Abstract SNACC-30

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Practical use of near infrared spectroscopy and somatosensory evoked potential monitors in carotid endarterectomy with routine shunting " A prospective study"

1Babakhani B, 1Hosseinitabatabaei N, 2Schott M, 2Jantzen J
1International Neuroscience Institute, Hannover, Niedersach, Germany; 2Academic and teaching hospital Nordstadt, Hannover, Niedersach, Germany

The major concern during carotid artery endarterectomy (CEA) procedure under general anesthesia is cerebral hypoperfusion.We describe the application of near infrared spectroscopy (NIRS) and somatosensory evoked potential (SEP) monitors in patients undergoing CEA using routine shunting.
Between July 2013 and January 2014, 34 consecutive patients undergoing 40 CEA procedures with patch closure using routine shunting were included. Age ranged from 48 to 86 years.
Standard anesthetic and monitoring techniques were used in all patients.
Bilateral regional cerebral oxygen saturation (rSO2) was recorded before preoxygenation and continued until recovery from anesthesia, using cerebral oximeter (Somanetic INVOS-5100 cerebral oximeter, COVIDIEN, USA).
An arterial line was placed. Blood pressure was kept stable within a range of ±20% of the pre-operative level.
SEP was performed from induction of to recovery from anesthesia (ISIS IOM Neuromonitoring, Inomed, GERMANY). The median nerve at the wrist contralateral to the operated side was stimulated and the peak-to-peak amplitudes and latency of the primary cortical response N19/P22 complexes were measured online. Any decrease of peak-to-peak amplitudes more than 50%, or increase of latency more than 10% vs the preclamping values, were documented as ischemic SEP change after ICA clamping and before shunt insertion.The surgical team was informed of any sudden decrease of the ipsilateral rSO2 measurement or ischemic SEP change after insertion of the shunt to check malfunction.All patients were extubated in the operation theater. At this point patients were tested for the development of any neurological deficit.
Reconstruction of ICA was successfully completed in all 40 surgeries. During ICA cross-clamp, there were no clinical significant changes in heart rate, mean arterial blood pressure, arterial oxygen saturation, end tidal CO2.No patient developed permanent or transient new neurological deficit on the side of endarterectomy.
The mean time between ICA cross-clamping and shunt insertion was 140±51 seconds, (range of 70 to 270 seconds). The mean shunting time was 36±9 minutes, (range of 22 to 60 minutes).
Accepting 20% and 12% reduction from preclamping values as ischemic threshold, 19 patients (47%) and 30 patients (75%) respectively, started rSO2 ischemic changes after ICA cross-clamping. Five patients (12%), showed ischemic SEP change after ICA cross-clamping. rSO2 and SEP returned to pre-clamp value in all cases after shunt insertion.
In 14 cases (35%) a sudden decrease in ipsilateral rSO2, prompted recheck of shunt function that after reposition and/or flushing the shunt, rSO2 returned to pre-malfunction values. In two of these patients SEP values changed significantly.
NIRS is able to rapidly detect rSO2 changes related to cerebrovascular perfusion changes(1).SEP responses require prolonged averaging. Therefore, the time required to determine if a significant change has occurred may be 3–5 minutes or more(2).
In CEA procedures using routine shunting, rSO2 monitoring can be superior to SEP monitoring.
1. Ghosh A et al. (2012) Anesth Analg. 115: 1373-83
2. Mark M. Stecker (2012) Surg Neurol Int. 3: S174–S187.

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