Local haemodynamic changes during carotid endarterectomy--the influence on cerebral oxygenation.

OBJECTIVES: To characterize carotid bifurcation haemodynamics and cerebral oxygenation during clamping and at reperfusion after carotid endarterectomy (CEA). MATERIALS AND METHODS: Sixty-two patients with a symptomatic high-grade stenosis of the internal carotid artery (ICA), who underwent CEA under general anaesthesia, were studied prospectively. Measurements of stump-pressure, volume flow (transit time flowmetry) and changes in cerebral oxygenation (near-infrared spectroscopy (NIRS)) were performed. Selective shunting was based on stump pressure only. RESULTS: Stump pressure correlated with both ICA flow before clamping (r=0.45; p=0.03) and changes in cerebral oxygenation (rSO2) during clamping (r=0.61; p=0.002), the latter was reversed by shunt placement. ICA flow before clamping also correlated with changes in rSO2 during clamping (r=0.41; p=0.01). CONCLUSION: Measurements with transit time flowmetry and cerebral oximetry are technically easy and help to determine the need for selective shunting during CEA. High ICA flow before clamping in combination with a low stump pressure usually indicates the need for a shunt. Volume flow measurements may also be useful in the quality assessment of the CEA.     

External carotid artery shunting during carotid endarterectomy: an alternative for cerebral protection?

OBJECTIVES: to assess the application of external carotid artery (ECA) shunting in cerebral protection during carotid endarterectomy (CEA). DESIGN: prospective study. MATERIALS AND METHODS: the study comprised 137 consecutive patients who underwent CEA under locoregional anaesthesia. Transcranial Doppler was used to monitor the mean velocity of the middle cerebral artery (mv-MCA): (1) before carotid clamping; (2) after clamping both the common and external carotid arteries; (3) after clamping the internal carotid artery alone ("ECA test"). The decision to shunt was based on the occurrence of neurological deficit during carotid clamping. If the ECA test revealed mv-MCA approaching the pre-clamping values ECA shunting was used, whereas the remaining patients in need of a shunt had a standard internal carotid artery (ICA) shunt. RESULTS: shunting was necessary in 12/137 cases (9%). The ECA test indicated that in four cases - 3% of the whole series or 33% of the shunted cases. In these four patients ECA shunting reversed the neurological deficit, and CEA was successfully performed without any complications. CONCLUSIONS: ECA shunting could be considered as an alternative to standard ICA shunting. Suitable cases can be identified on the basis of the ECA test.     

Cerebral oximetry monitoring during carotid endarterectomy: effect of carotid clamping and shunting

Cerebral oximetry is a simple method of measuring regional cerebral oxygen saturation (rSO(2)). One promising application is its use during carotid endarterectomy (CEA) to help minimize the risk of perioperative stroke. The authors used the INVOS-4100 cerebral oximeter at several steps during CEA to measure the effect of carotid clamping and shunting on rSO(2). The authors prospectively evaluated 42 consecutive CEAs in 40 patients. All had CEA under general anesthesia with the routine use of a Javid shunt. The INVOS-4100 oximeter was used to measure rSO(2) before clamping (t1), after clamping but before shunting (t2), 5 minutes after shunt insertion (t3), and after patch closure with reestablished flow (t4). The Wilcoxon signed-rank and rank-sum tests were used for analysis. Clamping of the internal carotid artery (t1 vs t2) resulted in a drop of ipsilateral rSO(2) by -12.3% (p < 0.001). Shunt insertion (t2 vs t3) increased rSO(2) by 10.9% (p < 0.001). Contralateral rSO(2) for the same time periods was insignificant. Patients with preoperative neurologic symptoms had a greater decrease in rSO(2) after clamping (-18.4%) compared with a decrease of -10.4% in asymptomatic patients (p = 0.037). Cerebral oximetry monitoring is simple and inexpensive. The study showed statistically significant changes in rSO(2) as a result of clamping and shunting of the carotid artery. Symptomatic patients had a greater drop in rSO(2).     

