Series 2520 www.thelancet.com Vol 386 December 19/26, 2015 Extreme medicine 1 Extreme, expedition, and wilderness medicine Christopher H E Imray, Michael P W Grocott, Mark H Wilson, Amy Hughes, Paul S Auerbach Extreme, expedition, and wilderness medicine are modern and rapidly evolving specialties that address the spirit of adventure and exploration. The relevance of and interest in these specialties are changing rapidly to match the underlying activities, which include global exploration, adventure travel, and military deployments. Extreme, expedition, and wilderness medicine share themes of providing best available medical care in the outdoors, especially in austere or remote settings. Early clinical and logistics decision making can often have important effects on subsequent outcomes. There are lessons to be learned from out-of-hospital care, military medicine, humanitarian medicine, and disaster medicine that can inform in-hospital medicine, and vice-versa. The future of extreme, expedition, and wilderness medicine will be defined by both recipients and practitioners, and empirical observations will be transformed by evidence-based practice. Introduction In 1952, the physiologist Griffith Pugh undertook a series of experiments on Cho Oyu to assess the effect of heavy supplemental oxygen equipment on the speed of climbing. 1 There was no beneficial physiological effect at a flow rate of 2 L/min, but the equipment was advantageous at more than 4 L/min. Pugh’s meticulous scientific approach to nutrition, hydration, supplemental oxygen, and climbing equipment was pivotal to the success of the 1953 Everest expedition, and helped to reduce mortality associated with climbing at extreme altitude. 2 Pugh’s investigations provided a milestone in the development of modern extreme medicine. 3 Extreme medicine, expedition medicine, and wilderness medicine share features but can be considered as distinct specialties. Extreme medicine can be defined as medicine or medical research practised in a challenging or hostile physical environment (eg, battlefield medicine or care delivered while on treacherous mountain terrain; panel). 4,5 Expedition medicine includes all facets of health care delivered in preparation for and during an expedition, often in a remote geographical setting. Wilderness medicine is the unique body of knowledge that encompasses the basic science, physiology and pathophysiology, clinical practice, and research related to human interactions with the natural environment, as well as medicine practised in remote locations or austere settings. The term encompasses a wide range of topics 6 including mountain, diving, polar, sailing, aviation, space, combat, disaster, jungle, desert, and other similar categories of medicine. Many of these sub-specialties have developed as a result of explorers, adventurers, scientists, artists, soldiers, humanitarians, athletes, and tourists requiring medical support as they challenge physical and physiological boundaries. The experience of delivering care despite these environmental challenges has resulted in novel medical and physiological insights, some of which might have clinical implications affecting more mainstream medical specialties. 7–12 Similarly, technological innovations developed for use in extreme or austere environments might have broader applicability by virtue of their simplicity, efficacy, or economy. 13,14 Such emerging technologies might also meet the stringent cost-effectiveness necessary for use in remote and low-income communities, and thereby improve health more widely. 15 Rapid changes in technology and huge growth in demand for adventure vacations and expeditions Lancet 2015; 386: 2520–25 This is the first in a Series of two papers about extreme medicine Division of Translational Medicine, Warwick Medical School, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK (Prof C H E Imray FRCS); Faculty of Medicine, University of Southampton, Southampton, UK (Prof M P W Grocott FRCA); Anaesthesia and Critical Care Research Unit, University Hospital, Southampton NHS Foundation Trust, Southampton, UK (M P W Grocott); Critical Care Research Area, NIHR Key messages The setting A remote and challenging environment can pose unique situations of access, communications, rescue, and treatment. Risks to caregivers must be weighed against likely benefits to the patients when assessing the safety of intervening. The medical challenges These are environment related (eg, hypothermia, high-altitude pulmonary oedema) and medicosurgical (predominately trauma, acute infection, or vascular). The delivered care This is resource limited. It is often temporising and not definitive, because prevention of deterioration is the best that can be accomplished. Improvisation is common. Delivering care on-site must be balanced against the need to move the patients and providers to a safe place. Non-medical skills and infrastructure The practitioner might need wilderness survival skills. Personal skills, such as leadership, non-hierarchical teamwork, and judgment under unfamiliar or stressful conditions, are important. Supportive elements, such as communication technology (eg, telemedicine), supply chain management, and transportation modes (eg, helicopters) can be as important as medical skills. Timing of interventions Early and timely interventions can have disproportionately important effects because delays to definitive care are common. When administered appropriately, early interventions might suffice for the majority of care, but, if inappropriate, can create an irretrievable situation. Research and translation of knowledge Insights can be physiological, medical, or technological. Discoveries in extreme or wilderness medicine have applications not only in austere settings, but in more traditional medical practice.