Instant Ice Packs

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;63:263-6

Kielblock AJ, Van Rensburg JP, Franz RM. Body cooling as a method for reducing hyperthermia. An evaluation of techniques. S Afr Med J. 1986;69:378-80

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