Intraoperative Correlation Of Transcranial Doppler And Cerebral Oximetry During Carotid Endarterectomy
Pooja Tekula, Charudatta Bavare, Busra Tok Cekmecelioglu, Kavya Sinha, Zsolt Garami, Martin Giesecke, Alan B Lumsden.
Houston Methodist Hospital, Houston, TX, USA.
Objective:Carotid artery stenosis is one of the major causes of ischemic stroke.Surgical revascularization through carotid endarterectomy(CEA) is not without risk.Intraoperative embolization and hemodynamics during carotid clamping and release; and shunt insertion can be assessed by transcranial doppler(TCD).Routine shunt insertion may prevent cerebral ischemia but it can increase risk of stroke.The purpose of study was to evaluate correlation between mean flow velocity(MFV) of middle cerebral artery(MCA) by TCD and cerebral oximetry(NIRS) to decide whether a shunt is necessary.Methods:15 patients(10male)of median age 70(59-85)were studied who underwent CEA between 2018-2020.All the patients underwent TCD monitoring during the procedures which were performed under general anesthesia.MFV,pulsatility index(PI) of MCA,mean arterial pressure(MAP) and NIRS were recorded.The CEA procedure was divided into 4phases:carotid clamp placement,shunt placement,shunt removal and clamp release.Results:Seven patients needed shunt insertion during the surgery.Shunt insertion was recommended in our protocol when MFV dropped more than 50% after clamp.In patient’s undergoing CEAs without shunt(n=8),MFV(44.3±23.5 to 39.7±24.6cm/s) and NIRS(72.8±8.4 to 66.3±7.3)decreased with cross clamp;however there was no significant difference(p>0.05).There was a significant increase in MFV(39.7±24.6 to 58.1±30.4,p=0.01)noticed at clamp release,whereas NIRS showed no change.We found significant correlation between MFV and NIRS value during clamp placement(p=0.013).In patient’s undergoing CEAs with shunt placement, MFV decreased with clamping(39.2±16.7 to 11.2±9.4,p=0.004),increased with shunt insertion(44±18.7,p=0.002)and increased above baseline after clamp release(54.8±26.4,p=0.049).NIRS values decreased with cross clamp(69.8±5.4 to 66.5±8),increased during shunt(68.2±8.1)and increased above baseline as well after clamp release(72.4±4.8).Correlation of MFV and NIRS during cross clamp (p=0.0001)and shunting (p=0.008)were significant,nonetheless there was no significant correlation after clamp release.MAP changes were not significant for all phases during the cases(p>0.05).Conclusion:MFV changes of MCA at clamp placement can assist the surgeon in deciding whether a shunt is necessary and by avoiding shunt placement we can decrease carotid injury and improve end point visualization.Our study showed significant correlation between MFV changes and NIRS values during clamp placement.Although they correlate in terms of flow-the most common reason for stroke is embolization,which NIRS cannot detect.Several studies have been published on cerebral oximetry during CEA,but there are few studies available on correlation with TCD.Further studies are necessary to establish a correlation between MFV and NIRS during CEA.
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