Intraoperative monitoring of cerebral function and carotid hemodynamics during carotid endarterectomy

The authors investigated the hemodynamics and monitored the cerebral function to perform the carotid endarterectomy (CEA) safely. The hemodynamics were investigated by measurements of carotid arterial blood flow by an electromagnetic flow meter before and after CEA. And a doppler flow meter applied directly to the carotid arteries to analyze the flow parameters such as peak frequencies (PF), mean frequencies (MF), mode frequencies (Mo F) and % window. We used routinely our specially designed shunt system during surgery, by which stump pressure of the ICA could be measured easily. The cerebral function was evaluated by the amplitude of N20-P25 component of somatosensory evoked potential (SEP). Flow parameters of doppler sounds demonstrated significant changes such as inversion of MF and Mo F, decrease in % window at the poststenotic ICA in the severe stenosis group. By these doppler sounds the extension of stenotic lesion could be detected clearly. The ICA flow showed evidently low values in patients with more than 80% stenosis, which was improved by CEA. With our specially designed T-tube shunt system, stump pressure, side pressure and direct pressure of the ICA could be monitored easily. The mean stump pressure was 52 mmHg and systemic arterial blood pressure was 99 mmHg on the average. SEP revealed evident changes during temporary occlusion in 10 out of 41 patients, which improved following the reflow with the shunt system. Mean stump pressure in the 11 patients was 33 mmHg, and that in the remaining patients were 59 mmHg on the average.(ABSTRACT TRUNCATED AT 250 WORDS)     

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%. CONCLUSION: Monitoring rSO2 with INVOS-3100 to detect cerebral ischemia during CEA has a high negative predictive value, but the positive predictive value is low.     

Near Infrared Spectroscopy Monitoring During Carotid Endarterectomy: Which Threshold Value is Critical?

OBJECTIVES: Retrospectively to verify which decreasing percentage in regional oxygen saturation (rSO(2)) identified patients with good collateralisation during carotid artery cross clamp. MATERIALS AND METHODS: During 594 endarterectomies under general anaesthesia the decreasing percentage from preclamp value to value detected in the first 2 min after clamping the CCA and/or ICA was calculated in real time. No temporary shunt was placed in any case. ROC analysis was performed to determine the optimal cut-off for rSO(2) decrease to identify the occurrence of neurological complications. RESULTS: A cut-off of 11.7% was identified as optimal. Sensitivity and specificity were 75% (95% CI 71-78) and 77% (95% CI 74-80), respectively. The cut-off of 20% had a lower sensitivity (30%) and a higher specificity (98%) to identify patients with complications, with positive and negative predictive value of 37 and 98%, respectively. CONCLUSIONS: The study suggest that a relative decrease in rSO(2) of <20% from preclamp to early cross clamp value has a high negative predictive value, i.e. if rSO(2) does non decrease more than 20%, ischemia by hypoperfusion is unlikely and a shunt should not be necessary. Moreover, a relative decrease >20% may not always indicate intraoperative neurological complications.     

Usefulness of regional cerebral oxygen saturation monitoring in balloon test occlusion

PURPOSE: Recently, temporary balloon test occlusion (BTO) of the internal carotid artery (IC) has become a well accepted procedure for preoperative evaluation of patients with IC large aneurysms. However, it might be dangerous to move patients fitted with a balloon catheter to the room for single-photon emission computed tomography (SPECT). We attempted to clarify the usefulness of regional cerebral oxygen saturation (rSO2) monitoring during BTO, comparing cerebral blood flow (CBF) obtained from SPECT. MATERIALS AND METHODS: Eight patients with an IC large aneurysm underwent BTO with rSO2 monitoring. Regions of interest in the SPECT were defined in the area below the rSO2 sensor of each hemisphere. Correlations among rSO2, CBF, stump pressure and appearance of symptoms were discussed. RESULTS: The rSO2 significantly reduced during BTO (74.1 +/- 1.2 to 60.4 +/- 2.7%, p < 0.001). The individual decreases in rSO2 correlated with decreases of CBF from SPECT (r = 0.966, P < 0.001). Four patients with deltarSO2 (baseline rSO2 - rSO2 during IC occlusion) less than 12 points had no symptoms, but 4 patients with deltarSO2 more than 14 points had some symptoms. The stump pressure had no correlation with CBF and rSO2. CONCLUSIONS: The rSO2 significantly correlated with CBF from SPECT and related with appearance of symptoms. Our results revealed that rSO2 monitoring was useful in BTO, and SPECT could be skipped in some cases to determine the strategies for treatment of IC large aneurysms.     

