To evaluate the utilization of the surgical step-down unit (SSDU) by a sample of patients who were preoperatively booked for admission to the unit, and to identify those patient characteristics and perioperative variables that are associated with an intervention in the unit.

Retrospective chart review.

Canadian tertiary-care facility.

Data from 133 elective surgery patients with prebooked SSDU beds were recorded, including comorbidities, Surgical Risk Scale (SRS), Surgical Apgar Score (SAS), and number and nature of interventions and events occurring in the SSDU.

Of the 133 patients scheduled for SSDU admission, 60 (45.1%) were actually admitted and the other 73 (54.9%) were admitted directly to the surgical ward or else discharged. Of the patients admitted to the SSDU, 48.3% had an intervention during their stay. In logistic regression, the SRS was a significant predictor (P < 0.001) of SSDU use, while the SAS was a significant predictor (P = 0.034) of the need for an intervention or the likelihood of an event while in the SSDU.

Less than half of patients identified were actually admitted to the SSDU postoperatively; of those, less than half required an intervention. The Surgical Apgar Score, a score based on intraoperative factors, predicted the need for an intervention during SSDU admission. Consideration should be given to the development of a predictive score that emphasizes intraoperative factors and early postoperative factors to optimize allocation of this scarce resource.