CPR-only survivors of out-of-hospital cardiac arrest: Implications for out-of-hospital care and cardiac arrest research methodology

Study objective: There is little evidence that cardiopulmonary resuscitatio n (CPR) alone may lead to the resuscitation of cardiac arrest victims with other than respiratory causes (eg, pediatric arrest, drowning, drug overdos e). The objective of this study was to identify out-of-hospital cardiac arr est survivors resuscitated without defibrillation or advanced cardiac life support. Methods: This observational cohort included all adult survivors of out-of-h ospital cardiac arrest of a cardiac cause from phases I and II of the Ontar io Prehospital Advanced life Support Study. During the study period, the sy stem provided a basic life support/defibrillation level of care but no adva nced life support. CPR-only patients were patients determined to be without vital signs by EMS personnel who regained a palpable pulse in the field wi th precordial thump or CPR only and then were admitted alive to the hospita l. Six members of a 7-member expert review panel had to rate the patient as either probably or definitely having an out-of-hospital cardiac arrest, an d a rhythm strip consistent with a cardiac arrest rhythm had to be present to be considered a patient. Criteria considered were witness status, citize n or first responder CPR, CPR duration, arrest rhythm and rate, and perform ance of precordial thump. Results: From January 1, 1991,to June 30, 1997, 9,667 patients with out-of- hospital cardiac arrest were treated. The overall survival rate to hospital discharge was 4.6%. There were 97 apparent CPR-only patients admitted to t he hospital. Application of the inclusion criteria yielded 24 CPR-only pati ents who had true out-of-hospital cardiac arrest and 73 patients judged not to have cardiac arrest. Of the 24 true CPR-only patients admitted to the h ospital, 15 patients were discharged alive, 10 patients were witnessed by b ystanders, and 7 patients were witnessed by EMS personnel. The initial arre st rhythm was pulseless electrical activity in 9 patients, asystole in 12 p atients, and ventricular tachycardia in 3 patients. One patient with ventri cular tachycardia converted to sinus tachycardia with a single precordial t hump. Conclusion: CPR-only survivors of true out-of-hospital cardiac arrest do ex ist; some victims of out-of-hospital cardiac arrest of primary cardiac caus e can survive after provision of out-of-hospital basic life support care on ly. However, many patients found to be pulseless by means of out-of-hospita l evaluation likely did not have a true cardiac arrest. This has implicatio ns for the survival rates of most, if not all, previous cardiac arrest repo rts. Survival rates from cardiac arrest may actually be lower if one exclud es survivors who never had a true arrest. The absence of vital signs by out -of-hospital assessment alone is not adequate to include patients in resear ch reports or quality evaluations for cardiac arrest.