Abstracts

Rationale: On the ictal-interictal continuum (ICC), generalized periodic discharges (GPDs) with triphasic morphology (“triphasic waves”) have traditionally been thought of as a mostly benign electrographic pattern that is the result of metabolic derangements. Recent studies have suggested, however, that they may be a biomarker of ongoing neuronal damage and may even warrant an anticonvulsant trial.(1) Specifically, Sutter et al. has postulated that GPDs with triphasic morphology are frequently linked to a triad of metabolic, infectious and structural comorbidities.(2) Our study seeks to externally validate both O’Rourke’s and Sutter’s work on outcomes and comorbidities(1,2). To date, there is very little data to validate Sutter’s proposed triad. In addition, treatment outcomes with anticonvulsants for GPDs with typical triphasic morphology are not well-established.

Methods: We are conducting an ongoing retrospective case series of adult critically ill patients who were found to have GPDs with typical triphasic morphology, as validated by two epileptologists, who have undergone at least 24 hours of continuous EEG monitoring without seizures. We are looking at how many components of Sutter’s triad where present for our primary outcome—mortality. These patients are further being characterized by anticonvulsant treatment, length of hospital stay, APACHE2 scores (3) and Modified Rankin Scale (MRS) at discharge. We will have an additional cohort of patients matched by APACHE2 scores as a control.

Results: In our preliminary cohort of 33 patients, 30% had all three of Sutter’s triad, while 67% had two of three, while only 3% had only one. Total in-hospital mortality was 57.6%, which is near the APACHE2-predicted rate of 57.0%. 69% of patients were treated with anticonvulsants. Of the 22 patients who received anticonvulsants, mortality was 68%, while mortality was only 36% among those who were not treated. While mortality was higher among those who received treatment, there were more patients in this group who were discharged with a good outcome, as defined by MRS (Fig. 1).

Conclusions: Our results in this preliminary series of 33 ICU patients with triphasic waves roughly mirror those of Sutter, demonstrating that GPDs with triphasic morphology are associated with high morbidity and mortality, as well as at least two of three of Sutter’s triad. In our population, treatment with anticonvulsants did not appear to improve mortality, but may have been associated with improved functional outcomes. Further work will focus on recruiting a larger cohort, as well as a second matched ICU cohort without triphasic waves.

Sources:
1. O'Rourke D, Chen PM, Gaspard N, Foreman B, McClain L, Karakis I, Mahulikar A, Westover MB. Response rates to anticonvulsive trials in patients with triphasic-wave EEG patterns of uncertain significance. Neurocritical Care. 2016;24:233-239

2. Sutter R, Stevens RD, Kaplan PW. Significance of triphasic waves in patients with acute encephalopathy: A nine-year cohort study. Clinical Neurophysiology. 2013;124:1952-1958

3. Knaus WA, Draper EA, Wagner DP, Zimmerman JE. Apache II: a severity of disease classification system. Critical Care Medicine. 1985;13:818-829

Funding: Please list any funding that was received in support of this abstract.: None.