Near-infrared Spectroscopy in Endovascular Treatment (Danish: Nær-infrarød Spektroskopi Ved endovaskulær Trombektomi)

Endovascular treatment is the revascularization after ischemic stroke due to large-artery occlusion by mechanical removal of thrombi with an intraarterial catheter. The area around the infarction called the penumbra, which has partial blood supply by collateral vessels, can thereby be salvaged and the neuronal function restored. EVT lowers the disabilities and the morbidity if it is performed within 6 hours of onset or within 24 hours in stroke patients with a significant penumbra (Rodrigues, Neves et al. 2016).

However, complications can arise during EVT including critically failing CBF, intracranial hemorrhage and embolization of the thrombus to more peripheral vessels, which can all result in further brain damage.

To avoid these repercussions or detect them as fast as possible as well as detecting successful interventions, a suitable method for monitoring CBF over time is needed. NIRS is a commonly applied method that examines CBF in the cerebral cortex, which has already been used as intraoperative monitoring during abdominal and cardiac surgery (Yu, Zhang et al. 2018), but only in minor studies of EVT patients, where results have been very promising and associated to long-term outcomes (Hametner, Stanarcevic et al. 2015, Ritzenthaler, Cho et al. 2017). NIRS exploits that absorption of infrared light is only changed by hemoglobin, which can therefore by measured over time. NIRS is a non-invasive and safe method that measures oxygenated and deoxygenated hemoglobin in the cerebral cortex (Ferrari and Quaresima 2012).

Cerebral autoregulation (CA) is a complex mechanism that maintains an relatively constant and adequate CBF, which is often impaired in acute stroke patients (Paulson, Strandgaard et al. 1990). The nature of CA can be examined with NIRS (Obrig, Neufang et al. 2000, Reinhard, Wehrle-Wieland et al. 2006, Schytz, Hansson et al. 2010, Zweifel, Dias et al. 2014) and impairment can be shown (Li, Wang et al. 2010, Han, Li et al. 2014, Han, Zhang et al. 2014, Phillip and Schytz 2014). NIRS examinations of CA has never been done during EVT and the relation between changes in CA and patient outcome remains unknown.

This leads to the following hypothesis: