New take on cardiac arrest treatment

Rapidly cooling a person in cardiac arrest may improve their chance of survival without brain damage, according to research presented at the American Heart Association's Scientific Sessions 2009.

"We now have a method that is safe and can be started within minutes of cardiac arrest to minimize damage during this very critical period," said Maaret Castrén, M.D., lead author of the study and professor of emergency medicine at the Karolinska Institute in Stockholm.

For years, people hospitalized after cardiac arrest have been cooled to reduce injury to the brain and other tissues that occurs when the blood supply returns after being temporarily halted.

PRINCE investigation

In the PRINCE (Pre-Resuscitation Intra-Nasal Cooling Effectiveness) investigation, Castr-n and colleagues at 14 other centres across Europe used a new tool, RhinoChill, which cools the brain during ongoing cardiopulmonary resuscitation (CPR).

Researchers randomized 200 adults going into witnessed cardiac arrest to receive either standard resuscitation or resuscitation with cooling started as soon as possible during the arrest, with ongoing CPR. All patients who survived to hospitalization were further cooled according to standard criteria. Eighteen patients were excluded from the analysis because a 'do-not-resuscitate' order was found or there was a non-cardiac reason for their cardiac arrest.

In the 182 patients reported, 83 (average age 66 years, 71% male) were randomized to receive nasal cooling (although two were not cooled because of user or device problems) and 99 (average age 64.8, 78% male) received standard care.

RhinoChill is a non-invasive device that introduces coolant through nasal prongs. The system is battery-powered and requires no refrigeration, making it suitable for emergency medical technicians in the field to use while a person is receiving CPR.

Median time - 23 minutes

The patients in each group were similar in their initial heart rhythms, how much time lapsed before CPR was started and whether CPR restored a pulse. The median time between arrest and the initiation of cooling was 23 minutes. On arrival at the hospital, the cooled patients' temperatures (measured at the eardrum) were significantly lower (average 34.2-C, 93.56-F) than those receiving standard care (35.5-C, 95.9-F, p = 0.0001).

In the total group:

• 46.7% of those cooled survived to hospital discharge, compared with 31% of those receiving standard care;
• 36.7% of those cooled were in good neurological condition on hospital discharge, compared with 21.4% of those receiving standard care. In the 137 patients in whom resuscitation efforts began within 10 minutes of cardiac arrest:
• 59.1% of those cooled survived to hospital discharge, compared with 29.4% of those receiving standard care;
• 45.5% of those cooled were neurologically intact at hospital discharge, compared with 17.6% of those receiving standard care>

The earlier the cooling, the better

"Our results show that the earlier you can do the cooling, the better," Castr-n said. "When resuscitation efforts were delayed, there was no significant difference in survival."

In a time analysis, patients who received a combination of early CPR started within six minutes of collapse and cooling had the best outcomes.

Patients with ventricular fibrillation (VF), whose heart chambers aren't pumping blood because they are twitching rapidly and erratically instead of fully contracting, are the subgroup of cardiac arrest patients most likely to survive. In this study, of the 56 patients who had VF:
**62.5% of those cooled survived to hospital discharge, compared with 47.6% of those who received standard care;
**50% of those cooled were neurologically intact at hospital discharge, compared to 28.6% of those who received standard care.

Safe outside of hospital environment

"RhinoChill is easy and safe to use during a cardiac arrest outside of the hospital," said Denise Barbut, M.D., senior author of the study and president and chairman of BeneChill, Inc., maker of the device. "Although the study was not powered to look at outcomes, there seemed to be a significant benefit on survival and neurologically intact survival, specifically in those treated within 10 minutes."

Eighteen adverse reactions were reported after the treatment, including three nosebleeds and 13 nasal discolorations. Colouring spontaneously returned to normal in all patients who survived. Serious adverse events, such as seizure or repeat cardiac arrest, occurred in seven cooled patients and 14 controls.

Source: American Heart Association