A comparison of computerized EEG with internal carotid artery stump pressure for detection of ischemia during carotid endarterectomy

Previous investigations appear to indicate that an ischemic EEG is not observed during carotid cross-clamping when the stump pressure is >/=60 mm Hg. In this report of 124 carotid endarterectomies (CEA) performed with selective shunting based on computerized EEG (CEEG), we compared the CEEG and this previously established critical stump pressure level of 60 mm Hg as methods of detecting cerebral ischemia during carotid clamping. A significant association between stump pressure and CEEG findings during clamping existed (p <0.05). Only 1 of 44 patients with a stump pressure >/=60 mm Hg received a shunt based on CEEG signs of cerebral ischemia. However, 62 of the remaining 80 patients did not receive a shunt and awoke neurologically intact despite a stump pressure <60 mm Hg. A highly significant association between the postoperative neurologic exam and the CEEG findings during carotid clamping was demonstrated (p <0.001). In contrast, for stump pressure, a correlation with the neurologic exam was not found. Compared to CEEG, these results appear to indicate that a critical stump pressure of 60 mm Hg is a sensitive but not specific indicator for the placement of a shunt selectively during CEA. The combined use of these two monitors should lead to reliable shunt selection, especially when stump pressure is <60 mm Hg.     

EEG bispectral index during carotid endarterectomy

PURPOSE: Carotid endarterectomy (CEA) is an established surgical procedure for the treatment of internal carotid artery stenosis. Stroke is the commonest risk factor during CEA, therefore, cerebral monitoring became essential. Currently the EEG bispectral index (BIS) is used as a monitor of depth of anesthesia and it has showed decreasing trend during cerebral ischemia. We conducted this study to document the changes of the BIS variable during CEA under anesthesia. METHODS: Ten patients who underwent CEA under general anesthesia were studied. The EEG BIS was measured during the perioperative period where five phases were identified: (A) before induction of anesthesia, (B) before clamping of ICA, (C) during clamping of ICA, (D) after declamping of ICA and (E) during the recovery from anesthesia. RESULTS: The age ranged between 53-69 yr. The mean values of the BIS were 91.4 +/- 5.6, 59.6 +/- 18.7, 44.3 +/- 6.8, 54.7 +/- 8.3 and 72.1 +/- 12.4 during A, B, C, D and E phases respectively with statistical significant low values during B, C, D and E phases versus phase A. CONCLUSION: The decreasing trend of the EEG BIS was shown during ICA clamping and whether this is an important quantitative variable to determine the adequacy of cerebral perfusion during CEA yet to be further studied.     

Cerebral oximetry for the detection of cerebral ischemia during temporary carotid artery occlusion

The near-infrared spectroscopy cerebral oximeter was assessed as a monitoring device for detecting and/or predicting cerebral ischemia during carotid endarterectomy (CEA) and the balloon occlusion test in 24 patients, 12 males and 12 females aged 28 to 77 years (mean 59.9 years). Tolerance testing of complete internal carotid artery (ICA) occlusion by balloon inflation for 20 minutes was performed in nine patients (cerebral aneurysm 6, neck tumor 3) and CEA was performed in 15 patients. The probe of the cerebral oximeter was placed on the forehead of the affected side and regional cerebral oxygen saturation (rSO2) was monitored continuously during all procedures. Stump pressure was measured just after ICA occlusion. Collateral circulation detected by digital subtraction angiography was classified into three groups: good, moderate, or poor. Stump pressure was 41-90 mmHg (mean 61.3 mmHg) in the good collateral circulation group, 40-43 mmHg (41.5 mmHg) in the moderate group, and 14-30 mmHg (23.8 mmHg) in the poor group. Change in rSO2 after ICA occlusion was +3.5(-)-4.2% (mean -1.6%) in the good collateral circulation group, -1.2(-)-6.6% (-3.2%) in the moderate group, and -2.4(-)-10.2% (-6.6%) in the poor group. Changes in rSO2 were significantly different between the good and poor collateral circulation groups (p < 0.01). A greater than 5% fall in rSO2 was observed in 0 of 15 patients in the good collateral circulation group, one of five in the moderate group, and three of four in the poor group. The cerebral oximeter is a useful, real-time, non-invasive method to measure brain oxygenation during CEA, skull base surgery, or other procedures which need to evaluate brain ischemia. A fall of greater than 10% from the rSO2 baseline value is dangerous, but less than 5% is safe.     

