Time to Awakening After Cardiac Arrest and the Association with Target Temperature Management

Aim: Target temperature management (TTM) at 32-36 °C is recommended in unconscious survivors of cardiac arrest. This study reports awakening in the TTM-trial. Our predefined hypotheses were that time until awakening correlates with long-term neurological outcome and is not affected by level of TTM.

Methods: Post-hoc analysis of time until awakening after cardiac arrest, its association with long-term (180-days) neurological outcome and predictors of late awakening (day 5 or later). The trial randomized 939 comatose survivors to TTM at 33 °C or 36 °C with strict criteria for withdrawal of life-sustaining therapies. Administered sedation in the treatment groups was compared. Awakening was defined as a Glasgow Coma Scale motor score 6.

Results: 496 patients had registered day of awakening in the ICU, another 43 awoke after ICU discharge. Good neurological outcome was more common in early (275/308, 89%) vs late awakening (142/188, 76%), p < 0.001. Awakening occurred later in TTM33 than in TTM36 (p = 0.002) with no difference in neurological outcome, or cumulative doses of sedative drugs at 12, 24 or 48 h. TTM33 (p = 0.006), clinical seizures (p = 0.004), and lower GCS-M on admission (p = 0.03) were independent predictors of late awakening.

Conclusion: Late awakening is common and often has a good neurological outcome. Time to awakening was longer in TTM33 than in TTM36, this difference could not be attributed to differences in sedative drugs administered during the first 48 h.