Intravenous (IV) infusion of cold fluids is often considered a heat stroke treatment, particularly during transport. But what does the evidence say about its efficacy? In short, the evidence supports the principle of "cool first, transport second". Given the critical 30-minute window to reduce an exertional heat stroke (EHS) victim's core temperature below 39ºC (~102ºF), powerful cooling modes are required. According to the highly cited systematic review by McDermott et al. ( 2009 ) ,  a cooling rate of 0.78 - 1.55 ºC per 10 minutes is considered acceptable, and >1.55ºC per 10 minutes is ideal in this regard. Hence, cooling of 0.78ºC per 10 minutes is considered the minimum threshold of acceptable cooling for EHS, and the minimum standard that IV infusion can be compared to. Cooling Rates The three studies summarised in Table 1 reveal modest core temperature cooling rates with IV infusion. These rates were either at the low end of the acceptable range or deemed unacceptable. For instance, infusing fluids at 4ºC versus 22ºC (66mL/min) improved the cooling rate by 14.3% (0.72ºC versus 0.63ºC per 10 minutes), but both options fell within the unacceptable range ( Morrison et al., 2018 ). Sinclair et al. (2009)  marginally achieved an acceptable cooling rate for EHS, but required an infusion rate of 84mL/min. While higher pre-treatment core temperatures may improve reported cooling rates ( Brearley et al., 2023 ), cold IV infusion appears inadequate as a stand-alone or primary treatment for EHS, even when infusing 2L of fluid. Table 1. Summary of core temperature cooling rates for IV infusion Core Temp. Cooling Rate (ºC/10mins) IV Temp.(ºC) IV Volume(L) IV Infusion (mL/min) Pre IV Core Temp (ºC) Reference 0.39 ± 0.05 2 0.84 28 38.8 McDermott and Atkins, 2023 0.63  ± 0.05 22 2.00 66 39.4 Morrison et al., 2018 0.72 ± 0.06 4 2.00 66 39.3 Morrison et al., 2018 0.80 ± 0.11 20 2.00 84 39.9 Sinclair et al., 2009 Guidance/Consensus Statements This conclusion is further supported by the Wilderness Medical Society Clinical Practice Guidelines (2024 update), which state: "Cold intravenous fluids may supplement cooling but have not been shown to adequately serve as a primary treatment for heat stroke. We recommend not using cold intravenous fluids as a primary cooling modality for the treatment of heat stroke" ( Eifling et al., 2024 ). Moreover, the November 2024 Consensus Statement on the Pre-Hospital Management of Exertional Heat Illness from the Royal College of Surgeons of Edinburgh emphasises that: "Current evidence does not support the routine use of IV fluids, cold or otherwise, to reduce core temperature in exertional heat illness patients in a pre-hospital setting" ( Hemingway et al, 2025 ). What role for IV infusion? The evidence strongly supports alternate cooling methods such as cold water immersion, whole body application of ice sheets or ice towels over IV infusion as the primary treatment for EHS ( Casa et al., 2015 ). Regardless, administering IV fluids is utilised in some field settings as part of the prevention or treatment of EHS. For example, whole body ice-sheet treatment of military heat casualties (including some EHS cases) was complemented by either ambient temperature or 4ºC IV ( Mok et al., 2017 ). That the cold IV cohort had a reduced duration of hospitalisation indirectly supports cold IV as a supplementary measure to more powerful cooling options, despite teh similar cooling rates reported in Table 1. An example of cold IV usage in the field by Phoenix Fire Department is profiled in the video below. Figure 1. Phoenix fire crews carry IV bags on ice (Credit -Arizona’s Family (3TV / CBS 5) Final Point In conclusion, while IV administration of cold fluids have a role in managing heat stress , they should not be relied upon as the primary treatment for EHS. Instead, IV infusion (cold or otherwise) may complement modalities that have demonstrated effective core temperature cooling rates. Originally posted 10 December, 2025 References Brearley M, Berry R, Hunt AP, Pope R. A Systematic Review of Post-Work Core Temperature Cooling Rates Conferred by Passive Rest. Biology. 