Temperature changes of CoolSticks during simulated use

Cold sensation is often used to check neuraxial anaesthesia and analgesia. One opportunity to reduce the carbon footprint of anaesthesia is to replace vapo-coolant sprays such as ethyl chloride with a reusable device called the CoolStick, which is cooled in a refrigerator between uses. We designed a study to investigate how long the CoolStick remains at its working temperature, which we defined as <15 °C.

Experiments were undertaken using a thermocouple and digital temperature sensor attached to the CoolStick. We conducted two experiments to assess temperature changes following removal from the refrigerator for 10 min; the first investigated passive re-warming in the ambient theatre environment and the second investigated re-warming in simulated use. In our third experiment, we investigated the time taken to cool the device in the refrigerator, following use. Each experiment was repeated three times.

In the passive re-warming experiment, the mean CoolStick temperature was 7.3 °C at the start, and 14.3 °C after 10 min. In the simulated use experiment, the mean CoolStick temperature was 7.3 °C at the start, and 18.9 °C at 10 min. In the cooling experiment, the mean CoolStick temperature was 15 °C at the start and 7.6 °C at 40 min.

Our study indicates that it is feasible to use the CoolStick for providing cold sensation in clinical practice. Further study would be required to directly compare the effectiveness of the device to existing methods such as coolant sprays or ice in the clinical setting.