Cpr Paper Review: Passive Leg Raising in Cardiopulmonary Resuscitation

“Not Bad…” the article begins as a simple technique re-shapes the paradigm of optimal out-of-hospital CPR. This article brings up the idea of raising the legs to some angle during CPR to increase venous return from the lower extremities and increase cerebral/coronary perfusion during chest compressions.

We begin with a mathematical model of cardiac output during CPR with two rescuers based on compression force, standard depths and rates for chest compressions, and simulated the transfer of blood from the legs to the heart based on different angles at the hip. The math was fascinating and the entire idea of modeling human physiology with differential equations blows my mind with endless possibility; however, I need to keep this review short! Simulations showed that cardiac output, coronary perfusion pressure, and cerebral perfusion were all drastically improved with moderate leg raising.

Additionally an interesting study in a swine model showed some promising results {ref} with increased coronary perfusion pressure and drastically improved neurologic outcomes at 24 hours in 10 pigs who received passive leg raising during CPR when compared to a control without leg raising.

The group went on to train EMS departments in leg raising during CPR and followed results over 5 years to culminate in the following paper.

The researchers included data from over 3400 out-of-hospital cardiac arrests (44% of which received some form of passive leg raising; usually hip flexion supported by a responder, propping the victim’s knees over a large backpack, etc), and yet their primary outcome resulted “Survival to 30 days was 7.9% among patients who received PLR and 13.5% among those who did not (OR 0.55; 95% CI 0.44–0.69; p < 0.0001)”. This is significant…significantly flying in the face of passive leg raising (PLR) in CPR! There was virtually no difference in distribution of age, gender, or cause of cardiac arrest, so why does this fly in the face of what we read earlier? Well, far be it from me to pick and choose data to support a narrative, but I thought this was a good time to point out several factors that were different between the two groups.

In the group that received CPR WITH leg raising:

  1. More cardiac arrests took place at home

Some confounding factors were discussed by the researchers, found to be “unequally distributed in the two groups”, and after a new multivariate analysis controlling for the potential confounders…they found that there was NO difference in 30-day survival. This result is not as exciting as some of the basic science that preceded the study; however, the confounders absolutely could explain some of the deficits seen in the leg-raising group. I don’t believe we can say at all that leg raising will actually improve outcomes in the field, but the common sense of it and promising science behind it makes me excited for further studies on this potentially life-saving intervention.

Resuscitation enthusiast