BETHESDA, Md -- November 06, 2009 -- Enrollment has ended early in a large, multicentre clinical trial comparing 2 distinct resuscitation strategies delivered by emergency medical service (EMS) providers to increase blood flow during cardiac arrest.
The study's independent monitoring board and the National Heart, Lung, and Blood Institute (NHLBI) stopped enrolment based on preliminary data suggesting that neither strategy significantly improved survival.
One strategy compared different durations of manual cardiopulmonary resuscitation (CPR) by EMS providers before they assessed whether defibrillation was needed, and the other strategy tested the potential benefits and risks of an investigational device to maintain pressure in the chest during CPR.
After reviewing data on approximately 11,500 study participants, the study's Data and Safety Monitoring Board (DSMB) recommended on October 23 that the NHLBI stop enrollment because sufficient data had been gathered, and continuing recruitment was unlikely to change the overall outcomes of the study. The board had no concerns about the safety of any of the interventions tested, and NHLBI accepted the DSMB recommendations on the same day.
Researchers will continue to monitor study participants who agree to follow-up visits for up to 6 months. They will analyse and publish the final data in the coming months.
The Resuscitation Outcomes Consortium (ROC) tested both resuscitation strategies as part of the Prehospital Resuscitation using an Impedance Valve and Early versus Delayed (ROC PRIMED) trial. Researchers found that ITD use did not significantly improve or worsen survival rates for cardiac arrest patients.
The early versus delayed strategy compared 2 currently used timing strategies of assessing the heart's rhythm in relation to when CPR is started by EMS providers. The study compared patient survival rates after EMS providers performed at least 30 seconds of CPR before assessing the need for defibrillation with delivering 3 minutes of CPR before the assessment. Based on current study data, both timing strategies were equally effective.
ROC PRIMED was designed to test the 2 promising strategies to increase the chance of survival without functional impairments of patients who suffer cardiac arrest outside of a hospital setting. To test the ITD strategy, patients were randomly assigned to receive standard CPR from participating EMS providers either with an ITD or with a non-working replica of an ITD.
The study's preliminary results indicate similar survival rates of patients with preserved neurologic function between both groups of patients, suggesting that standard CPR without an ITD is as effective as using an ITD.
"While the ITD is based on a sound physiologic principle, in this study it did not appear to improve survival rates for adults in cardiac arrest outside of the hospital," said ROC principal investigator Tom Aufderheide, MD, Medical College of Wisconsin, Milwaukee, Wisconsin, "We will continue to seek out and thoroughly test new devices as well as alternative applications that hold promise for saving the lives of cardiac arrest patients."
The other principal strategy studied in ROC PRIMED was the timing of assessing the heart's rhythm to determine whether defibrillation is needed in relation to when CPR is started. For patients randomly assigned to the Analyze Early group, EMS providers were instructed to perform CPR until they were able to analyse the patient's heart rhythm (~30-90 seconds). Patients in the Analyze Later group received CPR for at least 3 minutes before their heart rhythm was analysed. When indicated, defibrillation was provided.
"The ROC PRIMED study answers a long-standing question in the EMS community over whether it is better to defibrillate earlier or later when trying to resuscitate a patient," said princicpal investigator of ROC PRIMED Ian Stiell, MD, Department of Emergency Medicine, University of Ottawa, Ottawa, Ontario. "Both techniques appear to be equally beneficial."
SOURCE: National Institutes of Health
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