Ambient light levels and critical care outcomes

Purpose: Guidelines for the construction of critical care units require windows in room design to ensure a contribution of natural sunlight to ambient lighting. However, few studies have been published with evidence assessing this recommendation. We investigated the association of ambient light levels with clinical outcomes and sedative/analgesic/neuroleptic use in a medical intensive care unit (MICU). Methods: This is a retrospective, observational study at a tertiary care facility with a 29-bed MICU. First/single MICU admissions between April 19, 2006, and June 30, 2009 (N = 3577), were analyzed with respect to clinical outcomes and sedation use according to MICU room orientation and corresponding light levels. Results: Light levels were low but varied among the 4 room orientations. There were no significant differences in MICU mortality (north, 14.0%; east, 13.5%; west, 16.2%; south, 15.6%; P = .451), hospital mortality (20.8%, 20.9%, 22.2%, 22.3%; P = .796), 28-day intensive care unit-free days (17.6 ± 10.2, 18.0 ± 10.1, 17.7 ± 10.5, 17.2 ± 10.4; P = .555), 28-day ventilator-free days (16.3 ± 11.1, 16.5 ± 11.1, 15.5 ± 11.5, 15.4 ± 11.4; P = .273). No clinically significant differences in intravenous sedative/analgesic use occurred across room orientations. Conclusions: Despite differing ambient light, room orientation was not associated with critical care outcomes or differences in sedative/analgesic/neuroleptic use. Current guidelines positing that windows alone are necessary or sufficient for MICU room light management may require further investigation and consideration.