now thought to underlie headache and sleep disturbance during acute exposure to high altitude. Hence, these symptoms may not belong together as a single syndrome. Using a novel visual analogue scale (VAS), we sought to undertake a systematic exploration of the symptomatology of AMS using an unbiased, data-driven approach originally designed for analysis of gene expression. Symptom scores were collected from 292 subjects during 1110 subject-days at altitudes between 3650 m and 5200 m on Apex expeditions to Bolivia and Kilimanjaro. Three distinct patterns of symptoms were consistently identified. Although fatigue is a ubiquitous finding, sleep disturbance and headache are each commonly reported without the other. The commonest pattern of symptoms was sleep disturbance and fatigue, with little or no headache. In subjects reporting severe headache, 40% did not report sleep disturbance. Sleep disturbance correlates poorly with other symptoms of AMS (Mean Spearman correlation 0.25). These results challenge the accepted paradigm that AMS is a single disease process and describe at least two distinct syndromes following acute ascent to high altitude. This approach to analysing symptom patterns has potential utility in other clinical syndromes.

Efficacy and speed of onset of pain relief of fast-dissolving paracetamol on postsurgical dental pain: two randomized, single-dose, double-blind, placebo-controlled clinical studies

BACKGROUND

Paracetamol (APAP), also known as acetaminophen, is the most commonly used over-the-counter analgesic for the treatment of mild-to-moderate pain. However, the speed of onset of pain relief is limited mainly to the standard, immediate-release formulation. Efficacy and speed of onset of pain relief are critical in acute pain situations such as postsurgical dental pain, because reducing pain can improve clinical outcome and reduce the risk of transition from acute pain to more chronic pain. Efficacy and rapid onset also reduce the risk of excessive dosing with the analgesic.

OBJECTIVE

We sought to investigate the dose-response efficacy and speed of onset of pain relief of a fast-dissolving APAP formulation compared with lower doses of APAP and placebo in dental patients after impacted third molar extraction.

METHODS

Two single-center, single-dose, randomized, placebo-controlled, double-blind, double-dummy, parallel-group studies (Study I and Study II) were conducted to evaluate the efficacy and speed of onset of pain relief of different doses of a fast-dissolving APAP tablet (FD-APAP), standard APAP, and placebo in patients with postsurgical dental pain following third molar extraction. In Study I, a single dose of FD-APAP 1000 mg, FD-APAP 500 mg, or placebo was given to 300 patients; in Study II, a single dose of FD-APAP 1000 mg, standard APAP 650 mg, or placebo was given to 401 patients. All 701 patients from both studies were included in the analysis and safety assessment.

RESULTS

FD-APAP 1000 mg demonstrated significantly greater effect compared with FD-APAP 500 mg, APAP 650 mg, and placebo for all efficacy measurements, including sum of pain relief and pain intensity difference, total pain relief, sum of pain intensity difference, pain intensity difference, and pain relief score during 6 hours after the dose. Onset of confirmed first perceptible relief in subjects treated with FD-APAP 1000 mg was 15 minutes, which was 32% and 25% significantly shorter than onset of pain relief of FD-APAP 500 mg (22 minutes) and standard APAP 650 mg (20 minutes), respectively. FD-APAP 500 mg and APAP 650 mg demonstrated efficacy over placebo for most of the measurements; however, their effects were significantly lower and lasted for a shorter period of time than for FD-APAP 1000 mg. All study treatments were well tolerated.

CONCLUSIONS

FD-APAP 1000 mg tablets demonstrated efficacy over placebo. Also, FD-APAP 1000 mg had significantly superior effect, faster onset, and longer duration of pain relief compared with FD-APAP 500 mg and APAP 650 mg tablets.

Investigation of whole-brain white matter identifies altered water mobility in the pathogenesis of high-altitude headache

Elevated brain water is a common finding in individuals with severe forms of altitude illness. However, the location, nature, and a causative link between brain edema and symptoms of acute mountain sickness such as headache remains unknown. We examined indices of brain white matter water mobility in 13 participants after 2 and 10 hours in normoxia (21% O2) and hypoxia (12% O2) using magnetic resonance imaging. Using a whole-brain analysis (tract-based spatial statistics (TBSS)), mean diffusivity was reduced in the left posterior hemisphere after 2 hours and globally reduced throughout cerebral white matter by 10 hours in hypoxia. However, no changes in T2 relaxation time (T2) or fractional anisotropy were observed. The TBSS identified an association between changes in mean diffusivity, fractional anisotropy, and T2 both supra and subtentorially after 2 and 10 hours, with headache score after 10 hours in hypoxia. Region of interest-based analyses generally confirmed these results. These data indicate that acute periods of hypoxemia cause a shift of water into the intracellular space within the cerebral white matter, whereas no evidence of brain edema (a volumetric enlargement) is identifiable. Furthermore, these changes in brain water mobility are related to the intensity of high-altitude headache.

