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Sedation Variability Increases Incidence of Delirium in Adult Medical Intensive Care Unit Patients at a Tertiary Academic Medical Center

Ritchie, Brianne M., PharmD, MBA, BCPS1,*; Torbic, Heather, PharmD, BCPS2; DeGrado, Jeremy R., PharmD, BCPS, BCCCP3; Reardon, David P., PharmD, BCPS4

doi: 10.1097/MJT.0000000000000455
Brief Reports

Background: Variability in sedation may increase the incidence of delirium and mortality, as well as increased intensive care unit (ICU) and hospital lengths of stay (LOS), despite mean Richmond Agitation Sedation Scale (RASS) scores at goal. Coefficient of variation (CV) can be used to represent variability with a higher ratio indicating increased variability.

Study Question: Do patients with an increased variability in sedation, as evaluated by CV in RASS, have an increased incidence of delirium?

Methods: We conducted a retrospective chart review of adult medical ICU patients requiring mechanical ventilation (MV) for ≥24 hours between January and April 2013. Patients were excluded if intubated at an outside hospital, neuromuscularly blocked, suffering from anoxic brain injury, or had a goal RASS of −4 or −5. Outcomes assessed included the presence of delirium, as evaluated by the Confusion Assessment Method, RASS, CV in RASS, duration of MV, ICU, and hospital LOS, and survival.

Results: Of 45 included patients, 32 experienced delirium during their ICU admission and 13 did not. The groups were similar at baseline. There was no difference in mean RASS when comparing the delirium and nondelirium groups (−1.6 ± 1.3 vs. −1.8 ± 0.8, respectively; P = 0.61). Patients with delirium had a greater CV in RASS (0.3 ± 0.135 vs. 0.2 ± 0.105; P = 0.02), a longer MV duration [4 (2–8) vs. 3 (2–3) days; P = 0.045], and a trend toward increased ICU LOS [8 (5–12.25) vs. 4 (3–8) days; P = 0.096], but no difference in hospital LOS [13 (10–25) vs. 18 (9–39) days; P = 0.83] and survival (71.9% vs. 69.2%; P = 1.0).

Conclusion: Medical ICU patients with delirium had a higher CV in RASS compared with patients without delirium, suggesting that greater variability in sedation may increase the incidence of delirium. Patients with delirium also had a greater duration of MV and a trend toward longer ICU LOS.

1Department of Pharmacy, Mayo Clinic, Rochester, MN;

2Department of Pharmacy, Cleveland Clinic, Cleveland, OH;

3Department of Pharmacy, Brigham and Women's Hospital, Boston, MA; and

4Department of Pharmacy, Yale-New Haven Hospital, New Haven, CT.

Address for correspondence: Critical Care Clinical Pharmacist, Department of Pharmacy, Mayo Clinic, Saint Mary's Campus, 1216 Second St SW, Rochester, MN 55902. E-mail:

The authors have no conflicts of interest to declare.

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