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Therapeutic hypothermia has become all the rage lately, after a number of studies have showed its utility in a variety of conditions (although cardiac arrest is probably the best known of those).  A number of EMS agencies have jumped on the bandwagon, or are about to.

Needless to say, few (if any) EMS agencies could afford $40k Innercool units, and ice isn’t really an option in the back of an ambulance, which leaves one realistic option:  cold saline infusion.  This begs the question, how effective is dropping a liter of 4°C saline into someone’s arm?

Fortunately, some docs in the Pittsburgh area have worked on this.  The end result:  a 30mL/kg bolus, delivered over 30 minutes, dropped the core temperatures of the study subjects by a whopping 1°C–stopping at least a degree shy of the recommended range of 33-35 degrees, and only slightly larger than the 0.5°C drop shown by giving room-temperature saline. 

However, there are some limitations that mean EMS agencies could still find this useful.  First, the study used healthy volunteers aged 18-35:  not exactly the kind of population most likely to need therapy of any sort; these folks were able regulate their temperatures better than just about any post-cardiac-arrest victim you’ll ever meet.  Second, although EMS agencies may not be able to get a patient down to a therapeutic level using IV saline alone, they may be able to at least start the process, allowing the patient to reach the goal temperature that much more quickly at the hospital.  (For those of you with short transport times, it’s interesting to note that most of the cooling happened in the first 15 minutes.)

Conclusion:  Any EMS agency adding therapeutic hypothermia to its protocols should probably use cold saline bolus as its primary method–it’s cheap, easy, and probably as effective as anything else in the limited time available.

As a random side note, volunteers in this study were offered meperidine (Demerol) to control shivering…after it was taken off many ambulances due to concerns about its toxicity.