Peter H. Hackett

Wilderness medical society consensus guidelines for the prevention and treatment of acute altitude illness

To provide guidance to clinicians about best practices, the Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for the prevention and treatment of acute mountain sickness (AMS), high altitude cerebral edema (HACE), and high altitude pulmonary edema (HAPE). These guidelines present the main prophylactic and therapeutic modalities for each disorder and provide recommendations for their roles in disease management. Recommendations are graded based on the quality of supporting evidence and 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 the prevention and management of each disorder that incorporate these recommendations.

Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness: 2014 Update

To provide guidance to clinicians about best practices, the Wilderness Medical Society 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. These guidelines present the main prophylactic and therapeutic modalities for each disorder and provide recommendations about their role in disease management. Recommendations are graded based on the quality of supporting evidence and 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 disorder 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 Wilderness & Environmental Medicine 2010;21(2):146-155.

Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Frostbite

The Wilderness Medical Society convened an expert panel to develop a set of evidence-based guidelines for the prevention and treatment of frostbite. We present a review of pertinent pathophysiology. We then discuss primary and secondary prevention measures and therapeutic management. Recommendations are made regarding each treatment and its role in management. These recommendations are graded based on the quality of supporting evidence and balance between the benefits and risks/burdens for each modality according to methodology stipulated by the American College of Chest Physicians.

Wilderness Medical Society Practice Guidelines for the Out-of-Hospital Evaluation and Treatment of Accidental Hypothermia: 2014 Update

To provide guidance to clinicians, the Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for the out-of-hospital evaluation and treatment of victims of accidental hypothermia. The guidelines present the main diagnostic and therapeutic modalities and provide recommendations for the management of hypothermic patients. The panel graded the recommendations based on the quality of supporting evidence and the balance between benefits and risks/burdens according the criteria published by the American College of Chest Physicians. The guidelines also provide suggested general approaches to the evaluation and treatment of accidental hypothermia that incorporate specific recommendations.

Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Frostbite: 2014 Update

The Wilderness Medical Society convened an expert panel to develop a set of evidence-based guidelines for the prevention and treatment of frostbite. We present a review of pertinent pathophysiology. We then discuss primary and secondary prevention measures and therapeutic management. Recommendations are made regarding each treatment and its role in management. These recommendations are graded on the basis of the quality of supporting evidence and balance between the benefits and risks or burdens for each modality according to methodology stipulated by the American College of Chest Physicians. This is an updated version of the original guidelines published in Wilderness & Environmental Medicine 2011;22(2):156-166.

Ginkgo biloba Does—and Does Not—Prevent Acute Mountain Sickness

Abstract Objective.—To determine the efficacy of 2 different sources of Ginkgo biloba extract (GBE) in reducing the incidence and severity of acute mountain sickness (AMS) following rapid ascent to high altitude. Methods.—Two randomized, double-blind, placebo-controlled cohort studies were conducted in which participants were treated with GBE (240 mg·d−1) or placebo prior to and including the day of ascent from 1600 m to 4300 m (ascent in 2 hours by car). Acute mountain sickness was diagnosed if the Environmental Symptom Questionnaire III acute mountain sickness–cerebral (AMS-C) score was ≥0.7 and the Lake Louise Symptom (LLS) score was ≥3 and the participant reported a headache. Symptom severity was also determined by these scores. Results.—Results were conflicting: Ginkgo biloba reduced the incidence and severity of AMS compared to placebo in the first but not the second study. In the first study, GBE reduced AMS incidence (7/21) vs placebo (13/19) (P = .027, number needed to treat = 3), and it also reduced severity (AMS-C = 0.77 ± 0.26 vs 1.59 ± 0.27, P = .029). In the second study, GBE did not reduce incidence or severity of AMS (GBE 4/15 vs placebo 10/22, P = .247; AMS-C = 0.48 ± 0.13 vs 0.58 ± 0.11, P = .272). The primary difference between the 2 studies was the source of GBE. Conclusions.—The source and composition of GBE products may determine the effectiveness of GBE for prophylaxis of AMS.

Hypoxia and the Circulation

Risk of Cardiovascular Events During Mountain Activities.- Biventricular Function at High Altitude: Implications for Regulation of Stroke Volume in Chronic Hypoxia.- Control of Coronary Blood Flow During Hypoxemia.- Metabolic Consequences Of Intermittent Hypoxia.- Intermittent Hypoxia and Cognitive Function: Implications from Chronic Animal Models.- Vascular Consequences of Intermittent Hypoxia.- Angiotensin-Induced Hypoxia in the Kidney: Functional and Structural Changes of the Renal Circulation.- Role of Reactive Oxygen Species in Chronic Hypoxia-Induced Pulmonary Hypertension and Vascular Remodeling.- Hypoxia and Placental Remodelling.- Epithelial Sodium Channels in the Adult Lung - Important Modulators of Pulmonary Health and Disease.- Lung Interstitial Pressure and Structure in Acute Hypoxia.- Hypoxic Inhibition of Alveolar Fluid Reabsorption.- Regulation and Role of Neuroglobin and Cytoglobin Under Hypoxia.- Molecular Insights into the Functional Role of Myoglobin.- GenetiC Mechanisms Underlying Regulation of Hemoglobin Mass.- Control of the Respiratory Pattern in Insects.- Effects of Insect Body Size on Tracheal Structure and Function.- The Role of Hif-1 1 in Hypoxic Response in the Skeletal Muscle.- Gene Expression in Working Skeletal Muscle.- The Limits of Human Endurance: What is the Greatest Endurance Performance of All Time? Which Factors Regulate Performance at Extreme Altitude?.- Jim Milledge Hypoxia Honoree 2007.- Exploring Mountain Medicine and Physiology.- Carlos Monge Cassinelli: A Portrait.