Hypoxia-related altitude illnesses

BACKGROUND

Millions of tourists and climbers visit high altitudes annually. Many unsuspecting and otherwise healthy individuals may get sick when sojourning to these high regions. Acute mountain sickness represents the most common illness, which is usually benign but can rapidly progress to the more severe and potentially fatal forms of high-altitude cerebral edema and high-altitude pulmonary edema.

METHODS

Data were identified by searches of Medline (1965 to May 2012) and references from relevant articles and books. Studies, reviews, and books specifically pertaining to the epidemiology, prevention, and treatment of high-altitude illnesses in travelers were selected.

RESULTS

This review provides information on geographical aspects, physiology/pathophysiology, clinical features, risk factors, and the prevalence of high-altitude illnesses and also state-of-the art recommendations for prevention and treatment of such illnesses.

CONCLUSION

Given an increasing number of recreational activities at high and extreme altitudes, the general practitioner and specialist are in higher demand for medical recommendations regarding the prevention and treatment of altitude illness. Despite an ongoing scientific discussion and controversies about the pathophysiological causes of altitude illness, treatment and prevention recommendations are clearer with increased experience over the last two decades.

Altitude Sickness in Climbers and Efficacy of NSAIDs Trial (ASCENT): randomized, controlled trial of ibuprofen versus placebo for prevention of altitude illness

OBJECTIVE

To study the effectiveness of ibuprofen versus placebo in preventing acute mountain sickness (AMS) and high altitude headache (HAH).

METHODS

Double-blind, randomized, placebo-controlled trial.

RESULTS

Two hundred ninety-four healthy Western trekkers were recruited on the Everest approach at 4280 m or 4358 m and randomly assigned to receive either 600 mg of ibuprofen or placebo 3 times daily before and during ascent to 4928 m. One hundred eighty-three of 294 participants completed the trial. Of the participants who did not complete the trial, 62 were lost to follow-up and another 49 broke trial protocol. In an intent-to-treat analysis (232 participants), ibuprofen was found to be more effective than placebo in reducing the incidence of AMS (24.4% vs 40.4%; P = .01) and the incidence of HAH (42.3% vs 60.5%; P < .01). Ibuprofen was also superior to placebo in reducing the severity of HAH (4.9% vs 14.7%; P = .01). The end point of oxygen saturation was also higher in the ibuprofen group (80.8 % vs 82.4%; P = .035). For the 183 participants who completed the trial and conformed to the protocol, the incidence of AMS between placebo and treatment groups was not significant (32.9% vs 22.7%; P = .129 for AMS incidence, 9.6% vs 8.2%; P = .74 for AMS severity, 54.8% vs 42.7%; P = .11 for HAH incidence, and 8.2% vs 3.6%; P = .18 for HAH severity).

CONCLUSIONS

Ibuprofen was found to be effective in preventing AMS in the intent-to-treat analysis group but not in those who completed the trial. This loss of significance in the subjects who completed the trial may be explained by persons in the placebo group having a higher burden of illness and associated decreased compliance with the protocol. An important limitation of this study may be the possibility that ibuprofen can mask headache, which is a compulsory criterion for the diagnosis of AMS.

Can migraine prophylaxis prevent acute mountain sickness at high altitude?

