Objectives: Paramedic-initiated turndowns-to-BLS are a high-risk area for EMS. One non-clinical factor that might affect paramedics’ decision-making is a 24-hour work schedule. We attempted to determine the presence of circadian variation in the turndown rate from ALS to BLS when paramedics work 24-hour shifts.

Methods: Retrospective analysis of all 1994 ALS patient evaluations. Encounters were classified as: ALS transport; turndown-to-BLS; patient-initiated refusal of transport; other transport; field death. Analysis of variation in turndown rate by hour of ALS dispatch was performed using logistic regression to make paired comparisons for each hour.

Results: 17,877 patients were evaluated by ALS. Of these, 10,956 (61%) were ALS transports, 6,200 (35%) were not transported by ALS, and 721 (4%) were dead. Of the 6,200 alive non-ALS transports, 4,291 (69%) were turned down to BLS, 1,748 (28%) refused transport, and 161 (3%) were transported by others. One turndown-to-BLS was excluded due to missing dispatch time; for the remaining 4,290 the overall turndown rate was 25%. The turndown rates for 15 of 24 hours did not differ significantly (p >0.01) from any other hour. The rates at the following hours differed significantly: hour 3 < 13; hour 5 < 8,9,10,13,16,22; hour 9 > 20,22; hour 10 > 22; hour 13 > 20,22; hour 16 > 20,22.