Sedation Confounds Outcome Prediction in Cardiac Arrest Survivors Treated with Hypothermia

Abstract

Background Therapeutic hypothermia is commonly used in comatose survivors’ post-cardiopulmonary resuscitation (CPR). It is unknown whether outcome predictors perform accurately after hypothermia treatment. Methods 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 ≤12 h prior the 72 h neurological assessment. Results 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. Conclusions 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.

C‐GRApH : A Validated Scoring System for Early Stratification of Neurologic Outcome After Out‐of‐Hospital Cardiac Arrest Treated With Targeted Temperature Management

“…Prior to TTM, the “gold standard” for early prediction of neurologic outcomes was the 2006 American Academy of Neurology practice parameter, comprising 6 physical examination and diagnostic test findings on post‐arrest days 1 to 3, each with reported positive predictive value (PPV) of 100% for poor neurologic outcome 10. However, validity in the TTM population has been repeatedly questioned because of decreased individual and composite PPV 11, 12, 13. The current consensus recommendation is to delay prognosis ≥72 hours post‐arrest,14 consistent with a recent study reporting average time to awakening 3.2 days post‐arrest 15…”

Optic nerve sheath diameter on computed tomography not predictive of neurological status post-cardiac arrest

“…Clinicians may recognize abnormalities on imaging and restrict treatments, fostering a link between those findings and poor clinical outcome. 5,6 One prognostic factor on imaging that has received recent attention is the optic nerve sheath diameter (ONSD). The optic nerve sheath is an extension of the dura and contains cerebrospinal fluid (CSF) and the optic nerve.…”

The interrelation between clinical presentation and neurophysiology of posthypoxic myoclonus

“…A different source of uncertainty in this study was that the clinical assessment of PHM might have been challenging due to the dynamic and intermittent character of PHM and the use of video recordings leading to an observation that is less vivid 13, 14, 16. To circumvent this issue, three instead of one experienced neurologist interpreted the clinical videos.…”

“…However, one of the challenges for the use of PHM as prognosticator is that the clinical distinction between focal and generalized PHM is complicated; the assessment is hampered by the dynamic and intermittent character of PHM, hypothermia and medication effects 13, 14, 15, 16. In contrast to the current American guideline for postanoxic coma, the presence of PHM is not included as a criterion for poor prognosis in the European guideline 17.…”