Sedation Confounds Outcome Prediction in Cardiac Arrest Survivors Treated with Hypothermia

Therapeutic hypothermia is commonly used in comatose survivors' post-cardiopulmonary resuscitation (CPR). It is unknown whether outcome predictors perform accurately after hypothermia treatment. Post-CPR comatose survivors were prospectively enrolled. Six outcome predictors [pupillary and corneal reflexes, motor response to pain, and somatosensory-evoked potentials (SSEP) > 72 h; status myoclonus, and serum neuron-specific enolase (NSE) levels < 72 h] were systematically recorded. Poor outcome was defined as death or vegetative state at 3 months. Patients were considered sedated if they received any sedative drugs a parts per thousand currency sign12 h prior the 72 h neurological assessment. Of 85 prospectively enrolled patients, 53 (62%) underwent hypothermia. Furthermore, 53 of the 85 patients (62%) had a poor outcome. Baseline characteristics did not differ between the hypothermia and normothermia groups. Sedative drugs at 72 h were used in 62 (73%) patients overall, and more frequently in hypothermia than in normothermia patients: 83 versus 60% (P = 0.02). Status myoclonus < 72 h, absent cortical responses by SSEPs > 72 h, and absent pupillary reflexes > 72 h predicted poor outcome with a 100% specificity both in hypothermia and normothermia patients. In contrast, absent corneal reflexes > 72 h, motor response extensor or absent > 72 h, and peak NSE > 33 ng/ml < 72 h predicted poor outcome with 100% specificity only in non-sedated patients, irrespective of prior treatment with hypothermia. Sedative medications are commonly used in proximity of the 72-h neurological examination in comatose CPR survivors and are an important prognostication confounder. Patients treated with hypothermia are more likely to receive sedation than those who are not treated with hypothermia.