Characteristics of delirium and its association with sedation and in-hospital mortality in patients with COVID-19 on veno-venous extracorporeal membrane oxygenation

BACKGROUND: Veno-venous extracorporeal membrane oxygenation (VV-ECMO) has been used in patients with COVID-19 acute respiratory distress syndrome (ARDS). We aim to assess the characteristics of delirium and describe its association with sedation and in-hospital mortality. METHODS: We retrospectively reviewed adult patients on VV-ECMO for severe COVID-19 ARDS in the Johns Hopkins Hospital ECMO registry in 2020–2021. Delirium was assessed by the Confusion Assessment Method for the ICU (CAM-ICU) when patients scored−3 or above on the Richmond Agitation-Sedation Scale (RASS). Primary outcomes were delirium prevalence and duration in the proportion of days on VV-ECMO. RESULTS: Of 47 patients (median age = 51), 6 were in a persistent coma and 40 of the remaining 41 patients (98%) had ICU delirium. Delirium in the survivors (n = 21) and non-survivors (n = 26) was first detected at a similar time point (VV-ECMO day 9.5(5,14) vs. 8.5(5,21), p = 0.56) with similar total delirium days on VV-ECMO (9.5[3.3, 16.8] vs. 9.0[4.3, 28.3] days, p = 0.43). Non-survivors had numerically lower RASS scores on VV-ECMO days (−3.72[−4.42, −2.96] vs. −3.10[−3.91, −2.21], p = 0.06) and significantly prolonged delirium-unassessable days on VV-ECMO with a RASS of −4/−5 (23.0[16.3, 38.3] vs. 17.0(6,23), p = 0.03), and total VV-ECMO days (44.5[20.5, 74.3] vs. 27.0[21, 38], p = 0.04). The proportion of delirium-present days correlated with RASS (r = 0.64, p < 0.001), the proportions of days on VV-ECMO with a neuromuscular blocker (r = −0.59, p = 0.001), and with delirium-unassessable exams (r = −0.69, p < 0.001) but not with overall ECMO duration (r = 0.01, p = 0.96). The average daily dosage of delirium-related medications on ECMO days did not differ significantly. On an exploratory multivariable logistic regression, the proportion of delirium days was not associated with mortality. CONCLUSION: Longer duration of delirium was associated with lighter sedation and shorter paralysis, but it did not discern in-hospital mortality. Future studies should evaluate analgosedation and paralytic strategies to optimize delirium, sedation level, and outcomes.