Modifications in Near Infrared Spectroscopy for Cerebral Monitoring During Carotid Endarterectomy in Asymptomatic and Symptomatic Patients

Abstract

Background: To evaluate trends and differences in Near Infrared Spectroscopy (NIRS) monitoring during carotid endarterectomy (CEA) in patients affected by asymptomatic and symptomatic carotid artery stenosis, to predict postoperative neurological complications (PNCs).

Methods: NIRS data of CEAs performed in a University Hospital were retrospectively reviewed. All the interventions were performed under general anesthesia and patients with intraoperative complications were excluded. Mean regional Oxygen Saturation Index (rSO₂), pre-clamp values (mean baseline value, MBv and Single Mark Baseline value, SMBv) were collected and compared to the lowest rSO₂ values during carotid cross-clamp (LSO₂v) calculated within 3 min (percentage drop, PD). ROC curve analysis with Youden's Test was performed to determine the best threshold value of PD, in order to identify PNCs in both asymptomatic and symptomatic groups.

Results: Between 2007 and 2015, a total of 399 CEAs were consecutively performed with NIRS monitoring. Three-hundred-seventy-two CEAs in 355 patients were reviewed. Asymptomatic stenoses were 291 (81.9%), eleven (2.9%) PNC were registered (5 in asymptomatic and 6 in symptomatic group). Asymptomatic and symptomatic diseases had different MBv (69.5 ± 7.5 vs. 71.8 ± 6.9, respectively; P = 0.011) and similar rSO₂ value during carotid clamping (63.7 ± 8.0 vs. 63.7 ± 6.7, respectively: P = 0.958). Asymptomatic patients experiencing PNCs had a greater PD than non-PNCs group (20.5 ± 10.2% vs. 12.5 ± 7.6%, respectively using MBv as baseline value; P = 0.002), in contrast, in symptomatic patients, in which a low PD was associated with PNCs, it does not reach statistical significance (using MBv, 12.6 ± 5.4% vs. 14.8 ± 6.7%, respectively; P= 0.476). In order to detect PNCs, ROC analysis revealed an optimal PD cut-off value of -17% in asymptomatic CEAs. (Sensibility (Se) 0.80, Specificity (Sp) 0.76, PPV 0.05, NPV 0.99, Youden's index 0.56; P = 0.020) In symptomatic a threshold value of -9% was found, without reaching statistical significance.

Conclusions: NIRS as cerebral monitoring during CEA can predict PNCs in asymptomatic stenosis. Asymptomatic and symptomatic groups differ in baseline and intraprocedural cut-off values to detect an augmented PNCs risk.