Heat illness needs fast treatment, and to accomplish this many EMS agencies carry chemical cold packs. These are convenient in that they have long shelf lives, don’t require cold storage, and don’t leak or drip fluids.
According to this article, there really isn’t any prior testing to compare them to ice packs in human testing. This hasn’t changed with this paper, but they do directly compare the cooling effectiveness of CCPs to similarly sized ice packs in an insulated water bath. What they found might seem intuitive, just never documented. Cold packs do get cool quickly, but they don’t really get very cold, and they don’t last more than about 5 minutes. Ice packs remain cold significantly longer and perform better by reducing the temperature of the water bath more.
The authors use this data to extrapolate that 6 CCPs, strategically placed, would reduce the temperature of a hyperthermic male by less than 0.5°C. Ice would perform better, reducing the temperature by 2.5°C. They do discuss the logistical problems of using ice in the pre-hospital setting, and recommend more frequent checking and replacement of CCPs based on their short effective times. One limitation of the study is that they didn’t use more than one source of CCPs, so there could be a large difference in performance of other samples. The authors also present other treatments of hyperthemia in the discussion part of the article, so it’s worth a read.
Phan S, Lissoway J, Lipman GS. Chemical cold packs may provide insufficient enthalpy change for treatment of hyperthermia. Wilderness Environ Med. 2013 Mar;24(1):37-41. [PMID 23312558]
EBM Gone Wild