2023;12(5):695. Casa DJ, DeMartini JK, Bergeron MF, Csillan D, Eichner ER, Lopez RM, Ferrara MS, Miller KC, O'Connor F, Sawka MN, Yeargin SW. National Athletic Trainers' Association Position Statement: Exertional Heat Illnesses. J Athl Train. 2015;50(9):986-1000. Eifling KP, Gaudio FG, Dumke C, Lipman GS, Otten EM, Martin AD, Grissom CK. Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Heat Illness: 2024 Update. Wilderness Environ Med. 2024;35(1_suppl):112S-127S. Hemingway R, Stourton F, Leckie T, Fitzpatrick D, Jones G, Wood F, Boalch A, McNulty-Ackroyd J, Thurgood A, Boulter M, Hartle A, Walter E, Pynn HJ, Kipps C, Stacey MJ. Faculty of Pre-Hospital Care: consensus statement on the prehospital management of exertional heat illness. Emerg Med J. 2025;42(6):390-395. McDermott BP, Atkins WC. Whole-body cooling effectiveness of cold intravenous saline following exercise hyperthermia: A randomized trial. Am J Emerg Med. 2023;72:188-92. McDermott BP, Casa DJ, Ganio MS, Lopez RM, Yeargin SW, Armstrong LE, Maresh CM. Acute whole-body cooling for exercise-induced hyperthermia: a systematic review. J Athl Train. 2009 Jan-Feb;44(1):84-93. Mok G, DeGroot D, Hathaway NE, Bigley DP, McGuire CS. Exertional Heat Injury: Effects of Adding Cold (4°C) Intravenous Saline to Prehospital Protocol. Curr Sports Med Rep. 2017;16(2):103-108. Morrison KE, Desai N, McGuigan C, Lennon M, Godek SF. Effects of intravenous cold saline on hyperthermic athletes representative of large football players and small endurance runners. Clin J Sport Med. 2018;28(6):493-499. Sinclair WH, Rudzki SJ, Leicht AS, Fogarty AL, Winter SK, Patterson MJ. Efficacy of field treatments to reduce body core temperature in hyperthermic subjects. Med Sci Sports Exerc. 2009;41(11):1984-90.

COVID-19 has impacted organisations in a variety of ways. We were in the midst of a 7-day worksite visit when Australian case numbers surged in March 2020 and observed the rapid evolution of strategies to protect workers. Strategies include a voluntary declaration of travel history and acute symptoms, hand and respiratory hygiene, distancing of workers on-site, working from home for non-essential staff, additional cleaning of communal worksite facilities and increasingly, temperature screening of workers on entry to site. Temperature screening is presumably utilised due to fever being the most frequently reported symptom of the coronavirus (Tian et al., 2020). As detailed in our paper ( Daanen et al., 2020 ) , fever is defined as a core body temperature of >38ºC, but screening based upon core temperature is not a viable option for worksites given its invasive nature and logistics required. Hence, temperature measurement of the skin is utilised as a surrogate for core temperature. Essentially, temperature screening is relying on heat radiating from the skins surface to be representative of core body temperature, and that the measuring device accurately detects temperature of the skin. Given the factors that influence skin temperature (including ambient conditions) and accuracy issues of detection devices, the efficacy of temperature screening for the coronavirus is questionable. In fact, based upon a review of temperature screening for Severe Acute Respiratory Syndrome (SARS), Influenza Pandemic (H1N1) and Ebola Virus Disease, the authors reported that this method was ineffective (Mouchtauri et al., 2019). Effectiveness is determined by the ability to detect positive cases, which in turn is dependant upon the threshold temperature utilised. Choose too high a temperature and you're unlikely to detect any cases. Choose a temperature too low and you risk false positives which may require invasive temperature measurement for confirmation. Plus, fever is not present for all coronavirus patients. With these issues in mind, why is temperature screening utilised in airports, medical clinics and worksites (Figure 1). Irrespective of the ability to detect fever, temperature screening may have positive effects through raising awareness, education and discouraging movement of potentially infected persons (Mouchtauri et al., 2019). Additionally, in the pursuit of improving workforce health and safety, temperature screening provides organisations with a tangible strategy that is observed by workers. Lastly, workplace temperature screening