Acute mountain sickness (AMS) develops in people trekking at high altitude. The underlying mechanism is vasodilation due to low pressure of oxygen. However, individual susceptibility for AMS is unknown, thus, one cannot predict when or to whom it happens. Because AMS usually begins with headache, and because migraineurs are more vulnerable to AMS, we studied by the literatures review on the mechanism and clinical features in common, and assessed the treatment modalities for both disorders. This led to us the following hypothesis that, migraine prophylaxis may prevent or delay the onset of AMS at high altitude. Clinical features of AMS include nausea or vomiting when it progresses. Hypobaric hypoxia, dehydration or increased physical exertion trigger or aggravate both disorders. In migraine, cerebral vasodilation can happen following alteration of neuronal activity, whereas the AMS is associated with peripheral vessel dilation. Medications that dilate the vessels worsen both conditions. Acute treatment strategies for migraine overlap with to those of AMS, including drugs such as vasoconstrictors, or other analgesics. To prevent AMS, adaptation to high altitude or pharmacological prophylaxis, i.e., acetazolamide has been recommended. This carbonic anhydrase inhibitor lowers serum potassium level, and thus stabilizes membrane excitability. Acetazolamide is also effective on specific forms of migraine. Taken together, these evidences implicate that migraine prophylaxis may prevent or delay the onset of AMS by elevating the threshold for high altitude.

Visual analog scale (VAS) for assessment of acute mountain sickness (AMS) on Aconcagua

OBJECTIVE

The Lake Louise AMS Self-Report Score (LLSelf) is a commonly used, validated assessment of acute mountain sickness (AMS). We compared LLSelf and visual analog scales (VAS) to quantify AMS on Aconcagua (6962 m).

METHODS

Prospective observational cohort study at Plaza de Mulas base camp (4365 m), Aconcagua Provincial Park, Argentina. Volunteers climbing in January 2009 were enrolled at base camp and ascended at their own pace. They completed the LLSelf, an overall VAS [VAS(o)], and 5 individual VAS [VAS(i)] corresponding to the items of the LLSelf when symptoms were maximal. Composite VAS [VAS(c)] was calculated as the sum of the 5 VAS(i).

RESULTS

A total of 127 volunteers consented to the study. Response rate was 52.0%. AMS occurred in 77.3% of volunteers, while 48.5% developed severe AMS. Median (interquartile range, IQR) LLSelf was 4 (3-7). Median (IQR) VAS(o) was 36 mm (23-59). VAS(o) was linear and correlated with LLSelf: slope = 6.7 (95% CI: 4.4-9.0), intercept = 3.0 (95% CI: -10.0-16.1), ρ = 0.71, τ = 0.55, R(2) = 0.45, p < 0.001. Median (IQR) VAS(c) was 29 (13-44). VAS(c) was also linear and correlated with LLSelf: slope = 5.9 (95% CI: 4.9-6.9), intercept = -0.6 (95% CI: -6.3-5.1), ρ = 0.83, τ = 0.68, R(2) = 0.73, p < 0.001. The relationship between the 5 VAS(i) and LLSelf(i) was less significant and less linear than that between VAS(o), VAS(c), and LLSelf.

CONCLUSIONS

While both VAS(o) and VAS(c) for assessment of AMS appear to be linear with respect to LLSelf, the amount of scatter within the VAS is considerable. The LLSelf remains the gold standard for the diagnosis of AMS.

Efficacy and Safety of Ibuprofen and Acetaminophen in Children and Adults: A Meta-Analysis and Qualitative Review

Objective:

To evaluate the analgesic and antipyretic efficacy and safety of ibuprofen compared to acetaminophen in children and adults.

Data Sources:

Literature searches were performed using PubMed/MEDLINE (through August 2009) and EMBASE (through January 2008) and were restricted to the English language. In PubMed/MEDLINE, search terms used were ibuprofen, acetaminophen, paracetamol, clinical trials, and randomized controlled trials. EMBASE search terms included ibuprofen and acetaminophen, restricted to human and clinical trials.

Study Selection And Data Extraction:

All English-language articles identified from the data sources were reviewed. Multiple review articles were studied for any pertinent references and this yielded additional articles. Only articles that directly compared ibuprofen and acetaminophen were eligible for this review.

