Fluid Replacement and Heat Stress, 1993

Pp. 37-54. Washington, D.C.

National Academy Press

4

Considerations for Replacement Beverages: Fluid-Electrolyte Balance and Heat Illness

Lawrence E. Armstrong1

INTRODUCTION

Two case reports (attached as appendices) have been presented during this workshop. The first case report involved an endurathon staged on a hot, humid day at Fort Bragg, North Carolina. A group of 40 soldiers competed from 9 a.m. to 3 p.m. in the following seven consecutive events: an 8-km run, a 1-h road march while carrying 32 kg of equipment, a 2-h river excursion in a rubber boat, an 8-km run while wearing combat boots and full uniform, an obstacle course, a pistol marksmanship contest, and a 1.6 km team litter carry (68 kg weight). A 10-min rest period was allowed between each event for water consumption; soldiers ate a variety of snacks, but no meals were provided. Eight cases of heat illness (e.g. heat exhaustion, heat cramps, heat prostration) occurred after the fifth event. Prior to the sixth event, a carbohydrate-electrolyte solution was provided for these soldiers and no further heat illness episodes occurred. At 10 p.m., this unit was unexpectedly placed on alert and began several hours of mission preparation.

1  

Lawrence E. Armstrong, The Human Performance Laboratory, The University of Connecticut, Sprots Center, Room 223, U-110, 2095 Hillside Road, Storrs, CT 06269 MA



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FLUID REPLACEMENT AND HEAT STRESS Fluid Replacement and Heat Stress, 1993 Pp. 37-54. Washington, D.C. National Academy Press 4 Considerations for Replacement Beverages: Fluid-Electrolyte Balance and Heat Illness Lawrence E. Armstrong1 INTRODUCTION Two case reports (attached as appendices) have been presented during this workshop. The first case report involved an endurathon staged on a hot, humid day at Fort Bragg, North Carolina. A group of 40 soldiers competed from 9 a.m. to 3 p.m. in the following seven consecutive events: an 8-km run, a 1-h road march while carrying 32 kg of equipment, a 2-h river excursion in a rubber boat, an 8-km run while wearing combat boots and full uniform, an obstacle course, a pistol marksmanship contest, and a 1.6 km team litter carry (68 kg weight). A 10-min rest period was allowed between each event for water consumption; soldiers ate a variety of snacks, but no meals were provided. Eight cases of heat illness (e.g. heat exhaustion, heat cramps, heat prostration) occurred after the fifth event. Prior to the sixth event, a carbohydrate-electrolyte solution was provided for these soldiers and no further heat illness episodes occurred. At 10 p.m., this unit was unexpectedly placed on alert and began several hours of mission preparation. 1   Lawrence E. Armstrong, The Human Performance Laboratory, The University of Connecticut, Sprots Center, Room 223, U-110, 2095 Hillside Road, Storrs, CT 06269 MA

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FLUID REPLACEMENT AND HEAT STRESS Prior to the 15-hour flight to the Mid-East, each soldier received two box lunches and two 1-liter containers of Gatorade. Upon arrival, warm potable water was availabel, but it was not palatable. Gatorade powder was added to water storage containers at two-thirds strength. During the next 36 hours of duty there were no heat casualties. The second case report involved a Ranger Batallion of approximately 750 soldiers who were involved in a mission designed to rescue U.S. citizens in 1983. One half of these men flew from Fort Lewis, Washington (air temperature of 7°–13°C). Prior to this mission, soldiers were allowed to rest for 4 to 6 h. They remained in full combat gear for 6 h prior to their parachute jump and were not relieved until they had spent 6 h in intermittent combat at a site that was covered with dense plant growth (ambient conditions of 29°–32°C, 85% relative humidity). The load which the average soldier carried weighed 29 to 34 kg, but some men carried gear weighing more than 45 kg. Prior to this operation, Rangers drank 10 to 12 liters of water per day and a forced hydration program was followed during this mission; each man carried 4 liters of pure water. Gatorade also was utilized, by diluting it to one-quarter strength with water. This Ranger unit experienced no heat casualities during this mission despite being relatively unacclimatized. The purposes of this paper are to comment on the first case report by K. Alitz (Appendix 1) and the second by C. Donovan (Appendix 2) presented during this conference, and to emphasize the specific need (or lack of need) for carbohydrate-electrolyte solutions, which soldiers experience during duty in hot environments. Because this paper focuses on fluids and electrolytes, it is helpful to reiterate the following aspects of their reports: (1) Gatorade was used in dilute form at two-thirds (K. Alitz, Security Operations Training Facility, Fort Bragg, North Carolina, personal communication, 1989) and one-quarter (C. Donovan, Tuttle Army Health Clinic, personal communication, 1989) strength, (2) meals were sacrificed so that the mission could be accomplished, and (3) Donovan stated that a rigorous hydration program virtually eliminated heat illness at a time when other U.S. personnel experienced significant heat casualties. In regard to the third point, the Heat Research Division of the U.S. Army Research Institute of Environmental Medicine (USARIEM), has received a recent communication describing a similar hydration program at Fort McClellan, Alabama (D. Compton, USA MEDDAC, Fort McClelland, Alabama, personal communication, 1988). This program resulted in a decrease in July-August heat casualties from 21 (1987) to 6 (1988), when troops were placed on a regimen of drinking 0.5-1 quart of water per hour.

