By Mike McEvoy and David Rhodes
Hydration, or maintaining normal body fluid balance, is critical to any high-performance activity. Firefighter training emphasizes the need to maintain adequate hydration; multiple National Fire Protection Association (NFPA) standards address hydration. Despite this emphasis, there is little, if any, guidance for teaching firefighters how to monitor and maintain sufficient levels of personal hydration. This article will review the importance of hydration in firefighters, the changes in hydration science, personal hydration screening tools, developing a game plan to maintain hydration, and successful strategies used in high-performance firefighter training.
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| (1) Firefighters working in gear can lose two percent of body mass within 30 minutes. (Photo by Judy Glick-Smith.) |
Physical performance has an intimate relationship with hydration, more so than many firefighters may realize. Performance athletes invest considerable time, effort, and money optimizing their hydration to stay on top of their game; firefighters should do the same. Numerous studies suggest that small losses in body mass (BM) from fluids lost during exercise correlate to significant declines in muscle strength. A recent study of muscle strength in athletes showed a 16-percent reduction in muscle strength after only a two-percent reduction in BM.1 Earlier studies demonstrated that losses of one to two percent BM resulted in loss of ability to concentrate, lowered alertness, feelings of tiredness, and headaches.2 Increased body and/or environmental temperatures led to greater reductions in both physical and mental performance in the majority of studies.3 This can be a double whammy for firefighters; dehydration leads directly to increased body temperature.
Firefighting requires strenuous work in hot environments while wearing heavy and restrictive clothing and carrying heavy equipment. The average 200-pound firefighter assigned to interior operations at a typical structure fire could easily lose two percent of his BM within 30 to 60 minutes, depending on work intensity and environmental conditions. The decrease in muscle strength and reduced ability to concentrate from this loss of BM will affect fireground performance. Studies consistently find that 45 percent of firefighter injuries4 and more than half of all deaths5 occur on the fireground where firefighters spend, on average, less than 10 percent of their time (photo 1).
The same exercise studies that connect dehydration to decreased physical and mental performance clearly show that these effects can be prevented if steps are taken during the activity to maintain adequate hydration. (1, 2) The challenge, then, not only for athletes but also for firefighters is measuring hydration and selecting a functional means of maintaining adequate hydration. NFPA 1584, Standard on the Rehabilitation Process for Members During Emergency Operations and Training Exercises, 2015 edition,6 for the first time actually places responsibility for hydration directly on the shoulders of each firefighter. According to NFPA 1584, every member on scene must participate in rehab, maintain his own hydration, advise his company officer when his performance is affected, and maintain an awareness of the status of other members on scene.
Surprisingly, firefighters are often significantly dehydrated. Even firefighters participating in studies to measure their hydration status often arrive for these studies in seriously dehydrated states.7 This implies a fundamental knowledge gap in understanding both the importance of adequate hydration and firefighters maintaining an awareness of their personal hydration status. Maintaining normal hydration, also referred to as euhydration, is critical for any person participating in physically demanding, high-performance activities like firefighting or competitive sports. Given the need to start firefighting activities in a euhydrated state, prehydration is probably necessary for the majority of firefighters.8
The science of beverages has changed significantly in the past several years. Although continually evolving, we have considerably more information about the effects of water, sports drinks, energy beverages, and caffeine on athletes and firefighters. New recommendations have emerged regarding all these drinks.
Water remains the quintessential fluid for maintaining hydration. Humans consume water in food and in beverages. A typical adult diet provides one liter of water daily in the food itself.9 Unfortunately, an overemphasis on water consumption in sports, with the public, and sometimes in firefighters has led to an increased incidence of hyponatremia, a seriously lowered level of sodium in the bloodstream, usually resulting from excessive water intake. While hyponatremia can occur through other mechanisms, cases occurring in sports and activities involving intense physical exercise lasting four hours or less are nearly always from overconsumption of water before or during the event.10 Fluid shifts resulting from hyponatremia lead to swelling in the brain, seizures, coma, and death. Quite clearly, when it comes to water consumption, a “more is better” approach is ill advised. Water consumption needs are extremely variable from person to person; knowing your individual needs is the only means of maintaining a euhydrated state.
