Endovascular Cooling for OOH Arrest: Little Clinical Gain Seen

PARIS, FRANCE — Two targeted temperature management (TTM) strategies for out-of-hospital cardiac-arrest patients appear not to differ all that much on major clinical outcomes, new research suggests^[1].

The Clinical and Economical Interest of Endovascular Cooling in the Management of Cardiac Arrest (ICEREA) randomized controlled trial (RCT) of 400 patients showed no significant differences between those who underwent cooling with an endovascular femoral device and those who underwent basic external cooling, which included fans, ice packs, and/or a makeshift tent, on rates of survival without major neurological damages 28 days after the event (the primary end point) or on "improvement of favorable outcome at day 90."

However, there was a significantly shorter time to target temperature and better maintenance of target hypothermia in those undergoing endovascular cooling (both P<0.001).

"Endovascular cooling appears more efficient to rapidly reach and better control the 33^°C-[targeted temperature], with a decreased nurses' workload," write the authors, led by Dr Nicolas Deye (Hôpital Lariboisière, Paris, France). But they add that this group also had significantly more treatment-related minor side effects than the external cooling group.

The findings were published online June 19, 2015 in Circulation.

Three-Month Trend?

The ICEREA study included 400 patients between the ages of 18 and 79 years who were admitted to one of 18 intensive-care units in France after experiencing an out-of-hospital cardiac arrest between November 2006 and September 2009. Of these, 203 participants were randomly assigned to undergo endovascular cooling with the Icy catheter with Coolgard cooling system (Zoll, formerly Alsius) and 197 patients were assigned to undergo external cooling.

A total of 41.9% of the first group and 38.1% of the latter group survived through follow-up, which was not statistically different.

The primary end point, which was measured at 28-day follow-up using the Pittsburgh cerebral-performance categories, also showed no significant differences between the treatment groups, with 36% of the endovascular and 28.4% of the external group surviving without major neurological damage.

Although 90-day follow-up showed that a greater percentage of the endovascular group had improved neurological outcomes on observation vs the external group (34.6% vs 26%, respectively), it was not statistically significant (P=0.07). There was also a trend that just missed significance for the endovascular patients to have a higher "cumulative survival rate without major sequelae" (P=0.052).

However, more of the patients undergoing endovascular cooling had at least one minor side effect vs the other treatment group (P=0.009). This included "minor bleeding not requiring transfusion and microbiological colonization of central venous catheters," report the investigators, as well as three endovascular patients experiencing "deep accidental per-procedural hypothermia." There were no deaths related to therapeutic hypothermia.

Interestingly, the nurses' time spent initiating device implementation was significantly shorter for the endovascular group at 27.5 minutes (95% CI 20.0–40.0 min) vs 37 minutes (95% CI 25.0–54.0 min) for the external group (P=0.0001), as was time dedicated to the intervention itself (10.0 min vs 38 min, respectively; P<0.0001).

"The overall nurses' workload during the whole period of TTM . . . to implement the cooling system, to prepare and administer patients' drugs, to perform blood samples, and to perform general and specific nursing tasks was [also] significantly decreased" in the former vs latter group (428.5 min vs 530 min, respectively; P=0.03), report the researchers.

"Despite real differences regarding the temperature values during the TTM period, we found no major clinical difference in outcome at 1 month but a trend at 3 months by using in-hospital advanced endovascular devices," they summarize.

Answers Important Questions

"This is the first major study to directly compare the two fundamental cooling methodologies (ie, surface vs core cooling) in a prospective RCT; the authors are to be congratulated," Dr Kees H Polderman (University of Pittsburgh Medical Center, PA) writes in an accompanying editorial^[2].

However, Polderman noted several study limitations, including that "newer and more powerful surface cooling devices such as the Arctic Sun system were not used" and that the surface-cooling strategy used basic tools and devices. He also pointed out that 18% of the endovascular patients and 34% of the external cooling patients were lost to follow-up at 90 days.

"If all patients could have been followed the differences might well have reached statistical significance."

Still, he writes that "important clinical questions" were addressed in this study, including that "better temperature control can be achieved using modern cooling technologies" and that there was a trend to improved neurological outcome.

"Further studies will be needed to assess cooling efficacy for fever management, which is likely to be more difficult as the patients' heat-generating abilities will be greater at temperatures that are closer to normal," said Polderman.

The study was funded by a research grant from the French political health government. Deye reports no relevant financial relationships. Disclosures for the coauthors are listed in the article. Polderman reports receiving and/or mentoring trainees and residents who received restricted educational grants from cooling device manufacturers Bard, KCI International, Velomedix, and Zoll.

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