Near-infrared Cerebral Oximetry Research Articles

Cerebral Oximetry Monitoring in Patients Undergoing Surgery for Stanford Type A Aortic Dissection

The aim of this study was to evaluate the prognostic impact of cerebral regional oxygen saturation (crSO2) in patients undergoing surgery for Stanford type A aortic dissection (TAAD). Observational, retrospective, institutional study. University hospital. A total of 152 patients who underwent surgery for TAAD from June 2009 to December 2018 at the authors' institution. Surgery for TAAD using continuous perioperative monitoring of crSO2 with near-infrared cerebral oximetry (INVOS, Medtronic, MN). The rates of postoperative stroke/global brain ischemia were 22.4% and of hospital mortality 14.5%. Age, hemoglobin, and cardiogenic shock were independent predictors of nadir crSO2 from both frontal areas at arrival to the operating room. Repeated measures test showed that changes in crSO2 between the first measurement at operating room arrival, at the start of surgery, and at the end of surgery were not significant when measured on the right frontal area (p = 0.632), left frontal area (p = 0.608), as a nadir value from both frontal areas (p = 0.690), and as a difference between frontal areas (p = 0.826) in patients with and without major neurologic complications. Patients who had a nadir crSO2 <40% anytime during the perioperative period, had a numerically higher rate of major neurologic complications (27.3% v 20.4%, p = 0.354), but this difference did not reach statistical significance. The incidence of nadir of crSO2 value <40% at operating room arrival (5.9%, p = 1.000), at the start of surgery (5.3%, p = 0.685), and at the end of surgery (1.3%, p = 1.000) was rather low and not associated with these adverse events. Derangements in crSO2 detected by cerebral oximetry before and during surgery for TAAD did not predict postoperative stroke and/or global brain ischemia.

Diagnostic and prognostic values of cerebral oxygen saturations measured by INVOS™ in patients with ischemic and hemorrhagic cerebrovascular disease

ObjectivesIn this study it was aimed to investigate whether measurement of potential changes of cerebral oxygenation saturations due to ischemic or hemorrhagic cerebrovascular diseases have an early diagnostic and prognostic value. MethodsAdult patients (≥18 years old) having acute ischemic or hemorrhagic stroke were included in the study. Patients under 18-year-old, those with incomplete data or suspicious diagnosis were excluded.The cerebral oxygen saturations of the patients were compared with the healthy subjects. Patients were also grouped according to their clinical outcomes; good clinical status (group 1) and poor clinical status (group 2). These groups were compared according to the patients’ cerebral oxygen saturations. ResultsThe mean oxygen saturation of the patients and healthy people were similar (59.48% ± 10.6 versus 58.44% ± 9.6). There was no difference between patients and healthy population according to cerebral oxygen saturations. Furthermore, mean oxygen levels were also similar between the hemisphere without lesion and with lesion in the patients group (59.8% ± 11.8 versus 59.2% ± 10.4).When the patients were grouped according to their clinical status, there were 30 patients in group 1 and 15 in group 2. The cerebral oxygen saturations of the hemisphere with lesion were similar between these groups and no statistical difference was observed (59.2% ± 9.3 versus 59.1% ± 12.6, p = 0.9). There was also no statistical difference between the groups when delta oxygen levels of the affected and unaffected hemispheres of the groups were calculated (0.9% ± 6.1 versus 0.13% ± 8.4, p = 0.7). ConclusionResults of this study revealed that there was no difference in cerebral oxygen saturations measured by near-infrared cerebral oximetry system between the patients with cerebrovascular disease and healthy population. Furthermore, our results did not support that the cerebral oxygen saturations may be used for determining the prognosis of the patients with cerebrovascular disease.

Near-Infrared Cerebral Oximetry to Predict Outcome After Pediatric Cardiac Surgery: A Prospective Observational Study.

