Targeted Temperature Management: A Closer Look At The Controversy

Targeted temperature management has been a mainstay of post-cardiac arrest care since 2005, when it was endorsed by both the American Heart Association (AHA) and the International Liaison Committee on Resuscitation (ILCOR). For cardiac arrest patients who experience return of spontaneous circulation, the protocol involves cooling to 32°C-36°C for at least 24 hours, followed by gradual rewarming to normothermia.¹

But recent research has called this longstanding cooling practice into question, suggesting that maintaining normothermia may be a more appropriate target instead.

Keep reading as we explore the history of targeted temperature management, the recent change in the European Union (EU) and the research that precipitated it, and what it means for hospitals in the United States.

Targeted temperature management: A brief history

Targeted temperature management first came to the forefront of resuscitative care in 2002, after two randomized controlled trials showed that therapeutic hypothermia improved neurologic outcomes following cardiac arrest.^2,3

Its implementation was initially limited to academic medical centers until 2005, when it was recommended by both the AHA and ILCOR. Following this endorsement, targeted temperature management gained traction for both in-hospital and out-of-hospital cardiac arrest (OHCA) events and soon became an established component of post-cardiac arrest care.

The optimal temperature target was debated over the years, with the upper end of the recommended range later changed to 36°C from its original 34°C.⁴ Those modifications aside, the overall support for the cooling protocol remained in place for nearly 20 years.

New guidelines in the EU

That longstanding protocol changed in 2022, when the European Resuscitation Council and the European Society of Intensive Care Medicine published a new set of guidelines to replace the old.⁵

The new EU recommendations shift the focus away from therapeutic hypothermia to maintaining normothermia, stating that there is insufficient evidence to recommend for or against temperature control at the previous range of 32°C to 36°C.⁵ Instead, they call for the following for 72 hours post arrest⁵:

• Continuous monitoring of core temperature for patients who remain comatose after cardiac arrest
• Active prevention of fever (defined as greater than 37.7°C)

So why the change? The revised recommendations are largely based on the recent Targeted Temperature Management-2 (TTM-2) trial, which showed no benefit to targeted hypothermia versus targeted normothermia in comatose OHCA patients post-arrest.^3,5,6

And while the TTM-2 study is not without its own limitations, it did address many of the shortcomings of the initial 2002 studies, both of which were small, without blinding, and lacked standardization of neurological prognostication protocols between treatment groups.³

Where do we go from here?

The EU’s shift away from mild induced hypothermia marks a departure from the previous protocol, leading many to wonder whether the United States should follow suit. As hospitals in the United States grapple with the recent changes, here are a few key points to keep in mind:

1. The EU’s new protocol does not eliminate the need for temperature management post-arrest.

Given how common fever is in post-arrest patients, cooling strategies are often still indicated even when targeting normothermia. Case in point: In the TTM-2 trial, 46% of patients in the normothermia group received active cooling.³ The results of the TTM-2 study should not be interpreted to mean that temperature management is no longer necessary.³

2. Differences between the United States and the EU should be taken into account.

Before being too quick to adopt the EU’s revised stance, it’s important to consider other differences in systems of care between the two entities that might confound study results.

For example, unlike the United States, 44% of the EU requires cardiopulmonary resuscitation (CPR) certification to obtain a driver’s license.⁷ This requirement increases the likelihood of early bystander CPR in cardiac arrest, which can also have an effect on neurologic outcomes. This is particularly relevant given that the majority of patients in both groups of the TTM-2 trial received bystander CPR after a witnessed cardiac arrest.⁶

3. The bottom line: more research is needed.

As it currently stands, the research is conflicted. Some hospitals in the United States have changed their policies in light of more recent findings, while others have kept their existing protocol in place.

Each institution likely has good reasons for making those decisions. But one thing is clear: Particularly given the differences between the EU and United States discussed above, additional research is needed to provide guidance on United States-specific recommendations going forward.