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FLUID REPLACEMENT AND HEAT STRESS SALT DEFICITS If salt and water losses are compared for three continuous foot races--10 km (6.21 ml), 42.1 km (26.2 ml), and 161 km (100 ml)--the total sodium chloride (NaCl) loss on a hot day will be 0.5-6, 2-29, and 54-93 g, respectively. These calculated NaCl losses are based on total sweat losses of 0.5-1.5, 2-6.6, and 18-35 liters, respectively (R. Lind, Medical Director of Western States 100 Mile Race, personal communication, 1988), and sweat salt concentrations of 1-4 g of NaCl per liter. If these losses are compared with the daily NaCl intake in garrison dining facilities (95% confidence limits, 6-24 g of NaCl per day) (Rose et al., 1989), or by eating three meals-ready-to-eat (MRE's) (12.6 g of NaCl per day) (Popper et al., 1987), it is clear that NaCl supplementation may be required in certain physically demanding situations. Although the military relevancy of a 161-km foot race (lasting 17-26 h) can be questioned, it is clear that the stress of the endurathon and subsequent deployment, described in the case study of Alitz, probably lies somewhere between these 42.1-km and 161-km events. Table 4-1 clarifies this point in more relevant terms. These data (Armstrong et al., 1985) describe the effects of a 6-h simulated desert march on fluid-electrolyte balance. Our measurements (brisk walk, 5% incline, 30 min of exercise per hour, wearing shorts and sneakers) indicated that electrolyte deficits may be encountered (Table 4-1) when these losses are compared with the salt contents of the 24-h garrison meal [95% confidence limits, 101-415 meq of Na+ per day, 67-144 meq K+ per day (Rose et al., 1989)] and 24-h MRE [216 meq of Na+ per day; 71 meq of K+ per day (Popper et al., 1987)]. While 6-h sodium (Na+) deficits may be partially reduced via liberal seasoning of meals with table salt, the potassium (K+) deficits are less likely to be reduced in this manner. POTENTIAL OVERCONSUMPTION OF SALT In contrast, it is theoretically possible to consume more NaCl than is physiologically required. The calculated 24-h salt consumption in Alitz's and Donovan's case reports are as follows. Based upon the consumption of 10 liters of diluted Gatorade (0.9 g of NaCl per liter, full-strength) per day from Donovan's report, and three MRE per day [12.6 g of NaCl (Popper et al., 1987)], maximum total salt intakes are calculated, using Alitz's information, as 6 + 13 = 19 g of NaCl per day and, using Donovan's report, as 2 + 13 = 15 g of NaCl per day. If one MRE salt packet (4 g of NaCl) were consumed at each meal, these values would increase to 31 g and 27 g of NaCl per day, based respectively on the reports of Alitz and Donovan.

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FLUID REPLACEMENT AND HEAT STRESS consumed at each meal, these values would increase to 31 g and 27 g of NaCl per day, based respectively on the reports of Alitz and Donovan. Table 4-1 Projected Effects of a 6-h Simulated Desert March EXPERIMENTAL DESIGN Subjects, 12 healthy males Air temp, 40.6°C (dry bulb), 25.5°C (wet bulb) Treadmill walking at 1.34 m/s, 5% grade Ad libitum water intake FLUID-ELECTROLYTE LOSS PER 6 h Sweat loss, 3.5 ± 0.1 liter Sweat Na+ concentration, 12.7-46.7 meq/liter Sweat K+ concentration, 1.7-4.8 meq/liter Na+ loss, 72-244 total meqa K+ loss, 23-70 total meqa PROJECTED ELECTROLYTE LOSS PER 24 hb Na+ loss, 193-425 meq/liter K+ loss, 62-240 meq/liter a Urine + sweat (measured via whole-body washdown). b Based on 8 liters of sweat loss and constant urinary electrolyte loss per 24 h. It has been observed that soldiers eat approximately 70% of all MRE contents in a temperate environment and that few soldiers (<4%) use the MRE salt packets; therefore, a realistic estimate of these NaCl intakes then becomes 6 + 9 = 15 g (after Alitz) and 2 + 9 = 11 g (after Donovan) of NaCl per 24 h. Conn's research (1949) demonstrated that heat-acclimatized males adapted to diets containing 6 g of NaCl per day (from 12 g of NaCl per day) after 5-15 days of this diet. It is likely, then, that the military units described in these case reports consumed more NaCl each day than they required. The human kidney readily removes such levels of excess salt as