Evaluation of changes of systemic blood pressure and shunt incidence in CEA.

BACKGROUND: Induced hypertension is widely recommended as a protective measure in carotid endarterectomy (CEA) to prevent shunt insertion. In this study changes of systemic blood pressure were evaluated in relation to the shunt rate when CEA was performed under local anaesthesia. MATERIALS AND METHODS: In 930 CEAs performed for a high-grade (>70%) ICA stenosis under local anaesthesia the mean systemic blood pressure was measured preoperatively (RR1) and directly before carotid cross-clamping (RR2). A ratio was calculated from these values (RRR=RR2/RR1). A shunt was only inserted for clinical signs of cerebral ischemia. If that became necessary later after cross-clamping had been tolerated primarily, the blood pressure during this period was also recorded (RR3). Also the presence of a contralateral ICA occlusion and baseline blood pressure levels were considered as factors with potential impact on shunt necessity. RESULTS: Among the 638 male (69%) and 292 female (31%) patients with a median age of 70 years (ranging from 52 to 91 years) 82 (9%) had a contralateral ICA occlusion. A shunt was used in 177 operations (19%) and significantly more frequent in patients with a contralateral ICA occlusion (39/82=48% vs. 138/848=16%, p<0,001). RRR was significantly reduced in patients who needed a shunt (0.95 (0.41-1.53) vs. 1.0 (0.54-1.9), p=0.002) which was only true for patients with a patent contralateral ICA. The shunt rate did not differ when contrasting RRR thresholds (<0.7 vs. >1.3) or preoperative blood pressure levels (<100 mmHg vs. >120 mmHg) were compared. RRR did not differ between directly or delayed shunted patients. RR3 did not differ significantly from RR2. A regression analysis identified the presence of a contralateral ICA occlusion as the only independent parameter influencing shunt insertion. CONCLUSIONS: Changes in systemic blood pressure during CEA under local anaesthesia seem to influence shunting rather marginally. The value of induced hypertension to prevent cerebral ischemia should be newly discussed.     

Hemodynamic conditions at the carotid bifurcation during protective common carotid occlusion.

OBJECTIVES: Carotid angioplasty and stenting procedures are associated with an obligatory release of particulate debris into the distal cerebral circulation. Although most of the emboli are small and do not result in symptomatic neurologic deficits, some may be large enough to cause stroke. For this reason, a variety of filters and balloon occlusion devices have been employed as adjuvants to decrease the risk of distal embolization during carotid stenting. Some of these devices rely on the arrest of antegrade blood flow with the use of inflow arrest. The present study was undertaken to investigate the hemodynamic conditions that exist at the carotid bifurcation during common carotid artery (CCA) occlusion. METHODS: Internal carotid artery (ICA) and external carotid artery (ECA) stump pressures were measured in 29 patients undergoing carotid endarterectomy. Duplex ultrasound scanning was used to measure the direction and velocity of blood flow in the ICA and ECA with the CCA cross-clamped but the ICA and ECA open, a clinical scenario analogous to CCA balloon occlusion at the time of carotid angioplasty and stenting. The direction and magnitude of ICA and ECA flow were compared with the stump pressures to determine whether a correlation existed between these variables. RESULTS: The mean stump pressure in the ICA and ECA averaged 56 +/- 16 and 53 +/- 12 mm Hg, respectively. The ICA systolic stump pressure was lower than the ECA systolic stump pressure in six patients (21%), and all of these patients had persistent antegrade systolic duplex blood flow by duplex interrogation during CCA occlusion. The ICA systolic stump pressure exceeded the ECA systolic stump pressure in 19 patients (66%), and all of these patients had retrograde ICA flow during systole. Diastolic flow was also well correlated with the magnitude of the ICA/ECA stump pressure differential, with antegrade diastolic ICA blood flow in all nine patients with an ICA diastolic stump pressure less than the ECA diastolic stump pressure. None of the 10 patients with ICA diastolic stump pressure greater than ICA diastolic stump pressure maintained antegrade ICA diastolic flow, but four of these patients had flow to zero in diastole. Overall, 13 of 29 patients (45%) could be surmised to be at risk for distal embolization to the brain based on the persistence of some element of either systolic or diastolic antegrade ICA flow during common carotid occlusion. CONCLUSIONS: Common carotid occlusion alone appears insufficient to protect against distal embolization during manipulations of the carotid bifurcation. Persistent systolic or diastolic antegrade blood flow occurs in a high proportion of patients, lending credence to the use of additional protective strategies to ameliorate the risk of embolic complications.     

