A prospective observational study was carried out in a university hospital serving as reference center in Neurosurgery and Interventional Neuroradiology. We included all patients with acute ischemic stroke subjected to mechanical thrombectomy and admitted to the ICU between June 2012 and February 2014. Admission to the ICU was decided according to the criterion of the neurologist, based on the need for ventilation support, poor neurological condition after the procedure and/or complications related to EVT. The study was approved by the Research Ethics Committee of the Principado de Asturias (Spain)(reference no. 148/15).

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  Demographic: age and gender.

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  Clinical: history of cardiovascular risk factors and previous stroke, and the National Institutes of Health Stroke Scale (NIHSS) score upon hospital admission.

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  Related to the procedure: time to EVT, location of the obstruction, indication of treatment, previous IV r-tPA use, endovascular techniques employed, recanalization and complications.

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  Neurological complications during admission to the ICU: hemorrhagic transformation, hydrocephalus, seizures. Systemic complications: respiratory problems (pneumonia, tracheobronchitis, atelectasis, acute lung edema), cardiogenic shock. Requirements in the ICU: ventilatory support, need for vasoactive drugs.

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  Outcome variables: functional assessment and mortality at discharge from the ICU, mortality during the first year of follow-up, and degree of disability one year after the ischemic event.

Upon admission, the patients were evaluated by a neurologist. Computed tomography (CT) of the brain, CT angiography (CTA) and perfusion CT were performed to assess brain tissue viability, selecting those patients amenable to derive greater clinical benefit. Cerebral arteriography was performed to locate the vascular occlusion site and assess collaterality. The femoral artery was the access route used. Endovascular treatment was carried out by expert neuroradiologists under general anesthesia or sedation, depending on the clinical condition of the patient and the criterion of the anesthetist. Patients with a low level of consciousness or offering no collaboration underwent sedoanalgesia with mechanical ventilation. Following the procedure, the patients were admitted to the ICU.

Of the 207 patients with acute ischemic stroke subjected to EVT in our center, the 60 subjects (29%) meeting criteria of clinical severity were admitted to the ICU. The inclusion criteria for EVT are specified in Table 1. Patients were required to meet all these criteria in order to be included in the study. The indication of intravenous fibrinolytic treatment was based on the criterion of the neurologist.

Mechanical extraction of the thrombus was carried out using a self-expanding and extractable Solitaire FR® stent (Covidien-ev3Inc, Irvine, CA, USA). The technique consists of advancing a microguide (Concentric Medical Inc., CA, USA) and microcatheter with a Rapidtransit® balloon (Codman & Shurtleff, Inc., MA, USA) until the obstruction site is traversed. The device is then expanded and compresses the thrombus against the wall of the vessel to secure recanalization. The balloon of the guide catheter is insufflated, the stent is withdrawn with continuous aspiration to avoid embolisms, and the thrombus is extracted simultaneously with the stent. In the percutaneous transluminal angioplasty procedures we used UltraSoft® balloons (Stryker Neurovascular, Fremont, CA, USA). The stents placed corresponded to the Wingspan® Stent System in intracranial position and the carotid Wallstent® (both from Boston Scientific, MA, USA).

Arterial recanalization was scored by means of the arterial occlusive lesion (AOL) scale: 0=no recanalization; 1=partial or incomplete recanalization of the occlusion without distal flow; 2=partial or incomplete recanalization of the occlusion with distal flow; and 3=complete recanalization with distal flow.15 We defined treatment failure as AOL 0–1 and efficacy as AOL 2–3.

Symptomatic cerebral hemorrhage was defined according to the ECASS-II criteria as evidence of cerebral hemorrhage in any part of the brain, associated to neurological deterioration with an increase of at least four points on the NIHSS.16

The effect of treatment at discharge from the ICU was documented based on the NIHSS in all survivors. Functional assessment was based on the modified Rankin scale (mRS),17 with good functional status being defined by mRS≤2. Functional evaluation after one year was based on the data obtained from the clinical review made by the Department of Neurology, and through telephone conversation.

A descriptive analysis of the results was carried out using the SPSS version 19.0 statistical package for MS Windows (SPSS Inc., Chicago, IL, USA).

Continuous variables were reported as the mean and standard deviation (SD) in the presence of a normal sample distribution as confirmed by the Kolmogorov–Smirnov test. The median and interquartile range (IQR) were calculated in the presence of a non-normal distribution, in the case of time variables, or when the SD exceeded the mean. Categorical variables in turn were reported as absolute and relative frequencies.

The comparison of continuous variables (considering that only two independent samples were compared) was based on the Student t-test for independent samples in the presence of a normal distribution, and using the nonparametric Mann–Whitney U-test in the case of a non-normal distribution.

The analysis of a given variable at different timepoints was carried out using the Student t-test for paired samples or the Wilcoxon signed-rank test in the case of a non-normal frequency distribution.

The independence of categorical variables was contrasted using the Chi-squared test, with use of the Fisher exact test in those cases where the conditions for application of the Chi-squared test were not met.

The Mantel–Haenszel odds ratio (ORMH) was used as risk measure, with inclusion of the respective 95% confidence interval (CI).

Statistical significance was considered for p<0.05.