To assess whether near-infrared cerebral tissue oxygen saturation, measured with the FORESIGHT cerebral oximeter (CAS Medical Systems, Branford, CT) predicts PICU length of stay, duration of invasive mechanical ventilation, and mortality in critically ill children after pediatric cardiac surgery. Single-center prospective, observational study. Twelve-bed PICU of a tertiary academic hospital. Critically ill children and infants with congenital heart disease, younger than 12 years old, admitted to the PICU between October 2012 and November 2015. Children were monitored with the FORESIGHT cerebral oximeter from PICU admission until they were weaned off mechanical ventilation. Clinicians were blinded to cerebral tissue oxygen saturation data. None. Primary outcome was the predictive value of the first 24 hours of postoperative cerebral tissue oxygen saturation for duration of PICU stay (median [95% CI], 4 d [3-8 d]) and duration of mechanical ventilation (median [95% CI], 111.3 hr (69.3-190.4 hr]). We calculated predictors on the first 24 hours of cerebral tissue oxygen saturation monitoring. The association of each individual cerebral tissue oxygen saturation predictor and of a combination of predictors were assessed using univariable and multivariable bootstrap analyses, adjusting for age, weight, gender, Pediatric Index of Mortality 2, Risk Adjustment in Congenital Heart Surgery 1, cyanotic heart defect, and time prior to cerebral tissue oxygen saturation monitoring. The most important risk factors associated with worst outcomes were an increased SD of a smoothed cerebral tissue oxygen saturation signal and an elevated cerebral tissue oxygen saturation desaturation score. Increased SD of a smoothed cerebral tissue oxygen saturation signal and increased depth and duration of desaturation below the 50% saturation threshold were associated with longer PICU and hospital stays and with longer duration of mechanical ventilation after pediatric cardiac surgery.

Effects of intravenously administered indocyanine green on near-infrared cerebral oximetry and pulse oximetry readings.

Background Intravenously administered indocyanine green (ICG) may cause misreadings of cerebral oximetry and pulse oximetry in patients undergoing carotid endarterectomy under general anesthesia. The present study determined the effects of two different doses (12.5 mg vs. 25 mg) of ICG on regional cerebral tissue oxygen saturation (SctO2) and percutaneous peripheral oxygen saturation (SpO2).MethodsTwenty-six patients receiving ICG for videoangiography were divided into two groups according to the dosage (12.5 mg and 25 mg, n = 13 in each group). Heart rate, arterial blood pressure, SctO2, and SpO2 were measured before and after an intravenous bolus administration of ICG.ResultsFollowing the dye administration, no changes in heart rate or arterial blood pressure were noted in either group. SctO2 was increased in both groups; however, the magnitude of the increase was greater (21.6 ± 5.8% vs. 12.6 ± 4.1%, P < 0.0001) and more prolonged (28.4 ± 9.6 min vs. 13.8 ± 5.2 min, P < 0.0001) in the 25 mg group than in the 12.5 mg group. In contrast, SpO2 was decreased in both groups; the magnitude of the decrease was greater in the 25 mg group than in the 12.5 mg group (4.0 ± 0.8% vs. 1.6 ± 1.0%, P < 0.0001). There were no differences in the time to reach the peak SctO2 or to reach the nadir SpO2 between the two groups.ConclusionsIn patients given ICG for videoangiography, a 25 mg bolus results in a greater and more prolonged increase in SctO2 and a greater reduction in SpO2 than a 12.5 mg bolus, with no differences in the time to reach the peak SctO2 or to reach the nadir SpO2.

Intravenously Administered Indocyanine Green May Cause Falsely High Near-Infrared Cerebral Oximetry Readings

Near-infrared spectroscopy assesses cerebral tissue oxygen saturation (Scto2) based on the absorption spectra of oxygenated and deoxygenated hemoglobin. It has been reported that IV-administered dyes including methylene blue, indigo carmine, and indocyanine green (ICG) may cause falsely low-pulse oximetry readings (Spo2). Although methylene blue and indigo carmine may also decrease Scto2, the effect of ICG has not been documented. Simultaneous changes in the heart rate, arterial blood pressure, Scto2, and Spo2 were measured after IV administration of ICG (12.5 mg diluted in 5.0 mL 0.9% NaCl) in 15 patients undergoing carotid endarterectomy under sevoflurane-remifentanil anesthesia. After the dye administration, no change in heart rate or arterial blood pressure was observed in any patient. Scto2 increased by 13.3±4.0 percentage points, reaching the peak at 42.0±28.4 seconds after the administration, whereas Spo2 decreased by 1.9±1.2 percentage points, reaching the peak at 64.0±42.5 seconds (P<0.0001 both). ICG falsely increases the spectroscopy-determined cerebral oxygen saturation for up to 12 minutes but dampens pulse oximetry readings.

PS-101 New Developments In Autoregulation (ar) Analysis: Assessment Of Causality

<h3>Background</h3> Cerebral AR is a complex, developmentally regulated process still not well characterised in neonates. A number of factors interact with the smooth muscle cells regulating cerebral arterial tone and perfusion. Various analytical methods have been applied to explore AR¹. Although in this multifactorial process the assessment of synchronicity and causality is crucial, yet it has not been established. <h3>Objective</h3> To analyse the temporal causality between two biological signals in the frequency-domain by quantifying the influence of each signal to the other across the frequencies. To assess the predictive capacity of the method to classify infants at risk for adverse neonatal outcome. <h3>Methods</h3> Partial directed coherence (PDC)² and spectral coherence (COH) methods were used to analyse the relationship between spontaneous changes in mean arterial blood pressure (MABP) and near-infrared cerebral oximetry (TOI). PDC_MABP»TOI indicated that changes in TOI were induced by MABP changes and PDC_TOI»MABP,the opposite. <h3>Results</h3> PDC_MABP»TOI and PDC_TOI»MABPvalues differed. PDC_MABP»TOI and COH predicted low superior vena cava (SVC) flow (≤41 ml/kg per min) with an area under the ROC curve of 0.68 (95% CI: 0.63–0.77; p &lt; 0.001) and 0.60 (95% CI: 0.51–0.70; p &lt; 0.05), respectively; whereas PDC_TOI»MABP did not (p &lt; 0.248). The pPDC_MABP»TOI and pCOH were calculated as the averaged value per patient. pPDC_MABP»TOI but not pCOH predicted mortality. <h3>Conclusions</h3> PDC_MABP»TOIis a good classifier for infants at risk of brain hypoperfusion and adverse outcome. PDC_MABP»TOIallows a non-invasive physiological interpretation of the pressure-AR process in neonates. <h3>References</h3> Riera J <i>et al</i>. 2014 (submitted) Baccalá L, Sameshima K. <i>Biol_Cyber</i> 2001.

Survey of the Clinical Assessment and Utility of Near-Infrared Cerebral Oximetry in Cardiac Surgery

Near-infrared cerebral oximetry increasingly is used for monitoring during cardiac surgery. Nonetheless, the scientific basis for incorporating this technology into clinical practice, the indications for when to do so, and standard diagnostic and treatment algorithms for defining abnormal values are yet to be rigorously defined. The authors hypothesized that there would be (1) variation in clinical use and practices for near-infrared spectroscopy (NIRS), and (2) variation in management of patients when clinicians are provided with NIRS information. In order to test this hypothesis, they sought to assess the nature and strength of response heterogeneity among anesthesiologists and cardiac perfusionists when provided with cardiac surgery patient scenarios and cerebral oximetry data. A prospectively collected survey. A hospital-based, multi-institutional, multinational study. By e-mail, the authors surveyed the membership of the Society of Cardiovascular Anesthesiologists and the online Cardiovascular Perfusion Forum. This survey was focused on ascertaining what actions clinicians would take in each scenario, given case information and cerebral oximetry tracings. Questions were based on 11 patient scenarios selected to represent small, large, symmetric, or asymmetric decreases in measured regional cerebral oxygen saturation (rScO2) encountered during cardiac surgery. Information on the respondents' (n = 796; 73% anesthesiologists) clinical practice, demography, and cerebral oximetry utilization was collected. An index of dispersion was used to assess response heterogeneity overall and within demographic subgroups. The majority of respondents indicated that cerebral oximetry monitoring was either useful or an essential monitor, especially perfusionists and clinicians who used cerebral oximetry most frequently. There were marked differences in responses between perfusionists and anesthesiologists for 4 of the 6 scenarios (p<0.005 for each of these 4 scenarios) occurring during cardiopulmonary bypass. Scenarios having greatest rScO2 reduction or asymmetry in rScO2 were associated with the highest dispersion, indicating least agreement in management. Scenarios with mild or moderate rScO2 reduction were associated with the lowest dispersion, indicating greater agreement in management. Although experimental data gradually are accumulating to support the role for cerebral oximetry monitoring during cardiac surgery, the results of the present survey support the view that its role remains poorly defined, and consensus for its appropriate use is lacking. Importantly, the authors observed marked variation in the use, perceived utility, and management of patients for 4 of the 6 CPB scenarios between perfusionists and anesthesiologists who share the management of CPB. These findings support the need for well-designed, adequately-powered clinical trials examining the value of this technology.