kits and screening services are marketed as per this example, reinforcing the apparent suitability for organisational use. Figure 1. An example of Covid-19 temperature screening prior to worksite entry (Credit - Forbes Advocate). For sites with a large workforce, thermal imaging has emerged as an option to negate one-by-one assessment but again, this method is not supported by evidence. In fact, the Medicines and Healthcare products Regulatory Agency (MHRA) (UK) states "Many thermal cameras and temperature screening products were originally designed for non-medical purposes, such as for building or site security. Businesses and organisations need to know that using these products for temperature screening could put people’s health at risk". Read the full article here . In response to the MHRA article, Professor George Havenith, Director of the Environmental Ergonomics Research Centre at Loughborough University summed up why skin temperature assessment and thermal imaging should not be relied upon for worksite screening (Twitter, July 4, 2020): Figure 2.  Professor George Havenith's July 4, 2020 twitter post In summary, we urge employers not to rely on temperature screening to solely determine if a worker has a fever, and therefore, more likely to be infected with the coronavirus. A range of strategies are required to protect workers from the coronavirus, with the ability of medical personnel to interact with workers, albeit from a distance, a key benefit of temperature screenings as opposed to the assessment of temperature per se . References Daanen H, Bose-O'Reilly S, Brearley M, Flouris A, Gerrett N, Huynen M, Jones H, Lee JKW, Morris N, Norton I, Nybo L, Oppermann E, Shumake-Guillemot J, Van den Haze P. COVID-19 and thermoregulation-related problems: Practical recommendations. Temperature. 2021;8(1):1-11. Mouchtouri VA, Christoforidou EP, An der Heiden M, Menel Lemos C, Fanos M, Rexroth U, Grote U, Belfroid E, Swaan C, Hadjichristodoulou C. Exit and Entry Screening Practices for Infectious Diseases among Travelers at Points of Entry: Looking for Evidence on Public Health Impact. Int J Environ Res Public Health. 2019;16(23):4638. Tian S, Hu N, Lou J, et al. Characteristics of COVID-19 600 infection in Beijing. J Infect. 2020;80(4):401–406

Figure 1. Forearm immersion by basic trainees at Fort Jackson, Columbia, South Carolina (Credit - Robert Timmons/U.S. Army) Immersion of the forearms (Figure 1) is a cooling technique used predominantly in military and firefighting contexts. In conjunction with Dr Anthony Walker, we reviewed the core temperature cooling rates of forearm immersion, publishing our results in 2015. From the 12 studies reviewed, 10 - 24.9ºC (50 - 77ºF) forearm immersion yielded core temperature reductions of only 0.1 - 0.5ºC per 10 minutes, classifying this method as unacceptably slow (Table 1). We proposed the core temperature cooling rate classifications of Table 1 for time-limited firefighting operations, but they also apply to occupational settings where rest breaks are brief (up to 15 minutes) for commercial viability. Table 1. Proposed rates of cooling for firefighting operations to allow for the rapid safe re-entry of firefighters to emergency incidents Classification Core Temperature Cooling Rate Ideal >1.0ºC/10 mins Acceptable 0.7-1.0ºC/10 mins Unacceptable <0.7ºC/10 mins In 2016, a study by Yeargin and colleagues achieved a cooling rate of 1ºC per 10 minutes for 5ºC (41ºF) forearm immersion. Such a cooling rate significantly exceeded prior findings as it represented the first trial of water temperatures below 10ºC. So, is forearm immersion a viable workplace heat stress control? The answer depends on the immersion water temperature, tasks to be performed after cooling and logistical constraints. Water Temperature In addition to the 12 aforementioned studies reviewed in 2015, research continues to confirm the slow cooling rates for 10ºC or warmer forearm immersion (Nakamura et al., 2020; Iwahashi et al., 2023; Caballero et al., 2026). From these 15 studies, a total of 180 participants immersed their forearms in mean 15.0ºC (59ºF) water to lower their core temperature a mean of 0.35ºC per 10 minutes. It's probable that higher pre-treatment core