Identifying temporal patterns in trauma admissions: Informing resource allocation

Abstract

Background: Increased knowledge of the temporal patterns in the distribution of trauma admissions could be beneficial to staffing and resource allocation efforts. However, little work has been done to understand how this distribution varies based on patient acuity, trauma mechanism or need for intervention. We hypothesize that temporal patterns exist in the distribution of trauma admissions, and that deep patterns exist when traumas are analyzed by their type and severity.

Study design: We conducted a cross-sectional observational study of adult patient flow at a level one trauma center over three years, 7/1/2013-6/30/2016. Primary thermal injuries were excluded. Frequency analysis was performed for patients grouped by ED disposition and mechanism against timing of admission; in subgroup analysis additional exclusion criteria were imposed.

Results: 10,684 trauma contacts were analyzed. Trauma contacts were more frequent on Saturdays and Sundays than on weekdays (p<0.001). Peak arrival time was centered around evening shift change (6-7pm), but differed based on ED disposition: OR and ICU or Step-Down admissions (p = 0.0007), OR and floor admissions (p<0.0001), and ICU or Step-Down and floor admissions (p<0.0001). Step-Down and ICU arrival times (p = 0.42) were not different. Penetrating injuries peaked later than blunt (p<0.0001). Trauma varies throughout the year; we establish a high incidence trauma season (April to late October). Different mechanisms have varying dependence upon season; Motorcycle crashes (MCCs) have the greatest dependence.

Conclusion: We identify new patterns in the temporal and seasonal variation of trauma and of specific mechanisms of injury, including the novel findings that 1) penetrating trauma tends to present at later times than blunt, and 2) critically ill patients requiring an OR tend to present later than those who are less acute and require an ICU or Step-Down unit. These patients present later than those who are admitted to the floor. Penetrating trauma patients arriving later than blunt may be the underlying reason why operative patients arrive later than other patients.

Fig 1. Heatmap of trauma admissions by time of day versus day of week.

Each block of the heatmap represents a one hour block of one day of the week over the three year study period. The color corresponds to the relative frequency of contacts per hour as described by the color bar to the right of the image, where 1 represents the mean number of trauma contacts per hour. Weekend days have more trauma than weekdays, P<0.001. Mornings (4AM– 8AM) have less trauma than evenings (4PM– 8PM) on all days of the week, P<0.001.

Fig 2. Absolute frequency of trauma patients sent from the emergency department to each of these disposition by time of day.

Patients admitted to the floor peak earliest (red-dashed). Step-down (purple-dashed) and ICU (yellow-dashed) peak next during the day, and operative patients present latest.

Fig 3. Absolute frequency of trauma admissions versus time of day partitioned by blunt and penetrating and divided by injury severity score.

Fig 4. Smoothed, normalized relative trauma frequency per day throughout the year.

All trauma (blue) shows above-median trauma during mid year. Several of mechanisms of injury (see legend) are considered additionally. The first point marks the date (day 95: April 5^th) that this institution tends to see its median number of traumas. The second point (day 310: November 6^th) denotes the end of the above-median yearly peak in trauma contacts per day.