Endoprosthetic exclusion of type A aortic dissection through carotid artery

Even today, totally endovascular repair of the ascending aorta remains only anecdotally reported,1Roux D. Brouchet L. Rousseau H. Elghobary T. Glock Y. Fournial G. Treatment of a fistula at the distal anastomosis after Bentall operation with endoluminal covered stent.Ann Thorac Surg. 2002; 74: 2189-2190Abstract Full Text Full Text PDF PubMed Scopus (9) Google Scholar although arch2Siniscalchi G. Tozzi P. Ferrari E. Delay D. Ruchat P. von Segesser L. Endovascular repair of aortic arch aneurysm after achievement of local anesthesia.J Thorac Cardiovasc Surg. 2007; 133: 262-263Abstract Full Text Full Text PDF PubMed Scopus (6) Google Scholar and descending aorta endoprosthetic replacements are currently performed. Recognized treatment of type A dissection still remains emergency replacement of the ascending aorta, with adequate aortic valve and coronary ostial management.3Pretre R. von Segesser L.K. Aortic dissection.Lancet. 1997; 349: 1461-1464Abstract Full Text Full Text PDF PubMed Scopus (185) Google Scholar We describe a case in which the surgical strategy had to be somewhat innovative. A 64-year-old white man with a history of subtotal pericardiectomy for constrictive pericarditis had undergone a transseptal mechanical valve replacement 33 years previously to treat a degenerative mitral regurgitation. Because of a severe mediastinal fibrosis, we proceeded through a right anterolateral thoracotomy and right venoarterial femoral cannulation. Because of severe hemodynamic instability during cardiopulmonary bypass, arterial cannulation problems were suspected. Finally, retrograde iatrogenic aortic dissection with involvement of the ascending aorta was confirmed by transesophageal echocardiography. An attempt to replace the ascending aorta was undertaken but discontinued because of the extremely dense, fibrous tissue surrounding all cardiovascular structures. The patient's postoperative course was uneventful, with a computed tomographic (CT) scan confirming an untreated type A dissection without aortic regurgitation and with a reentry tear in the ascending aorta (Figure 1, A). The patient was discharged on postoperative day 11 with adequate dosages of β-blocker and angiotensin-converting enzyme inhibitor. Three months later, control CT scan showed a marked 9-mm increase in the aortic diameter (Figure 1, B and C). The only option was an endoprosthetic repair of the ascending aorta. After consent had been obtained, a customized 44 × 70-mm polytetrafluoroethylene-covered endoprosthesis with distal open web (EndoFit; LeMaitre Vascular, Inc, Burlington, Mass) was inserted through a cutdown to the left common carotid artery, the only nondissected supra-aortic vessel. Good positioning of the endoprosthesis, with confirmation of tear and false-lumen exclusion, was checked by intraoperative transesophageal echocardiography. The postoperative course was clinically uneventful, with the absence of any aortic regurgitation on transthoracic echocardiography. CT scan on postoperative day 2 (Figure 2, A) revealed free coronary ostia and aortic valve commissures, with complete thrombosis of the false lumen an without endoleak. At 1-year follow-up, CT scan showed a complete repair of the aortic wall without compromise on the brachiocephalic trunk at the distal part of the prosthesis (Figure 2, B and C). Treatment of iatrogenic type A dissection is emergency replacement of the ascending aorta.4Ruchat P. Hurni M. Stumpe F. Fischer A.P. von Segesser L.K. Acute ascending aortic dissection complicating open heart surgery: cerebral perfusion defines the outcome.Eur J Cardiothorac Surg. 1998; 14: 449-452Crossref PubMed Scopus (53) Google Scholar We had to consider, however, that the only available solution for our threatened patient was an endovascular procedure with remote insertion through the left common carotid artery.5Heidenreich J.H. Neschis D.G. Costanza M.J. Flinn W.R. Endovascular repair of a penetrating thoracic aortic ulcer by way of the carotid artery.J Vasc Surg. 2003; 38: 1407-1410Abstract Full Text Full Text PDF PubMed Scopus (20) Google Scholar Common carotid clamping is rarely associated with brain ischemia because of collateralization through the external carotid and contralateral facial arteries. In this procedure, we monitored brain ischemia by near-infrared cerebral oximetry with the patient under general anesthesia. This technique is well correlated with clinical neurologic surveillance during carotid endarterectomy with the patient under local anesthesia. Endoprosthesis insertion into the ascending aorta to exclude pseudoaneurysms has already been described,1Roux D. Brouchet L. Rousseau H. Elghobary T. Glock Y. Fournial G. Treatment of a fistula at the distal anastomosis after Bentall operation with endoluminal covered stent.Ann Thorac Surg. 2002; 74: 2189-2190Abstract Full Text Full Text PDF PubMed Scopus (9) Google Scholar but to our knowledge this is the first description of a mandatory endovascular treatment of type A aortic dissection.