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FLUID REPLACEMENT AND HEAT STRESS they are consumed, yet salt supplementation has been recommended (Hubbard et al., 1986; Leighthead and Lind, 1964; Hubbard and Armstrong, 1988) during the initial 3-5 days of heat exposure because the kidneys require 3-5 days (and the sweat glands require 5-10 days) of heat exposure to maximally conserve Na+ (Hubbard et al., 1986). Symptoms and casualties of heat syncope and heat exhaustion are greatest during this period and decrease notably after day 5 (Hubbard and Armstrong, 1988). This can best be explained by the fact that the primary adaptations during the initial 3-5 days of heat acclimatization are cardiovascular, and emphasizes the need for adequate salt intake to maintain extracellular fluid and plasma volumes. Dasler et al. (1973) have published the only study that has examined extremely high salt consumption during heat acclimatization. They found that subjects exhibited impaired heat acclimatization responses when they ate high levels of salt (22.5-30 g of NaCl per day). These responses included cardiovascular impairment; decreased optimal work capacity; and increased excretion of K+, bicarbonate, and other anions. This impaired heat acclimatization response may have been due to inadequate water intake by their subjects, because the water requirement increases approximately 1 liter for each 5 g of NaCl added to the diet (Baker et al., 1963). In addition, Knochel and Vertel (1967) have implicated salt loading as a possible factor in the production of potassium deficiency, rhabdomyolysis, and heat injury. These two reports impact on the evaluation of carbohydrate-electrolyte replacement beverages, because a soldier could theoretically exceed the NaCl intake in the study of Dasler et al. (1973) if he ate three MRE (13 g of NaCl per day), ate three MRE salt packets (12 g of NaCl per day), and drank 10 liters of Gatorade (12 g of NaCl per day, full-strength) in a 24-h period. In Alitz's, and Donovan's units, these theoretical NaCl totals would be 31 g and 27 g, respectively. CASE REPORT A: TEN HEATSTROKE PATIENTS During the past 2 years, we evaluated the time course and extent of recovery in prior heatstroke patients. Ten active-duty male soldiers came to our laboratory for 14-day investigations of their thermoregulatory and heat-acclimatization abilities, as well as for evaluations of blood chemistry values and fluid-electrolyte balance. This work has been published elsewhere (Armstrong et al., 1989), showing that it is useful to consider the events of the day on which these men experienced heatstroke. Nearly all of these soldiers experienced heatstroke (verified by rectal temperature of >106°F, elevated serum enzymes, and altered mental status) at Fort Benning, Georgia, which presents a hot, humid environment at mid-day. In most

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FLUID REPLACEMENT AND HEAT STRESS cases, they were running in formation at a 7.0-8.5 min/mile pace for 21-43 min. However, 8 of 10 of these men collapsed prior to 7:30 a.m., when the ambient dry bulb temperature was 69°-79°F or lower--certainly not the environmental conditions that would be expected to induce heatstroke. Prior to the initiation of testing, each volunteer was interviewed in regard to the factors that may have predisposed him to heatstroke. Based on daily physical training and environmental conditions, we defined five of these men to be heat acclimatized and five to be nonacclimatized. The climate of their residence (for 4 years prior to the heatstroke) varied from very hot to temperate. Table 4-2 further defines the predisposing factors which these Table 4-2 Predisposing Factors for Heatstroke Reported by Soldiers from Fort Benning, Georgia Predisposing Factorsa Soldiers Reportingb Sleep loss 7 Fatigue 6 Long exercise bout(s) 5 Long heat exposure 5 Heat wave 4 Reduced sweat secretion 3 Concurrent fever or disease 3 Excessive use of alcohol 1 Excessive use of tobacco 1 Eating a low-salt diet 1 Recent visit to doctor 1 Taking medication for other complaint 1 Dehydration 1 a During the 5 days prior to heatstroke. b Out of a total of 10 subjects. soldiers reported. Four factors were verified by at least 50% of these volunteers: sleep loss, fatigue, lengthy heat exposure, and a long exercise bout or workout within the 5 days prior to heatstroke. Considering all predisposing factors, it is unlikely that carbohydrate-electrolyte replacement drinks per se would have prevented heatstroke in these soldiers, who were not deprived of food or fluids unless they chose to eat only a portion of the meals offered to them. This may occur in some field situations, but the survey of basic trainee eating habits by Rose et al. (1989) indicated that males left on their plates only 2%-3% of the daily Na+ offered in their three garrison meals, while females did not eat 7%-10% of the daily Na+ offered

