Multimodal evoked potential monitoring in asleep patients versus neurological evaluation in awake patients during carotid endarterectomy: a single-centre retrospective trial of 651 patients.

BACKGROUND: A controversy exists regarding which monitoring technique is superior in cases in which general anesthesia (GA) is necessary for carotid endarterectomy (CEA). Multimodal evoked potential (mEP) monitoring was investigated under GA during CEA and compared with a historical control group undergoing neurological evaluations awake under loco-regional anesthesia (LA). METHODS: We retrospectively studied 651 patients undergoing elective CEA. In groupHISTORY (N.=349; 1997-1999) LA was provided using superficial or deep/superficial cervical plexus blocks. In groupmEP, (N.=302; 2009-2013) GA was performed by administering remifentanil/propofol infusion. The multimodal EPs included the median-nerve-somatosensory and motor evoked potentials. The primary outcome was the rate of technical failure. The arterio-arterial shunt rate and immediate postoperative motor outcomes were also compared. RESULTS: GroupmEP showed a significantly lower rate of technical failure (OR 0.17; CI 0.03-0.6; P=0.002). Because the groups differed systematically, logistic regression analysis was used to compare shunt rates and motor outcomes. Since shunt rates were 8.3% (groupmEP) versus 8.2% (groupHISTORY), but logistic regression model showed significant differences (OR 3.77; CI 1.67-8.95; P=0.001) correct comparison was impossible. Immediate postoperative deficits were 4.3% (groupmEP) and 4.9% (groupHISTORY); logistic regression analysis: transient OR 0.77, CI 0.28 to 0.22, P=0.61 and permanent OR 0.37, CI 0.02-7.74, P=0.49. CONCLUSION: Monitoring mEPs was associated with less technical failure than awake evaluation and showed similar motor outcomes. Because the groups differed systematically, the interpretation of shunt rates was impossible. Monitoring mEP should be considered to detect intraoperative ischemia in cases in which patients undergo CEA under GA.

Transcranial motor evoked potentials during anesthesia with desflurane versus propofol--A prospective randomized trial.

OBJECTIVE: This study aimed to evaluate differences in transcranial electrical motor evoked potential (tcMEP) amplitudes between desflurane/remifentanil and propofol/remifentanil anesthesia treatment plans in patients without preexisting motor deficits (PMDs) undergoing carotid endarterectomy (CEA). METHODS: This prospective trial included 21 patients who were randomly assigned to an effect group (Group(DESFLURANE); n=14) or a control group (Group(STANDARD-PROPOFOL); n=7). tcMEP amplitudes were measured 35 min post-induction (T1) either with desflurane or propofol. Treatment was then changed to propofol in Group(DESFLURANE). After an additional 35 min, the tcMEP amplitudes were reevaluated (T2). Differences in amplitudes (DW) between T1 and T2 were calculated for each patient, and the means of these differences were compared between groups. RESULTS: tcMEPs were recorded in all 21 patients. At T1, the mean amplitude was 840.1 (SD 50.3) µV and 358.9 (SD 74) µV for Group(STANDARD-PROPOFOL) and Group(DESFLURANE), respectively. The absolute mean difference (T1-T2) between groups was -496.75 µV (p=0.0006). CONCLUSION: Desflurane reduces the tcMEP amplitude significantly more than propofol in patients without PMDs undergoing CEA. SIGNIFICANCE: TcMEPs were recorded in all patients regardless of the anesthesia regimen. In patients with initially small amplitudes, desflurane may limit tcMEP recording because it produces a remarkable amplitude reduction, even in patients without PMDs.

Intraoperative monitoring of carotid endarterectomy by transcranial motor evoked potential: a multicenter study of 600 patients.

OBJECTIVE: This study was to investigate the utility of motor evoked potential monitoring elicited by transcranial electrical stimulation (tcMEP) during CEA in addition to the established median nerve somatosensory evoked potentials (mSSEPs). METHODS: We retrospectively reviewed data from 600 patients undergoing CEA under general anesthesia with monitoring of mSSEPs and tcMEPs in a multicenter study. MSSEP and tcMEP parameters were recorded during internal carotid artery (ICA) cross clamping and compared with the postoperative motor outcome, demographic and patient history data. RESULTS: The intraoperative monitoring of tcMEPs was successful in 594 of the patients (99%) and selective shunt was performed in 29 of them (4.83%). Nine of the patients showed a transient contralateral loss of tcMEPs, without changes in mSSEPs and required intervention (1.5% "false-negative"). Three of them showed postoperative motor deficits. The time period from tcMEP loss to intervention was significantly longer (p = 0.01) in this group compared to the patients without postoperative motor deficit. CONCLUSION: TcMEPs during CEA may be an adjunct to mSSEP monitoring to avoid "false-negative" mSSEP results, as mSSEPs seem to lack specificity for detecting isolated ischemia of corticospinal pathway. SIGNIFICANCE: TcMEPs seem to improve postoperative outcome, especially in case of a timely correction of cerebral ischemia.