temperatures would improve reported cooling rates (Brearley et al., 2023), but they are unlikely to approach acceptable cooling rates. Task Performance Evidence supporting forearm immersion is limited to one study that utilised 5ºC water Yeargin et al., 2016). To achieve a core temperature reduction of ~1ºC during a rest break, the required duration of 5ºC forearm immersion water is 10 minutes. In that time, workers may report numbness and discomfort of the hands and forearms while experiencing diminished manual dexterity (Cheung et al., 2003) and ability to generate force (Mallette et al., 2018) upon return to work. Logistics Provision of ample 5ºC water for cooling a workforce may require substantial ice or a reliable power source where water chillers are used. Given that water immersion facilities are likely to be shared (Figure 1), water sanitation requires consideration for repeated use and/or large workforces. Whole-body application of ice cold towels are an effective substitute for cold water immersion when treating exertional heat stroke in resource limited settings (Rogerson and Brearley, 2024), however, they do not produce rapid cooling when solely applied to the forearms. Adams and colleagues (2021) reported cooling of just ~0.22ºC per 10 minutes when ice cold towels (1-3ºC) were rotated on the forearms every three minutes. Figure 2. Basic trainees at Fort Sill, Lawton, Oklahoma, carrying bags of ice for immersion (Credit - U.S. Army) Final Point Forearm immersion requires cold water (~5ºC) to be effective, poses logistical challenges and may impair work performance post-cooling. If these factors can be managed, forearm immersion may be worth considering as a workplace heat stress control. Originally posted 20 October, 2021. Updated 4 April, 2026. References Adams WM, Morris EC, Walton SL, Karras EM. Comparing the Cooling Rates of Rotating Forearm Ice Towels and Passive Rest Following Exercise-Induced Hyperthermia. J Athl Train Sports Health Care. 2021;1:e1-6. Brearley M, Berry R, Hunt AP, Pope R. A Systematic Review of Post-Work Core Temperature Cooling Rates Conferred by Passive Rest. Biology. 2023;12(5):695. Brearley M, Walker A (2015). Water immersion for post incident cooling of firefighters; a review of practical fire ground cooling modalities. Extrem Physiol Med. 2015;4:15. Caballero R, Navarro S, Vanos J, Wardenaar FC. No differential effects among cooling strategies on post-exercise core temperature recovery in male athletes. Temperature. 2026;1-4. Cheung SS, Montie DL, White MD, Behm D. Changes in man- ual dexterity following short-term hand and forearm immersion in 10 C water. Aviat Space Environ Med. 2003;74:990–993. Iwahashi M, Chaen Y, Yanaoka T, Kurokawa Y, Hasegawa H. Cold water immersion of the hand and forearm during half-time improves intermittent exercise performance in the heat. Front Physiol. 2023;14:1143447. Mallette MM, Green LA, Gabriel DA, Cheung SS. The effects of local forearm muscle cooling on motor unit properties. Eur J Appl Physiol. 2018;118(2):401-410. Nakamura D, Muraishi K, Hasegawa H, Yasumatsu M, Takahashi H. Effect of a cooling strategy combining forearm water immersion and a low dose of ice slurry ingestion on physiological response and subsequent exercise performance in the heat. J Therm Biol. 2020;89:102530. Rogerson S, Brearley M. Suspected exertional heat stroke: A case study of worker cooling in a hot and humid field environment. Work. 2024;79(4):2103-2108. Yeargin S, McKenzie AL, Eberman LE, Kingsley JD, Dziedzicki DJ, Yoder P. Physiological and Perceived Effects of Forearm or Head Cooling During Simulated Firefighting Activity and Rehabilitation. J Athl Train. 2016;51(11):927-935.

Children are recognised as a vulnerable cohort when it comes to heat related illnesses. Several factors elevate their risk, including an under-developed thermoregulatory system, excessive physical activity (playing to exhaustion), potential communication issues, and inaccessibility of cooling without assistance in some cases. We recommend parents/carers and anyone with oversight of children watch the video below to assist identification of symptoms and appropriate treatment. An excellent resource provided by the Victorian Government.

