Delirium in the ICU: Best sedation practices lead to the best outcomes
Which sedation agent to choose?
While the negative effects of benzodiazepine-based sedation are well established, the optimal sedation agent remains unclear. Several other drugs are commonly used in the ICU, including propofol, dexmedetomidine, and opioid agents such as fentanyl and morphine. Propofol and dexmedetomidine are used specifically for their sedative properties, though they have dramatically different effects on the depth of sedation and different mechanisms of action. Opioid agents are most commonly used for their analgesic effect; however, in higher doses or combined with other medications, they have the secondary effect of inducing sedation. No particular sedation agent, however, beyond the avoidance of benzodiazepines has been recommended for use in the most recent guidelines. In the PRODEX and MIDEX studies, dexmedetomidine was noninferior to both midazolam and propofol in achieving targeted light to moderate sedation, and dexmedetomidine was associated with a shorter duration of mechanical ventilation compared to midazolam (Jakob SM et al. JAMA. 2012;307[11]:1151-60). More recently, the SPICE-III trial studied dexmedetomidine vs. usual care and found no difference in 90-day mortality (Shehabi Y et al. N Engl J Med. 2019;380[26]:2506-17).
In choosing the best sedation agent to avoid delirium, the largest and most applicable trial to date is the “Maximizing the Efficacy of Sedation and Reducing Neurological Dysfunction and Mortality in Septic Patients with Acute Respiratory Failure,” or MENDS2 trial (Hughes CG et al. N Engl J Med. 2021;384:1424-36). This study was a double-blind, multicenter randomized controlled trial of dexmedetomidine vs propofol in critically ill patients with sepsis receiving mechanical ventilation. The primary outcome was days alive without delirium or coma over the 14-day intervention period. The study enrolled 438 patients between 13 sites, with 422 patients receiving either dexmedetomidine or propofol. Hughes and colleagues found no difference in the primary outcome of days alive without delirium or coma between the dexmedetomidine and the propofol arms. The study also found no difference in secondary outcomes, including ventilator-free days, 90-day mortality, and 6-month global cognition, as well as no difference in safety endpoints. Importantly, there was excellent compliance with guideline-recommended practices of spontaneous awakening and breathing trials and early mobility, both of which are associated with reduced sedation exposure. The study did have some notable nuances, however. The overall doses of trial drugs were relatively low, and there was a moderate use of rescue sedation. There was also a small amount of crossover use of propofol and dexmedetomidine between treatment arms (10%), although the authors note that this was lower than in prior related studies. Overall, the MENDS2 study suggests there is likely clinical equipoise between propofol and dexmedetomidine in terms of delirium outcomes when combined with best practices, such targeted light sedation, paired awakening and breathing trials, and early mobility.
How should we manage sedation to prevent delirium?
Building off of the recent MENDS2 study and earlier work in the field, along with the 2018 PADIS guidelines, the general paradigm of sedation management should be focused on using light sedation with sedation interruptions to minimize overall sedation exposure. Based on the best available evidence to date, targeting less overall sedation leads to improved outcomes in critically ill patients, including mortality and duration of mechanical ventilation. Benzodiazepines should be avoided due to their association with delirium, but currently there is no evidence to suggest one nonbenzodiazepine sedative is better than another. Intensivists can feel comfortable choosing between agents based on a patient’s individual clinical needs, especially when patients are receiving paired spontaneous awakening and breathing trials and early rehabilitation. These same principles should be applied to sedation management and delirium patients in COVID-19 patients as well. While certain circumstances will necessitate deeper sedation at times (e.g., refractory hypoxemia due to ARDS from COVID-19), clinicians should continually reassess the actual sedation needs of the patient with the goal of reducing overall sedation. Focusing effort on these evidence-based practices will help reduce the incidence of delirium and ultimately improve patient outcomes.
Dr. Mart is with the Division of Allergy, Pulmonary, and Critical Care Medicine, Vanderbilt University Medical Center; Critical Illness, Brain Dysfunction, and Survivorship (CIBS) Center; and VA Tennessee Valley Healthcare System Geriatric Research Education and Clinical Center (GRECC), Nashville, Tennessee.
