The Impact of Near-Infrared Spectroscopy in Early Detection of Cerebral Deterioration After Aneurysmal Subarachnoid Haemorrhage

<b>Background/Objectives</b>: Delayed cerebral ischemia (DCI) represents a major cause of morbidity and mortality after aneurysmal subarachnoid haemorrhage (aSAH). Early identification of developing cerebral ischemia is essential for timely prevention of DCI. Near-infrared spectroscopy (NIRS) provides continuous, non-invasive bedside monitoring of regional cerebral oxygen saturation (rSO₂); however, its clinical value in patients with aSAH has not yet been fully established. The primary objective of this study was to investigate whether NIRS-detected rSO₂ desaturation can serve as an early indicator of cerebral vasospasm (CV) and predict the occurrence of DCI. Secondary objectives were to examine the associations between rSO₂ changes and other cerebral deterioration events, length of intensive care unit stay, functional outcome, and in-hospital mortality. <b>Methods</b>: This prospective, single-centre study included 30 patients with aSAH admitted to the intensive care unit (ICU) of Riga East University Hospital between January 2019 and January 2023. Bilateral frontal near-infrared spectroscopy (NIRS) monitoring (Covidien INVOS™ 5100C-PB) was initiated within 72 h after ictus and continued for up to 7 days. Cerebral desaturation was defined as a >20% reduction from baseline (BL) or an absolute regional cerebral oxygen saturation (rSO₂) value < 50% lasting ≥30 min. CV and DCI were diagnosed according to established clinical and radiological criteria. Receiver operating characteristic (ROC) analysis was performed to evaluate the sensitivity and specificity of rSO₂ thresholds for the detection of CV, DCI, and other cerebral deterioration events. <b>Results</b>: CV occurred in 10 patients (33%); however, only four cases were detected during the NIRS monitoring period. NIRS demonstrated very high sensitivity (97.5%) but extremely low specificity (6%) for the early detection of CV. In contrast, diagnostic accuracy for DCI was high. An absolute rSO₂ cut-off value of 52% yielded a sensitivity of 97.5% and a specificity of 95%, whereas a decrease of ≥26% from baseline (BL) demonstrated a sensitivity of 98% and a specificity of 93%. Significant rSO₂ reductions were also observed during aneurysm re-rupture, hydrocephalus, cerebral edema, and postoperative ischemia; however, the sensitivity of NIRS for detecting these events was negligible. Patients with ≥20% desaturation tended to have longer ICU stays, and lower mean rSO₂ values as well as greater desaturation were associated with poorer functional outcomes as assessed by the modified Rankin Scale. Patients who died exhibited more pronounced rSO₂ decreases and less recovery compared with survivors. <b>Conclusions</b>: In this cohort, NIRS demonstrated limited specificity for the early detection of CV but showed strong associations with DCI and neurological outcome. NIRS may be useful as a non-invasive adjunct to multimodal neuromonitoring rather than as a stand-alone diagnostic tool for cerebral vasospasm. Larger, prospective studies incorporating standardized imaging protocols and optimized rSO₂ thresholds are required to more clearly define the role of NIRS in the management of aSAH.