Comparison of Internal Shunts during Carotid Endarterectomy under Routine Shunting Policy

We compared patients who underwent carotid endarterectomy (CEA) using two-way and three-way internal shunts and discussed which shunt was more appropriate and effective for surgeons. Eighty-two patients (mean 69.5 ± 6.1 years old, mean degrees of stenosis 79.6 ± 10.4%) who had undergone CEA by our routine shunting policy were examined concerning the difference of Sundt and Pruitt-Inahara (P-I) shunts in clinical use. Carotid clamping time for the P-I shunt was over 2 minutes longer than that by Sundt in either split or conventional continuous arteriotomy (p < 0.001). The proportions of cases with multiple trials of either arteriotomy or insertion of a shunt tube, cases detected more than one high-intensity spot on diffusion-weighted images of magnetic resonance imaging after CEA, and cases detected postoperative intimal flaps detected by multi-detector CT angiography showed no significant differences between the two shunt groups. The two-way Sundt shunt was quicker than the three-way P-I shunt in placement with no remarkable problems. Split arteriotomy was not useful in shortening the placement time for either Sundt or P-I shunt tubes, compared with continuous arteriotomy. A simple two-way shunt with easy handling like the Sundt shunt would be also appropriate to choose in selective shunting under the unfamiliarity of treating shunts.     

Evaluation of a Cerebral Oximeter as a Monitor of Cerebral Ischemia during Carotid Endarterectomy

Background: Stroke is an important contributor to perioperative morbidity and mortality associated with carotid endarterectomy (CEA). This investigation was designed to compare the performance of the INVOS-3100 cerebral oximeter to neurologic function, as a means of detecting cerebral ischemia induced by carotid cross-clamping, in patients undergoing carotid endarterectomy with cervical plexus block.

Methods: Ninety-nine patients undergoing 100 CEAs with regional anesthesia (deep or superficial cervical plexus block) were studied. Bilateral regional cerebrovascular oxygen saturation (rSO2) was monitored using the INVOS-3100 cerebral oximeter. Patients were retrospectively assigned to one of two groups: those in whom a change in mental status or contralateral motor deficit was noted after internal carotid clamping (neurologic symptoms; n = 10) and those who did not show any neurologic change (no neurologic symptoms; n = 90). Data from 94 operations (neurologic symptoms = 10 and no neurologic symptoms = 84) were adequate for statistical analyses for group comparisons. A relative decrease in ipsilateral rSO2 after carotid occlusion (calculated as a percentage of preocclusion value) during all operations (n = 100) was also calculated to determine the critical level of rSO2 decrease associated with a change in neurologic function.

Results: The mean (+/- SD) decrease in rSO2 after carotid occlusion in the neurologic symptoms group (from 63.2 +/- 8.4% to 51.0 +/- 11.6%) was significantly greater (P = 0.0002) than in the no neurologic symptoms group (from 65.8 +/- 8.5% to 61.0 +/- 9.3%). Logistic regression analysis used to determine if a change in rSO2, calculated as a percentage of preclamp value, could be used to predict change in neurologic function was highly significant (likelihood ratio chi-square = 13.7;P = 0.0002). A 20% decrease in rSO2 reading from the preclamp baseline, as a predictor of neurologic compromise, resulted in a sensitivity of 80% and specificity of 82.2%. The false-positive rate using this cutoff point was 66.7%, and the false-negative rate was 2.6%, providing a positive predictive value of 33.3% and a negative predictive value of 97.4%.     

Adenosine: A Sensitive Indicator of Cerebral Ischemia during Carotid Endarterectomy

Background: For the human brain, there are no data available concerning the significance of adenosine and its metabolites as biochemical indicators of cerebral ischemia. Since adenosine may counteract key pathogenetic mechanisms during cerebral ischemia, its sensitivity and specificity as a marker of cerebral ischemia was investigated in relation to hypoxanthine and lactate.

