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Background: Spinal cord ischemic injury is the most devastating sequela of descending and thoracoabdominal aortic surgery. Motor-evoked potentials (MEPs) have been used to intraoperatively assess motor tract function, but it remains unclear whether MEP monitoring can decrease the incidence of postoperative motor deficits. Therefore, we reviewed multicenter medical records of patients who had undergone descending and thoracoabdominal aortic repair (both open surgery and endovascular repair) to assess the association of MEP monitoring with postoperative motor deficits., Methods: Patients included in the study underwent descending or thoracoabdominal aortic repair at 12 hospitals belonging to the Japanese Association of Spinal Cord Protection in Aortic Surgery between 2000 and 2013. Using multivariable mixed-effects logistic regression analysis, we investigated whether intraoperative MEP monitoring was associated with postoperative motor deficits at discharge after open and endovascular aortic repair., Results: We reviewed data from 1214 patients (open surgery, 601 [49.5%]; endovascular repair, 613 [50.5%]). MEP monitoring was performed in 631 patients and not performed in the remaining 583 patients. Postoperative motor deficits were observed in 75 (6.2%) patients at discharge. Multivariable logistic regression analysis revealed that postoperative motor deficits at discharge did not have a significant association with MEP monitoring (adjusted odds ratio [OR], 1.13; 95% confidence interval [CI], 0.69-1.88; P = .624), but with other factors: history of neural deficits (adjusted OR, 6.08; 95% CI, 3.10-11.91; P < .001), spinal drainage (adjusted OR, 2.14; 95% CI, 1.32-3.47; P = .002), and endovascular procedure (adjusted OR, 0.45; 95% CI, 0.27-0.76; P = .003). The sensitivity and specificity of MEP <25% of control value for motor deficits at discharge were 37.8% (95% CI, 26.5%-49.5%) and 95.5% (95% CI, 94.7%-96.4%), respectively., Conclusions: MEP monitoring was not significantly associated with motor deficits at discharge.

Background: It is crucial to evaluate cerebral blood flow (CBF) during carotid endarterectomy (CEA). However, it is difficult to measure CBF in the operating room. The recent development of high-accuracy near-infrared spectroscopy (NIRS) has enabled the measurement of regional CBF following injection of indocyanine green (ICG). We aimed to measure changes in regional CBF by clamping the carotid artery during CEA and to analyze factors affecting the blood flow index (BFI) in CEA., Methods: Patients undergoing elective CEA were enrolled in this study after it was approved by the institutional ethical board. All patients underwent CEA under general anesthesia. Intraoperative blood pressure was controlled about 30% higher than the precarotid cross-clamping during carotid cross-clamping. ICG (0.5 mg/kg) was injected before, during, and after carotid cross-clamping. The kinetics of an intravenous bolus of ICG were monitored by a NIRS oximeter (NIRO200NX) and the BFI was calculated using the slope of the ICG concentration. The impact of carotid cross-clamping on the BFI was evaluated, along with factors influencing changes in the BFI., Results: A total of 50 patients were enrolled. The BFI significantly decreased during carotid cross-clamping compared with baseline values (from 0.077±0.019 to 0.0054±0.0019 μmol/L/s) (P<0.01). After unclamping the common carotid artery, the BFI recovered to the preclamping level (0.0073±0.0023 μmol/L/s) (P<0.01). Multiple logistic regression analysis revealed that abnormalities of the circle of Willis correlated significantly with reduced BFI (odds ratio=12.07, P=0.036)., Conclusions: The BFI was significantly reduced by carotid artery clamping during CEA. Abnormalities of the circle of Willis were a significant factor contributing to reduced BFI.

Surgical clipping may cause stenosis of parent arteries or occlusion of perforating arteries in cerebral aneurysm surgery. To prevent postoperative motor deficits, motor-evoked potentials (MEPs) have been used. This enables to detect cerebral ischemia. However, the rate of false negatives (motor deficits with preserved MEP) has been relatively higher than in aortic surgery. We hypothesized that postoperative motor deficits with preserved intraoperative MEP do not always represent false negatives. We reviewed medical records of patients for cerebral aneurysms surgery with transcranial MEP monitoring from September 2003 to March 2009. We reviewed aneurysm location and size, abnormal computed tomography findings, and clinical outcome. Motor status was evaluated immediately after extubation and anytime when the symptom of motor deficits was found. One hundred and eleven patients underwent cerebral aneurysm clipping with transcranial MEP. Ninety-eight patients manifested no intraoperative MEP changes and no postoperative motor deficits. Six patients showed intraoperative MEP changes, resulting in no motor deficits in 4 patients with MEP recovery and hemiparesis in 2 without MEP recovery. Four patients of 6 had aneurysm in anterior choroidal artery (AchA). Other 6 patients showed postoperative motor deficits despite preserved intraoperative MEP. Two of 6 patients showed no motor deficits just after extubation, but developed deficits 5 hours after coming out of anesthesia. Only 1 of the 6 patients had aneurysm in AchA. In AchA aneurysm surgery, intraoperative MEP monitoring seems to be useful. False negative in MEP monitoring may include new-onset hemiparesis despite preserved intraoperative MEP.

