Holly E. Hinson
Identifying the reversible causes is a key tenet in the immediate post-arrest algorithm after cardiac arrest. While less frequent, neurologic causes of cardiac arrest occur often enough to be considered when the five “Hs and Ts” in the advanced cardiac life support algorithm have been exhausted. In the most current guidelines, routine head computed tomography (CT) is not required, though Head CT may illuminate the etiology of an arrest, prompt changes in management, or provide information on prognosis. The question remains what the role of Head CT should be in after out of hospital cardiac arrest (OHCA)?
In this issue of Resuscitation, Reynolds et al. performed a single center retrospective study describing the use of Head CT in adult OHCA patients surviving at least 24?h after arrest. Only about half of subjects underwent Head CT. These subjects were healthier and had shorter arrest resuscitation times than those who did not undergo Head CT, suggesting the etiology of the arrest was not immediately apparent to the providers. Just over 1/3 of those scans were abnormal, prompting management changes in about 1/3 of those abnormal scans. Head CT was obtained per clinical discretion, so these estimates reflect a highly selected patient population instead of a representative sample of all comers. We cannot infer the true incidence of abnormality on Head CT after OHCA from this observational study, though the estimates reported in this article echo previous estimates in similarly designed retrospective, observational studies., From data obtained about a decade previous to the current report, Naples et al. reported that Head CTs were obtained in under 25% of patients versus over 50% of patients in the current report. The increasing utilization of Head CT may reflect increasing awareness of neurologic causes of cardiac arrest in the last 10 years, or may reflect the increasing involvement of Neurologists in post-arrest care. The authors cite changing institutional protocols facilitating neurologic consultation. Neurologic consultation and multi-modal assessment for prognosis for comatose OHCA survivors appears to be commonplace.
A striking finding in both the current report and the Naples study was the low rate of survival to discharge amongst patients with abnormalities on Head CT, particularly hemorrhage. This observation raises the question of what role the Head CT plays in the decision to withdraw care. Predictions of poor prognosis may become a self-fulfilling prophecy if the decision to withdraw life sustaining care is made based on that poor prognosis. There is evidence that different subspecialists approach early withdrawal of care differently, weighting different factors in the consideration of “poor prognosis”. For example, in one qualitative study the circumstances surrounding the resuscitation such as “time down” were rated as very influential by medical intensivists, while neurointensivists focused on clinical exam findings such as lack of brain stem reflexes to influence the determination of prognosis. This finding highlights how a multidisciplinary approach to prognosis might avoid such self-fulfilling prophecies.
Resource stewardship may preclude a definitive study on the utility of routine Head CT for survivors of OHCA. A future avenue of exploration might be how a multi-disciplinary team including Neurologists identify neurologic causes of arrest, modify therapies based on their observations (e.g. treating cerebral edema), and prognosticate in comparison to conventional treatment protocols.
No known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome.