Air Rescue of Patients With Acute Aortic Syndromes

An Evaluation of 3750 Mission Protocols

In 1–2 of 10 000 cases treated in German emergency departments, acute aortic dissection (AAD) is diagnosed (1). Type A AAD requires immediate surgical repair. The need for prompt interventional or surgical management may also be pressing in cases of type B dissections with end-organ damage. The mortality rate in patients with AAD increases by 0.5–2% per hour. Thus, patients with AAD are reliant on both rapid diagnostic confirmation and prompt transport to a specialized center with expertise in cardiac surgery. The decision on whether to transport by air or ground is time-critical and has a major impact on patient survival.

Up to now, there is a scarcity of data on transport times and time efficiencies for airborne transport in patients with AAD. In this study, we evaluate transport routes and transport times based on a retrospective analysis of the logs of 3750 helicopter transport missions in patients with AAD.

Methods

Mission protocols of airborne transports of patients with AAD according to ICD-10 (diagnosis code I71.x) were identified in collaboration with ADAC-Luftrettung gGmbH. These are digital logs that are fed into an internal database of the institution via mobile device enrollment. All mission protocols nationwide from 2010 to 2020 were included.

This comprised both primary rescue missions with suspected diagnosis of aortic dissection and interhospital transfers with confirmed diagnosis. Dissections of both Stanford types were included in the analysis. The data on 3750 transports could be analyzed.

The transport times were measured from the time the rescue vehicle was alerted by the rescue coordination center. The distances correspond to the flight routes recorded in the mission protocol. Data sets were anonymized for statistical analysis. SPSS version 29.0 was used for all statistical analyses. Data are presented as absolute and relative frequencies for categorical variables and as median and interquartile ranges for continuous variables. The Mann-Whitney U test was used for comparisons between primary rescue missions and patient transfers.

Results

After the exclusion of incomplete datasets and cases where airborne transport was not possible, 3188 cases remained for analysis (Table, Figure). In 29.4% of all transports, it took more than 30 minutes for the rescue vehicle to reach the patient, and in 8.8% of cases it took more than 45 minutes. Short transport distances of less than 25 km accounted for 12% of the missions. The transport distance was less than 50 km in 44.9% of the cases. Mortality during the entire rescue or transport operation amounted to 1.9% (n = 60). In-flight death was much less common at 0.5% (n = 16).

Figure

Transport times and distances for airborne transport in acute aortic dissection

Table

Correlation of the transport distance (km) with the time from the alert of the rescue vehicle by the rescue coordination center to the arrival of the patient at the destination hospital (min)

Approach distances and times as well as transport distances and times seem to correlate in most cases. Isolated cases stood out for exceptionally long travel times. The time efficiency of the transport (time required per kilometer of transport distance) proved to be better for longer transport distances. Curve fitting showed an inverse relationship (1/n) with a coefficient of determination r² of 0.582 for transport distance in relation to time efficiency (time from alerting the rescue vehicle to arrival at the destination hospital per route kilometer). From a travel distance of about 30 km, the time efficiency approaches a linear course with a value of about 1–2 min/km.

Discussion

Our data show that in most cases a fast and time-efficient helicopter transport is accomplished. However, given such a time-sensitive condition, a mean inter-hospital transfer time of 82.1 min certainly makes one wish for improvements. Time delays from confirmation of diagnosis to surgical repair correlate directly with increased mortality in AAD (2).

In Germany, the time to arrival of a rescue vehicle is on average 9.7 min for primary rescue missions and 25.5 min for urgent patient transfers (3). Due to the greater availability of ground-based transport, the approach times in our analysis appear long in comparison, at 23.4 min for primary rescue and 38.6 min for patient transfers. We observed approach times of more than 30 min in 29.4% and of more than 45 min in 8.8% of the cases of all airborne transports. Depending on the German federal state, statutory response times of usually less than 15 min must be met in the rescue service. While primary rescue operations met the response time on average in our analysis, the time to arrival of patient transfers was significantly higher at a median of 28 min. Inter-hospital transfers of patients with AAD are currently treated as intensive care transports and thus are given lower priority than primary rescue missions. However, a recently published legal opinion concludes that in patients with AAD the statutory rescue time also applies to patient transfers (4). Due to the logistical challenges of helicopter transport, time efficiency is poorer for relatively short transport distances. From a distance of about 30 km, transport efficiency increases significantly.

Comparable data on time efficiency for ground-based transports of patients with AAD are not available. The mortality rates reported for transfers of patients with type A AAD are similar for ground- and air-based transports (5). The exact distance at which helicopter transport offers a time advantage over ground-based transport is still unknown. Raising awareness of the need for the most time-efficient transportation possible in patients with such a time-critical condition is imperative. The question of whether helicopter transport is useful should always be asked, especially in the case of relatively short transport distances.

Dustin Greve*, Daniel Werner*, Andrea Stroux, Martin Möckel, Volkmar Falk, Stephan Dominik Kurz

*These authors are co-first authors.

Deutsches Herzzentrum der Charité – Medical Heart Center of Charité and German Heart Institute Berlin, Department of Cardiothoracic and Vascular Surgery, Berlin; Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany (Greve, Falk, Kurz), [e-mail]

ADAC Luftrettung gGmbH, Munich; Hospital of the Ludwig-Maximilians-University Munich (LMU), Department of Anesthesiology, Munich, Germany (Werner)

Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Biometry and Clinical Epidemiology, Berlin, Germany (Stroux)

Charité – Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Department of Emergency and Acute Medicine, Campus Mitte and Virchow, Berlin, Germany (Möckel)

DZHK (German Centre for Cardiovascular Research), Partner Site Berlin, Berlin, Germany (Falk)

Swiss Federal Institute of Technology, Department of Health Science and Technology, Zurich, Switzerland (Falk)

Ethics

The study was conducted in accordance with the Declaration of Helsinki and applicable German law. Ethics committee approval was not required as this retrospective study did not analyze identity-related data.

Conflict of interest statement
The authors declare no conflict of interest.

Translated from the original German by Ralf Thoene, MD.

Manuscript received on 9 November 2022, revised version accepted on 9 February 2023

Cite this as:
Greve D, Werner D, Stroux A, Möckel M, Falk V, Kurz SD: Air rescue of patients with acute aortic syndromes—an evaluation of 3750 mission protocols. Dtsch Arztebl Int 2023; 120: 483–4. DOI: 10.3238/arztebl.m2023.0043

References

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2. Matthews CR, Madison M, Timsina LR, Namburi N, Faiza Z, Lee SL: Impact of time between diagnosis to treatment in acute type a aortic dissection. Sci Rep 2021; 11: 3519

3. SQR-BW – Stelle zur trägerübergreifendenQualitätssicherung im Rettungsdienst Baden-Württemberg: Qualitätsbericht Berichtsjahr 2019. 2020.

4. Kurz SD, Falk V, Buschmann CT, Peters M: Medikolegale Aspekte des präklinischen Managements von „akuten Aortensyndromen“. Notarzt 2020; 36: 207–9

5. Knobloch K, Dehn I, Khaladj N, Hagl C, Vogt PM, Haverich A: HEMS vs. EMS transfer for acute aortic dissection type A. Air Med J 2009; 28: 146–53