Integrating therapeutic hypothermia (TH) protocols into a regional STEMI network can be an effective rescue therapy for out-of-hospital cardiac arrest (OHCA) that can help improve survival, according to a study published in Circulation: Journal of the American Heart Association. In fact, researchers from the Minneapolis Heart Institute (MHI) found that after integration of the protocol, 56 percent of these patients survived to hospital discharge.
"Approximately 300,000 out-of-hospital cardiac arrests (OHCA) occur annually in the United States, and these events are typically catastrophic,” Michael R. Mooney, MD, of the MHI and the Abbott Northwestern Hospital in Minneapolis, and colleagues wrote. Survival for patients with the condition is low, a mere 6 to 9 percent, and adverse neurological sequelae are frequent.
The regional STEMI network at Abbott Northwestern Hospitals spans across 33 hospitals within a 210-mile radius. In 2006, staff at the hospital developed a standardized protocol for cardiac arrest that includes a timely initiation of TH. The protocol, called "Cool It," involves the rapid, coordinated and consistent delivery of TH and attempts to promote supportive care of TH patients throughout the entire care continuum from transport to rewarming.
Between February 2006 and August 2009, 140 OHCA patients who were unresponsive after return of spontaneous circulation (ROSC) were cooled and rewarmed with the use of an automated, noninvasive cooling device.
The researchers reported that 107 patients were transferred to the TH-capable hospitals from referring hospitals within the STEMI network. The average transport distance was 56 miles. The researchers defined positive neurological outcome as Cerebral Performance Category 1 or 2 at discharge.
Sixty-eight patients within the cohort had concurrent STEMI and received cardiac intervention and cooling simultaneously. Additionally, 32 patients had asystole/PEA and 61 patients were in cardiogenic shock.
Mooney and colleagues reported that overall survival to hospital discharge was 56 percent and 51 percent had a positive neurological outcome. The authors reported survival for transferred and non-transferred patients to be similar.
The authors reported a 20 percent increase in the risk of death for every hour of delay to initiation of cooling. The median time from arrest to ROSC during the study was 22 minutes, and the median time between ROSC and application of the cooling device was 117 minutes. “A shorter interval between collapse and ROSC was strongly associated with survival,” the authors wrote. Only 36 percent of patients who were down for more than 30 minutes survived to hospital discharge.
When the elapsed time between ROSC and the application of the cooling device at ANW was greater than 2.5 hours, patients had a 63 percent less likely chance of survival to discharge than when time elapsed less than 1.5 hours.
“Advanced age, asystole/PEA, and cardiogenic shock were all associated with increased mortality, but among survivors, only advanced age was associated with adverse neurological sequelae,” the authors noted.
Integration of the protocol has significantly reduced the time that elapses between patient arrival in the emergency department and the application of a cooling device, from 96 minutes to a median of 20 minutes. The number of patients who received cooling at Abbott has increased from 6 percent in year one to 69 percent in year four.
“We have demonstrated that simple cooling with ice bags initiated soon after arrest can be associated with incrementally improved outcomes, even if transfer to a specialized TH center is required, and that TH is an achievable standard of care that can be applied in urban and rural settings equally where regional systems of care have been developed,” Mooney and colleagues wrote.
Mooney et al offered that those thinking of expanding access to TH should “capitalize on established emergency cardiac care networks with refined patient transfer mechanisms.” Secondly, the authors said that TH and PCI for STEMI patients can be achieved concomitantly without delay.
“Education and resources should be directed toward EMS and community hospitals to ensure execution of the simple but seemingly effective practice of initiating cooling with ice packs immediately on ROSC,” Mooney and colleagues wrote.
The researchers also said that the TH population can be expanded and researchers at Abbott have expanded these populations to