Heat stress is not confined to humans, pets and in particular, dogs are also susceptible where hot conditions are combined with physical activity. And like humans, dogs need to dissipate body heat to prevent hyperthermia and ultimately heat stroke. A common method for dogs to cool is through water immersion in small tubs, human pools, creeks, dams or at the beach, with research supporting this form of cooling. Davis et al. (2019) elevated the body temperature of a sample of dogs (n=9) through brief bouts of treadmill running in 30°C on three occasions, followed by 5mins of 30°C water immersion, laying on a 4°C cooling mat or passive rest. Water immersion produced cooling rates twice that of the cooling mat and three times that of passive rest. Avoiding physical activity during hot weather is a key control to limit canine heat stress. Where this is not possible, providing access to a water body, even if it's relatively warm (30°C), will expedite the reversal of elevated core temperature for your furry friends. Reference Davis MS, Marcellin-Little DJ, O'Connor E (2019). Comparison of Postexercise Cooling Methods in Working Dogs. Journal of special operations medicine: a peer-reviewed journal for SOF medical professionals. 19(1):56-60.

Weather is a regular discussion point irrespective of the conditions. Sure, certain weather events demand an extended discussion, but good, bad or indifferent, there's always something to discuss. Most weather discussions focus on ambient temperature as this variable is routinely reported and forecasted. For planning purposes, it's beneficial to know the weather we are likely to be exposed to but what does the forecast maximum temperature actually mean? Figure 1.  A standard and thermal image of a heat exposed worksite Take the outdoor workers as an example in the images above. The forecast temperature for this workday (hot/dry summer climate) was 39ºC. By mid-afternoon, the Bureau of Meteorology station (~11km away) reported a temperature of 38.8ºC yet the local ambient temperature measured by a high quality calibrated weather station was substantially hotter. This local heating effect (a substantial 5ºC) was due to the high ground and surface temperatures, in turn, a product of solar radiation (Figure 1). Had the forecast stated 44ºC, it's highly likely that modifications to work schedules would have occurred. The point here is that solar radiation contributes to the thermal load, and therefore needs to be accounted for when planning work activities. Despite the omission of solar radiation from the majority of laboratory-based heat stress research, there's evidence of impact upon endurance, ability to perform complex tasks, recovery and heat stress symptoms. Figure 2. Time to exhaustion while exercising at 70% maximum in 30ºC/50% relative humidity with various solar radiation loads  Resting in the shade during rest breaks is a common approach as it expedites the reduction of core temperature compared to resting in the sun (DeMartini et al., 2011). Solar radiation also limits tolerance of physical work in a step-wise manner (Figure 2) (Otani et al., 2016). Furthermore prolonged exposure to simulated solar radiation of the head and neck impairs performance of cognitively dominated (such as mathematic calculations) and motor task performances (fine adjustments of force) (Pill et al., 2020). By impacting work and recovery periods, solar radiation contributes to heat stress symptoms. We recently reported that for workers based in Northern Australia, chronic heat stress was strongly associated with increased exposure to direct sunlight and hot surfaces (Carter et al., 2020). While the lack of solar radiation - heat stress research requires addressing, the example and limited evidence presented here support the need to account for solar radiation during the planning of work activities. Such planning should include controls to mitigate the impact of solar radiation on workers health, safety and performance. References Carter S, Field E, Oppermann E, Brearley M. The impact of perceived heat stress symptoms on work-related tasks and social factors: A cross-sectional survey of Australia's Monsoonal North. Applied Ergonomics. 82:102918, 2020 DeMartini JK, Ranalli GF, Casa DJ, Lopez RM, Ganio MS, Stearns RL, McDermott BP, Armstrong LE, Maresh CM. Comparison of body cooling methods on physiological and perceptual measures of mildly hyperthermic athletes. The Journal of Strength & Conditioning Research. 25(8):2065-74, 2011 Otani H, Kaya M, Tamaki A, Watson P, Maughan RJ. Effects of solar radiation on endurance exercise capacity in a hot environment. European journal of applied physiology. 116(4):769-79, 2016 Piil JF, Christiansen L, Morris NB, Mikkelsen CJ, Ioannou LG, Flouris AD, Lundbye-Jensen J, Nybo L. Direct exposure of the head to solar heat radiation impairs motor-cognitive performance. Scientific Reports. 8;10(1), 2020

During a recent heat stress seminar, superstar educator Laura (pictured), introduced herself as the new face and intellect of the business. For those that haven't met the Thermal Hyperformance crew, we don't take ourselves too seriously and Laura fits in perfectly. She enjoys the fieldwork and is passionate about making a difference. Keep up the great work Laura and we trust you won't abandon us when you complete your studies next year.