Methods: Arterial and jugular venous concentration changes of adenosine, hypoxanthine, and lactate were studied in 41 patients undergoing carotid endarterectomy. Cerebral tissue oxygenation was monitored continuously by somatosensory-evoked potentials. A carotid artery shunt (n = 6) was placed only after complete loss of somatosensory-evoked potentials.

Results: Before carotid artery clamping jugular venous concentrations of adenosine, hypoxanthine, and lactate in subsequently shunted patients were 229 +/- 88 nM, 1105 +/- 116 nM, and 0.85 +/- 0.52 mM, respectively (mean +/- SD). In patients who required shunting, carotid artery clamping induced a significant increase in jugular venous adenosine (389 +/- 114 nM) and jugular venous hypoxanthine (1444 +/- 168 nM). In contrast, the increase in jugular venous lactate (0.91 +/- 0.48 mM) did not reach statistical significance. Focal cerebral ischemia was indicated by jugular venous adenosine with a sensitivity and specificity of 0.83 and 0.71, respectively.     

Carotid Endarterectomy in an Awake Patient with Contralateral Carotid Occlusion: Influence of Selective Shunting

n = 198 - group II, n= 1068) who required CEA. In 77 patients of group I, a shunt was systematically adopted (subgroup A); in the other 121 patients (subgroup B) and in all patients of group II a selective shunting policy was adopted. The risk for the patients with contralateral carotid occlusion was not significantly higher than that for patients without occlusion. Results were not influenced by systematic/selective shunting policy, and the incidence of signs of cerebral ischemia was higher in patients with contralateral carotid occlusion.     

The Influence of Routine Completion Arteriography on Outcome following Carotid Endarterectomy

n = 69) normal; Group B (n= 29), abnormal, severe defects; Group C (n= 56), abnormal, mild–moderate defect. RCA detected 32 defects in Group B: 10 internal carotid (ICA), seven endpoint flaps, two kinks, one dissection; 16 external carotid (ECA), 10 severe endpoint defects and six total occlusion; six common carotid (CCA), five irregular proximal shelfs, one web. Thirty of 32 defects were successfully repaired as confirmed by normal repeat RCA studies; one ECA defect was not repaired and the ICA dissection was irreparable. In Group C, 67 mild–moderate defects were identified, but not corrected. These included <30% stenosis in the ICA (12), ECA (18), CCA (24), and vein patch corrugation or irregularity (13). For the entire series the postoperative ICA occlusion rate was 2% (3/154), stroke rate 2.6% (4/154), and a subsequent >50% restenosis rate of 7% (11/154). The yield from routine carotid completion arteriograms was significant, with 19% of studies identifying a severe defect that required repair. Although the difference in stroke rates and restenosis between the different groups did not reach statistical significance, patients with normal intraoperative arteriograms initially or after correction of a significant RCA defect had no early carotid occlusion (p= 0.05, Fisher's exact test) compared to patients with residual RCA defects. All early carotid occlusions occurred in patients with unrepaired defects. We conclude that RCA is an important method of quality control after CEA and exerts a subtle, but real, reduction in postoperative complications.     

TCD-Detected Cerebral Embolism in Carotid Endarterectomy Versus Angioplasty and Stenting of the Carotid Bifurcation

Purpose: In this article we will review some of the issues surrounding the relationship between TCD-detect-ed emboli and brain function and architecture, both during conventional surgical carotid endarterectomy (CEA) and carotid angioplasty and stenting (CAS).

Material and methods: In both procedures, the cerebral embolic load was semi quantitatively assessed and associated with clinical outcome during the procedure and after a symptom free interval within 7 days.

Results: In CEA, particulate emboli that occurred during the wound closure stage were associated with intraoperative stroke and stroke related death, odds ratios [OR] 2.3 95%CI 1.2–4.4, p = 0.007. In CAS, showers of microemboli that appeared at postdilatation of the stent (OR 3.2, 95%CI 1.5–6.9, p = 0.002), particulate macroembolism (relative risk [RR] 10.2, 95%CI 5.9–17.3, p < 0.001), and massive air embolism (RR 10.2, 95%CI 5.8–17.7, p < 0.001) were associated with new transient and persistent cerebral deficits.