The mean patient age was 68.90±8.84 years (males 67.12±8.26; females 73.41±8.89). Males predominated: 43 (71.7%). There was no statistically significant association between age and mortality or functional status either at discharge or after one year. Likewise, there were no gender differences in relation to the clinical outcomes.

Most of the patients (83.3%) had at least one cardiovascular risk factor: arterial hypertension (n=36; 60%); diabetes mellitus (n=13; 21.7%); dyslipidemia (n=23; 38.3%); smoking, 11 (18.3%). Six patients (10%) had suffered previous stroke. The etiology of stroke is reported in Table 2.

The median time from the onset of symptoms to the start of EVT was 180min (interquartile range: 131.25–237.50). There were no statistically significant differences in functional status or mortality according to the time elapsed to the start of treatment.

The median NIHSS score upon admission was 17.5 points (interquartile range: 14–20). The NIHSS score could not be determined in two patients admitted in deep coma. There were no statistically significant differences in NIHSS score upon admission between the patients that died and those that survived. However, higher NIHSS scores upon admission were associated to poorer functional status at discharge from the ICU and after one year (p=0.027 and p=0.036, respectively). The median NIHSS score upon admission among the patients with favorable outcomes one year after stroke was 16.5 points (interquartile range: 13–19).

The median NIHSS score at the time of discharge from the ICU was 3 points (interquartile range: 1.25–11.50). Statistically significant differences were observed on comparing the NIHSS score upon admission versus the score at discharge (p<0.01). The median decrease in NIHSS score at discharge was 11 points (interquartile range: 6–15).

The indication of EVT was established as a result of failure of fibrinolysis with IV r-tPA in 8 patients (13.3%); the contraindication of fibrinolytic treatment in 8 patients (13.3%); and the location of large vessel obstruction in 44 subjects (73.3%). Of these, 7 patients (11.6%) received incomplete treatment with alteplase until the endovascular procedure was available. In relation to this latter indication, we observed an association between the administration of IV r-tPA and good functional status at discharge from the ICU (p=0.014), as well as survival after one year (p=0.037).

The location of arterial occlusion is reported in Table 2. A total of 56.6% of the patients had two or more affected arteries. There was no statistically significant relationship between any of the obstruction sites and mortality or functional status. Internal carotid artery-middle cerebral artery (ICA-MCA) tandem lesions were likewise not related to poorer functional status or increased mortality risk.

The technique employed, the results and the complications are reported in Table 3.

Of the 54 patients subjected to effective recanalization treatment (AOL 2 and 3), 35 showed good functional status at discharge (64.9%). In contrast, of the 6 patients in which recanalization did not prove effective (AOL 0 and 1), none presented good functional status at discharge (p<0.01). After one year, 30 of the patients with effective treatment maintained good functional status (55.6%), while all patients in the failed therapy group showed poor functional status (p=0.024).

One patient suffered arterial perforation during the treatment and died in the ICU. Other serious complications were detachment of the thrombus extracting device in a patient that likewise died during admission, and stent stenosis in a patient that died after 5 months. The patients that suffered complications during the procedure had a 3.7-fold lesser probability of presenting good functional status after one year than the patients that did not suffer complications (p=0.019; ORMH 0.27 [95%CI: 0.1–0.8]).

The median stay in the ICU was days (interquartile range: 2–5.75).

The requirements and complications in the ICU are summarized in Table 4.

The median duration of mechanical ventilation was 7.5h (interquartile range: 2–41). Of the 49 patients that required invasive ventilatory support, 24 presented poor functional status at discharge (48%), versus a single subject among the 11 patients that did not require such support (9.1%) (p=0.019).

Of the 23 patients requiring vasoactive drugs, 8 died during admission (34.8%), versus none of the 37 patients that did not require such medication (p<0.01). At discharge from the ICU, 14 of the patients that required vasoactive drugs showed poor functional status (60.9%). In comparison, 11 of the patients that did not require vasoactive drugs showed poor functional status (29.7%) (p=0.017).

Following EVT, 39 patients received antiplatelet medication (65%) and 9 received anticoagulants (15%).

With regard to mortality, 8 patients died in the ICU (13.3%) – in two cases due to causes unrelated to stroke (cardiogenic shock and acute renal failure with acute lung edema). The stroke-related causes of death were intracranial hypertension syndrome secondary to cerebral infarction (4 patients), associated to hemorrhagic transformation in two cases, and limitation of therapeutic effort (due to a lack of neurological recovery) in two cases. Another 14 patients died during the year of follow-up (23.3%) – in 5 cases due to causes unrelated to stroke (acute myocardial infarction, pancreatic tumor, respiratory failure in two cases, and infectious complications in one patient).

With regard to functional status, during the year of follow-up 30 patients showed a favorable course, with mRS≤2 (50%). The distribution of functional course is shown in Fig. 1.

Figure 1.

Scores of the modified Rankin scale (mRS) one year after the ischemic event. The percentage of patients with scores between 0 and 6 on the mRS are shown: 0=no symptoms; 1=no major disability (able to carry out routine activities and duties); 2=mild disability (unable to carry out some previous activities, but able to care for own interests and concerns without help); 3=moderate disability (symptoms that significantly restrict lifestyle or impede full autonomy: some help required); 4=moderately severe disability (symptoms that clearly impede independent living, though without the need for continuous care: unable to attend personal needs without help); 5=severe disability (totally dependent: needs constant attention, day and night); 6=death.

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