Figure 1.  Symptoms reported by Queensland based heat-exposed workers on a daily or weekly basis from October to April Google ‘heat-related illness’ and you’re likely to see an identical spectrum of illness cited on each website: heat stroke, heat exhaustion, heat syncope, heat cramp and heat rash (listed in order of seriousness). Interactions with heat-exposed workers over the past 12 years have identified a disconnect between this spectrum and self-reported symptoms as a result of prolonged occupational heat exposure, a view supported by heat stress survey data. For example, from 918 outdoor workers based in Queensland, Australia, fatigue, headache and irritability were frequently reported on a daily or weekly basis during October to April period (Figure 1; Rogerson et al., 2020). Similar findings were reported for outdoor workers across Northern Australia during October to December (harshest three months for thermoregulation) (Carter et al., 2020). ​ The similarity of symptoms and delayed onset (latency period between heat exposure and fatigue, headache and irritability symptoms) to an alcohol hangover, has led to this condition being termed a ‘heat hangover’ (Figure 2; Brearley, 2016). Figure 2. What a heat hangover may look like Given that heat exhaustion is defined by the inability to effectively exercise in the heat (Casa et al., 2015), it is differentiated from a heat hangover as it occurs at a given point in time. Furthermore, heat exhaustion symptoms typically resolve promptly with proper hydration and cooling (Glazer, 2005). Conversely, heat hangover symptoms persist beyond the work shift.​ ​ The workplace consequences of heat hangovers are yet to be fully understood. Areas of interest include vigilance, concentration, decision making, execution of physical skills and susceptibility to additional heat hangovers during subsequent work shifts. Negative impact on these and other factors may explain the prevalence of workplace accidents during the hottest months of the year (Xiang et al., 2015) and during severe and extreme heatwaves (Varghese et al., 2019). The impact of heat hangovers is not limited to work, with extended recovery periods for workers in their home environment following 7-28 day work swings where heat hangovers were prevalent.  ​ Figure 3. Core temperature comparison of two underground workers We are working on identifying the contributing factors. At this stage, it appears that heat hangovers are associated with the area under a worker’s core temperature curve. For example, the blue and green curves of Figure 2 depict the core temperature curves for two workers across a 12-hour shift. Note that the curve of Worker B (Blue) reaching 39.1ºC at ~300 minutes resulting in his immediate cooling and redeployment to a less heat exposed role for the remainder of the shift. This strategy assisted in keeping his core temperature relatively low for the second half of shift whereas the core temperature of Worker A (Green) remained elevated during this period. Overall, the area under the core temperature curve was ~37% higher for Worker A, likely contributing to his heat hangover symptoms at the conclusion of the shift.  References Brearley M (2016). Preliminary evidence of a heat hangover, a new heat illness classification for occupational settings? Proceedings of Science of Sport, Exercise and Physical Activity in the Tropics, Townsville. Brearley M, Harrington P, Field E, Oppermann E, Lee D (submitted). Impact of hot and humid work conditions on perceived heat stress symptoms and management strategies. Carter S, Field E, Oppermann E, Brearley M (2020). The impact of perceived heat stress symptoms on work-related tasks and social factors: A Cross-Sectional Survey of Australia’s Monsoonal North. Applied Ergonomics. 82:102918 Glazer JL (2005). Management of heatstroke and heat exhaustion. American Family Physician. 71(11): 2133-40 Xiang J, Hansen A, Pisaniello D, Bi P (2015). Extreme heat and occupational heat illnesses in South Australia, 2001-2010. Occupational and Environmental Medicine 72(8): 580-86

In a collaboration with Menzies School of Health Research, we conducted a multi-faceted heat stress research project at McArthur River Mine over a 15-month period. We had a great research team and a motivated group of workers involved in the study. The weather was perfect (heatwave most days) and ABC News visited to see what we were up to – see the story below (note that we do not handle the ingestible thermometers, this was 'mocked up' for the camera).

