Targeted temperature management (TTM), previously called therapeutic hypothermia, is a treatment used in intensive care after cardiac arrest to reduce brain injury. It involves carefully controlling the patient’s body temperature to prevent additional damage during the critical recovery period after the heart restarts.
Why temperature matters after cardiac arrest
When blood flow stops during cardiac arrest, brain cells are deprived of oxygen. When circulation is restored, a reperfusion response occurs: the sudden return of oxygen triggers further cellular damage through inflammation and free radical production. Controlling body temperature can slow these harmful processes and give brain cells a better chance of survival.
How it works
After resuscitation, unconscious patients are cooled to a target temperature, typically between 32 and 36 degrees Celsius, and held at that temperature for 24 hours. Cooling is achieved using special cooling blankets, ice packs, or internal cooling catheters. The patient is then gradually warmed back to normal temperature (around 37 degrees) over several hours. Active fever prevention continues for at least 72 hours, as even mild fever worsens neurological outcomes.
The evidence
Early studies showed significant benefit from cooling to 32 to 34 degrees, and hypothermia became standard practice. More recent large trials (TTM1 and TTM2) found that strict temperature control at 36 degrees was as effective as deeper cooling for many patients, while avoiding some of the complications of profound hypothermia. Current guidance focuses on preventing fever rather than mandating deep cooling for all patients.
Who receives TTM
TTM is primarily used in patients who remain unconscious after resuscitation from out-of-hospital cardiac arrest. The treating team assesses each patient individually, considering the likely cause of the arrest, the duration of resuscitation, and the patient’s overall condition.
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