Temperature and prognostication after cardiac arrest

The temperature evidence has evolved through three stages, and the candidate who can recount them demonstrates the depth of understanding. The early trials of 2002 — the Hypothermia After Cardiac Arrest study and the Bernard trial — found that cooling the comatose survivor of a witnessed VF arrest to 32 to 34 degrees improved the neurological outcome, and the practice of therapeutic hypothermia was adopted worldwide. The 2013 Targeted Temperature Management trial then found no difference between targeting 33 and 36 degrees, narrowing the target and blurring the distinction between hypothermia and controlled normothermia. The TTM2 trial, in 2021, was the decisive study: it found that targeting hypothermia at 33 degrees did not improve the outcome over normothermia, and that it caused more arrhythmia.^[1] The contemporary practice, codified by the guidelines, is to maintain normothermia and to treat fever actively, for at least 72 hours; the routine induction of hypothermia to 33 degrees is no longer recommended.^[2]

The prognostication is multimodal and deferred, and the candidate must resist the early pessimism. It is performed at 72 hours or more after the ROSC, ideally after the sedation has been off for long enough to examine, and it integrates several modalities: the clinical examination (the brainstem reflexes, the motor response, the presence of the myoclonus or the status myoclonus), the electrophysiology (the continuous or the standard EEG, and the bilateral absence of the N20 somatosensory evoked potential), the biomarkers (the trend of the neuron-specific enolase), and the imaging (the cerebral computed tomography or the magnetic resonance). No single predictor is sufficient, and the algorithm is applied as a whole by a team. The self-fulfilling prophecy — the prognostication that is too early, too single-modal, or made under sedation, leading to the premature withdrawal of care — is pitfall candidate must explicitly name and avoid.^[2]