Increased Oxygen Administration Improves Cerebral Oxygenation in Patients Undergoing Awake Carotid Surgery

During regional anesthesia for carotid endarterectomy (CEA), 10% to 15% of patients develop signs of cerebral hypoxia after cross-clamping, manifested as changes in speech, cerebration or contralateral motor power. Reversal of such neurological deficits using administration of 100% O2 has been described. We used near-infrared cerebral oximetry to assess whether 100% O2 reliably improves regional cerebral oxygenation (rSO2) during carotid cross-clamping. Sixteen patients undergoing awake CEA were studied. Bilateral rSO2 optodes were applied before the initiation of sedation and the conduct of the regional blockade. Patients received 28% oxygen by Venturi facemask. Perioperative blood pressure was maintained at or within 10% above the patient's normal limits during carotid cross-clamping. After cross-clamping, 100% O2 was administered for 5 min by a close-fitting anesthetic facemask. The O2 mask was then removed and the patient breathed room air. The effects on rSO2 readings and arterial blood gases were observed after each intervention. Data were analyzed for 15 patients. Ipsilateral rSO2 values decreased by 7.4% +/- 5% after carotid cross-clamping. Administration of 100% O2 resulted in an increase in ipsilateral rSO2 in all patients of 6.9% +/- 3.3% (range, 1%-12%) (paired t-test, P < 0.001) over the cross-clamped value while receiving 28% O2. Hemodynamic variables and arterial PaCO2 values were unaltered. With the carotid cross-clamped, ipsilateral rSO2 was reliably increased by the administration of 100% O(2) compared with 28% O2. The etiology of this increase is unclear, but may relate to the associated increase in O2 content of the blood or to an improvement in cerebral blood flow. Thus administration of 100% O2 during carotid cross-clamping may be beneficial for all patients undergoing CEA.

The Effect of Intravenous Indigo Carmine on Near-Infrared Cerebral Oximetry

The Effect of Intravenous Indigo Carmine on Near-Infrared Cerebral Oximetry

The Effect of Intravenous Indigo Carmine on Near-Infrared Cerebral Oximetry

The effects of IV-administered dyes on pulse oximetry have been well described. However, the effects on near-infrared cerebral oximetry have not been well documented. We report a series of four patients undergoing radical prostatectomy who were monitored with cerebral oximetry during surgery. After the administration of indigo carmine, intraoperative desaturations were observed for an extended period. Because clinical use of near-infrared cerebral oximetry is increasing, anesthesiologists should be aware of this issue.