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FLUID REPLACEMENT AND HEAT STRESS in their three garrison meals. The issue of anorexia on arrival in a hot environment is unresolved. CASE REPORT B: HEAT EXHAUSTION IN PANAMA A scenario similar to the one that Donovan described, as part of this workshop, occurred in Panama during 1985. Eleven cases of heat exhaustion occurred during one field training exercise (FTX) at the Gatun drop zone. The ambient temperature and humidity, which are very stable year-round in Panama, evidently had not changed prior to this FTX, but the events which occurred during the 36 h prior to this incident were crucial. This FTX occurred on a clear, sunny day (air dry bulb temperature >80°F). The troops were wearing full combat gear, including rucksack, weapon, parachute, and reserve chute. Most were heat acclimatized, and most were trained to drink and sprinkle water on their bodies. This paratrooper unit had spent 24-36 h prior to the FTX packing gear, organizing, and planning the next day's activities; this led to sleep loss. Although these soldiers carried 1- and 2-quart (0.95- and 1.9-liter) canteens, their busy schedule resulted in inadequate water and meal intakes. Heat exhaustion is usually a fluid depletion problem that is aggravated by exercise in the heat, resulting in circulatory collapse. It appears that a lengthy period of fluid imbalance, coupled with a 2-h wait on the runway in non-air-conditioned aircraft, precipitated these 11 cases of heat exhaustion. Dense foliage [8-10 feet tall (2.4 - 3 m); little or no air movement] at the drop zone was the final contributing factor. As soldiers landed, they were required to move through this dense foliage to a pickup point. It is likely that a carbohydrate-electrolyte replacement fluid, availabel during the 36-h preparation period, would have helped these soldiers maintain performance throughout the FTX and might have helped them avoid heat exhaustion (Armstrong et al., 1988; Hubbard and Armstrong, 1988). CASE REPORT C: HEAT EXHAUSTION AMONG RESERVISTS IN TEXAS Members of the Fifth Army Reserve conducted their annual 2-week FTX at Fort Hood, Texas, in June 1988. Our research team evaluated heat-exhaustion patients who were sent to the 44th Evacuation Hospital. Blood chemistry, hematological, and total body water (TBW) measurements were made on four heat-exhaustion patients (three males and one female). Table 4-3 describes the TBW values [deuterium oxide (D2O)] for these four patients and two control subjects. The percentage of body weight that TBW

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FLUID REPLACEMENT AND HEAT STRESS Table 4-3 Total Body Water (D2O) Comparison Subject Sex Age (yr) Wt (kg) Hta (cm) TBWb(liter) TBW: Wt(%) Urine (specific gravity) Normal subjects A M 29 102.5 183 60 58 1.024 B F 28 52.8 154 30 57 1.006 Heat-exhaustion patientsc C M 45 115.7 193 81 70 1.025 D M 28 107.5 180 99 93 1.005 E F 24 49.4 157 41 83 1.024 F M 25 72.6 183 62 86 1.002 a Ht = Height b TBW = Total body water c Fort Hood, Texas, June 1988. represents in normal males has been reported as 55.6% ± 5.0%, as determined in 25 measurements on 11 subjects (Faller et al., 1955a). This agrees well with the values (expressed as TBW:Wt) for normal subjects presented in Table 4-3 (58% and 57%), but not for the four heat-exhaustion patients, who had ratios of 70%, 93%, 83%, and 86%. A plausible hypothesis involves disrupted fluid absorption at the intestine, leading to impaired or delayed D2O equilibration with TBW. Our experiments indicate that plasma D2O equilibration occurs in 2-4 h in normal subjects. We believe that minimal D2O entered the body water space through the intestine, the TBW pool appeared to be larger than it actually was (Table 4-3), and TBW was thereby overestimated. The involvement of impaired intestinal absorption in patients with heat exhaustion (Armstrong et al., 1988; Hubbard and Armstrong, 1988) and other illnesses (Faller et al., 1955b) has been described elsewhere. These results, similar to malnutrition cases (Brown, 1985), may mean that a carbohydrate-electrolyte solution optimizes intestinal water absorption.

