Diagnostic value of somatosensory evoked potential changes during carotid endarterectomy for 30-day perioperative stroke
Introduction
Carotid Endarterectomy (CEA) is a standard surgical treatment in the secondary prevention of stroke performed in patients with both symptomatic and asymptomatic carotid stenosis (CS) (Malcharek et al., 2013, Pennekamp et al., 2011, Pulli et al., 2002, Reinert et al., 2012). CEA is shown to benefit symptomatic and asymptomatic patients, when compared to medical management alone in the short term and long term due to decreased stroke (Akhmedov et al., 2013, Baton et al., 2007, Floriani et al., 1989, Hartmann et al., 1999, Kang et al., 2014, Biller et al., 1998, Meschia et al., 2014, Bonati et al., 2015). An uncommon complication of CEA is the risk of perioperative stroke, which has been defined in clinical trials as clinically identified stroke within the first 30 days of the CEA procedure that is mainly thought to be a result of intraoperative cerebral hypoperfusion or emboli secondary to atherosclerotic plaque disruption (Brott et al., 2010, Guerit et al., 1997, Pistolese et al., 1993). Cerebral hypoperfusion is inadequate cerebral blood flow that may result from multiple factors including contralateral carotid stenosis (Prokop et al., 1996), vertebral artery stenosis (Kobayashi et al., 2012), intracranial stenosis (Klopfenstein et al., 2005), and poor collateralization in the Circle of Willis (Moritz et al., 2007), or decreased cerebrovascular reserve capacity (Caplan and Hennerici, 1998).
Intraoperative intraluminal shunting is often used to prevent hypoperfusion following cross-clamping of the ipsilateral carotid artery (Guerit et al., 1997, Astarci et al., 2007, Friedell et al., 2008, Uno et al., 2001). Although shunting is effective in maintaining perfusion in patients with inadequate collateral circulation, routine shunting carries the risk of embolic stroke or distal vessel injury (Chongruksut et al., 2014). Therefore, selective shunting, in conjunction with intraoperative neurophysiological monitoring (IONM) using either somatosensory evoked potentials (SSEPs), and/or electroencephalography (EEG), has been utilized during carotid clamping as a simple and reliable method to assess the effect of carotid clamping on the maintenance of adequate cerebral blood flow and tissue oxygenation (Manninen et al., 2001).
Historically, SSEP monitoring has been used to assess the adequacy of collateral circulation for selective shunt insertion during CEA (Malcharek et al., 2013, Moritz et al., 2007, Astarci et al., 2007, Manninen et al., 2001, De Vleeschauwer et al., 1988, Linstedt et al., 1998, Manninen et al., 2004). A previous meta-analysis showed that patients with symptomatic CS who underwent CEA and had a stroke within the first 24 h were more likely to have significant intraoperative SSEP changes (Nwachuku et al., 2015). In clinical practice, significant changes in SSEP waveforms that serve as alarm criteria for inadequate cerebral blood flow are usually defined as a decrease of greater than 50% of the cortical N20-P25 SSEP amplitude and/or a 10% increase in the latency of the same cortical SSEP, after cross-clamping of the carotid artery (De Vleeschauwer et al., 1988, Nwachuku et al., 2015, Haupt and Horsch, 1992, Horsch et al., 1990).
However, it is possible intraoperative hypoperfusion increases the risk of stroke during the entire perioperative period, i.e 30 days, but no clear data exists. The Centers for Medicare and Medicaid Services (CMS) defines the perioperative period as up to 30 days postoperatively, but no outcome analysis has been conducted in the 30-day period for CEA. Hence we evaluate the efficacy of intraoperative SSEP change in predicting the risk of perioperative stroke beyond the 24-hour period and into the 30-day perioperative period. The results will provide information about the diagnostic accuracy of SSEPs changes in predicting stroke and serve as a predictor for therapeutic intervention intraoperatively.
In addition, the specific subcategories of significant intraoperative SSEP changes and their contribution to the risk of perioperative stroke in CEA have not been evaluated. This is a valuable piece of information, as it can indicate the varying degree of need for reperfusion.
The primary objective of this meta-analysis is to evaluate the efficacy of intraoperative SSEP change in predicting the risk of stroke in the postoperative period beyond 24 h but within 30 days. Our secondary aim is to evaluate the subcategories of significant changes in SSEP, including transient change, persistent change, transient loss, and persistent loss, and their individual predictive value for perioperative stroke. We will also be assessing the predictive value of SSEP for stroke risk in the postoperative period within 24 h of the operation.
Section snippets
Protocol and registration
This meta-analysis followed the PRISMA procedure as shown in Fig. 1. It has been registered in the NIH PROSPERO international register on 04/18/2016 The registration number is CRD42016037624.
Eligibility criteria
We performed a meta-analysis of the literature using PubMed, Web of Science, and Embase to retrieve published reports and/or experiments on intraoperative SSEP monitoring for postoperative outcomes in patients undergoing CEA for symptomatic and/or asymptomatic carotid artery disease. Reports utilizing other
Literature search
There were 660 articles retrieved based on the title and abstract from a literary database search (PRISMA chart). After full assessment of the abstract by the authors, 53 articles remained. This number was further reduced to 25 articles upon review of the full papers based on study inclusion criteria. Our statistical analysis included data from these 25 published studies that satisfied the inclusion criteria of the meta-analysis and raw data from 1165 asymptomatic patients operated upon for
Discussion
Our results indicate that SSEP changes are useful in predicting the risk of perioperative stroke not only within the 24-hour postoperative period, but also into the 30-day postoperative period. Patients with significant SSEP changes were almost 33 times more likely to develop perioperative stroke within 24 h of the operation. However, the novel piece of information is that patients with intraoperative SSEP changes were almost 9 times more likely to develop perioperative stroke beyond 24 h but
Conclusion
Patients with SSEP changes are at increased risk of perioperative stroke within the entire 30-day postoperative period. There is a noticeable step-wise increase in the predicted risk of stroke with the severity of SSEP changes. Thus, loss of SSEP generally indicates greater perioperative stroke risk than change in SSEP and persistent SSEP change generally indicates greater perioperative stroke risk than a transient SSEP change. This is a valuable piece of information, as it can indicate the
Sources of funding
None
Disclosures
None
Conflict of interest
None of the authors have potential conflicts of interest to be disclosed.
Registration
Trial Registration-URL: http://www.crd.york.ac.uk/PROSPERO/display_record.asp?ID=CRD42016037624.
Unique identifier: CRD42016037624.
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