Extracorporeal Life Support Improves Survival in Cardiac Arrest

Extracorporeal life support combined with conventional cardiopulmonary resuscitation (CPR) roughly doubles survival over CPR alone in patients with in-hospital cardiac arrest of cardiac origin, a new study suggests [1]. The study, published online July 7, 2008 in the Lancet, was conducted by a group led by Dr Yih-Sharng Chen (National Taiwan University Hospital, Taipei, Taiwan).

They note that sudden cardiac arrest has a low survival rate despite the introduction of CPR, and that survival rate declines rapidly when the duration of CPR exceeds 10 minutes, and even more rapidly if it exceeds 30 minutes. Extracorporeal life support, which involves the insertion of a catheter into the femoral artery/vein and circulating blood through a pump, heat-exchanger, and oxygenator before returning it to the body, was proposed as a device for cardiac resuscitation in the early 1960s. Chen et al report that despite promising results in pediatric patients, no comparative data have been assessed in adults undergoing CPR with extracorporeal life support.

They therefore conducted a three-year prospective observational study that compared conventional CPR alone with extracorporeal life support in patients 18 to 75 years of age with witnessed in-hospital cardiac arrest of cardiac origin who underwent CPR for more than 10 minutes. A matching process based on propensity score was done to equalize potential prognostic factors in both groups. In the study, 113 patients were enrolled in the conventional CPR group and 59 were enrolled in the extracorporeal CPR group. Results showed that patients given extracorporeal CPR had a higher survival rate to discharge and a better one-year survival rate than those who received conventional CPR; these differences remained significant after adjustment for other confounders.

Percent of Patients Alive at Various Time Points

Hazard Ratio for Survival Based on Propensity-Score-Matched Groups (Extracorporeal Life Support vs CPR Alone)

In an accompanying editorial [2], Drs Sung-Woo Lee and Yun-Sik Hong (Ansan Hospital, Seoul, South Korea) explain that extracorporeal circulation enhances coronary blood flow and preserves myocardial viability, thereby reducing time to the return of spontaneous circulation and supplying oxygenated blood to multiple organs, which prevents organ dysfunction. In addition, hypothermia can be easily induced to reduce hypoxic brain injury.

They congratulate Chen and colleagues for their efforts to develop an evidence base for extracorporeal life support, and add that future studies should focus on identifying appropriate candidates for the procedure. Noting that the upper limit for continuing CPR before extracorporeal life support has not been established, and that protracted CPR decreases survival rates during extracorporeal life support and conventional CPR, they suggest that extracorporeal life support is probably better used as soon as possible to keep ischemic times to a minimum and to improve outcomes. They also recommend that extracorporeal life support be extended to out-of-hospital patients when basic life support before the patient reaches hospital sufficiently maintains perfusing rhythms, if only transiently.

1. Chen Y-S, Lin J-W, Yu H-Y et al. Cardiopulmonary resuscitation with assisted extracorporeal life-support versus conventional cardiopulmonary resuscitation in adults with in-hospital cardiac arrest: an observational study and propensity analysis. Lancet 2008. DOI:10.1016/S0140-6736(08)60958-7. Available at www.thelancet.com/.
   
2. Lee S-W, Hong Y-S. Extracorporeal life-support in patients requiring CPR. Lancet 2008. DOI:10.1016/S0140-6736(08)60959-9. Available at www.thelancet.com/.