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FLUID REPLACEMENT AND HEAT STRESS SCENARIO-SPECIFIC NEEDS Recent review articles (Lamb and Brodowicz, 1986; Murray, 1987) have emphasized the fact that the efficacy of consumption of carbohydrate-electrolyte solutions depends on the research protocol employed. There are two situations in which carbohydrate-electrolyte beverages clearly appear to maintain performance: (1) when a deficiency exists in either carbohydrate or electrolyte stores, and (2) when prolonged, continuous exercise of at least 60-min duration (Murray, 1987) is performed. Coyle and Coggan (1984) described, earlier in this workshop (See Chapter VIII), the importance of timing as a factor determining the efficacy of carbohydrate consumption. Lamb and Brodowicz (1986) also published a review paper which noted that (1) carbohydrate consumption 0-15 min before exercise may positively affect endurance performance, and (2) there is no published report of a positive effect of carbohydrate intake on performance when carbohydrate is fed 15-60 min before exercise. This is probably due to a reduced blood glucose level following a rapid rise in insulin concentration. Although many stressful military scenarios suggest that carbohydrate-electrolyte supplements would improve performance (i.e., missed meals, lack of heat acclimatization, diarrheal disease, and exercise in impermeable protective clothing), some scenarios contraindicate the consumption of carbohydrate-electrolyte supplements. For example, total dissolved solids may reach 1.0 g/liter in fresh water, 1-20 g/liter in brackish water, and >35 g/liter in saline water (Daniels, 1988). NaCl constitutes 85% of these total dissolved solids by weight. For soldiers drinking 10-18 liters of fresh water per day (see above), this amounts to 9-15 g of NaCl added to an individual's total solute load. This amount of NaCl would be much larger if brackish or saline water were consumed. The task performed by soldiers also should be considered in determining whether carbohydrate-electrolyte fluids are necessary to maintain performance. Table 4-4 presents the Military Occupational Specialty (MOS) classifications of the U.S. Army, as described by Sharp et al. (1980). Note that these classifications have been categorized by fitness requirements (high, medium, or low) for strength and stamina. It is instructive to note that 47% of all enlisted personnel work in MOS categories that require medium to low strength and stamina. Thus it appears that they seldom are placed in situations that require carbohydrate-electrolyte supplementation. Their normal dietary intake (e.g., garrison meals or MRE) will usually replace all metabolized carbohydrates and lost electrolytes.

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FLUID REPLACEMENT AND HEAT STRESS Table 4-4 Military Occupational Specialty (MOS) Classifications Fitness Requirements Strength Stamina Branch Total MOSs Percent of Enlisted Personnel High High Engineer, Field artillery, Infantry 10 19 High Medium Artillery, Field artillery, Medical 39 13 High Low Engineer, Munitions, Transportation 63 21 Medium Low Intelligence, Signal, Engineer, Quartermaster 53 21 Low Low Admin. Engineer, Intelligence, Transportation 184 26 Source: Sharp et al., 1980. SUMMARY The above facts have been presented to support the concept that carbohydrate-electrolyte replacement fluids may be necessary in some, but not all, military field situations. The greatest need for carbohydrate-electrolyte replacement fluids is experienced by soldiers who (1) lose more than 8 liters of sweat per day; (2) are not heat acclimatized (e.g., during the initial 8 days of field living); (3) are performing a prolonged, continuous exercise bout (>60 min); (4) skip meals, have meals interrupted, or encounter anorexia because of a hot environment; (5) experience a caloric deficit of >1,000 kcal per day; or (6) are ill with diarrheal disease. The fluid-electrolyte needs of soldiers are specific to the intensity, frequency, and duration of the exercise involved, as well as the environmental stress encountered. This information is not presented to imply that many different solutions are required, but rather that the best use of such fluids can be recognized with proper soldier training (i.e., when to use them) and simple instructions for field implementation. It appears that carbohydrate-electrolyte replacement fluids, like weapons, should be availabel to the soldier for use when needed.

