For comatose adult survivors of out-of-hospital cardiac arrest (OHCA), controlling body temperature to less than 37.5° C is a “reasonable and evidence-based approach,” a new American Heart Association (AHA) scientific advisory suggests.
On the basis of data from recent trials, the International Liaison Committee on Resuscitation and other organizations have altered their treatment recommendations for temperature management after cardiac arrest.
The AHA will present guidelines on this topic in a focused update to be published later in the year. Meanwhile, AHA’s Emergency Cardiovascular Care Committee convened a writing group to review the Hypothermia Versus Normothermia After Out-of-Hospital Cardiac Arrest (TTM2) trial in the context of other recent evidence and rendered an expert opinion on how the trial may influence clinical practice. These findings will be incorporated into the upcoming guidelines.
“Many centers have already moved toward controlled normothermia for post-arrest patients, so we think this guidance will be welcomed by many,” said Sarah Perman, MD, of the Yale School of Medicine, and Kate Berg, MD, of Beth Israel Deaconess Medical Center, who are both members of the AHA Emergency Cardiovascular Care Committee that authored the advisory.
“For those who continue to favor temperatures in the 32° to 36° range for some or even all patients, the guidance that we have drafted leaves room for clinicians to make patient-centered decisions,” they told theheart.org | Medscape Cardiology.
“Certainly, a finite guideline that recommends one temperature for all would be easier to apply,” the authors acknowledge. “However, cardiac arrest is a heterogenous event and brain injury is variable, and definitive evidence that one temperature in the range of 32-37.5 is superior to another is lacking. We hope that clinicians find that this guidance supports and informs their practice.”
The advisory was published online August 14 in Circulation.
The new guidance is based largely on findings from the TTM2 trial, a multicenter, randomized clinical trial of temperature management for neuroprotection after cardiac arrest that included 1900 unresponsive adult patients successfully resuscitated from OHCA.
Patients were randomly assigned to receive hypothermia, defined as a target temperature of 33° C for 28 hours, followed by gradual rewarming to 37° C, or normothermia, defined as a target temperature <37.8° C, with early treatment of fever.
No significant between-group difference was seen in the primary outcome of death at 6 months, nor were there any significant differences by subgroups of sex, age, time to return of spontaneous circulation, initial rhythm, or circulatory shock on admission.
Although it’s still not clear whether certain patients might benefit from lower target temperatures, the authors note, major international organizations now suggest a target post–cardiac arrest temperature of less than 37.5° C.
By contrast, current AHA guidelines endorse targeting a temperature between 32° C and 36° C for 24 hours.
Between now and the forthcoming formal guidance in the “2023 American Heart Association Focused Update on Advanced Cardiovascular Life Support,” the scientific advisory writing group agreed: “For unresponsive post–cardiac arrest adult patients with characteristics similar to those of individuals included in the TTM2 trial (OHCA of cardiac or unknown cause, excluding those with unwitnessed asystole), controlling patient temperature to <37.5°C is a reasonable and evidence-based approach.
“For the broader group of patients with in-hospital cardiac arrest or OHCA of noncardiac (other medical) cause, evidence for the ideal approach to temperature management after return of spontaneous circulation is less certain; whether some of these patients might benefit from temperature control at temperatures between 33°C and 37.5°C remains unclear.”
Unless a catastrophic brain injury results from OHCA, the group writes, “strictly preventing fever with continuous temperature monitoring, providing comprehensive critical care support, and deploying multimodal evidence-based strategies for neuroprognostication at a minimum of 72 hours after normothermia remain essential….”
Perman and Berg conclude, “We hope that this guidance continues to encourage aggressive post-arrest care that includes focus on temperature control as well as the other major contributors to post-arrest bundles of care including hemodynamic optimization and guideline concordant neuro-prognostication.”
No funding was reported. Berg has received grant support from AHA/ILCOR, and Perman, from NIH/NHLBI.
Circulation. Published online August 14, 2023. Abstract
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