NIRS and BIS Monitoring During Cerebral Aneurysm Coiling

Cerebral aneurysm coil embolization carries a potential risk of cerebral hypoperfusion and ischemia during the intraoperative period. Near-Infrared Spectroscopy (NIRS) provides continuous, non-invasive monitoring of regional cerebral oxygen saturation, while Bispectral Index (BIS) allows assessment of anesthetic depth.

In this prospective observational study, adult patients undergoing endovascular coil embolization for cerebral aneurysms under general anesthesia will be monitored using standard anesthesia monitoring, including NIRS and BIS, which are part of routine clinical practice at the study center.

Baseline NIRS and BIS values will be recorded prior to anesthetic induction, followed by continuous intraoperative monitoring at predefined time points. A decrease of ≥20% from baseline rSO₂ will be defined as clinically significant cerebral desaturation. Relationships between NIRS values, BIS measurements, and hemodynamic parameters will be evaluated.

The study aims to contribute to the understanding of multimodal neuromonitoring during neuroendovascular procedures and to support clinical decision-making regarding cerebral protection strategies.

• Near-Infrared Spectroscopy (NIRS) and Bispectral Index (BIS) Monitoring (Other): Near-infrared spectroscopy (NIRS) and bispectral index (BIS) monitoring are performed as part of routine intraoperative anesthesia monitoring during endovascular coil embolization for cerebral aneurysm. No additional intervention beyond standard clinical care is applied; data are recorded observationally.

Primary outcomes

• Correlation between intraoperative cerebral desaturation and intraoperative hemodynamic parameters [During the intraoperative period]: Correlation between intraoperative cerebral desaturation episodes (defined as a ≥20% decrease from baseline regional cerebral oxygen saturation \[rSO₂\], measured as percentage (%) using Near-Infrared Spectroscopy \[NIRS\]) and the following intraoperative parameters: * Mean arterial pressure (mmHg), measured via invasive arterial catheter * Heart rate (beats per minute, bpm), measured using electrocardiography (ECG) * Peripheral oxygen saturation (SpO₂, %), measured via pulse oximetry * End-tidal carbon dioxide (EtCO₂, mmHg), measured using capnography * Bispectral Index (BIS, unitless scale 0-100), measured using a BIS monitor Correlation will be analyzed using Pearson or Spearman correlation coefficients, as appropriate.

Secondary outcomes

• Correlation between Bispectral Index (BIS) values and regional cerebral oxygen saturation (rSO₂) [From induction of anesthesia until completion of the endovascular procedure]: Assessment of the correlation between intraoperative BIS values and bilateral regional cerebral oxygen saturation (rSO₂) levels recorded at 5-minute intervals during the procedure.

Sex: All, ages: 18 Years to 75 Years

* Age ≥18 years
* Patients scheduled for endovascular coil embolization for intracranial (cerebral) aneurysm
* American Society of Anesthesiologists (ASA) physical status I-III
* Undergoing the procedure under general anesthesia
* Ability to provide written informed consent Criteria

Exclusion Criteria:

* Refusal or inability to provide informed consent
* History of severe cerebrovascular disease other than the target aneurysm
* Severe cardiac, pulmonary, hepatic, or renal dysfunction
* Pre-existing neurological deficits interfering with NIRS or BIS interpretation
* Known scalp or skin conditions preventing proper placement of NIRS or BIS sensors
* Emergency procedures
* Pregnancy -