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FLUID REPLACEMENT AND HEAT STRESS REFERENCES Armstrong, L.E., R.W. Hubbard, P.C. Szlyk, W.T. Matthew, and I.V. Sils. 1985 Voluntary dehydration and electrolyte losses during prolonged exercise in the heat. Aviat. Space Environ. Med. 56:765-770. Armstrong, L.E., R.W. Hubbard, P.C. Szlyk, I.V. Sils, and W.J. Kraemer. 1988 Heat intolerance, heat exhaustion monitored: a case report. Aviat. Space Environ. Med. 59:262-266. Armstrong, L.E., J.P. DeLuca, R.W. Hubbard. 1989 Time course of recovery and heat acclimation ability of prior exertional heatstroke patients. Med. Sci. Sports Exercise 22(1):36-48. Baker, E.M., I.C. Plough, and T.H. Allen. 1963 Water requirements of men as related to salt intake. Am. J. Clin. Nutr. 12:394-398. Brown, J.D. 1985 Oral rehydration therapy for diarrhea. Mil. Med. 150:577-581. Conn, J.W. 1949Acclimatization to heat. Ann. Intern. Med. 3:337. Coyle, E.F., and E.R. Coggan. 1984 Effectiveness of carbohydrate feeding in delaying fatigue during prolonged exercise. Sports Med. 1:446-458. Daniels, J.I., ed. 1988 Evaluation of Military Field-Water Quality: Health Criteria and Recommendations for Standards, vol. 4, part 1. Chemicals and Properties of Military Concern Associated with Natural and Anthropogenic Sources. Publication No. UCRL-21008. Lawrence Livermore National Laboratory, Livermore, Calif. 281 pp. Dasler, A.R., S. Karas, J.S. Bowman, and E. Hardenbergh. 1973 Adverse effects of supplementary sodium chloride on heat adaptation (abstr. 677). Fed. Proc. Fed. Am. Soc. Exp. Biol. 32:336. Faller, I.L., D. Petty, J.H. Last, L.R. Pascale, and E.E. Bard. 1955a A comparison of deuterium oxide and antipyrine dilution methods for measuring total body water in normal and hydropic human subjects J. Lab. Clin. Med. 45:748-758. Faller, I.L., E.E. Bard, D. Petty, and L.R. Pascale. 1955b The use of deuterium oxide concentrations in a simple method for measuring total body water. J. Lab. Clin. Med. 45:759-764. Hubbard, R.W., and L.E. Armstrong. 1988 The heat illnesses: biochemical, ultrastructural, and fluid-electrolyte considerations. Pp. 305-360 in Human Performance Physiology and Environmental Medicine at Terrestrial Extremes, K.B. Pandolf, M.N. Sawka, and R.R. Gonzalez, eds. Benchmark, Indianapolis, Ind. Hubbard, R.W., L.E. Armstrong, P.K. Evans, and J.P. DeLuca. 1986 Long-term water and salt deficits: a military perspective. Pp. 29-53 in Predicting Decrements in Military Performance Due to Inadequate Nutrition, Food and Nutrition Board. National Academy Press, Washington, D.C. Knochel, J.P., and R.M. Vertel. 1967 Salt loading as a possible factor in the production of potassium depletion, rhabdomyolysis, and heat injury. Lancet I:659-661.

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FLUID REPLACEMENT AND HEAT STRESS Lamb, D.R., and G.R. Brodowicz. 1986 Optimal use of fluids of varying formulations to minimize exercise-induced disturbances in homeostasis. Sports Med. 3:247-274. Leighthead, C.S., and A.R. Lind. 1964 Heat Stress and Heat Disorders. Davies, Philadelphia. Murray, R. 1987 The effects of consuming carbohydrate-electrolyte beverages on gastric emptying and fluid absorption during and following exercise. Sports Med. 4:322-351. Popper, R.E. Hirsch, L. Lesher, D. Engell, B. Jezior, B. Bell, and W.T. Matthew. 1987 Field Evaluation of Improved MRE, MRE VII, and MRE IV. Technical Report Natick/TR-87-027. United States Army Natick Research, Development and Engineering Center, Natick, Mass. Rose, R.W., C.J. Baker, C. Salter, W. Wisnaskas, J.S.A. Edwards, and M.S. Rose. 1989 Dietary Assessment of U.S. Army Basic Trainees at Fort Jackson, South Carolina. Technical Report No. T6-89. U.S. Army Research Institute of Environmental Medicine, Natick, Mass. 297 pp. Sharp, D.S., J.E. Wright, J.A. Vogel, J.F. Patton, W.L. Daniels, J. Knapik, and D.M. Kowal. 1980 Screening for Physical Capacity in the U.S. Army:. An Analysis of Measures Predictive of Strength and Stamina. Technical Report No. T8/80. U.S. Army Research Institute of Environmental Medicine, Natick, Mass. 113 pp.

