Method of cold saline storage for prehospital induced hypothermia

Research over the last decade has supported the use of cold intravenous (IV) fluid as a method for initiating therapeutic hypothermia in post-cardiac arrest resuscitation. However, prehospital care programs employing this treatment have encountered various difficulties. Barriers to prehospital induced hypothermia (IH) protocols include the lack of effective or economically reasonable methods to maintain cold saline in the field. Validation of a simple method could allow agencies to equip numerous rigs with cold saline. The aim of this study was to determine whether a standard commercial cooler can maintain two 1-L normal saline solution (NSS) bags below 4 degrees C in three different environments.

Environments simulating those of an ambulance compartment were created for the experiment. NSS temperatures were continuously recorded inside a standard commercial cooler under one of three scenarios: ambient room temperature (25 degrees C) without ice packs, ambient room temperature with ice packs, and 50 degrees C ambient temperature with ice packs. Four trials under each condition were performed.

In a room-temperature environment without ice packs, the NSS warmed to 4 degrees C in a mean interval of 1 hour 21 minutes. Using room temperature with ice packs, the NSS warmed to 4 degrees C in a mean interval of 29 hours 53 minutes. In a constant hot environment of 50 degrees C, the NSS warmed to 4 degrees C in a mean interval of 10 hours 50 minutes. A significant difference was found between the three environments (log-rank = 17.90, df = 2, p = 0.0001).

Prehospital refrigeration devices are needed for current and future IH protocols. Low-technology methods in the form of a cooler and ice packs can provide cold saline storage for longer than a full 24-hour shift in a room-temperature ambulance. In extremely hot conditions, 4 degrees C NSS can be maintained for nearly 11 hours using this method. This model exhibits an economical, easily deployable cold saline storage unit.