Optic nerve sheath diameter and acute mountain sickness.

OBJECTIVE Increased intracranial pressure (ICP) may contribute to acute mountain sickness (AMS). Measuring optic nerve sheath diameter (ONSD) by ultrasound (US) is a noninvasive technique to detect elevated ICP, and increased ONSD has been associated with AMS. We hypothesized that ONSD would increase with acute, rapid ascent to 4300 m and that increased ONSD would be associated with symptoms of AMS. We further hypothesized that treatment with oxygen at 4300 m would reduce symptoms and ONSD. METHODS A cohort study was performed comparing US measurement of ONSD in healthy subjects at 1400 m and 18 hours after rapid ascent to 4300 m, both before and after oxygen treatment and between subjects with and without AMS (Lake Louise Score ≥3). RESULTS Among 57 subjects, 29 (51%) experienced AMS after rapid ascent to 4300 m. In subjects without AMS, mean ONSD did not increase at 4300 m. In subjects with AMS, mean ONSD increased at 4300 m and was higher than in those without AMS. Treatment with oxygen lowered mean ONSD in subjects with AMS but not in those without AMS. Individual responses to altitude and oxygen varied greatly within groups, and the relationship between ONSD and AMS symptoms was weak. CONCLUSIONS In this controlled study, mean ONSD increased in subjects with AMS at high altitude. However, individual variation was high, and most ONSD values were below the clinical threshold for raised ICP. Observed differences were small, of questionable clinical importance, and within the range of precision of the US machine. Overall, our data do not support a role for increased ICP in mild to moderate AMS.

High altitude and common medical conditions

Increasing numbers of people are traveling to high altitude for work or pleasure. Given the prevalence of medical conditions in the general population, it is likely that many of these travelers will have one or more underlying medical problems. Unsure of how they will tolerate high altitude, these patients often seek input from their primary care physicians or travel clinical providers to determine if it is safe for them to make such a sojourn and, if so, what precautions should be taken during their trip to avoid problems that might lead to unplanned interruption of their trip. Clinicians faced with these concerns must address whether the underlying medical condition could be adversely affected by the hypoxic environment or alters the traveler’s risk for developing high-altitude illness. This chapter provides information to guide clinicians in answering these questions as they pertain to patients with a wide variety of medical problems including pulmonary diseases such as chronic obstructive pulmonary disease, asthma, and obstructive sleep apnea; cardiac problems including coronary artery diseases, cardiomyopathy, and adult congenital heart diseases; as well as gastrointestinal, endocrine, hematologic, neurologic, and renal disorders. For each disorder we consider the primary challenges faced by those patients at altitude and provide recommendations for pretravel assessment as well as risk mitigation during the trip. The chapter concludes by considering medication use at high altitude and, in particular, whether medications used for treatment of underlying disorders have the potential for adverse interactions with medications used in the prophylaxis and treatment of acute altitude illness and whether the dose and choice of altitude illness medication needs to be altered depending on the patients underlying health issues.

A new proposal for management of severe frostbite in the austere environment

Despite advances in outdoor clothing and medical management of frostbite, individuals still experience catastrophic amputations. This is a particular risk for those in austere environments, due to resource limitations and delayed definitive treatment. The emerging best therapies for severe frostbite are thrombolytics and iloprost. However, they must be started within 24 hours after rewarming for recombinant tissue plasminogen activator (rt-PA) and within 48 hours for iloprost. Evacuation of individuals experiencing frostbite from remote environments within 24 to 48 hours is often impossible. To date, use of these agents has been confined to hospitals, thus depriving most individuals in the austere environment of the best treatment. We propose that thrombolytics and iloprost be considered for field treatment to maximize chances for recovery and reduce amputations. Given the small but potentially serious risk of complications, rt-PA should only be used for grade 4 frostbite where amputation is inevitable, and within 24 hours of rewarming. Prostacyclin has less risk and can be used for grades 2 to 4 frostbite within 48 hours of rewarming. Until more field experience is reported with these agents, their use should probably be restricted to experienced physicians. Other modalities, such as local nerve blocks and improving oxygenation at high altitude may also be considered. We submit that it remains possible to improve frostbite outcomes despite delayed evacuation using resource-limited treatment strategies. We present 2 cases of frostbite treated with rt-PA at K2 basecamp to illustrate feasibility and important considerations.