Conclusion: In both CEA and CAS, recording of cerebral emboli by TCD ultrasonography provides insight in the pathogenesis of procedure related adverse cerebral outcome. In several centres TCD monitoring during CEA is now accepted as a clinically relevant tool that helps the surgeon to make the operation safer. In CAS more research is needed, particularly with respect to the impact of cerebral protection devices.     

Transcranial Doppler Intraoperative Monitoring during Carotid Endarterectomy: Experience with Regional or General Anesthesia,with and without Shunting

p = 0.05). There was no significant difference when particulate and air microemboli were compared. During surgery TCD identified residual flow of less than 40% in the MCA in 17 patients (18.8%). TCD also identified hyperperfusion in two patients, shunt abnormalities in three patients, and influenced postop treatment in four patients, one of whom was returned to surgery. TCD is an important tool for identifying patients who would benefit from a shunt, preventing hyperperfusion, identifying postop emboli, and detecting technical errors.     

Comparison of Single and Dual Monitoring during Carotid Endarterectomy

We compared the rate of selective shunt and pattern of monitoring change between single and dual monitoring in patients undergoing carotid endarterectomy (CEA). A total of 121 patients underwent 128 consecutive CEA procedures. Excluding five procedures using internal shunts in a premeditated manner, we classified patients according to the monitoring: Group A (n = 72), patients with single somatosensory evoked potential (SSEP) monitoring; and Group B (n = 51), patients with dual SSEP and motor evoked potential (MEP). Among the 123 CEAs, an internal shunt was inserted in 12 procedures (9.8%) due to significant changes in monitoring (Group A 5.6%, Group B 15.7%, p = 0.07). The rate of shunt use was significantly higher in patients with the absence of contralateral proximal anterior cerebral artery (A1) on magnetic resonance angiography (MRA) than in patients with other types of MRA (p <0.001). Significant monitor changes were seen in 16 (12.5%) in both groups. In four of nine patients in Group B, SSEP and MEP changes were synchronized, and in the remaining five patients, a time lag was evident between SSEP and MEP changes. In conclusion, the rate of internal shunt use tended to be more frequent in patients with dual monitoring than in patients with single SSEP monitoring, but the difference was not significant. Contralateral A1 absence may predict the need for a shunt and care should be taken to monitor changes throughout the entire CEA procedure. Use of dual monitoring can capture ischemic changes due to the complementary relationship, and may reduce the rate of false-negative monitor changes during CEA.     

Fatal Intracerebral Haemorrhage Following Carotid Endarterectomy in a Patient with Cerebral Amyloid Angiopathy

A 68-year-old man underwent carotid endarterectomy for symptomatic carotid artery stenosis. Immediately after surgery the patient suffered dramatic neurological deterioration, due to massive cerebral bleeding. Pathological examination revealed cerebral amyloid angiopathy. This condition is known to predispose to spontaneous, as well as anticoagulation induced, cerebral haemorrhage. Surgical intervention needing anticoagulation in elderly patients at risk for congophilic angiopathy should be performed with extreme caution.     

A Randomized Crossover Comparison of the Effects of Propofol and Sevoflurane on Cerebral Hemodynamics during Carotid Endarterectomy

Background: Intravenous and inhalational anesthetic agents have differing effects on cerebral hemodynamics: Sevoflurane causes some vasodilation, whereas propofol does not. The authors hypothesized that these differences affect internal carotid artery pressure (ICAP) and the apparent zero flow pressure (critical closing pressure) during carotid endarterectomy. Vasodilation is expected to increase blood flow, reduce ICAP, and reduce apparent zero flow pressure.

Methods: In a randomized crossover study, the gradient between systemic arterial pressure and ICAP during carotid clamping was measured while changing between sevoflurane and propofol in 32 patients. Middle cerebral artery blood velocity, recorded by transcranial Doppler, and ICAP waveforms were analyzed to determine the apparent zero flow pressure.