Data Synthesis:

Eighty-five studies that directly compared ibuprofen to acetaminophen were identified; 54 contained analgesic efficacy data, 35 contained antipyretic/temperature reduction data, and 66 contained safety data (some articles contained more than 1 type of data). Qualitative review of the literature revealed that, for the most part, ibuprofen was more efficacious than acetaminophen for the treatment of pain and fever in both pediatric and adult populations, and that these 2 drugs were equally safe. Meta-analyses on the subset of randomized clinical trial articles that reported sufficient quantitative information to calculate either an odds ratio (adverse event [AE]) or standardized mean difference (pain and fever) confirmed the qualitative results for adult (standardized mean difference [SMD] 0.69; 95% CI 0.57 to 0.81) and pediatric (SMD 0.28; 95% CI 0.10 to 0.46) pain at 2 hours postdose and pediatric fever (SMD 0.26; 95% CI 0.10 to 0.41) at 4 hours postdose. Conclusions regarding adult fever/temperature reduction could not be made due to a lack of evaluable data. The combined odds ratio for the proportion of adult subjects experiencing at least 1 AE slightly favored ibuprofen; however, the difference was not statistically significant (1.12; 95% CI 1.00 to 1.25). No significant difference between drugs in AE incidence was found for pediatric patients (0.82; 95% CI 0.60 to 1.12).

Conclusions:

Ibuprofen is as or more efficacious than acetaminophen for the treatment of pain and fever in adult and pediatric populations and is equally safe.

Environmental issues for team physicians

As outdoor sports continue to gain popularity, understanding the environmental factors that may influence athletes is becoming a more important aspect of medical care for team physicians. Temperature, ultraviolet light, lightning, and altitude are some of the most common elements that cause illness. Understanding how to prevent, diagnose, and promptly treat conditions caused by environmental factors is essential to optimizing athletic performance in outdoor sports and avoiding morbidity.

Antiarrhythmic properties of acetaminophen in the dog

Mongrel dogs bred for research and weighing 25 +/- 3 kg were used to test the hypothesis that acetaminophen has antiar-rhythmic properties. Only ventricular arrhythmias defined by the Lambeth Conventions were investigated. Dogs were exposed either to 60 mins of regional myocardial ischemia followed by 180 mins of reperfusion (n = 14) or were administered a high dose of ouabain (n = 14). Both groups of 14 dogs were further divided into vehicle and acetaminophen treatment groups (n = 7 in each). During selected 10-min intervals, we recorded the numbers of ventricular premature beats, ventricular salvos, ventricular bigeminy, ventricular tachycardia (nonsustained and sustained), and we recorded the heart rate, systemic arterial blood pressure, and left ventricular function. Neither heart rate nor the number of ventricular arrhythmias differed significantly under baseline conditions. Conversely, the combined average number of ventricular ectopic beats during ischemia and reperfusion was significantly less in the presence of acetaminophen (28 +/- 4 vs. 6 +/- 1; P < 0.05). Similarly, percent ectopy during reperfusion in vehicle- and acetaminophen-treated dogs was 1.4 +/- 0.4 and 0.4 +/- 0.2, respectively (P < 0.05). The number of all ventricular ectopic beats except ventricular salvos was also significantly reduced in the presence of acetaminophen. Similar results were obtained with ouabain. Our results reveal that systemic administration of a therapeutic dose of acetaminophen has previously unreported antiarrhythmic effects in the dog.

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.

Reliability And Utility of A Visual Analog Scale for The Assessment of Acute Mountain Sickness

Acute mountain sickness (AMS) is a common condition that affects people that ascend too rapidly to high altitude. It is typically assessed with the Lake Louise AMS Self-report Score (LLSelf) that uses a categorical numeric rating scale to answer five questions addressing AMS-related symptoms, such as headache. A 100-mm visual analog scale (VAS) is commonly used to assess subjective phenomena such as pain, but this scale has never been used for the self-assessment of AMS. The purpose of this study was to compare a VAS score to the total LLSelf and to evaluate the test-retest and interrater reliability of the VAS when used as an assessment of AMS. Participants (N = 356) completed both the LLSelf and the VAS on the summit of Mt. Whitney (4419 m). There was a significant relationship (r = 0.65, p < 0.01) between the LLSelf (2.8 +/- 2.0, mean +/- SD) and the VAS (14.4 +/- 14.1 mm). Fifty-seven participants were randomly selected for reliability testing of the VAS. Both test-retest reliability (ICC = 0.996, 95% CI = 0.992 to 0.998) and interrater reliability (ICC = 1.000, 95% CI = 0.999 to 1.000) were high. The mean difference in the VAS score between tests was <1 mm, as was the difference between raters. These results demonstrate excellent reliability for the VAS as an assessment of AMS.

Environmental illness in athletes

This article examines environmental illness in athletes. Causes, symptoms, and treatment of heat-related illness, cold-related illness, and altitude-related illness are discussed.