The risk of workplace injuries in the heat is not equal for all workers. Click below for an overview of who's at the greatest injury risk. Credit to co-authors Dr Tom Longden (ANU), Dr Simon Quilty (Alice Springs Hospital/ANU) and editor Sunanda Creagh.

The December 2019 death of two toddlers in a hot car highlights the danger posed by heated enclosures to children as we head into summer. Despite the collective grief following this tragedy, it’s unlikely to be the last case of vehicular infant heat stroke this season. While the annual number of Australian hot car infant deaths is not available, KidsAndCars.org, the US-based advocacy group, has tracked 53 US hot car infant deaths so far in 2019, second only to the 54 deaths reported in 2018. Since 1998, over 800 children have died in hot cars according to the National Safety Council (USA), with these fatalities on the rise. The frequency of these deaths has contributed to the phrase of 'Forgotten Baby Syndrome'. The obvious question is “how can this happen so frequently?” or as posed by University of South Florida's Professor David Diamond “How can loving and attentive parents, with no evidence of substance abuse or an organic brain disorder, have a catastrophic lapse of memory that places a child’s welfare in jeopardy? In his recent paper addressing the question, Prof. Diamond identified that loss of awareness of a child in a car is a failure of prospective memory, that is, failure to remember to execute a plan in the future. He summarised the factors that contribute to prospective memory failure in the figure below. Figure 1. Factors that contribute to a failure of prospective memory (PM). The core feature common to all PM failures is the loss of awareness of an intended action It could be argued that the majority of these causes are considered part of everyday life, and as such, reversing their contribution would be challenging. So, what can be done to prevent these tragedies? Guard and Gallagher concluded from their analysis of 171 infant hot car deaths that prevention could have been achieved by: keeping cars locked educating parents (Australian government online resources ) implementing informed childcare transportation policies passing relevant laws (Currently vary between states - up to $36K fine/10yrs prison) working with auto and child safety seat manufacturers to build in warnings and other design features. Combining the factors of Figure 1 and the above prevention strategies, the provision of a reminder cue could prove to be the most effective. In early November, Italy legislated the use of car seat safety devices that alert drivers when a child has been left in the vehicle for infants under 4 years of age. Parents that do not utilise the devices are fined and lose points on their licence for the initial offence, and a 15-day loss of licence for a second breach. Other countries are likely to follow the Italian lead with the Hot Cars Act of 2019 currently under consideration by US politicians. We urge Australian legislators to review current safety guidelines in an effort to prevent a repeat of the December 2019 tragedy. References Diamond DM (2019). When a child dies of heatstroke after a parent or caretaker unknowingly leaves the child in a car: How does it happen and is it a crime? Medicine, Science and the Law 59(2):115-126. Guard A, Gallagher SS (2005). Heat related deaths to young children in parked cars: an analysis of 171 fatalities in the United States, 1995-2002. Injury Prevention 11(1):33-7.