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FLUID REPLACEMENT AND HEAT STRESS Appendix 1 A CASE REPORT FROM FORT BRAGG K. Alitz This unit is a small, elite Special Forces Group consisting of carefully selected and highly trained non-commissioned officers (NCOs) and officers. The mission is to deploy worldwide on short notice in support of Department of the Army (DA) directed missions. Much of the equipment is nonstandard and mission dependent. Operational techniques are very specialized and vary greatly with the task. The age varies from 24-39 with the average being 31. The soldiers are extremely physical and maintain themselves in excellent condition. All training is as realistic and demanding as possible. The following case history, which occurred in the recent past, is not untypical of the demands soldiers in this unit face. It explains why carbohydrate-electrolyte replacement beverages are needed by our soldiers: It was a hot, humid August day at Fort Bragg, North Carolina. Group A, about 40 men, scheduled endurance training that day. Group A' s endurathon consisted of a 7 event exercise. The first event started with a 12,500 foot HALO combat equipment jump from a CH-47 helicopter, followed by a 5 mile, 1 hour road march with weapon, 25 lbs load bearing equipment, and a 45 lb rucksack; a 2 hour rubber boat trip down the Cape Fear River; a 5 mile run in boots and fatigues; a difficult obstacle course; a complex shooting drill with the 45 caliber pistol; and culminating with a 1 mile, 150 lb litter carry. The endurathon occurred between 0900 h and 1500 h, the average temperature was in the upper 90s with humidity in the high 60s. Individuals carried their own water and there was a 10 minute break at each water point between events. They could snack but no meal was provided. No medical problems were encountered until after Event 5—the obstacle course. Of the 40 participants, there was 1 case of mild heat exhaustion (rectal temperature 100.5 degrees), 4 cases of heat cramps, and 3 cases of heat prostration (nl temperature, extreme fatigue). All 8 individuals responded rapidly to 2 liters D5RL intravenously administered IV and were pulled from further training. Of these, only 2 have had any heat injuries before and they relate a 3-6 quart water intake during training. Prior to the 6th event, which was shooting, an electrolyte solution was brought out to the water points and individuals were encouraged to consume at least 1 quart. There were no further incidents, training was completed, and soldiers were released.

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FLUID REPLACEMENT AND HEAT STRESS Group B started this same August day at 0800 h with 2 hours of range firing and then individual physical training for 1 1/2 hours. After the lunch meal, Group B flew via C-130 Aircraft to Hunter Army Airfield in Georgia to participate in specialized assault training. Temperatures at the airfield approached 100 degrees F; uniform was a Nomex flight suit and assault gun with Kevlar vest--total weight about 20-25 lbs. Training continued into the evening hours; water was readily availabel and a supper meal was provided. Training was demanding, but there were no medical problems; however, several soldiers complained of weakness and fatigue. At about 2200 hours the unit was alerted to respond to an incident in the Mid-East. Group B returned immediately to Fort Bragg where the entire unit had been mustered. Equipment was packed and loaded and plans were formulated. After several hectic hours, Groups A and B, along with a support package, departed that night from Fort Bragg via Air Force aircraft to the crisis area. Each individual was issued 2 box lunches and 2 1-quart jars of cold gatorade for the 15-hour, non-stop flight. Water jugs were on the aircraft, but because of space constraints, they were difficult to get to. Upon arrival in the staging country, the unit was housed in an empty aircraft hangar. The temperature was high, but humidity was low. Potable water was availabel, but it was warm and not very palatable. Gatorade powder was added to the lister bags at 2/3 strength. The unit spent the next 36 hours preparing for a mission. There were no heat casualties. This case history illustrates several points which are unique to this unit: (1) demanding physical training often under hostile environments and conditions; (2) short, or no-notice worldwide deployments into combat-type situations; (3) the philosophy that the mission has utmost importance and the soldier will adapt to accomplish the mission; (4) that our soldiers operate often under fluid deficits with excessive water loss and potential electrolyte imbalances. Gatorade supplement and beverages are used to rehydrate, balance electrolytes, and provide some calories. Gatorade has been found, when used in training and missions, to increase fluid intake, increase morale, be convenient, and decrease the incidents of heat related injuries, if used under the supervision of medical personnel. This unit is eager to try other carbohydrate electrolyte replacement supplements and beverages that will assist in accomplishing the mission.