Background: Previous studies documented that near-infrared spectroscopy values were affected by factors related to optical path length, such as hemoglobin concentration, the differential path length factor, skull thickness (t-skull), and the area of the cerebrospinal fluid layer (a-CSFL). Lately, the NIRO-100 (Hamamatsu Photonics, Hamamatsu, Japan) has provided a tissue oxygen index (TOI) that theoretically is not supposed to be affected by optical path length. Therefore, the authors hypothesized that TOI is not influenced by the above-described individual factors., Methods: Cardiac surgical or neurosurgical 103 patients (65 men and 39 women; aged 63 +/- 14 yr) were studied. TOI and regional cerebral oxygen saturation (rSO2) (INVOS 4100; Somanetics, Troy, MI) were measured sequentially on patients in a resting state. The t-skull and a-CSFL were calculated using computed tomographic image slices of the head corresponding with the position of near-infrared spectroscopy sensors. The effects of these two factors, hemoglobin concentration and mean arterial pressure, on TOI and rSO2 values were evaluated by linear regression analysis., Results: Simple linear regression analysis showed that mean arterial pressure (r = 0.27, P = 0.008), t-skull (r = 0.22, P = 0.034), a-CSFL (0.26, P = 0.012), and hemoglobin concentration (r = 0.42, P < 0.0001) were significant determinants of rSO2. Multiple linear regression analysis showed that hemoglobin concentration (r = 0.34, P < 0.001), a-CSFL (r = -0.252, P = 0.012), and t-skull (r = 0.22, P = 0.037) were significant determinants of rSO2. On the other hand, simple and multiple linear regression analysis showed that there was no significant determinant of TOI., Conclusion: rSO2 values were affected by hemoglobin concentration, a-CSFL, and t-skull, but TOI values were not affected by individual factors.

Background: Near infrared spectroscopy (NIRS) has been used during cardiac surgery to monitor cerebral oxygenation although the validity of this technique has yet to be established. Although optical pathlength included in the algorithm for calculating NIRS values is supposed to be constant, recent evidence has suggested that optical pathlength could be affected by acute hemodilution in animals. We conducted the present study to investigate whether optical pathlength changes during cardiopulmonary bypass (CPB), and whether these changes affect NIRS values in adult patients., Methods: Nine patients undergoing elective cardiac surgery with CPB were enrolled in this study. Optical pathlength and cerebral NIRS values (oxyhemoglobin [DeltaO(2)Hb] and tissue oxygen index) were measured by phase-resolved spectroscopy and NIRO 100, respectively. Optical pathlength, hemoglobin concentration, and NIRS values were measured at the following points: 1) after the induction of anesthesia, 2) 10 min after the start of CPB, 3) 60 min after the start of CPB, and 4) 1 h after CPB. The associations between optical pathlength and other variables were analyzed by Pearson correlation coefficients and multiple regression analysis., Results: Optical pathlength significantly increased starting at 27.7-30.8 cm at 10 min, and 31.3 cm at 60 min after the start of CPB (P < 0.0001). Hemoglobin concentrations significantly decreased (from 11.2 to 7.1 g/dL at 10 min and 7.7 g/dL at 60 min P < 0.0001). There was a significant correlation (r = 0.55, P < 0.001) between percentage changes in pathlength and hemoglobin concentration. Multiple regression analysis showed that optical pathlength was a significant determinant of DeltaO2Hb., Conclusion: The results indicate that optical pathlength can change during CPB and its changes may affect DeltaO2Hb.

Cardiac output (CO) determination using transesophageal Doppler is based on the measurement of descending aortic blood flow. Because cerebral blood flow is dependent on PaCO2, an increase in PaCO2 would result in an increase of CO because of the increase in cerebral blood flow and vice versa. We enrolled 30 patients undergoing off-pump coronary artery graft surgery in the study. The CO was determined by both transesophageal Doppler and thermodilution while PaCO2 was maintained at either 30 mmHg or 40 mmHg in random order. The CO by thermodilution was significantly higher at PaCO2 of 40 mmHg (4.17 +/- 0.94 L/min) than at 30 mmHg (3.78 +/- 0.85 L/min). On the other hand, there were no significant differences in CO by transesophageal Doppler: 3.85 +/- 0.76 L/min at PaCO2 of 40 mmHg and 3.77 +/- 0.74 at 30 mmHg. Bland-Altman analysis yielded bias and precision of -0.32 and 0.49 L/min at PaCO2 of 40 mmHg, and -0.01 and 0.34 L/min at 30 mmHg. These results indicate that both methods of CO measurement are in agreement at 30 mmHg of PaCO2, but the thermodilution method provides higher values at 40 mmHg of PaCO2.