Multifaceted implementation and sustainability of a protocol for prehospital anaesthesia: a retrospective analysis of 2115 patients from helicopter emergency medical services

Ethics

The study protocol was approved by the authorities of Helsinki University Hospital (§17 HUS/278/2018). Additional approval by an ethics committee was not required under Finnish legislation, as only anonymous registry data were collected, and the study had no effect on patient treatment. The change in clinical practice was to implement a prehospital anaesthesia protocol irrespective of data collection. The study did not affect patient treatment and therefore patient consent was not required nor acquired. The STROBE guidelines were followed in reporting the study [16].

Study design

We performed a retrospective observational study in one HEMS unit. We analysed HEMS mission database data accomplished with airway registry and patient charts before (2012–2014) and after (2016–2020) implementation of the PHEA protocol. The implementation year (2015) was excluded from the analysis. The primary end-points were OST, FPS rate, and three protocol compliance indicators — the use of esketamine, rocuronium, and mechanical ventilation. We also included a description of the entirety of the PHEA protocol implementation in this study.

Setting

The study was performed in a HEMS unit (FinnHEMS 10) serving a population of approximately 1.3 million in southern Finland over an area of 10,000 square km [17]. The collaborative ground EMS system consists of 100–120 ambulances and approximately 500 prehospital care professionals (advanced life support nurses and basic life support technicians) working for six different employers. The HEMS unit is also assisted by several rescue departments.

The HEMS unit is staffed by a three-member crew: a physician, a HEMS crew member, and a pilot. The physicians are mainly experienced specialists in anaesthesiology with postgraduate training in prehospital medicine. During the study period (2012–2020), 22 physicians were employed by the service. The HEMS crew members are firefighters or prehospital nurses with extensive training in aviation and prehospital critical care working exclusively in HEMS.

The emergency dispatchers dispatch the unit according to the predefined criteria, for example, major trauma, cardiac arrest, and unconsciousness. Also, the ambulance crews can request the HEMS response. The unit does not play a role in interfacility transfers. The HEMS unit is dispatched annually approximately 2500 times and performs prehospital anaesthesia about 250 times. Ambulance crews in the area do not perform tracheal intubation, except during a cardiac arrest.

The new protocol for PHEA was implemented in the HEMS unit and the collaborative EMS system at the beginning of 2015. The protocol consists of an inclusive description of the process, and it defines all actions from receiving the dispatch to handing over the patient at the hospital (Fig. 1). This protocol changed practice in several ways. The team is already organised with radio communication before the HEMS unit arrives to the patient. The EMS crews systematically prepare patients for induction of anaesthesia with a specific checklist while the HEMS unit is still en route. After arriving at the scene, the physician hears the report, examines the patient, and verifies the plan. The pre-anaesthesia checklist is read before induction.

Fig. 1figure 1

Flow chart of study population (2012–2020). HEMS helicopter emergency medical services. *Includes airway management without drugs, e.g. during cardiopulmonary resuscitation

Anaesthesia is primarily induced using esketamine, and a neuromuscular blocking agent (NMBA) (rocuronium > 1 mg kg−1) is mandatory. Use of fentanyl and propofol instead of esketamine is favoured in patients with status epilepticus, or markedly hypertensive patients with suspected intracranial haemorrhage, or isolated traumatic brain injury.

The intubation is always performed by the HEMS physician with a video laryngoscope (C-MAC pocket monitor, KARL STORZ Gmbh, Tuttlingen, Germany) and a bougie (Frova Intubating Introducer, 700 mm length, 3 mm diameter, no stiffening stylet, Cook Medical, Bloomington, USA), with the HEMS crew member assisting. The ambulance crew and sometimes rescue personnel are included in the assigned roles. Standard communication is used during laryngoscopy, and a pre-defined sequence is followed if visualisation of vocal cords is not achieved immediately. Because the routine use of a method combining video laryngoscopy and the Frova introducer was not described in earlier literature at the time of preparation of the protocol, we analysed the success rate shortly after implementation of the protocol to confirm the safety [7]. Mechanical ventilation is strongly favoured after intubation. Target values of vital signs and plans for treatment during transportation are defined aloud using the before-transportation checklist to ensure the whole team’s situational awareness.