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FLUID REPLACEMENT AND HEAT STRESS Appendix 2 CASE STUDY FROM GRENADA W. Donovan General: This study is submitted in reference to the ranger participation in operation “Urgent Fury”. This was a U.S. Military operation to rescue American nationals caught in the military/political upheaval on the island nation of Grenada in October of 1983. Purpose: To discuss the means by which the rangers addressed the problem of preventing heat casualties at a time when their physical and mental limitations were being put to the ultimate test. Mission: The mission was operation “Urgent Fury”. The rangers were tasked to secure, either by airborne or airland assault, the Point Salinas airfield, and rescue American medical students to forestall a possible Iran-style hostage situation. Units: The 1st and 2nd ranger battalions were initially involved in the operation. A ranger battalion is a “Light Infantry” unit that is organized and equipped to conduct both special and conventional combat operations. It consists of a battalion headquarters, a headquarters company, and three ranger rifle companies. Approximately 750 rangers were involved in the Grenada operation. Terrain: The initial ranger area of operation was the 10,000 foot Point Salinas airfield. The airfield was still under construction at the time and offered few prominent terrain features. Consequently, the airfield did offer unobstructed fields of fire. Follow-on missions which took the rangers even a short

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FLUID REPLACEMENT AND HEAT STRESS distance from the runway found them quickly encountering the typically steep and thickly covered countryside of Grenada. Temperature: When the 1st ranger battalion departed from Hunter Army airfield in Georgia the temperature was approximately 70 degrees. The 2nd ranger battalion departed out of Ft. Lewis, Washington where the approximate temperature was 45 to 55 degrees. The average temperature on the ground in grenada was 85 to 90 degrees. Weather conditions: The weather in the ranger area of operations was clear and balmy. The temperature at the time of the drop was 80 degrees, mid-day temperature was 85 to 90 degrees. The humidity was 85%. Combat loads: The combat load that the average ranger carried weighed between 65 to 75 pounds. Ranger medical and communication personnel carried rucks weighing 90 to 100 pounds. Mortar and anti-tank teams carried rucks weighing in excess of 100 lbs. Work/Rest cycle: All rangers involved in the Grenada operation had a mandatory rest period approximately 4 to 6 hours prior to loading the mission aircraft. Unfortunately, the rangers did not rest again until they were relieved in place by follow-on units some 18 hours later. Rations used: The rangers involved in the operation were issued C-rations and MRE 's. Water availability: The majority of the rangers went into the operation carrying 4 quarts of water. Initially, well water located at the medical school was the primary source of water resupply. Some streams were also utilized. Iodine tablets were used throughout the mission.

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FLUID REPLACEMENT AND HEAT STRESS Unusual physical or operational demands: There are several areas of interest worth mentioning: This was an actual combat mission. The rangers were carrying heavy combat loads. Flack jackets were utilized. The rangers were rigged in their parachutes for 6 hours prior to a combat jump. The rangers jumped into a “hot” drop zone. Rangers were initially involved in a fire fight lasting approximately 45 minutes, and sporadic fire fights for the next 2 days. Movement to contact operations in the hills and dense growth surrounding the airfield. Additionally, the rangers had to evacuate WIA's and KIA's to the ranger casualty collections point; this also included the wounded civilians, Grenadian Militia and Cubans. The rangers did utilize a glucose-electrolyte solution (Gatorade) during the operation. Rangers were instructed to dilute the solution at a 1:4 ratio. After-Action observations: The rangers experienced no heat casualties during the Grenada Operation despite drastic changes in temperature, while other U.S. forces experienced significant problems with heat casualties. Reasons: The rangers were in excellent physical condition. Heat casualty prevention was highlighted in the medical annex during the planning phase of the operation. A prehydration program was immediately initiated with rangers drinking 10 to 12 quarts of water per day. A forced hydration program was rigorously adhered to during the operation. Rangers utilized tropical uniforms. Rangers only carried mission essential equipment. There was excellent leader supervision oriented toward preventing heat casualties.

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FLUID REPLACEMENT AND HEAT STRESS Summary: In summation, the rangers involved in the Grenada Operation suffered no heat casualties because of a vigorous hydration program and prior operational planning. Throughout numerous deployments to temperate climates like Hondorus, Panama and Jordan, the rangers have suffered few significant heat related injuries.