To avoid being caught up in marketing campaigns and advertising appeals, firefighters need to keep abreast of scientific evidence and endeavor to see through commercial bias that seems to have invaded many sports drink studies.11 In fact, fire departments should study their own uses of hydrating fluids and carefully consider whether published evidence yields the desired results in their members.
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| (2) Firefighters are responsible for determining their individual hydration needs, use of products, and strategy. (Photo by David Rhodes.) |
Long marketed as an ideal hydration maintenance beverage, sports drinks have recently come under scrutiny. In 2012, the British Medical Journal conducted an extensive review of the evidence behind sports performance products; the findings were startling. Nearly all sports drink studies conducted to date had industry ties to sports drink manufacturers; most did not reach the scientific rigor needed to sufficiently demonstrate any significant benefit from sports drinks, and many of the researchers and experts involved in sports drinks research had undeclared conflicts of interest. (11) There is little doubt that industry marketing of sports drinks has been successful; sales in the United States alone are estimated to reach $2 billion by 2016.
Energy beverages, not to be confused with sports drinks, contain stimulant drugs such as caffeine, taurine, ginseng, and guarana and are marketed to provide physical or mental stimulation. Although they are often touted as performance enhancers, there are multiple reports of cardiac arrhythmias, seizures, hospitalizations, and deaths associated with consumption of energy drinks, particularly in younger individuals.12 An executive fire officer (EFO) research study found that consumption of energy drinks by wildland firefighters resulted in significant dehydration and cardiac stress.13 In collective response to adverse effects, the 2015 edition of the NFPA 1584 rehab standard strongly discourages consumption of energy drinks by firefighters at any time, both on and off duty. (6)
Caffeine has long been associated with dehydration owing to a perceived increase in urine output observed after consumption. Although largely ignored, there has actually been reasonably good evidence since the 1980s that debunks this myth.14 One of the better analyses of the effects of caffeine consumption as it relates to firefighters was published in 2007 by Matthew S. Ganio and colleagues who examined multiple studies of low-dose [less than 300 milligrams (mg)] and high-dose [greater than 600 mg or 8.2 to 10.2 mg/kilograms (kg)] caffeine consumption. For reference, a typical cup of coffee contains roughly 100 mg of caffeine. At low-caffeine doses (250 to 300 mg or 1.4 to 3.1 mg/kg), urine volume increased for three hours following caffeine consumption but, when measured out to four hours, was no different than urine volume in people who drank an equal amount of water. High-dose caffeine consumption resulted in variable urinary increases, reaching up to 41 percent above baseline in some subjects; but when monitoring extended out to 24 hours, it did not seem to result in any long-term changes in hydration status, perhaps because of a compensatory decline in urine production following the increased output.15 Earlier studies found increased urinary output only in coffee drinkers who were not chronic caffeine users, whereas those who regularly consumed caffeine appeared to have developed a tolerance. (14)
Curiously, high-dose caffeine consumption one to two hours prior to significant exercise did not increase urine output or affect hydration status, perhaps owing to decreased renal blood flow during exercise. Conclusively, there is little to no evidence to suggest that low to moderate levels of caffeine consumption (less than 300 mg or < 3.1 mg/kg daily) alter hydration status at rest or during exercise.
Ganio also examined the effects of varying levels of caffeine consumption, increasing between low and high levels over 12 days, on hydration and thermoregulation while exercising in a hot environment. Varying levels of caffeine consumption between low and high showed no effect on hydration status or thermoregulatory ability while exercising in a hot environment or at rest. (15)
The one missing piece of evidence on caffeine is whether it improves performance or endurance. Many athletes and firefighters believe that caffeine enhances alertness and provides a competitive advantage during high-performance activities. To date, no good evidence exists to substantiate these claims. (12)
No two people respond alike to fluids or to the rigors of firefighting. Measuring hydration, then, becomes one of the most difficult challenges for firefighters, just as it does for performance athletes. The age-old belief that thirst is a reliable indicator of dehydration remains controversial, although our understanding of the role thirst plays in hydration continues to improve. Recent studies of competition cyclists have found thirst as one of the most reliable indices for optimizing hydration.16 However, it is well known that thirst response becomes blunted with aging (14) and in situations involving very high sweat rates, thirst will often lag behind (a phenomenon called “voluntary dehydration”). (15) Although you should not rely on thirst as the sole indicator of hydration status, it is a dynamic physiologic indicator, and it should not be ignored.17 The role of thirst as a feedback mechanism is almost certainly helpful in preventing both overdrinking and underdrinking.
