Hydration Strategies at Altitude

Dr Lari Trease / Sports and Exercise Medicine Physician / University of Tasmania, Australia

Dr Trease is an Australian Sport and Exercise Physician and the Unit Coordinator for Extreme Sports Medicine, a subject that will be offered for the first time in 2021 as part of the Healthcare in Remote and Extreme Environments program at the University of Tasmania, Australia. Lari is also a back-country skier, mountain biker and trail runner in her spare time.

In a recent collaboration between the University of Tasmania, School of Medicine, Healthcare in Remote and Extreme Environments faculty of doctors, Edi Albert, Glenn Singleman and myself; combined with the UK Diploma in Mountain Medicine crew of doctors, Jeremy Windsor and Stuart Allan, researched and published a practical guide to hydration for physical activity and endurance events at altitude (> 2,500m)‘ in the Clinical Journal of Sports Medicine earlier in March this year.

Dr Stuart Allan recently published his summary article based on our paper; ‘Myth-busting in Endurance Physiology‘ on Adventure Medic in May this year and promised a follow-up Adventure Medic article from the CJSM paper – specifically focussed on the ‘how-to’ for hydration up high. In this article I will attempt to answer these questions.

Summary of Recommendations from the CJSM Paper:

Weight loss at altitude does not imply dehydration but rather a readjustment of adaptive physiology

• Acclimatisation to altitude results in a bicarbonate diuresis and can cause subsequent reduction in body weight of up to 2-3kg ¹.
• Research study participants who failed to reduce their body weight when acutely exposed to altitude were more likely to develop symptoms of HAIs ^2.
• Research study participants who had their total body water increased had lower oxygen saturation and higher symptom scores for HAIs ³.
• We hypothesised that ‘euhydration’ at high altitude during endurance races could exceed 2-4%.

Hydration strategies recommended for sea level endurance activities, team sports, or sporting activities in the heat are not appropriate for direct application to high altitude cold environments

• The strategy of ‘drink to thirst’ (DTT) has been shown to be non-detrimental to performance in cold environments ⁴.
• On the other hand, ‘programmed drinking’ (PD) is more relevant to warm climates ⁵.
• Studies examining barriers and enablers to hydration in team sports are not applicable to individual pursuits in the mountains at altitude.

The clinical presentation of altered hydration status and High Altitude Illness’ is similar and could be difficult to distinguish in the field in the absence of point of care testing

• Mild Acute Mountain Sickness (AMS) and hydration disorders present with headache, light headedness, dizziness and gut disturbance ^(6-8).
• The distinguishing feature of dehydration is thirst, which is absent in AMS and hyperhydration (EAH) ⁸.
• High Altitude Cerebral Edema (HACE) and EAH encephalopathy (EAHE) both result in ataxia and confusion, headache and fatigue ^(6,9).

Hydration strategies for physical activity at altitude should include considerations for sourcing water

• Many mountainous regions have a lesser level of sanitation that can result in water-borne diseases.
• High altitude activities, above the snow line, can reduce accessibility to water and may require the carrying of fuel to melt snow.
• The weight of water should be considered in the planning of hydration strategies for self-supported events.

Hypohydration is a lesser health risk than hyperhydration

• Hyperhydration and subsequent EAH and EAHE has greater health risks in an austere environment than mild and moderate level dehydration which can be seen with prolonged physical activity ⁹.
• Often the high-altitude environment results in a reduced capacity to access prompt tertiary level medical support which lends weight to the argument of adopting the lowest risk approach to any problem.

Medications used for HAIs can affect health and performance and may be restricted under the WAD Code for elite athletes

• Acetazolamide has both performance and anti-doping considerations in elite athletes. It is a WAD (World Anti-Doping) code-S5 diuretic and masking agent, prohibited both in and out of competition ^(10-14).
• Ibuprofen: We discourage the use of Ibuprofen for HAI due to demonstrated exacerbation of EAH in endurance athletes at sea-level ⁴.

Elite athlete performance considerations

• The role of fluids for achieving other nutrition goals including carbohydrate intake and the use of ergogenic aids.
• The need for individual experience at altitude to understand personal physiological response.

The local experience

• Sherpas who compete in Everest Original Marathon consume butter tea and tsampa (a roasted barley dish) which are both high in fat and salt. They often also consume Chang beer, which acts as a diuretic and can counteract the increased ADH production associated with stress.

In summary, an individualised hydration approach, based on previous experience, tailored to the event and the conditions will result in the best opportunity for successful completion unhindered by physiological or pathological challenges.

References

1. Jain SC, Bardhan J, Swamy YV, Krishna B, Nayar HS. Body fluid compartments in humans during acute high-altitude exposure. Aviation, space, and environmental medicine. 1980;51(3):234-6.
2. Gatterer H, Wille M, Faulhaber M, Lukaski H, Melmer A, Ebenbichler C, et al. Association between body water status and acute mountain sickness. PLoS One. 2013;8(8):e73185.
3. Swenson ER, Bärtsch P. High-altitude pulmonary edema. Comprehensive Physiology. 2012;2(4):2753-73.
4. Cheuvront SN, Carter R, 3rd, Castellani JW, Sawka MN. Hypohydration impairs endurance exercise performance in temperate but not cold air. Journal of applied physiology (Bethesda, Md : 1985). 2005;99(5):1972-6.
5. Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377-90.
6. Loeppky JA, Icenogle MV, Maes D, Riboni K, Hinghofer-Szalkay H, Roach RC. Early fluid retention and severe acute mountain sickness. Journal of applied physiology (Bethesda, Md : 1985). 2005;98(2):591-7.
7. Bärtsch P, Pfluger N, Audétat M, Shaw S, Weidmann P, Vock P, et al. Effects of slow ascent to 4559 M on fluid homeostasis. Aviation, space, and environmental medicine. 1991;62(2):105-10.
8. Kenefick RW. Drinking Strategies: Planned Drinking Versus Drinking to Thirst. Sports Med. 2018;48(Suppl 1):31-7.
9. Hackett PH, Rennie D. Avoiding mountain sickness. Lancet (London, England). 1978;2(8096):938.
10. WADA. Prohibited list https://www.wada-ama.org/sites/default/files/resources/files/2016-09-29_-_wada_prohibited_list_2017_eng_final.pdf2017
11. Posch AM, Dandorf S, Hile DC. The Effects of Acetazolamide on Exercise Performance at Sea Level and in Hypoxic Environments: A Review. Wilderness & environmental medicine. 2018;29(4):541-5.
12. Elisabeth E, Hannes G, Johannes B, Martin F, Elena P, Martin B. Effects of low-dose acetazolamide on exercise performance in simulated altitude. International journal of physiology, pathophysiology and pharmacology. 2017;9(2):28-34.
13. Bradwell AR, Ashdown K, Rue C, Delamere J, Thomas OD, Lucas SJE, et al. Acetazolamide reduces exercise capacity following a 5-day ascent to 4559 m in a randomised study. BMJ open sport & exercise medicine. 2018;4(1):e000302.
14. Bradbury KE, Yurkevicius BR, Mitchell KM, Coffman KE, Salgado RM, Fulco CS, et al. Acetazolamide does not alter endurance exercise performance at 3,500-m altitude. Journal of applied physiology (Bethesda, Md : 1985). 2020;128(2):390-6.
15. Hydration Strategies for Physical Activity and Endurance Events at High (>2500 m) Altitude. Trease L, Singleman G, Windsor J, Allan S, Albert E. Clinical Journal of Sport Medicine. 2021. Accessed at: https://journals.lww.com/cjsportsmed/Abstract/9000/Hydration_Strategies_for_Physical_Activity_and.98885.aspx

Images provided by Lari Trease