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%.     

Carotid endarterectomy with routine electroencephalography and selective shunting: Influence of contralateral internal carotid artery occlusion and utility in prevention of perioperative strokes

OBJECTIVE: Carotid endarterectomy (CEA) is associated with a risk of cerebral ischemia during carotid clamping, particularly in the face of contralateral internal carotid artery (ICA) occlusion. We examined the results of CEA with continuous electroencephalography in patients without and with contralateral ICA occlusion. DESIGN AND SETTING: We reviewed 564 primary CEAs with routine electroencephalography and general anesthesia performed between April 1, 1989, and March 31, 1999, in a community teaching medical center. Main outcome measures were perioperative stroke, temporary lateralizing neurologic deficit, and death. Shunts were placed primarily for significant electroencephalographic changes after carotid clamping but also selectively for contralateral ICA occlusion, prior stroke, or surgeon choice. CEA was performed for asymptomatic disease in 35% of cases. RESULTS: Significant electroencephalographic changes occurred in 16% versus 39% (P <.001) and shunts were placed in 13% versus 55% (P <.001) of patients with patent (n = 507) versus occluded contralateral ICA (n = 57), respectively. The fraction of CEAs with significant electroencephalographic changes during clamping was stable, but shunt use declined slightly over time as our confidence in electroencephalography increased. Patches were placed more often (86% versus 65%; P =.002), but other operative details were similar when the contralateral ICA was occluded. Five early (30 days) strokes (0.9%) and eight early temporary postoperative neurologic events (1.4%) occurred, all ipsilateral to CEA and all after the patient left the operating room with none in patients with contralateral ICA occlusion. Two perioperative deaths occurred, one in a patient without and one in a patient with contralateral ICA occlusion. Neither of these deaths was related to ipsilateral stroke. No increase in stroke rate with decreased shunt use over time was seen. CONCLUSION: Routine use of electroencephalography was associated with apparent complete elimination of intraoperative strokes and less than 1% risk of perioperative strokes. These observations appear to be true even in the face of contralateral ICA occlusion. Electroencephalography is a sensitive detector of cerebral ischemia and a valuable tool for determination of need for shunting during CEA. Surgeons should consider routine use of electroencephalography and selective shunting for significant electroencephalographic changes with clamping.     

Noninvasive analysis of conjunctival microcirculation during carotid artery surgery reveals microvascular evidence of collateral compensation and stenosis-dependent adaptation

OBJECTIVE: Hemodynamically relevant internal carotid artery (ICA) stenosis is a major cause of ischemic stroke. Despite its long-term benefit, carotid endarterectomy may also be associated with severe neurologic deficits. Intraoperative and early recognition of ischemia in the region of the ICA may reduce this risk. To date, direct imaging and quantitative analysis of microvascular structures and function in the human ICA region have not been possible. We purposed to visualize and quantify ischemia/reperfusion-induced microcirculatory changes in the terminal vascular bed of the ICA in patients undergoing unilateral ICA endarterectomy. METHODS: Sequential analysis of the ipsilateral and contralateral conjunctival microcirculation was performed with orthogonal polarized spectral imaging in 33 patients undergoing unilateral ICA endarterectomy because of moderate or severe ICA stenosis (North American Symptomatic Carotid Endarterectomy Trial score, 75% +/- 13%), before clamping the ICA (baseline), during clamping of the external carotid artery and ICA, during reperfusion of the ICA (intraluminal shunt), during the second clamping of the ICA (shunt removal), after declamping (reperfusion) of the external carotid artery and ICA, and 15 to 20 minutes after the second ICA reperfusion. RESULTS: During ICA clamping for shunt placement, ipsilateral and contralateral conjunctival capillary perfusion was significantly decreased, but it was completely restored after reperfusion with carotid shunting. Reclamping of the ICA for shunt removal caused microvascular dysfunction, which was significantly less pronounced than that observed during the first clamping. The individual degree of ICA stenosis was inversely correlated with the ipsilateral and contralateral decrease in conjunctival functional capillary density during the first ICA clamping. CONCLUSIONS: These results suggest adaptive mechanisms of capillary perfusion with increasing stenosis and development of collateral compensatory circulation in the vascular region of the human ICA. Conjunctival orthogonal polarized spectral imaging during unilateral ICA reconstruction enables continuous noninvasive analysis of bilateral conjunctival microcirculation in the terminal region of the ICA and enables monitoring for efficient carotid shunt perfusion during and after endarterectomy.     

