Ahh, another (f)utility study. Does it work, or doesn’t it? And yes, I know. It’s another animal study. But it may give us a glimpse of where we are really going with this.
A team at the University of Tennessee – Knoxville devised a dog experiment to study how well performing CPR works in critically hypovolemic animals. They used three groups of dogs that received a severe shock insult: hemorrhage until loss of pulse, then waiting for 30 minutes in that pulseless state. At that point, one of three interventions was performed for 20 minutes.
One group received CPR only, another group underwent CPR plus fluid administration, and the last group got fluids only.
Here are the factoids:
- The insult to all three groups was similar.
- Vital signs and lab studies were similar in the CPR+fluid and fluid only groups.
- The CPR only group had significantly lower mean arterial pressures and higher pulse rates than the other CPR+fluid and fluid only groups.
- Ejection fraction was lower in the CPR only group, and it also had a higher incidence of end organ damage.
- Two of the six dogs in the CPR only group died before the end of the study.
Bottom line: Tread with caution here. It makes sense that pounding on an empty tank won’t do much. But this study doesn’t exactly prove this. Only the vital signs measurements were significantly different. All other results are just trends in this very small study. And finally, dogs are (obviously) different than people, in their physiology and their chest wall shape. This can certainly make a difference, and does not mean that we should abandon CPR in humans in hemorrhagic shock.
Reference: Utility of CPR in hemorrhagic shock, a dog model. EAST 2016 Oral abstract #8, resident research competition.