Two new studies question the usefulness of therapeutic hypothermia in patients with nonshockable heart rhythm and traumatic brain injury. The first study, published online Feb. 14 in Circulation, found that therapeutic hypothermia nearly doubles the chances of survival with good neurological function for cardiac arrest patients resuscitated from ventricular fibrillation or pulseless ventricular tachycardia (VF/VT) but doesn’t appear to be much help in patients who have a nonshockable heart rhythm, such as pulseless electric activity or asystole (PEA/asystole).
Researchers prospectively collected data on 1,145 consecutive out-of-hospital cardiac arrest patients who were successfully resuscitated. About 65 percent of 708 patients in VF/VT and 60 percent of 437 patients in PEA/asystole received hypothermia when they were admitted to the ICU. In all, 30 percent survived to discharge with good neurological function, including 39 percent who were in VF/VT and 16 percent of those with PEA/asystole.
After adjusting for other variables, those who received therapeutic hypothermia after an initial VF/VT rhythm had nearly twice the chances of surviving with good neurological function compared to those who did not receive hypothermia. However, the analysis found no statistically significant improvement in outcome for those with a nonshockable rhythm.
The most recent American Heart Association guidelines for CPR recommend the routine use of therapeutic hypothermia for survivors of out-of-hospital cardiac arrest, especially for those who experienced VF. The recommendations also say that the research on the effectiveness of hypothermia for nonshockable patients is limited, according to theheart.org.
The second study, reported in February’s Lancet Neurology, found that inducing hypothermia even very soon after a traumatic brain injury didn’t result in better outcomes for patients. A multi-center clinical trial conducted in the U.S. and Canada found the outcome was poor, meaning severe disability, vegetative state or death, in 31 of 52 patients in the hypothermia group and 25 of 56 who were kept at normal temperature. The trial was terminated early “for futility,” according to the study.
Mechanical CPR May Be no Better than Manual CPR
There isn’t enough research to determine whether mechanical chest compression devices for patients in cardiac arrest are any better than manual chest compressions, according to a review of randomized controlled trials.
Researchers analyzed data from four trials involving nearly 900 patients. Three small studies suggested that mechanical devices were superior to compressions done by people. But the largest study, which involved 767 patients who suffered out-of-hospital cardiac arrest, found that those who received mechanical CPR fared worse than those who received CPR manually. About 7.5 percent of those who received compressions by hand survived to hospital discharge with good neurological function, compared with only 3.1 percent of the patients who received mechanical chest compressions.
The authors note that because of methodological problems with the study, this isn’t enough to conclude that mechanical CPR devices are harmful. (Patients who received mechanical CPR were more likely to be thin or morbidly obese, which could skew results, and also waited longer to be defibrillated, possibly because using the mechanical device delayed the start of compressions.)
“Based on the evidence as it currently stands, it’s difficult to say for sure whether these devices harm or benefit,” lead study author Steven C. Brooks, M.D., assistant professor of medicine at the University of Toronto, told Health Behavior News Service. “There is a need for more studies.”
The latest American Heart Association CPR guidelines emphasize the importance of doing good-quality chest compressions, including proper rhythm and depth and minimizing interruptions. But that’s proved challenging: Prior studies have shown that improper technique and fatigue can make it difficult even for trained rescuers to maintain good-quality compressions for long. Meantime, several manufacturers have developed mechanical devices that squeeze the chest and, they say, perform high-quality chest compressions more consistently than people.
Robert E. O’Connor, M.D., chair of emergency medicine at the University of Virginia in Charlottesville, told Health Behavior News Service that the question is not “whether the devices work—in the laboratory they do—but whether you can get them on quickly enough without interrupting chest compressions for any length of time. You pay a price for applying any device. The question is whether the price is worth it.” O’Connor was not involved in the research.
The study was published Jan. 19 online in Cochrane Database of Systematic Reviews.
Few Injuries From Mistaken CPR
Few bystanders are doing CPR when it’s not needed, and even when they do mistakenly attempt CPR on someone not in cardiac arrest, injuries are rare.
Researchers from the Medical College of Wisconsin and other Milwaukee hospitals looked at records of all patients treated by Milwaukee County EMS from March 2003 to February 2009 who had received bystander CPR. EMS determined that about 11.5 percent of the 672 patients who received chest compressions had probably not been in cardiac arrest. Of those patients, only one had a muscle injury that was documented in the medical record as possibly CPR-related. “Our results suggest that the benefits of bystander CPR for adults who suddenly collapse outweigh the risk of injury for those not in cardiac arrest,” the researchers wrote.
The research was published online Jan. 20 in the Prehospital Emergency Care Journal.