Cerebral oximetry in patients undergoing carotid endarterectomy: preliminary results

Carotid endarterectomy (CEA) is an appropriate treatment for carotid occlusive disease. The risk of stroke during CEA ranges from 1.1% to 7.5%. Shunting is usually advised when severe ischemia during cross-clamping of the internal carotid artery is suspected. Routine use of an intraluminal shunt may increase the perioperative stroke rate. Popular and well documented methods of neurologic monitoring for ischemia during general anesthesia are electroencephalography (EEG) and transcranial Doppler ultrasonography (TCD) of the middle cerebral artery. The purpose of this prospective study was to compare cerebral oximetry using near infrared spectrophotometry (NIRS) with EEG and TCD. Preliminary data on 14 patients scheduled for elective carotid endarterectomy were included and a literature search was performed to correlate the findings. No postoperative neurologic events occurred. During carotid clamping there was a significant decrease in regional oxygen saturation (rSO2) but there was only a weak correlation with the decrease in mean Doppler flow (R = 0.74; P = 0.02) and no correlation with EEG changes (R = 0.49; P = 0.18). A useful rSO2 cut-off value predictive for cerebral ischemia could not be defined.     

Carotid Artery Stump Pressure (CASP) in 1135 consecutive endarterectomies under general anesthesia: an old method that survived the test of times

AIM: Intraoperative electroencephalography, somato-sensory evoked potentials and transcranial Doppler have been proposed to replace carotid artery stump pressure measurement (CASP) as the test of choice in the evaluation of cerebral tolerance during temporary carotid occlusion. CASP is a simple, inexpensive test that does not require an additional specialist in the operating room. Herein, we attempt to demonstrate that CASP is a reliable test that does not need to be replaced by more sophisticated and expensive techniques. METHODS: Over the last 6 years, 1 135 consecutive carotid endarterectomies (CEA) were performed under general anesthesia at our institution. There were 592 males and 429 female patients with an age range of 39 to 95 years (mean 72 +/- 9 years). Hypertension, diabetes, smoking, coronary artery disease and chronic renal insufficiency were present in 71%, 39%, 36%, 32% and 26%, respectively. Internal carotid artery (ICA) stenosis ? 70% was confirmed by duplex scanning in 92% of the cases. The remaining 8% of cases had 50% to 69% ICA stenosis in neurologically symptomatic patients. Asymptomatic patients accounted for 75% of the cases. Contralateral ICA occlusion was observed in 57 cases (5%). Indwelling shunts were used when CASP was < 45 mmHg. Carotid patches were used in 233 cases. Completion duplex scanning was performed in all cases. CASP was measured by inserting a 23-gauge needle into the common carotid artery (CCA) after clamping the ICA to avert possible embolization during needle insertion. Once the tip of the needle was confirmed intraluminally by pressure measurement and triphasic waveform tracing, the CCA and the external carotid artery were clamped. After a flat line tracing was depicted on the monitor, ICA clamp was released and CASP was recorded. RESULTS: CASP was < 45 mmHg in 233 cases (21%) (Group I) and > or = 45 mmHg in 902 cases (79%) (Group II). The mean CASP in presence of contralateral ICA occlusions was 40 +/- 15 mmHg while it was 65 +/- 27 mmHg for patent contralateral ICAs (P < 0.0001). The overall 30-day stroke rate was 1% (1 135 cases). It was 3% (7/233) for group I and 0.5% (4/902) for group II (P < 0.01). In patients with postoperative strokes CASP ranged from 23 to 44 mmHg (mean 33 +/- 8) in group I (shunted) and it varied from 59 to 116 mmHg (mean 99 +/- 28) in group II (non-shunted) with P < 0.001. The causes of stroke in group I were hyperperfusion (2), partial ICA thrombosis (2), embolization (2) and worsening of acute stroke (1). In group II there were 2 cases of embolization and 2 of ICA thrombosis. No patient had a stroke caused by decreased intraoperative global cerebral perfusion. The overall 30-day mortality rate was 0.5%. The overall combined stroke/death rate was 1.5%. CONCLUSION: CASP > or = 45 mmHg was a reliable predictor of adequate cerebral perfusion during 1,135 consecutive CEAs performed under general anesthesia. The percentage of indwelling shunts utilized in this series was not significantly different from the ones using more expensive and sophisticated techniques.     