Results: ICAP increased when changing from sevoflurane to propofol, causing the mean gradient between arterial pressure and ICAP to decrease by 10 mmHg (95% confidence interval, 6-14 mmHg; P < 0.0001). Changing from propofol to sevoflurane had the opposite effect: The pressure gradient increased by 5 mmHg (95% confidence interval, 2-7 mmHg; P = 0.002). Ipsilateral middle cerebral artery blood velocity decreased when changing from sevoflurane to propofol. Cerebral steal was detected in one patient after changing from propofol to sevoflurane. The apparent zero flow pressure (mean +/- SD) was 22 +/- 10 mmHg with sevoflurane and 30 +/- 14 mmHg with propofol (P < 0.01). There was incomplete drug crossover due to the limited duration of carotid clamping.     

Preoperative Magnetic Resonance Angiography as a Predictive Test for Cerebral Ischemia During Carotid Endarterectomy

Background

To evaluate whether the preoperative magnetic resonance angiography (MRA) can predict the risk of cerebral ischemia associated with the carotid endarterectomy (CEA).

Methods

Between January 2004 and December 2010, 382 consecutive patients (mean age: 56.6 years; range: 45–78 years) were identified to have undergone preoperative MRA and the CEA under regional anesthesia. It was determined that the patient needs shunting during the CEA by intraoperative monitoring of patient’s neurology. All patients were divided into two subgroups: shunt group or no-shunt group. Imaging findings on preoperative MRA were correlated to shunting using univariate and multivariate logistic regression analyses combined with patient’s demographic and clinical features to identify predictors of cerebral ischemia during the CEA.

Results

In 37 of 382 CEA cases (9.7 %), shunting had been performed intraoperatively because the patient had a neurologic deficit. At multivariate analysis, preoperative MRA findings such as the absence of patent communicating arteries (odds ratio [OR], 5.56; 95 % confidence interval [CI], 3.05–9.69; p = 0.013) and the increase of intracranial arteries which were not patent in the contralateral hemisphere (OR, 4.277; 95 % CI, 2.575 to 7.104; p < 0.0001) were significantly associated with shunting.

Conclusions

Preoperative MRA is valuable when predicting cerebral ischemia leading to an inevitable shunting during CEA. Therefore, if there are preoperative MRA findings such as multiple occlusive intracranial arteries in the contralateral hemisphere or the absence of patent communicating arteries, it is recommended that CEA be performed under general anesthesia with routine shunting to avoid a serious shunt-related complication.     

Correlation of Regional Cerebral Blood Flow with Ischemic Electroencephalographic Changes during Sevoflurane-Nitrous Oxide Anesthesia for Carotid Endarterectomy

Background: Carotid endarterectomy necessitates temporary unilateral carotid artery occlusion. Critical regional cerebral blood flow (rCBF) has been defined as the rCBF below which electroencephalographic (EEG) changes of ischemia occur. This study determined the rCBF50, the rCBF value at which 50% of patients will not demonstrate EEG evidence of cerebral ischemia with carotid cross-clamping.

Methods: Fifty-two patients undergoing elective carotid end-arterectomy were administered 0.6-1.2% (0.3-0.6 minimum alveolar concentration) sevoflurane in 50% nitrous oxide (N2 O). A 16-channel EEG was used for monitoring. The washout curves from intracarotid133 Xenon injections were used to calculate rCBF before and at the time of carotid occlusion by the half-time (t1/2) technique. The quality of the EEG with respect to ischemia detection was assessed by an experienced electroencephalographer.

Results: Ischemic EEG changes developed in 5 of 52 patients within 3 min of carotid occlusion at rCBFs of 7, 8, 11, 11, and 13 ml [center dot] 100 g sup -1 [center dot] min sup -1. Logistic regression analysis was used to calculate an rCBF50 of 11.5 +/- 1.4 ml [center dot] 100 g sup -1 [center dot] min sup -1 for sevoflurane. The EEG signal demonstrated the necessary amplitude, frequency, and stability for the accurate detection of cerebral ischemia in all patients within the range of 0.6-1.2% sevoflurane in 50% N2 O.