Before the implementation of the PHEA protocol (2012–2014), preparation, drugs and laryngoscopy strategy used for prehospital intubation were not standardised. The physician on call determined the details individually. A traditional Macintosh laryngoscope and a stylet were the only equipment available in the years 2012–2013. In addition, the C-MAC video laryngoscope and the Frova introducer were available from the year 2014. During 2015, the conventional laryngoscope was removed, and only the C-MAC video laryngoscope was available. The use of NMBA was not mandatory and was based on clinical judgement. Succinylcholine and rocuronium were available, latter used usually at dose of 0.5 mg kg−1.

Implementation of the protocol

The pre-implementation phase started during the preparation phase in autumn 2014, and implementation was accomplished during an intensive three-month period from January to March 2015. The implementation strategy was multifaceted, consisting of several methods and target populations (Table 1). The strategy and methods were planned after familiarising ourselves with applicable implementation frameworks and process models [14, 18,19,20,21]. Continuous support for protocol sustainability was offered after the implementation. The support consisted of identifying persistent deviations from protocol, regular on-duty training, and annual protocol development days at the HEMS base, simulation training with prehospital personnel, and scientific evaluation of the PHEA process.

Table 1 Implementation methods used to change clinical practice in prehospital anaesthesiaInclusion criteria

The inclusion criterion for this study was drug-facilitated advanced airway management performed in adult patients (≥ 18 years) on the study units’ HEMS missions. Advanced airway management was defined as attempted tracheal intubation or surgical airway. Patients were divided into two groups: those treated in the three-year period (2012–2014) before implementation of the protocol and those treated in the five-year period (2016–2020) after its implementation. The implementation year (2015) was excluded from the analysis to avoid bias due to the sequential implementation process. The same general airway management indications existed throughout the study period, although they were made more visible to the prehospital community by the PHEA protocol.

Data sources

The data were gathered primarily from a national HEMS mission database that has been used in Finland since 2012 [17, 22]. The physician on call enters the data into the database. The data consist of general alarm information, timestamps, patient characteristics and categorisation, and comprehensive records of procedures and treatment. From 2014, they also include structured prehospital airway data in accordance with recommendations for data gathering in prehospital settings [23]. The number of intubation attempts and dosage of induction agents in 2012 and 2013 had been reported in a structured way in patient charts, and these data were manually transferred to the study database for analysis.

Outcome measurements

The OST was defined as the time from the HEMS unit reaching the scene to beginning their transportation (or leaving the scene, in cases in which the patient died on the scene). The OST was calculated from the timestamps in the database for the whole study period.

The FPS is defined as successful intubation on the first laryngoscopy attempt. The number of intubation attempts has been included in the structured HEMS patient record sheet for years before the launch of the national HEMS database. Since 2014, it has also been collected in the national HEMS database. Thus, FPS data were collected systematically during the study period.

The protocol compliance was evaluated through the use of esketamine and rocuronium in the induction of anaesthesia and the use of mechanical ventilation after intubation. The data concerning these drugs were collected from HEMS patient record sheets for 2012–2013 and from the database since 2014. The data on mechanical ventilation after intubation were available in the database for the whole study period.

Statistical analyses

The normal distribution of continuous variables was tested using the D’Agostino and Pearson omnibus normality test. As virtually all parameters had a skewed distribution, we reported continuous variables as the median and interquartile range (IQR). The categorical parameters were compared between groups with Fisher’s exact test in cases of two categories and the chi-square test in cases of three or more categories. The continuous variables were compared with the Mann–Whitney U test. For proportions, 95% confidence intervals were calculated using the modified Wald method. The analyses were performed using GraphPad Prism, version 9.0.0, for Mac OS X (GraphPad Software, USA). A p-value of less than 0.05 was considered significant.

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