Evaluating the obtunded patient after cardiac surgery: the role of continuous electroencephalography

The Impact of Nonconvulsive Status Epilepticus after Cardiac Surgery on Outcome

Neurological complications after heart surgery are associated with tremendous morbidity and mortality. Nonconvulsive status epilepticus (NCSE), which can only be verified by EEG, may cause secondary brain damage. Its frequency and its impact on outcomes after cardiac surgery is still unclear. We collected the neurological files and clinical data of all our patients after heart surgery who, in the course of their ICU stay, had been seen by a neurologist who ordered an EEG. Within 18 months, 1457 patients had cardiac surgery on cardiopulmonary bypass. EEG was requested for 89 patients. Seizures were detected in 39 patients and NCSE was detected in 11 patients. Open heart surgery was performed in all 11 NSCE patients, of whom eight showed concomitant brain insults. None had a history of epilepsy. Despite the inhibition of seizure activity with antiseizure medication, clinical improvement was only noted in seven NCSE patients, three of whom were in cerebral performance category 2 and four in category 3 at hospital discharge. The four patients without neurological benefit subsequently died in the ICU. The occurrence of NCSE after open cardiac surgery is significant and frequently associated with brain injury. It seems prudent to perform EEG studies early to interrupt seizure activity and mitigate secondary cerebral injury.

Electroencephalography and delirium in the postoperative period

Delirium commonly manifests in the postoperative period as a clinical syndrome resulting from acute brain dysfunction or encephalopathy. Delirium is characterized by acute and often fluctuating changes in attention and cognition. Emergence delirium typically presents and resolves within minutes to hours after termination of general anaesthesia. Postoperative delirium hours to days after an invasive procedure can herald poor outcomes. Easily recognized when patients are hyperactive or agitated, delirium often evades diagnosis as it most frequently presents with hypoactivity and somnolence. EEG offers objective measurements to complement clinical assessment of this complex fluctuating disorder. Although EEG features of delirium in the postoperative period remain incompletely characterized, a shift of EEG power into low frequencies is a typical finding shared among encephalopathies that manifest with delirium. In aggregate, existing data suggest that serial or continuous EEG in the postoperative period facilitates monitoring of delirium development and severity and assists in detecting epileptic aetiologies. Future studies are needed to clarify the precise EEG features that can reliably predict or diagnose delirium in the postoperative period, and to provide mechanistic insights into this pathologically diverse neurological disorder.

The impact of an interdisciplinary electroencephalogram educational initiative for critical care trainees

PURPOSE

The purpose of this study is to evaluate the effectiveness of an interdisciplinary electroencephalogram (EEG) educational module for critical care training. Electroencephalogram is increasingly used for diagnosis, monitoring, and treatment decisions in critically ill patients with neurologic and nonneurologic disorders. Continuous EEG monitoring has an expanded role in the intensive care unit as an additional evaluation tool for critically ill patients with altered mental status.

MATERIALS AND METHODS

During a neurosurgical intensive care rotation, pulmonary critical care fellows participated in an EEG curriculum covering didactics, clinical exposure, and EEG interpretations. Using 25-question evaluation tools, including EEG interpretations, participants were assessed before EEG instruction and after curriculum completion.

RESULTS

Nine fellows completed the pilot study. Evaluation scores increased from 7.56±2.24 to 16.67±2.96 (P<.001).

CONCLUSIONS

An interdisciplinary approach was effective for increasing EEG knowledge in critical care fellows as measured by the assessment tools. As an added potential benefit, the pulmonary fellows also learned about sleep disorder-related EEG. This model can be replicated in other institutions for trainees of other specialties interested in critical care.