Given that firefighters seem to have a propensity toward baseline dehydration (7), there is a strong imperative to encourage proper hydration before initiating training. Firefighters also need tools to help them maintain their personal hydration status on a day-to-day basis so they are equally well prepared to respond to emergency calls. If dehydration is suspected before training activities, a urine sample could be requested and analyzed using the National Collegiate Athletic Association rules. A urine specific gravity (USG) of greater than 1.020 or urine color less than or equal to four is considered the upper endpoint of allowable, and the firefighter should not begin training. (7) USG or urine osmolality (UOsmol) and urine color charts can be valuable tools for learning about and maintaining hydration (photo 3).
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| (3) Dark cloudy urine (left) could indicate dehydration. Clear specimens (right) could indicate hyperhydration. Both would need additional testing and follow-up with the firefighter. (Photo by David Rhodes.) |
Multiple hydration assessment tools have been studied in performance athletes and firefighters. All have limitations; understanding those limitations can help firefighters and their company officers best interpret the results. Urine color charts and USG or UOsmol offer an inexpensive, quick, and efficient test and are often used to assess firefighters’ and athletes’ hydration status. Urine color charts are standardized, can be posted in restrooms, and allow self-evaluation of results. Urine dipsticks and urine meter devices can be used to measure USG or UOsmol and provide information about dehydration [USG > 1.020 or UOsmol > 700 osmoles (mOsm)/kg] as well as overhydration (USG < 1.010 or UOsmol < 300 mOsm/kg). (8) Both urine color charts and urine sampling are accurate when used to assess the first morning void. Their value declines considerably later in the day and is highly confounded by rapid rehydration (drinking large volumes of fluid); severe dehydration; alcohol consumption within the previous 24 hours; caffeine consumption; critical illness; and (for urine color charts) ingestion of certain foods, vitamins, and medications.18
Measurements of blood and plasma (laboratory tests) do not appear to add enough value to some of the less invasively obtained measurements. (18) Saliva osmolality had been proposed as a less invasive hydration assessment test (7), especially given the development of a novel field instrument that could be used on the fireground (Cantimer Corporation, Menlo Park, CA). More recent studies suggest that rehydration is likely to confound results.
In the end, when evaluating all of the sports and firefighter literature assessing hydration status, it would appear that body weight in concert with a specific hydration measurement like USG or urine color (on the first morning void) are probably the most accurate combination of tools for firefighters and performance athletes. (8, 9, 18) Ideally, firefighters would weigh themselves on three consecutive mornings without their clothes (nude weight) and assess their urine color or USG. If their urine color or USG was within normal limits (color between 1 and 3 or USG between 1.010 and 1.020), then the average nude weight represents their euhydrated weight. On their return from a fire or training exercise, the change in nude weight from baseline defines the fluid volume loss. A change of > 2 percent represents significant dehydration and requires consumption of about 1.5 liters of fluid for every kilogram (2.2 pounds) below baseline. (8) It is important to recognize that no two firefighters are alike in muscle and fat composition or total body water content. Meals also contain significant fluid volumes and need to be considered in fluid replacement. Regardless, nude weights and urine measurements can provide individual firefighters with valuable feedback on their personal needs for hydration.
Fluid replacement can be an art unto itself. A significant body of literature pegs potential firefighter fluid losses at up to two liters per hour or more. Yet, consuming large quantities of fluid over short periods is more likely to overwhelm the body, increasing urinary output and resulting in considerably less fluid retention than desired. (9) This mechanism also explains why urine is not a reliable tool for evaluating rehydration. Hence, for firefighters and performance athletes, consuming 500 milliliters (mL) aliquots of water spaced in 20- to 30-minute intervals optimizes fluid retention. This raises an obvious question about the comparative efficacy of other rehydration regimens. This, too, has been studied in firefighters. Rehydration with water, sports drinks, and IV normal saline showed no difference in their effects on performance in continuous heavy-work scenarios.19 Hence, whenever possible and practical, rehydration with water is most practical. This should not diminish the obvious benefits of flavored powders to increase the appeal of water or the role of carbohydrates and sodium in sports drinks during very prolonged incidents.
