Factors influencing on-scene time in a rural Norwegian helicopter emergency medical service: a retrospective observational study

Abstract

Background: Critically ill patients need to be immediately identified, properly managed, and rapidly transported to definitive care. Extensive prehospital times may increase mortality in selected patient groups. The on-scene time is a part of the prehospital interval that can be decreased, as transport times are determined mostly by the distance to the hospital. Identifying factors that affect on-scene time can improve training, protocols, and decision making. Our objectives were to assess on-scene time in the Helicopter Emergency Medical Service (HEMS) in our region and selected factors that may affect it in specific and severe conditions.

Methods: This retrospective cohort study evaluated on-scene time and factors that may affect it for 9757 emergency primary missions by the three HEMSs in western Norway between 2009 and 2013, using graphics and descriptive statistics.

Results: The overall median on-scene time was 10 minutes (IQR 5-16). The median on-scene time in patients with penetrating torso injuries was 5 minutes (IQR 3-10), whereas in cardiac arrest patients it was 20 minutes (IQR 13-28). Based on multivariate linear regression analysis, the severity of the patient's condition, advanced interventions performed, mode of transport, and trauma missions increased the on-scene time. Endotracheal intubation increased the OST by almost 10 minutes. Treatment prior to HEMS arrival reduced the on-scene time in patients suffering from acute myocardial infarction.

Discussion: We found a short OST in preselected conditions compared to other studies. For the various patient subgroups, the strength of association between factors and OST varied. The time spent on-scene and its influencing factors were dependent on the patient's condition. Our results provide a basis for efforts to improve decision making and reduce OST for selected patient groups.

Conclusions: The most important factors associated with increased on-scene time were the severity of the patient's condition, the need for intubation or intravenous analgesic, helicopter transport, and trauma missions.

Keywords: Air ambulances; Emergency medical services; First hour quintet; Helicopter; Hems; Norway; On-scene time; Scene time.

Fig. 1

Flow chart showing all primary HEMS dispatches, with excluded and completed missions. Primary missions were defined as responses to patients outside hospitals. ^aDeclined dispatches or aborted missions were due to medical indication no longer being present, weather, concurrent missions, unable to perform a flight, or other reasons; 109 of the declined and 33 of the aborted missions (total 0.8% of the dispatches) were transferred to another HEMS in the area. Therefore, these incidents are reported as two separate dispatches. ^bThe characteristics of the 41 entrapped patients are presented in Additional File 1. ^cHEMS base very close to the incident, completed without using a vehicle

Fig. 2

On-scene times and distribution of GCS and NACA in primary emergency missions (N = 9757). The boxes illustrate median, quartile 25 and quartile 75 on-scene times for the various values of Glasgow Coma Scale (GCS) values and National Advisory Committee for Aeronautics (NACA) scores. Whiskers indicate 5-, and 95-percentile. Missing GCS values (n = 5436) were replaced with a normal value (GCS = 15)

Fig. 3

Distribution of on-scene time in cardiac arrest (N = 659) and penetrating torso injuries (N = 57). The overall median refers to the median OST in the five subgroups, 11 min. Patients suffering cardiac arrest were in most cases transported after ROSC were achieved. In a few cases, transported was initiated with continuous CPR using a chest compression device

Fig. 4

On-scene time and affecting factors (dichotomous) in subgroups of primary emergency missions with patient encounter (N = 2372). The subgroups included patients with a NACA score of 4–6 only. “Median of all included patients” refers to the median OST, 9 min, in all patients in subgroups except cardiac arrest (top panel). In the cardiac arrest subgroup, 647 (94.7%) patients were classified by a NACA score of 6. Patients suffering cardiac arrest were in most cases transported after ROSC were achieved. In these patients, a low NACA or a high GCS indicates successfully resuscitation before HEMS arrived, as our GCS and NACA variable describes the patient’s condition during HEMS patient care. In a few cases, transported was initiated with continuous CPR using a chest compression device