Impact of Non-Optimal Transfer Strategy On Rapid Emergency Medicine Score For Emergent Interfacility Transfers By Air Ambulance In Ontario

Abstract

Introduction Ornge is the sole air ambulance service in Ontario, Canada and provide interfacility transfers for severely ill patients. Sometimes the closest aircraft or most optimal resource is unavailable resulting in a transport delay. These patients may experience a clinical deterioration as a result. The primary objective of this study is to determine if a non-optimal transfer strategy is associated with a clinical deterioration as measured by a change in Rapid Emergency Medicine Score (REMS) compared to patients with an optimal transfer strategy. The secondary objective was to determine which factors were associated with a non-optimal transfer strategy. Methods This was a retrospective population-based cohort study using a health administrative database looking at all emergent adult interfacility transfers over a 5-year period. All interfacility transfers during that time were analyzed by sending-receiving pair and mean overall transport times calculated for reach unique resource to determine the fastest and most utilized resource for each sending-receiving pair. An optimal transfer strategy was defined by three conditions 1) the resource used was both the fastest and most utilized 2) the fastest fixed-wing resource if distance was greater than 240 km or 3) the fastest rotor-wing resource if distance was less than 240 km. The primary outcome, delta REMS was calculated by subtracting the REMS at time of request from the REMS at time of paramedic arrival. Therefore an increase in delta REMS would correlate with a clinical deterioration of a patient. Descriptive statistics were performed on patient, paramedic, institutional and time-level factors. A generalized linear model was used to determine the effect of transfer strategy on change in REMS score while adjusting for the other variables of interest and accounting for clustering by sending facility. For the secondary outcome a logistic regression model was used to explore factors associated with a non-optimal transfer strategy. Results The final study cohort included 9,687 patients and the median delay in interfacility transfer caused by a non-optimal transfer strategy was 35.7 minutes. Transfer strategy did not significantly affect change in REMS (beta coefficient 0.002; 95% CI: -0.08 - 0.82) in the adjusted linear regression model. The only patient characteristic found to be associated with a change in REMS in both the unadjusted and adjusted analysis was whether the patient was mechanically ventilated. Paramedic level of care of advanced (OR 0.37; 95% CI: 0.22 - 0.63) and critical care (OR 0.28; 95% CI: 0.16 - 0.49) as well as spring season (OR 0.75; 95% CI: 0.66 - 0.84) had lower odds of non-optimal transfer strategy in the generalized logistic regression model. Additionally, nursing stations had higher odds of non-optimal transfer strategy (OR 2.84; 95% CI: 1.19 - 6.83). Conclusion In conclusion, in this study population a non-optimal transfer strategy for air ambulance interfacility transfers did not result in patient deterioration as measured by a change in REMS score. Additionally, decreasing sending facility size was associated with higher odds of non-optimal transfer strategy while patients on a ventilator, requiring advance or critical care level of care and spring season had lower odds of non-optimal transfer strategy.