Elsevier

Injury

Volume 43, Issue 9, September 2012, Pages 1362-1367
Injury

The effect of Helicopter Emergency Medical Services on trauma patient mortality in the Netherlands

https://doi.org/10.1016/j.injury.2012.01.009Get rights and content

Abstract

Introduction

Object of this study was to evaluate the effect of the Helicopter Emergency Medical Services (HEMS) on trauma patient mortality and the effect of prehospital time on the association between HEMS and mortality.

Materials and methods

Trauma patients admitted to a level 1 trauma centre and treated on-scene by the HEMS and Emergency Medical Services (EMS) between 2003 and 2008 were included (n = 186). A control group treated by EMS only (n = 186) was created by matching on ISS, age and severe traumatic brain injury (TBI). Mortality was compared by calculating odds ratios (OR) and numbers needed to treat (NNT), with adjustment for prehospital coded Revised Trauma Score. The effect of prehospital time mortality was tested by a logistic regression. Analyses were made for patients with and without TBI.

Results

The OR of early trauma fatality for the HEMS/EMS versus EMS-only groups was 0.8 for patients both with TBI (95% CI 0.4–1.7; NNT: 22) and without TBI (95% CI 0.2–3.3; NNT: 273). The risk of in-hospital mortality was non-significantly higher for patients with TBI in the HEMS/EMS group (OR = 1.3; 95% CI 0.6–2.7; NNT: −15) compared to the EMS-only group and non-significantly lower for patients without TBI (OR = 0.9; 95% CI 0.3–2.5; NNT: 129). After adjustment for prehospital time, the risk of early trauma fatality for patients with TBI treated by the HEMS decreased (OR = 0.6; 95% CI 0.3–1.6). The risk of in-hospital mortality for these patients decreased from 1.3 to 0.8 (95% CI 0.4–2.0). The effect of the HEMS on patients without TBI did not change after adjustment for prehospital time.

Discussion

HEMS treatment is associated with a non-significantly higher risk of in-hospital mortality for patients with TBI and a non-significantly lower risk for patients without TBI. This increased risk of mortality in TBI patients is attributable to the increased prehospital time. These results indicate that HEMS does not have a positive impact on survival.

Introduction

In the Netherlands, all emergency medical services (EMS) are staffed by paramedics who have years of clinical experience and education (e.g., in intensive care or emergency medicine), supplemented with three additional years of specific ambulance training. All paramedics are Pre-Hospital Trauma Life Support (PHTLS) certified. Since 1997, in addition to the EMS, Helicopter Emergency Medical Services (HEMS) have been available to provide on-scene assistance to trauma patients. The aim of the HEMS is to provide an on-demand upgrade to standard care at the scene to improve the outcome of severely injured patients. The HEMS is always staffed by a specially trained anaesthesiologist or trauma surgeon and nurse. HEMS is called in by the same EMS dispatcher who dispatched the EMS to the scene, based on criteria like suspicion of high energetic trauma, entrapment and drowning or secondary criteria based EMS on-scene observations of patient conditions.1 The dispatch of the HEMS is not related to distance because of the relatively short distances to hospitals in the Netherlands.2 The specific dispatch criteria approved by the Ministry of Health are shown in Table 1.1 Patients are transported to a hospital predominantly by ambulance. Currently, there are four HEMS (in Groningen, Amsterdam, Rotterdam, Nijmegen) that can reach about 75% of the Dutch population within 13 min of dispatch.1, 3

The St. Elisabeth Hospital in Tilburg is a level I trauma centre in the middle of Noord-Brabant county. The hospital serves an area of 5082 km2 and 2.4 million inhabitants.4 The hospital does not have its own HEMS. The hospital is served by the HEMS of Nijmegen and Rotterdam, which are just outside the county borders. In Noord-Brabant, five teaching and seven non-teaching hospitals are capable of resolving acute problems concerning airway, breathing and life-threatening haemorrhaging. All of these hospitals can be reached within 15 min by ambulance from anywhere in the county. The St. Elisabeth Hospital has a large neurosurgical unit. Patients with severe head injury are either taken directly from the scene to the unit or are secondarily transferred from a primary hospital after stabilisation. Because of the flat Dutch topography, short distances and a high hospital density, the EMS dispatcher does not have much difficultly in sending EMS for “scoop and run” of patients without dispatch of the HEMS.

The main goal of the introduction of the HEMS in 1997 was to improve the survival chances of severely injured patients. However, the value of the HEMS is still a subject of discussion, and scientific evidence to support the benefits of the HEMS in the Netherlands is still scarce. In addition, the role of time from trauma until definitive diagnosis and medical treatment in the survival of severely injured patients remains unclear in prehospital care.2, 5, 6, 7 In the present study, the assumption that treatment by the on-scene HEMS decreases the mortality of trauma patients was investigated. Also, the effect of time between trauma and hospital treatment on the association between treatment by HEMS and mortality was studied.

Section snippets

Trauma registry and study population

In the Netherlands, both immediately admitted trauma patients and secondary referrals are registered in a prospective, comprehensive nationwide registry. Trauma victims who are dead on arrival or who die in the emergency department of a hospital are also included. The validated Abbreviated Injury Scale (AIS-90, update 98)8, 9 is used to define the severity of separate injuries and forms the basis of the ISS that assesses overall trauma severity. To compute the ISS, each of six anatomical

Results

The mean age of the study population (n = 372) was 37.8 with a standard deviation (SD) of 20.3 years, and 25% (n = 93) were female. The mean ISS was 22.7 (SD 14.2), and 43% of patients (n  = 158) suffered TBI.

Table 2 shows the differences between patients treated by EMS only and patients treated by EMS and HEMS categorised by whether or not the patient suffered TBI. The ISS of the patients with TBI and treated by EMS only was not significantly lower (30.8, SD 11.6) than the ISS of the patients treated

Discussion

In the present study, the value of a HEMS, staffed by a trained and experienced anaesthesiologist or surgeon, added to the regular EMS by ambulance, staffed by highly trained and experienced paramedics, in improving mortality outcomes for trauma victims in the Netherlands was investigated. A group of patients treated by the EMS with the assistance of the HEMS was compared to a matched group of patients treated by the EMS only. The patients were matched by ISS, age, gender, mechanism of trauma

Conclusions

Our results cannot prove the benefit of the HEMS in the Netherlands and suggest in particular for TBI patients that prehospital times should be shortened to decrease in-hospital mortality.

Conflict of interest statement

There are no conflicts of interest.

Acknowledgment

We thank the regional EMS services for providing access to their registration systems.

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