Commercially available heat stress kits (see Figure 1 for example) contain instant ice packs. According to the associated information of the kits, the listed items are for the prevention of heat-related illness, including heat stroke. While the kits do not state they are intended for treatment, instant ice packs have been observed within worksite first aid facilities and/or response vehicles in anticipation of treating exertional heat stroke in the field. Figure 1. Commercially available heat stress kit for industry and its composition, including four instant ice packs Whereas standard ice packs require a means of producing and/or storing ice plus prevention of melting during transportation, instant ice packs simply require breaking the barrier between water and the solid chemical, traditionally ammonium nitrate but more recently, ammonium chloride. Once this ‘activation’ occurs, most brands claim the pack will remain consistently cold for up to 20 minutes of clinically recommended application. Most brands suggest pack usage for sports injury, sprains and minor pain ailments. Exertional Heat Stroke (EHS) treatment is rarely mentioned in this regard. Yet, based upon the theoretical basis for use on an EHS patient and recommendations to do so within Australian first aid training curriculum (no differentiation between standard ice and instant ice packs), it seems intuitive to have a supply of instant ice packs for resource limited settings. Their low cost, ease of storage and transport likely enhance their use. Use by NSW Ambulance Arguably the strongest support for instant ice packs comes from emergency medical response teams. Use of instant ice packs by NSW Ambulance (Australian Paramedical Organisation) for heat stroke treatment was revealed during the 2024 inquest into the death of Keith Titmuss, the 20-year-old Manly Sea Eagle rugby league athlete that suffered EHS during a training session and died on November 23, 2020. Figure 2. Sentry Medical instant ice pack and NSW Ambulance Protocol E3 Hyperthermia Treatment During the inquest into his death, Senior Staff Specialist in Emergency Medicine, Associate Professor Anna Holdgate, testified on behalf of NSW Ambulance that their ambulances carry 4 to 6 Sentry Medical instant ice packs (Lee, 2024). While the size was not provided, they are likely similar to the commercially available instant ice pack of Figure 2. The inquest also identified that the NSW Ambulance protocol for treatment of heat stroke requires removal of patient from the heat source followed by the steps detailed in Figure 2. Note that NSW Ambulance Protocol E3 Hyperthermia does not differentiate between classical and EHS. Lack of Evidence Despite use by NSW Ambulance, rotation of instant ice packs on the neck, arm pits/axillae and groin confer cooling rates so low (Kielblock et al., 1986), that they are deemed ‘unacceptable’ for heat stroke treatment. McDermott et al. (2009) stated in their review paper that: “……….the use of ice packs or ice bags for the treatment of EHS should be discontinued, because the extraction of heat from the body is ineffective for the body temperatures typically associated with EHS”. While it’s apparent that the instant ice packs lack the cooling power to rapidly reduce core temperature, how do they compare to standard ice packs? The respective cooling power of instant ice and standard ice packs was compared by pack immersion in two litres of water (Phan et al., 2013). Despite the packs being matched on the basis of physical size, the standard ice packs (570g) were ~2.4 times heavier than the instant ice packs (238g; 147mL water and 91g ammonium nitrate). This disparity likely contributed to the superior cooling rate of the standard ice packs (3.8 times that of the instant ice packs). When compared on the basis of mass, the standard ice packs had 60% more cooling power than the instant ice packs. Effective treatment of EHS requires a cooling rate sufficient to rapidly lower core body temperature, typically achieved through methods such as cold water immersion or the application of ice-cold towels (Rogerson and Brearley, 2024), which far exceed the cooling power provided by either type of ice pack. Three years post the passing of Keith Titmuss, NSW Ambulance seemingly agreed. During the 2024 inquest, Assoc. Prof. Holdgate stated: “So of the various methods of cooling, that method (ice pack application to the neck, arm pits/axillae and groin) is probably one of the least effective methods of cooling. So it doesn't - won't cause any harm if it can be done, but it may not cause much benefit”. Enough said. Take Home Message Cooling by ice packs applied to the shallow arteries, whether chemically cooled or formed by frozen water, is not supported as a primary treatment for EHS. For organisations that plan to use ice packs in their management of EHS, we suggest reviewing the evidence (Brearley, 2019). References Brearley MB. Are Recommended Heat Stroke Treatments Adequate for Australian Workers? Ann Work Expo Health. 2019;63:263-266. Kielblock AJ, Van Rensburg JP, Franz RM. Body cooling as a method for reducing hyperthermia. An evaluation of techniques. S Afr Med J. 1986;69:378-380. Lee, D. Inquest into the death of Keith Titmuss. Coroner’s Court of New South Wales. File 2020/333632 McDermott BP, Casa DJ, Ganio MS, Lopez RM, Yeargin SW, Armstrong LE, Maresh CM. Acute whole-body cooling for exercise-induced hyperthermia: A systematic review. J Athl Train. 2009;44:84-93. Phan S, Lissoway J, Lipman GS. Chemical cold packs may provide insufficient enthalpy change for treatment of hyperthermia. Wilderness Environ Med. 2013;24(1):37-41. Rogerson S, Brearley M. Suspected exertional heat stroke: A case study of worker cooling in a hot and humid field environment. Work. 2024;79(4):2103-2108.