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Impact of Cerebral Monitoring and Shunting on Outcomes in Carotid Endarterectomy
Clay P Wiske, Robert B Patterson
Brown University, Providence, RI

BACKGROUND: Carotid endarterectomy has been a staple of vascular surgery for decades, yet significant variation in practice patterns exists. While many studies have evaluated the accuracy of cerebral monitoring techniques, we aim to compare the impact of cerebral monitoring and anesthesia choices on outcomes including death and stroke, as well as length of stay.
METHODS: We analyzed the Vascular Study Group of New England (VSGNE) carotid endarterectomy database from January 2003-February 2015, and grouped patients into three categories: no shunting (N=364), routine shunting (N=5,673), and selective shunting (N=7,046). We also subdivided the selective shunting group based on cerebral monitoring technique [(a) local or regional anesthesia with intra-operative sensory exams (N=1,047) b) EEG cerebral monitoring without routine shunting (N=5,761), and c) stump pressure monitoring without routine shunting (N=219)] and excluded all patients who underwent a concomitant procedure from the analysis (N=239). A univariate analysis was used to evaluate peri-operative death and stroke with respect to a number of patient-level variables that might impact these outcomes. We subsequently created a multivariate model for each outcome, adjusting for any patient-level variables significant at p < 0.10 in the univariate analyses. We also conducted an ANOVA analysis of length of stay following surgery.
RESULTS: Across 13,047 patients included in the analysis, the total rate of peri-operative death was 0.28% (95% CI 0.19%, 0.36%) and stroke was 0.89% (95% CI 0.73%, 1.05) (Table 1). In the multivariate regression analysis, odds ratios for of death and stroke were not different among the groups (Table 1). There was no statistically significant difference in rate of stroke or death in the EEG group, compared to either universal shunting or the other selective monitoring groups. None of the groups had a mean length of stay that was significantly different from the mean. Repeating the analysis for the subset of the database that distinguished between pre-operative and intra-operative indications for shunting did not significantly change the results.
CONCLUSIONS: This analysis suggests that key outcome measures following carotid endarterectomy do not significantly differ based on cerebral monitoring techniques. In particular, EEG monitoring, which requires additional expense in equipment and personnel, may incur costs that do not translate to better patient outcomes. The rate of EEG monitoring is high, and use of stump pressures low in the VSGNE database compared to the national experience in the Vascular Quality Initiative, thus stump pressure monitoring warrants investigation using the national database.
Table 1: Rates of Key Outcomes and Multivariate Analysis
Rates of Outcome Variables by GroupMultivariate Analysis
GroupRate (95% CI)Rate (95% CI)aORP-ValueaORP-Value
Routine shunting (N=5,656)0.30% (0.16%, 0.44%)0.95% (0.70%, 1.20%)----
No shunting (N=364)0.00% (0.00%, 0.00%)0.55% (0.00%, 1.31%)0.9970.3290.9950.341
Selective Shunting - all (N=7,027)0.27% (0.15%, 0.39%)0.85% (0.64%, 1.07%)1.0000.8751.0000.964
With local or regional anesthesia (N=1047)0.10% (0.00%, 0.28%)0.76% (0.24%, 1.29%)0.9980.2600.9990.774
With EEG monitoring (N=5,761)0.29% (0.15%, 0.43%)0.83% (0.60%, 1.06%)1.0000.9111.0000.949
With stump pressure monitoring (N=219)0.45% (0.00%, 1.34%)1.82% (0.05%, 3.58%)1.0020.6061.0100.134
Total (N=13,047)0.28% (0.19%, 0.36%)0.89% (0.73%, 1.05%)

Figure Notes:
1. Death adjusted for age > 70, age > 80, history of ipsilateral cortical stroke, any prior vertebral symptoms, any smoking, COPD, CHF, urgent procedure, emergent procedure, and chronic beta-blocker and statin use
2. Stroke adjusted for age > 80, urgent procedure, pre-op ASA, ipsilateral stenosis > 60%, ipsilateral stenosis > 70%, history of ipsilateral cortical TIA or stroke, diabetes, and contralateral occlusion

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