Thrombectomy

A series of polygons was calculated for the zones covered (isochrones) representing the distance that can be attained from each stroke treatment facility in a particular length of time. The first stage thus consists of listing and geolocalising each stroke treatment infrastructure. Thus, public hospital emergency departments, Primary Stroke Center (PSC) and Comprehensive Stroke Center (CSC) [35 (link)] in the Rhône and neighbouring counties were geolocalised using their precise postal addresses (Table 2).Table 2

Distribution of patient admission infrastructure

Infrastructure	County	Staff
Emergency department	Rhône (69)	7
	Ain (01)	3
	Saône-et-Loire (71)	6
	Isère (38)	7
	Loire (42)	6
PSC	Rhône (69)	2
	Ain (01)	1
	Saône-et-Loire (71)	1
	Isère (38)	2
	Loire (42)	2
CSC	Rhône (69)	1
	Ain (01)	0
	Saône-et-Loire (71)	0
	Isère (38)	1
	Loire (42)	1

Preliminary measurement of accessibility to facilities from all points in the network with 10, 20, 30, 45 and 60-min access time was thus calculated. These time steps were chosen after bibliographic analysis [7 (link), 16 (link)–19 (link), 36 (link), 37 (link)]. Each scenario was applied to this modelling.
Although it is pertinent to characterise the area according to the time required for travel from any point in the network to the treatment facility, it is even more interesting to model overall admission time. Treatment of stroke requires the best possible upstream taking in hand of the patient [4 (link), 38 (link)]. This means that it is necessary to know the pattern of the territory according to the type of transport and also the positions of stroke treatment facilities. In our case, the development of thrombectomy and recent studies have shown its advantages for patients [39 (link)–41 (link)] and modelling overall patient reception was performed using the location of the CSC. With this model it is possible to characterize the territory by care delays from the emergency call to the admission in nearest CSC. It is a global approach of care because all the times of pre-hospital emergency care for stroke patients are taken into account. The second phase of our study was therefore aimed at georeferencing each fire station in the Rhône and neighbouring counties, together with each SMUR team, using their precise addresses. After this georeferencing, supply zones were calculated for these facilities and then for each CSC to finally show total admission time—i.e. the estimated times from SMUR centres or fire stations to all the points in the network and then from any point to the CSC (Fig. 2). In this model, private car is not considered because it is not possible for patient to go directly to the CSC by his own. It was interesting to take intervention and triage times into account to better estimate the time. Thus, after a review of the literature, average time for ambulance dispatch, time spent at the scene and transport to a Comprehensive Stroke Center and intervention at the site of occurrence determined by Adeoye [19 (link)] were chosen (Fig. 2). The final times were calculated using the United States EMS (Emergency Medical Service) register for stroke cases alone.Fig. 2

Diagrammatic representation of overall journey time modelled according to the type of transport (SMUR and fire brigade)

This overall approach was represented on the basis of IRIS area units (Ilots Regroupés pour l’Information Statistique, small zones grouped for statistical information), the smallest administrative division of Insee (Institut National de la Statistique et des Etudes Economiques) and that respect demographic (populations of 2000) and geographic criteria [42 ]. This representation gives an accurate view and characterisation of areas according to access time to an CSC. For thrombectomy, discussions are in progress with regard to direct admission to CSC (Mothership) or a first stop at PSC (‘Drip ‘n Ship’) [35 (link)]. In this study accessibility has been modelled using the Mothership pattern.

