Orlando, Fla.—European researchers found that a trans-nasal cooling approach that lowers body temperature while cardiopulmonary resuscitation (CPR) is performed can be used effectively in the pre-hospital setting and appears to improve outcomes, based on the PRINCE study presented at the 2009 American Heart Association conference.
"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 lead researcher Maaret Castrén, MD, a professor of emergency medicine at the Karolinska Institute in Stockholm, Sweden. “This cooling mechanism is different from other methods.”
In 2003, the American Heart Association and the International Liaison Committee on Resuscitation recommended that unconscious adult patients with spontaneous circulation after out-of-hospital cardiac arrest be cooled to 32 ºC to 34 ºC for 12 to 24 hours when the initial rhythm was ventricular fibrillation. The statement, which was updated in 2005, was originally based on two articles published in February 2002 in the New England Journal of Medicine that showed the advantage of post-cardiac arrest therapeutic hypothermia.
Traditionally, 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, Castrén explained.
In the PRINCE (Pre-Resuscitation Intra-Nasal Cooling Effectiveness) investigation, Castrén and colleagues at 14 other centers in Europe used an evaporated cooling tool, RhinoChill, to cool the brain during ongoing CPR in 182 randomized patients. Evaporated cooling administers a mix of the coolant plus oxygen directly into the nose, and Castrén said it can replace other technologies, such as cooling blankets.
The patients received 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. The researchers excluded 18 patients because a 'do-not-resuscitate' order was found or there was a non-cardiac reason for their arrest.
Of the patient group, 83 (average age 66 years, 71 percent male) were randomized to receive trans-nasal cooling (although two were not cooled because of user or device problems) and 99 (average age 64.8, 78 percent male) received standard care.
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 were significantly lower (average 34.2ºC) than those receiving standard care.
While the study was powered to look at efficacy, the differences in survival and neurological function between the two arms show an interesting trend.
In the total group:
- 46.7 percent of those cooled survived to hospital discharge, compared with 31 percent of those receiving standard care;
- 36.7 percent of those cooled were in good neurological condition on hospital discharge, compared with 21.4 percent of those receiving standard care.
Neither of the differences were significant.
In the 137 patients in whom resuscitation efforts began within 10 minutes of cardiac arrest, the differences between the two arms were significant:
- 59.1 percent of those cooled survived to hospital discharge, compared with 29.4 percent of those receiving standard care;
- 45.5 percent of those cooled were neurologically intact at hospital discharge, compared with 17.6 percent of those receiving standard care.
In a time analysis, patients who received a combination of early CPR started within six minutes of collapse and cooling had the best outcomes.
“Our results show that the earlier you can do the cooling, the better," Castrén said. "When resuscitation efforts were delayed, there was no significant difference in survival."
Also, the study was not powered for survival, she said.
Of the 56 patients who had VF, 62.5 percent of those cooled survived to hospital discharge, compared with 47.6 percent of those who received standard care; and 50 percent of those cooled were neurologically intact at hospital discharge, compared with 28.6 percent of those who received standard care.
However, 18 adverse reactions were reported