A large-scale study reveals 24-h operational rhythms in hospital treatment

Hydralazine order and first-dosing times were nonuniformly distributed over 24 h [Kuiper's test (3), P 0.01], marked by distinct morning-time surges and overnight lulls (Figure 1). Nearly twice as many treatments were ordered between 8:00 AM and 6:00 PM (2,842) compared to 10:00 PM and 8:00 AM (1,652). The profiles were described by 24-h rhythms using 3 separate detection methods [cosinor analysis (4), Jonckheere-Terpstra-Kendall (JTK)_CYCLE (5, 6), and Rhythmicity Analysis Incorporating Nonparametric (RAIN) (7), P 0.05] (Figure 1B and Dataset S1). The morning surge in hydralazine order times coincides with team rounding and a medical staff shift change (Figure 1C). Caretaker shifts at our institution include 7:00 AM to 7:00 PM, 7:00 AM to 3:00 PM, and 7:00 PM to 7:00 AM shifts.