Sports drinks do not increase acute kidney injury risk in males during industrial work in the heat when euhydration is maintained, a randomized crossover trial.

Industrial workers regularly perform physical labor under high heat stress, which may place them at risk for dehydration and acute kidney injury. Current guidelines recommend that workers should consume sports drinks to maintain euhydration during work shifts. However, the impact of fructose sweetened sports drinks on acute kidney injury risk is unknown. The purpose of this study was to investigate the effects of sports drink consumption on markers of acute kidney injury following simulated industrial work in the heat. Twenty males completed two matched 2 h simulated industrial work trial visits in a warm and humid environment (30 °C and 55% relative humidity). During and following the bout of simulated work, participants consumed either a commercially available sports drink or a noncaloric placebo. Urine and blood samples, collected pre-, post-, and 16 h post-work were assayed for markers of hydration (plasma/urine osmolality, and urine specific gravity) and acute kidney injury (KIM-1 and NGAL). There were no differences in physiological or perceptual responses to the bout of work (interaction p > 0.05 for all indices), and markers of hydration were similar between trials (interaction p > 0.05 for all indices). KIM-1 (Placebo: Δ Ln 1.18 ± 1.64; Sports drink: Δ Ln 1.49 ± 1.10 pg/mL; groupwide d = 0.89, p < 0.001) and NGAL (Placebo: Δ Ln 0.44 ± 1.11; Sports drink: Δ Ln 0.67 ± 1.22 pg/mL; groupwide d = 0.39, p = 0.03) were elevated pre- to post-work, but there were no differences between trials (interaction p > 0.05). These data provide no evidence that consumption of fructose sweetened sports drinks increases the risk of acute kidney injury during physical work in the heat.

A new occupational heat tolerance test: A feasibility study.

Heat tolerance tests identify those susceptible to heat illnesses and monitor heat adaptations. Currently, tolerance tests do not replicate the uncompensable heat strain environments experienced in some occupations. In addition, tests can take up to 2 h to complete, and cannot offer intra and inter individual comparisons, due to the use of a fixed exercise intensity. This study aimed to assess the validity and reliability of a new heat occupational tolerance test (HOTT: 40 min at 6 W kg-1 metabolic heat production, 50 °C 10% RH, in protective clothing) to the standard heat tolerance test (HTT: 2 h walk at 5 km h-1 1% gradient, 40 °C 40% RH, in shorts and t-shirt). Eighteen participants (age: 21 ±â€¯3 yrs, body mass: 81.3 ±â€¯5.9 kg) completed trials to assess the validity and/or reliability of the HOTT. Peak rectal temperature (Tre) displayed strong agreement and low measurement error (0.19 °C) between HTT (38.7 ±â€¯0.4 °C) and HOTT (38.6 ±â€¯0.4 °C). Strong agreement was also displayed for physiological and perceptual measures between the two HOTT trials, including peak Tre (38.5 ±â€¯0.4 °C vs. 38.5 ±â€¯0.4 °C) and peak heart rate (182 ±â€¯20 b min-1 vs. 182 ±â€¯21 b min-1). The HOTT is the first tolerance test that assesses individuals' responses whilst wearing protective clothing in high temperatures. It can consistently identify individuals' levels of heat tolerance within a reduced time frame. In addition, it allows for participant monitoring over time and comparisons between individuals to be made. A continuum based approach is recommended when assessing individuals' responses to the HOTT.

High prevalence of hypohydration in occupations with heat stress-Perspectives for performance in combined cognitive and motor tasks.

PURPOSE: To evaluate the prevalence of dehydration in occupational settings and contextualize findings to effects on performance in cognitively dominated tasks, simple and complex motor tasks during moderate and high heat stress. METHODS: The study included an occupational part with hydration assessed in five industries across Europe with urine samples collected from 139 workers and analyzed for urine specific gravity. In addition, laboratory experiments included eight male participants completing mild-intensity exercise once with full fluid replacement to maintain euhydration, and once with restricted water intake until the dehydration level corresponded to 2% bodyweight deficit. Following familiarization, euhydration and dehydration sessions were completed on separate days in random order (cross-over design) with assessment of simple motor (target pinch), complex motor (visuo-motor tracking), cognitive (math addition) and combined motor-cognitive (math and pinch) performance at baseline, at 1°C (MOD) and 2°C (HYPER) delta increase in body core temperature. RESULTS: The field studies revealed that 70% of all workers had urine specific gravity values ≥1.020 corresponding to the urine specific gravity (1.020±0.001) at the end of the laboratory dehydration session. At this hydration level, HYPER was associated with reductions in simple motor task performance by 4±1%, math task by 4±1%, math and pinch by 9±3% and visuo-motor tracking by 16±4% (all P<0.05 compared to baseline), whereas no significant changes were observed when the heat stress was MOD (P>0.05). In the euhydration session, HYPER reduced complex (tracking) motor performance by 10±3% and simple pinch by 3±1% (both P<0.05, compared to baseline), while performance in the two cognitively dominated tasks were unaffected when dehydration was prevented (P>0.05). CONCLUSION: Dehydration at levels commonly observed across a range of occupational settings with environmental heat stress aggravates the impact of hyperthermia on performance in tasks relying on combinations of cognitive function and motor response accuracy.

Personal risk factors associated with heat-related illness among new conscripts undergoing basic training in Thailand.

