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Sometimes, it’s a good idea to not do something, such as CPR in the back of a moving ambulance on a patient who isn’t going to survive.  Once you’ve accepted this idea, the next step is to figure out who isn’t going to survive.

The Canadians developed a couple of rules, one for ALS and one for BLS, which have since been validated (the BLS one in more studies) to miss very, very few survivors (the BLS rule only would have stopped resuscitation on 5 people who later survived to hospital discharge, out of more than 10,000 arrests.  Keep in mind that is to discharge, not to discharge with good neurological outcome).

Meanwhile, a group in California had developed a rule to predict who would be discharged with a good neurological outcome (which they defined as GCS of 13+).  This rule has not since been studied nearly as well as the Canadian rules.

The latest study is a comparison of all 3 rules using a Denver cardiac arrest database.  Of the three, the Canadian BLS rule–which also happens to be the easiest to apply–performed the best.  It didn’t miss a single survivor, and would have kept more than a third of resuscitations from packing up and heading to the hospital (which is a dangerous time for EMS providers, and a bad time medically as well, because it’s more difficult to work a patient appropriately while you’re in motion).  The ALS rule, by comparison, would have stopped only a fourth of resuscitations, and the California rule only 6%.

There is only one wrinkle that the authors have noted, which is fairly major:  the study database takes patients from 2003-4, before the days of specialized post-arrest care such as hypothermia.  It’s going to take a little while to work out whether these rules continue to work in the modern era of post-arrest care.

(Keep reading for a comparison of the rules.)

Canadian BLS Rule:  you may terminate resuscitation if:

1. The arrest was not witnessed by EMS,
2. You did not defibrillate the patient before transport, and
3. There was no ROSC before transport.

Canadian ALS Rule:  you may terminate resuscitation if:

1. The arrest was not witnessed by EMS or bystanders,
2. No bystanders performed CPR,
3. You did not defibrillate the patient before transport, and
4. There was no ROSC before transport.

California Rule (referred to as “Neuro” rule in the study):  you may terminate resuscitation if:

1. The arrest was not witnessed by EMS or bystanders,
2. The patient is at least 78 years old, and
3. The patient’s initial rhythm is asystole.