2258. Correlation of Electroencephalogram Findings and Dose Relative to Renal Function among Patients with Possible Cefepime-Induced Encephalopathy

BACKGROUND: Cefepime-induced encephalopathy (CIE) is thought to be a rare toxicity, with an overall incidence of <1%. However, the low incidence may be a result of under-recognition and difficulty in identifying the exact etiology of encephalopathy in hospitalized patients. Among patients with suspected CIE, electroencephalograms (EEGs) sometimes show abnormal activity like triphasic waveforms (TPWs). We asked whether the incidence of EEG findings consistent with CIE varies with cefepime (CFP) dose relative to eGFR (dose/eGFR). We also compared the incidence of these EEG findings in patients receiving CFP to the incidence in patients receiving piperacillin–tazobactam (PT). METHODS: In a retrospective analysis, data between 8/1/2016 and 5/24/2018 were extracted from the University of Chicago Clinical Data Warehouse. Patients 20–79 years old who received PT or CFP were included; those requiring renal replacement therapy or who had eGFR <10 mL/minute/BSA at baseline were excluded. The average daily dose of PT or CFP was calculated to determine dose/eGFR. Linear or logistic regressions were performed in STATA. RESULTS: EEGs were obtained in 66 (4.3%) of 1525 patients receiving CFP and in 28 (3.3%) of 842 receiving PT. TPWs were present in 19 (28%) of EEGs from the CFP group, and in none of the EEGs from the PT group. Figure 1 shows the correlation between CFP dose/eGFR ratio and occurrence/severity of TPWs. Ordered logistic regression analysis identified a coefficient of 20.9 (95% CI; 3.7–38.2). Figure 2 shows only a weak association between CFP dose/eGFR and background frequency (BFS; R2 = 0.05). In the PT group, BFS was not correlated with PT dose/eGFR (R2 = 0.01). CONCLUSION: TPWs were more likely to be found in patients receiving CFP than PT, suggesting that in the absence of other metabolic abnormalities, TPWs might be specific for CFP. Higher CFP dose-to-eGFR ratios predispose to and potentially worsen the severity of TPWs. Unlike TPWs, BFS was only weakly associated with CFP dose/eGFR and even less associated with PT dose/eGFR ratio. [Image: see text] [Image: see text] DISCLOSURES: All authors: No reported disclosures.