Cases of exertional heat stroke have been reported every year during basic training for Royal Thai Army (RTA) conscripts. Prevention is an important strategy to reduce the incidence of heat-related illnesses. We conducted a study to identify potential indicators for the prevention and monitoring of heat-related illnesses among military conscripts undergoing basic training in Thailand. All newly inducted RTA conscripts in 5 basic training units in 5 regions in Thailand were invited to participate in a prospective cohort study from May 1 to July 9, 2013. The incidence rate of heat-related illnesses and the incidence rate ratio (IRR) based on a Poisson regression model were used to identify the independent factors associated with heat-related illnesses, daily tympanic (body) temperatures higher than 37.5°C, >3% decreases in body weight in one day, and the production of dark brown urine. Eight hundred and nine men aged 21.4 (±1.13) years were enrolled in this study. The prevalence of a body mass index (BMI) ≥30 kg/m2 was 5.5%. During the study period, 53 subjects (6.6%) representing 3.41/100 person-months (95% confidence interval (CI), 2.55-4.23) developed heat-related illnesses (excluding heat rash), and no subjects experienced heat stroke. The incidence rates of a daily tympanic temperature >37.5°C at least once, body weight loss of >3% per day, and the production of dark brown urine at least once were 8.27/100 person-months (95% CI, 7.69-8.93), 47.91/100 person-months (95% CI, 44.22-51.58), and 682.11/100 person-months (95% CI, 635.49-728.52), respectively. The sole identified independent factor related to the incidence of heat-related illnesses was a BMI ≥30 kg/m2 (adjusted IRR = 2.66, 95% CI, 1.01-7.03). In conclusion, a high BMI was associated with heat-related illnesses among conscripts undergoing basic training in Thailand. Daily monitoring of heat-related illnesses, body temperature, body weight and urine color in each new conscript during basic military training was feasible.

Routine Screening Laboratory Studies for Nonheat Stroke Field Heat Injuries Are Unnecessary: A Retrospective Review.

BACKGROUND: Heat injuries are common in the military training environment. Base policies often mandate that heat causalities require evaluation at a higher level of care, which comes at significant use of resources. Laboratory studies are often ordered routinely, but their utility is unclear at this time. METHODS: This project evaluated the use of screening laboratory studies for heat casualties brought to Bayne-Jones Army Community Hospital, Fort Polk, Louisiana. Casualties brought from the field directly to the emergency department (ED) were included. Abnormalities in laboratory study findings, admission/discharge rates, and length of stay were documented. RESULTS: From May through September 2014, 104 casualties were seen in the ED because of heat injury. Laboratory tests were ordered for 101 patients. Of these, 11 patients were admitted to the hospital because of laboratory, history, and/or physical examination abnormalities. Nine were discharged in less than 24 hours. The remaining two were discharged within 48 hours; both had documented altered mental status on arrival to the ED. Laboratory test abnormalities were seen in most of the patients and appeared to have no impact on the decision to admit. CONCLUSION: Routine laboratory studies appeared to have low clinical utility in this patient population. A more targeted approach based on the history and physical examination may reduce military resource use.

Assessment of construction workers' hydration status using urine specific gravity.

OBJECTIVES: The study objective was to assess hydration status by measuring USG among construction workers in Iran. MATERIALS AND METHODS: The study design was comparative and experimental. Sixty participants were randomly selected from the construction workers from a construction campus with a similar type of work, climate and diet and formed 2 groups (individuals exposed to the sun and non-exposed individuals). TWL and USG were measured in both groups on 2 consequent days, at the beginning, mid and end of the work shift. RESULTS: USG test showed that mean USG was 1.0213±0.0054 in the control group and in the exposed group, where it was significantly higher, it amounted to 1.026±0.005. In the exposed group, 38% of workers had a USG level between 1.026-1.030, representing a higher risk of heat illness and impaired performance and 12.72% had a USG level above 1.030 representing a clinically dehydrated status, while this proportion in the control group was 15.2% and 0.58%, respectively. The mean TWL index measure was 215.8±5.2 W/m2 for the control group and 144±9.8 W/m2 for the exposed group, where, again, it was significantly higher. The Pearson correlation measure showed a significant correlation between USG and TWL. CONCLUSIONS: Strong correlation between TWL, as an indicator of thermal stress and USG shows that USG can be considered as a predictor of thermal stress. The difference between USG among the exposed and non-exposed workers and the increase in USG during midday work show the sensitivity of this measure in different thermal and climatic conditions, whereas, the high level of dehydration among workers despite acceptable TWL level, shows that heat stress management without considering the real hydration status of workers, is insufficient.

Urine dipstick testing to rule out rhabdomyolysis in patients with suspected heat injury.

BACKGROUND: Heat injury is a common, potentially life-threatening medical condition. In austere or mass-casualty conditions an easy to use, sensitive screening test could be a valuable tool to care providers and evacuation planners. OBJECTIVE: The objective of the study was to determine if a simple urine dipstick test for blood is sensitive for detection of rhabdomyolysis in the suspected heat injury patient. MATERIAL AND METHODS: A convenience sample of patients presenting to a military community hospital Emergency Department during summer months with a presenting complaint consistent with suspected heat injury had urine dipstick testing performed for blood and compared with the results of formal urinalysis and serum creatine kinase. RESULTS: 60 patients were enrolled in the study, seven had creatine kinase levels greater than 1000 U/L, 14 had levels greater than 500 U/L, and 26 had levels greater than 250 U/L. Using 1000 U/L, urine dipstick testing had a sensitivity of 14% and a specificity of 85%. CONCLUSIONS: Urine dipstick testing for blood is not a useful screening test for rhabdomyolysis in patients suspected to have significant heat injury.