If patients were eligible for intravenous thrombolysis, 0.9 mg/kg recombinant tissue-type fibrinogen activator (rt-PA) was administered before mechanical thrombectomy according to Chinese guidelines for the endovascular treatment of acute ischemic stroke (15 (link)). The mechanical thrombectomy procedure was performed by two interventional neuroradiologists with 10 years of practice in neurointerventions. The choice of STR or ADAPT was left to the discretion of the operator, usually based on the anatomical location of the thrombus obstruction, preoperative judgment of the etiology and pathogenesis, and the size of the thrombus. All patients were treated with local anesthesia, preferably through the right femoral artery, to establish access. A balloon guide catheter (BGC) was not used in all procedures due to limitations in available device conditions. The ADAPT and SRT techniques have been described previously (16 (link), 17 (link)). Patients received ADAPT using AXS Catalyst-6 (Stryker, USA) as front-line therapy. All stent retriever procedures were performed using the Solitaire FR (Covidien, USA). Meanwhile, intermediate catheters (AXS Catalyst-6) were routinely used. The operator could choose any necessary thrombectomy device and method to obtain an acceptable therapeutic effect if a successful recanalization could not be accomplished after three attempts using SRT or ADAPT.

The “ResISSSTE Cerebro” program includes seven urban healthcare facilities located in Mexico City and one in each of the neighboring states of Morelos and Hidalgo. According to the World Stroke Organization global stroke services guidelines and action plan (9 (link)), seven facilities are cataloged as essential stroke centers (ESC). Thus they offer access to non-contrast computed tomography (NCCT), clinical evaluation, and potentially IVT (according to IVT criteria cited below). At ESC, there is no personnel with expertise in AS treatment. The eighth facility is an advanced stroke center (ASC) capable of providing advanced stroke services on a 24/7 basis, including multidisciplinary stroke expertise, multimodal imaging, and acute reperfusion therapies for ischemic stroke.
Since its approval in 2019, the program has operated as a modified hub-and-spoke model. It receives funding from the Mexican government through the ISSSTE healthcare system and has access to ambulance services available 24/7. It also includes a stroke telemedicine network to facilitate the evaluation and care of potential patients.
As mentioned above, the program's functioning is mainly based on the hub-and-spoke model but with certain adequations to the Mexican Healthcare system. For example, most hub-and-spoke models function by offering daytime AS treatment at local centers, and the patients in need of treatment out-of-hours and on weekends are treated at hub hospitals. But, in the “ResISSSTE Cerebro” program, all centers provide AS treatment regardless of time or day, with the only difference being that advanced modalities of treatment (EVT and IVT guided by perfusion imaging up to 9 h after the onset of symptoms) are available only at the ASC. Similarly, the drip-and-ship model, as initially conceived, assumes that all centers within a network can diagnose LVO, thus allowing emergency medical services (EMS) to move patients to the closest hospital and only transfer to a thrombectomy-ready hospital for those patients with confirmed LVO. The drip-and-ship model was only partially implemented in our program due to constrained access to ambulances and human and technological infrastructure to perform advanced imaging in stroke patients at the ESC. Our model also accommodates that most of the patients in Mexico arrive at a hospital by their means (for example, the family car or public transportation), with few coming by EMS; therefore, prenotification is uncommon. Consequently, by concentrating the human and technological resources in a single center, the “ResISSSTE Cerebro” program can deliver advanced AS treatment 24/7 while preserving the capability of ESC to provide telemedicine supervised IVT also 24/7.
The stroke telemedicine network utilizes an instant messaging app that includes all the emergency room staff of all shifts grouped by each ESC. Each group, in turn, has all the stroke team members located at the ASC. Emergency room physicians are in charge of all initial evaluations and are responsible for alerting the stroke team and carrying out their instructions regarding treatment. At the same time, they order the NCCT and arrange for a possible transfer to the ASC. The ESC prenotifies all transfers to ASC. The protocol is known by all the staff at the emergency rooms of the ESC, and a print or electronic copy is available for consultation at the office of the head of the emergency department. Figure 1 depicts the pathway for patients initially arriving at ESC, and Figure 2 is that of patients coming directly to the ASC. All the ESCs are staffed 24/7 with emergency physicians, residents (emergency medicine is a 3-year residency program in Mexico), and radiologists. At the ASC, the staff comprises emergency physicians and emergency medicine residents, radiologists, neuroradiologists, clinical neurologists and clinical neurology residents, neurosurgeons and neurosurgery residents, and interventional neurologists and interventional neurology residents.