Limit the role of physiologic assessments such as vital signs in hydration assessment to situations where dehydration or hyperhydration is already suspected. In firefighting, as in performance sports, clinical signs such as dizziness, headache, dry skin, and tachycardia tend to be extremely imprecise and are often related to the environment and activity rather than hydration status. (9) A useful vital sign, especially in firefighter rehab, is blood pressure. Dehydration is well known to increase resting heart rate and lead to orthostatic hypotension (18), and this indeed has been seen in firefighter studies. Hypotension measured in firefighter rehab very likely suggests significant dehydration. Emergency medical services providers with experience in firefighter rehab place much more significance on hypotension than they do on hypertension for this very reason.
How could you put all of this information into practice? The Georgia Smoke Divers School, an advanced firefighter training program, has, for many years, incorporated much of the science of hydration into its programs. One of its key beliefs is that hydration during firefighter training must be considered when planning any session that will require extended time in structural firefighting gear, regardless of weather. As previously mentioned, it is the firefighter’s responsibility to report to the training ground hydrated. Each member should have a hydration plan that takes into consideration the weather, the time in gear, the amount of exertion, and the loss of fluid through the sweat rate. The command staff and instructors are responsible for educating the students and instructors about the signs and symptoms of heat-related injuries including heat exhaustion and heat stroke.
Longer-duration training sessions typically held at a recruit academy or other heavily hands-on type courses (live fire, SCBA confidence, and so on) should consider stricter hydration monitoring. The Georgia Smoke Divers School uses several medical tools to assist in determining the hydration levels of students. It is impossible to know a firefighter’s hydration level solely by documentation of fluid consumption. Each firefighter is unique and processes fluid differently. Additionally, individual medical conditions and medications affect fluid needs and absorption.
The Georgia Smoke Diver School uses a medical screening questionnaire to determine use of certain medications, medical conditions, and current illness that could lead to the inability to remain hydrated during its 60-plus-hour course. Urine samples are collected from each student on reporting the first day and each morning thereafter. Specific gravity is tested as an initial screening along with a visual comparison with a standardized urine color hydration chart. Additional testing can be completed with a urine dipstick, which is a rapid field test that identifies proteins and blood (as well as several other constituents) in urine. Any specific gravity of more than 1.020 or an appearance of a dark tea or a pink coloration requires further investigation by the medical officer. This consists of an additional interview to see if something may have been missed on the screening questionnaire. Often, a student may not have listed vitamins or nutritional supplements that could be responsible for urine discoloration. A prestart initial specific gravity of more than 1.030 requires notification of the course director, additional fluid intake, and retesting before starting physical activity. A dipstick test indicating blood requires that the student be removed from class and referred to a medical practitioner (photo 4).
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| (4) An instructor checks and documents the specific gravity of a firefighter’s urine using a refractometer. (Photo by David Rhodes.) |
Anytime a student experiences a problem that requires a medical evaluation, the student is retested to check his hydration status. It is important to understand the limits of field screening and to use it as only one part of a complete rehab and hydration program that includes constant self-assessment by the students, evaluation by the instructors, and documentation of fluid intake as well as active and passive cooling. One of the best ways to reduce the sweat rate is to get students out of their personal protective equipment anytime they are not engaged in an activity. This includes predrill briefings, demonstrations, and downtime while waiting their turn in an activity.
Hydration is critical to firefighter performance. Firefighters are often dehydrated, which may explain many fireground injuries; no two firefighters require the same fluid intake to maintain a euhydrated state. Optimizing individual firefighter hydration status can best be achieved by using several first morning USGs or urine color analyses in concert with nude body weight to serve as a basis for fluid replacement following response to fires. Our use of fluids on the fireground should be based on science and individual needs. Every firefighter must assume personal responsibility for his hydration status. Departments need to provide the tools needed to maintain hydrated members.
REFERENCES
1. Rodrigues R, Baroni BM, Pompermayer MG, et al. Effects of acute dehydration on neuromuscular responses of exercised and nonexercised muscles after exercise in the heat. J Strength Cond Res. 2014;28:3531–3536.
2. Maughan RJ. Impact of mild dehydration on wellness and on exercise performance. Eur J Clin Nutr. 2003; 57: Suppl 2, S19–S23.
