Abstract & Commentary
Efficacy of Continuous EEG Monitoring in Critical Care Units
By Elayna Rubens, MD
Assistant Professor of Neurology, Weill Cornell Medical College
Dr. Rubens reports no financial relationships relevant to this field of study.
This article originally appeared in the February issue of Neurology Alert.
SOURCE: Utilization of continuous EEG monitoring in mechanically ventilated patients in the ICU was associated with a reduction in hospital mortality without sigificantly affecting hospital costs or length of stay.
SYNOPSIS: Ney JP, et al. Continuous and routine EEG in intensive care. Neurology 2013;81:2002-2008.
As the technology for obtaining, storing, and reviewing digital EEG has expanded over the last 10 years, so has the utilization of continuous electrocencephalography monitoring (cEEG). In the ICU setting, cEEG has become an important tool in the diagnosis and management of non-convulsive seizures, status epilepticus, and other changes in cerebral function such as ischemia. With its increased utilization, controversy has emerged about the cost effectiveness of cEEG and its overall impact on patient outcome. In this study, Ney et al examined the effect of cEEG monitoring in critically ill patients on inpatient mortality, length of stay, and hospital charges.
This is a retrospective, cross-sectional study conducted using data from the Nationwide Inpatient Sample (NIS), the largest all-payer inpatient database containing clinical and demographic information from approximately 20% of all discharges from non-federal U.S. hospitals. All patients who underwent mechanical ventilation and EEG (either cEEG or routine EEG) between 2005-2009 were included in the study. In-hospital mortality was the primary outcome measure, while length of stay and hospitalization charges were secondary outcomes. The group undergoing cEEG was compared to the group that had routine EEG alone for all outcome measures. Multivariate regression analysis included comorbidities, demographics, and hospital variables. In addition, separate subgroup analysis was performed on groups of patients with epilepsy/seizure diagnosis, neurologic diagnosis, or EEG performed on the day of discharge.
A total of 40,945 inpatient discharges were included in the analysis. Of these, 5949 underwent cEEG monitoring and 34,996 underwent routine EEG only. The group undergoing cEEG was significantly younger, less likely to have Medicare, and more likely to have a neurologic or epilepsy diagnosis. Hospitals performing cEEG were more likely to be larger, academic centers. The use of cEEG increased dramatically from 2005 to 2009 (by 263%). Inpatient mortality in ventilated patients receiving cEEG was significantly reduced when compared to patients undergoing routine EEG only (25% vs 39%; odds ratio [OR], 0.54) even when adjusting for demographics, hospital characteristics, and comorbidities (OR, 0.63; P < 0.001). Total hospital charges and length of stay tended to be increased in the cEEG group compared to the routine EEG group, but were not significantly different. Subgroup analysis of patients with neurologic/epilepsy diagnosis revealed that these diagnoses were more common in the cEEG group and were positively associated with survival. Routine EEG performed on the day of discharge was highly associated with mortality, since EEG is used to confirm brain death in some hospitals. When any of these subgroups was used as a covariate in the analysis, or excluded from the multivariate regression calculations, there was no change in the association between cEEG and inpatient mortality.
The authors concluded that cEEG monitoring in ICU patients is associated with improved patient survival compared to routine EEG alone. They propose that the survival benefit stems from the ability to detect and, therefore, treat brain dysfunction more accurately and responsively with cEEG monitoring. In addition, the study found no significant increase in hospitalization cost or length of stay in those patients undergoing cEEG monitoring. Together, these results support the use of cEEG monitoring in the ICU setting as a clinically valuable and potentially cost-effective tool.
COMMENTARY
Previous research on cEEG monitoring in critically ill patients has focused on the diagnostic value of cEEG monitoring and its role in modifying ICU management and clinical decision-making. Such research has demonstrated that the diagnostic effectiveness of cEEG monitoring in critically ill patients exceeds that of routine EEG. It is now well established that utilizing cEEG monitoring in the ICU leads to change in management in a significant number of patients. The current study is an important contribution to the cEEG literature, as it takes the impact of cEEG a step further: patient outcome. By demonstrating an association of cEEG with improved survival in a large cohort of patients, the authors are able to provide further justification for cEEG monitoring and its implicit resource utilization among critically ill patients.
The study's design as a retrospective study allowed the researchers to obtain a large enough sample size to test outcome-based hypotheses. The limitations of the design, however, are that the results cannot be used to infer causation. There may be a number of alternative explanations (differences between comparison groups, improvement in ICU care concurrent with cEEG utilization, etc.) for the association of cEEG with improved survival, only some of which can be adequately adjusted for in the data analysis. Further prospective studies of cEEG in critically ill patients are needed to confirm the survival benefits and cost effectiveness of cEEG monitoring.
EDITOR's COMMENTARY
David J. Pierson, MD
The authors' examination of data from the 2005-2009 Nationwide Inpatient Sample showed that mechanically ventilated patients who received cEEG monitoring had 36% lower in-hospital mortality compared to those who received routine EEGs only (25% vs 39%; OR, 0.54; 95% confidence interval [CI], 0.45-0.64; P < 0.001). After adjustments for patient demographics, hospital characteristics, comorbidities, and other factors by multivariate regression, the association persisted, with an OR of 0.63 (95% CI, 0.52-0.76; P < 0.001). Ney et al posit that the survival benefit may result from the ability to detect and treat brain dysfunction more accurately and responsively with cEEG monitoring. This is plausible, but the magnitude of the observed effect on survival is enormous: consider the effect sizes produced by other major breakthroughs in critical care during the last 20 years. I think the authors' statement that "our analysis has important implications for clinical care and health care policy" warrants clarification.
The subspecialty of neurocritical care is one of the newest in our field, its professional society and dedicated journal having been founded only in 2002 and 2004, respectively, and the first neurocritical care certifications having been issued in 2007. The period covered by the data in the present study was one of rapid increases in the numbers of neuro-ICUs, specialist physicians and nurses, guidelines for management of neurological critical illness, and other aspects of management — along with documentation of improved patient outcomes in several conditions. It was a time of dramatic advances in the care of patients with neurological injury, including as the authors point out a huge, steady increase in cEEG usage. A great deal was changing in addition to how patients were being monitored. This context presents a formidable challenge in any attempt to account for all potential confounders affecting an observed difference between retrospectively identified patient groups.
Thus, while the findings of this study are heartening, as with other retrospective, observational studies they can more confidently be used for hypothesis generation than for statements about causation. Ney et al acknowledge this, concluding that, "if confirmed in well-designed, prospective clinical studies, would indicate that the use of this emerging technology should be encouraged by health policymakers."
