Adopting the pre-hospital index for interfacility helicopter transport: a proposal

Abstract

Background: Interfacility helicopter transport is expensive without proven outcome benefit in trauma patients. Our objectives were to determine the fastest method of rural to urban interfacility transport, and develop a triage tool to identify patients most in need of rapid transport. Methods: Retrospective cohort study. Adults ISS≥12 transported from January 1996 to December 1998. Transport time variables were compared between geographical zones. A pre-transport index (PTI) identified two patient cohorts in which outcome was assessed. Results: Air ambulance was faster than ground transport, with helicopter overall superior to fixed-wing (<225 km range). Seventy-two percent of patients with PTI<4 (n=196) had no outcome indicating severe injury versus 29% of the PTI≥4 cohort (n=151). Mortality for PTI<4 was 1.4% versus 22% for PTI≥4. Conclusion: Interfacility helicopter transport of severely injured rural trauma patients was the overall fastest method within a 225 km range. PTI>4 identifies patients most in need of this fast but expensive method of transport.

Introduction

The need to provide rapid access to tertiary care for critically injured patients from both urban and rural locations is an essential element of a regionalized trauma care system [1], [2], [3]. Approximately 70% of trauma deaths occur in rural areas with an average death rate for rural trauma patients twice as high as for patients in urban centers [4], [5], [6]. The American College of Surgeons Committee on Trauma has stated that, “in any trauma system, the goal is to transport the injured patient to definitive care in the shortest possible time” [1]. Implicit in this position, and given the relatively higher mortality of rural trauma patients, it is an imperative for regional trauma centres receiving patients from rural centres to identify the best method of transfer [7], [8].

Studies supporting the use of helicopters in air ambulance programs have identified two major factors contributing to improved patient outcome: level of skill provided by the transport team and shorter transport times to definitive care [9], [10], [11]. However, helicopters are an expensive resource, limiting their use in many jurisdictions. Fixed-wing and ground transport with similar equipment and staff may offer equivalent care and outcome but with less cost. Although studies have explored the association of transport team composition, none have analyzed the time elements involved in a rural to tertiary care transportation system [12]. An analysis of these time elements may be useful in determining the most effective method of transport and for quality assurance within existing systems.

Effective triage and transport of a trauma patient is a complex process of appropriately allocating resources for each patient situation. For rural trauma patients, these decisions include which patient, what method of transport (ground versus fixed-wing versus helicopter), and whether the patient should be triaged to a secondary (local) or tertiary (level 1) trauma centre. Unfortunately, standardized criteria to assist in these triage decisions do not exist. Attempts have been made to facilitate decision making using patient-based survey systems [13]. The most widely used pre-hospital scoring systems in the past have been the trauma score and revised trauma scores [14], [15]. A more recent revision of the trauma score, the pre-hospital index (PHI), is currently used by several trauma systems in Canada. Its accuracy in conjunction with mechanism of injury criteria has recently been published [16], [31].

As indicated by name, the PHI is intended for use by pre-hospital personnel at the scene of an accident. The situation for rural trauma patients is unique in that a qualified physician makes triage decisions for transport to tertiary care in the setting of a rural hospital emergency department, often after initial resuscitation measures. A more representative assessment of the severity of injury of a trauma patient in a rural hospital would be a ‘pre-transport’ evaluation, rather than a ‘pre-hospital’ evaluation.

The objectives of this study were: (1) to explore time related elements involved in the interfacility transfer of critically injured patients from rural hospitals to regional tertiary care (level 1) trauma centers, and to determine the fastest method of transport for any trauma patient injured at a distance from the trauma center; and (2) to develop and test a triage tool, the pre-transport index (PTI), which would allow us to identify those patients with severe injury who require the most rapid transport to a level 1 trauma center.