3. Pompermayer MG, Rodrigues R, Baroni BM, et al. Rehydration during exercise in the heat reduces physiological strain index in healthy adults. Rev Bras Cineantropom Desempenho Hum. 2014; 16:629-637.
4. Karter MJ, Molis JL. U.S. Firefighter Injuries – 2012. National Fire Protection Association. October 2013.
5. United States Fire Administration. Firefighter Fatalities in the United States in 2012. FEMA; August 2013.
6. National Fire Protection Association. NFPA 1584: Standard on the Rehabilitation Process for Members During Emergency Operations and Training Exercises. Quincy, MA: National Fire Protection Association, 2015.
7. Horn GP, DeBlois J, Shalmyeva I, et al. Quantifying dehydration in the fire service using field methods and novel devices. Prehosp Emerg Care. 2012;16:347–355.
8. Sawka MN, Burke LM, Eichner ER, et al. American College of Sports Medicine Position Stand: Exercise and Fluid Replacement. Med Sci Sports Exerc. 2007; 39:377-390.
9. Casa DJ, Clarkson PM, Roberts WO. American College of Sports Medicine Roundtable on Hydration and Physical Activity: Consensus Statements. Curr Sports Med Rep. 2005, 4:115–127.
10. Denny S. What are the guidelines for prevention of hyponatremia in individuals training for endurance sports, as well as other physically active adults? J Am Diet Assoc. 2005; 105:1323.
11. Cohen D. The truth about sports drinks. BMJ. 2012;345:e4737.
12. Heneghan C, Gill P, O’Neill B, et al. Mythbusting sports and exercise products. BMJ. 2012;345:e4848.
13. Abbott S. Assessing the effects of energy drinks on firefighter health and safety. North County Fire Protection District, Fallbrook, CA. Executive Fire Officer Program, 2010.
14. Grandjean AC, Reimers KJ, Buyckx ME. Hydration: Issues for the 21st Century. Nutrition Reviews. 2003;61:261-271.
15. Ganio MS, Casa DJ, Armstrong LE, et al. Evidence-approach to lingering hydration questions. Clin Sports Med. 2007;26:1-16.
16. Heneghan C, Howick J, O’Neill, et al. The evidence underpinning sports performance products: a systematic assessment. BMJ Open 2012;2:e001702.
17. Hew-Butler T, Verbalis JG, Noakes TD. Updated fluid recommendation: Position statement from the International Marathon Medical Directors Association (IMMDA). Clin J Sport Med. 2006;16:283-292.
18. Kavouras S. Assessing hydration status. Curr Opin Clin Nutr Metab Care. 2002; 5:519-524.
19. Hostler D, Bednez JC, Kerin S, et al. Comparison of rehydration regimens for rehabilitation of firefighers performing heavy exercise in thermal protective clothing: a report from the fireground rehab evaluation (FIRE) trial. Prehosp Emerg Care. 2010;14:194-201.
MIKE McEVOY, PhD, NRP, RN, CCRN, is the emergency medical services (EMS) coordinator for Saratoga County, New York, and the chief medical officer and firefighter/paramedic for the West Crescent Fire Department (Clifton Park, New York). He is a nurse clinician in the adult and pediatric cardiac surgery intensive care units at Albany Medical Center, where he also teaches critical care medicine and chairs the hospital Resuscitation Committee. McEvoy is the EMS editor for Fire Engineering and a paramedic supervisor for Clifton Park and Halfmoon Ambulance and is actively involved in fire, EMS, and resuscitation research. He is an EMS section board member for the International Association of Fire Chiefs.
DAVID RHODES is a 30-year fire service veteran serving with an urban fire department in Georgia. He is a chief elder for the Georgia Smoke Diver Program, a member of the Fire Department Instructors Conference (FDIC) Executive Advisory Board, a hands-on-training coordinator for FDIC, an editorial advisor and author for Fire Engineering, an advisory board member for the UL Fire Safety Research Institute, and an adjunct instructor for the Georgia Fire Academy. He serves as a Type III incident commander for the Georgia Emergency Management–Metro Atlanta All Hazards Incident Management Team and is a task force leader for the Georgia Search and Rescue Team. He is president of Rhodes Consultants, Inc., which provides public safety training, consulting, and promotional assessment centers.
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