Fixative method of carotid shunt using a Sugita's fenestrated aneurysm clip as a device in carotid endarterectomy technical note

BACKGROUND: Difficulty for distal exposure of the ICA is sometimes encountered during CEA. A carotid shunt is used to maintain sufficient cerebral blood flow during CEA but requires fixative materials, such as a string or a metallic ring, which often restrict the operative field, especially that of the distal ICA. METHODS: Here, we describe a novel technique for carotid shunt fixation using a unique fixative device in CEA. In the method presented here, the carotid shunt is fixed with an inflated balloon and a conventional vascular tourniquet proximally, but distal fixation is achieved using a Sugita's fenestrated clip that catches the mid portion of the carotid shunt and surrounding tissue. RESULTS AND CONCLUSION: The device prevents the distal carotid shunt slipping out of the distal ICA. The present method allows mobilization of the shunt position during CEA and facilitates far-distal exposure of the ICA.     

Clamping ischemia, threshold ischemia and delayed insertion of the shunt during carotid endarterectomy with patch.

BACKGROUND: Shunt insertion during carotid endarterectomy (CEA) is mandatory to avoid neurological damage due to clamping ischemia; however shunt insertion before plaque removal has many inconveniences (atheroembolism, intimal dissection, difficulty of endarterectomy). The aim of this study is to verify whether and how long shunt insertion may be safely delayed to permit plaque removal and ensure cerebral perfusion during the further time consuming manoeuvres of CEA (peeling, patch angioplasty). METHODS: From July 1990 to February 1996 383 patients underwent 411 CEAs under general anesthesia with EEG continuous monitoring and PTFE patch angioplasty. A Pruitt-Inahara shunt was routinely inserted only after atherosclerotic plaque removal. In 316 CEAs (76.9%) without EEG signs of cerebral ischemia (Group A) the mean clamping time was 10 min +/-4.8 (range 2-37 min). In 95 CEAs (23.1%) with EEG signs of cerebral ischemia (Group B) it was 7.3 min +/-3.5 (range 3-20 min). All patients had normal EEG signals after delayed shunt insertion and reperfusion (mean 21 min, range 5-45 min). RESULTS: In the short term results (within 30 days) there was a relevant neurological complication rate of 0.96% (2 major stroke and 2 lethal stroke); at awakening we observed 5 RINDs (1.21% of total) 1 in a patient of Group A (0.31%) and the other 4 in patients of Group B (4.21%). CONCLUSIONS: These data confirm the rationale of a delayed insertion of the shunt: actually the cerebral parenchyma may tolerate under general anesthesia a sufferance due to carotid clamping, EEG detectable, without neurological deficits for at least 7.3 min. This time is sufficient to perform the most difficult steps of CEA (plaque removal, distal intima checking) allowing shunt insertion in a clean operatory field, without inconveniences. Finally the shunt allows complementary time consuming steps, as patch angioplasty, with improvement of both short- and long-term results.     

Reducing the Risk of Intraoperative Neurological Complications during Carotid Endarterectomy with Early Distal Control of the Internal Carotid Artery

AIM OF THE STUDY: To assess the feasibility and effectiveness of a modified surgical technique with early clamping of the distal internal carotid artery (ICA) during carotid endarterectomy in a single centre experience. STUDY DESIGN: Retrospective study, teaching hospital. MATERIAL AND METHODS: Between 1996 and 2002, 2235 CEAs were performed. Until April 1999, the intra-operative strategy consisted of standard isolation and dissection of the carotid bifurcation preliminary to ICA clamping (group 1; 1090 interventions). Starting from May 1999, we performed early isolation and clamping of the distal ICA, followed by dissection of the carotid bifurcation and clamping of the external and common carotid artery (group 2; 1145 interventions). RESULTS: The modified technique was feasible in all the patients of group 2. In group 2 there was a significantly lower incidence of neurological deficit on waking than in group 1 (0.4% and 1.8%, respectively; p=0.02). CONCLUSIONS: Early distal control of the internal carotid artery during CEA is feasible and could contribute to reducing intra-operative neurological events.