Cerebral Oxygen Desaturation After Cardiopulmonary Bypass in a Patient with Raynaud's Phenomenon Detected by Near-Infrared Cerebral Oximetry

Raynaud's phenomenon is characterized by episodes of arterial vasospasm precipitated by cold stress, usually affecting the digits of the hands. There is controversy about the occurrence of vasospasm in internal organ systems. In this report, we present a case of Raynaud's peripheral vasospasm accompanied by cerebral oxygen desaturation as detected by near infrared cerebral oximetry after separation from cardiopulmonary bypass.

A clinical evaluation of near-infrared cerebral oximetry in the awake patient to monitor cerebral perfusion during carotid endarterectomy

A clinical evaluation of near-infrared cerebral oximetry in the awake patient to monitor cerebral perfusion during carotid endarterectomy

Clinical Evaluation of Near-Infrared Cerebral Oximetry in the Awake-Patient Carotid Endarterectomy

Clinical Evaluation of Near-Infrared Cerebral Oximetry in the Awake-Patient Carotid Endarterectomy

A Clinical Evaluation of Near-Infrared Cerebral Oximetry in the Awake Patient to Monitor Cerebral Perfusion During Carotid Endarterectomy

Survey of Anesthesiology: December 2006 - Volume 50 - Issue 6 - p 292-294 doi: 10.1097/01.sa.0000238956.12486.0e

A clinical evaluation of near-infrared cerebral oximetry in the awake patient to monitor cerebral perfusion during carotid endarterectomy

Study Objective To evaluate the relationship between continuous noninvasive monitoring of cerebral saturation (regional cerebral oxygen saturation [rS o 2]) and occurrence of clinical and electroencephalographic (EEG) signs of cerebral ischemia during carotid cross-clamping. Design Prospective clinical study. Setting University hospital. Patients Fifty ASA physical status II and III inpatients undergoing elective carotid endarterectomy with a cervical plexus block. Interventions rS o 2 was continuously monitored throughout surgery, while an independent neurologist evaluated the occurrence of both clinical and EEG signs of cerebral ischemia induced during carotid cross-clamping. Measurements and Main Results rS o 2 was recorded 1 and 3 minutes after clamping the carotid artery during a 3-minute clamping test. In 5 patients (10%), the carotid clamping test was associated with the occurrence of clinical and EEG signs of cerebral ischemia. All these patients were treated with the placement of a Javid shunt, which completely resolved the symptoms. In no patient was permanent neurological injury reported at hospital discharge. In 4 of these patients, EEG signs of cerebral ischemia were present at both observation times, and in one of them, the duration of cerebral ischemia was less than 2 minutes. The percentage rS o 2 reduction from baseline during the carotid clamping test was 17% ± 4% in patients requiring shunt placement and only 8% ± 6% in those who did not require it ( P = .01). A decrease in rS o 2 15% or greater during the carotid clamping test was associated with a 20-fold increase in the odd for developing severe cerebral ischemia (odds ratio, 20; 95% confidence interval, 6.7-59.2) ( P = .001); however, this threshold had a 44% sensitivity and 82% specificity, with only 94% negative predictive value. Conclusions Continuous rS o 2 monitoring is a simple and noninvasive method that correlates with the development of clinical and EEG signs of cerebral ischemia during carotid cross-clamping; however, we could not identify an rS o 2 threshold that can be used alone to predict the need for shunt placement because of the low sensitivity and specificity.

Neurological Monitoring for Congenital Heart Surgery

The incidence of neurological complications after pediatric cardiac surgery ranges from 2% to 25%. The causes are multifactorial and include preoperative brain malformations, perioperative hypoxemia and low cardiac output states, sequelae of cardiopulmonary bypass, and deep hypothermic circulatory arrest. Neurological monitoring devices are readily available and the anesthesiologist can now monitor the brain during pediatric cardiac surgery. In this review we discuss near-infrared cerebral oximetry, transcranial Doppler ultrasound, and electroencephalographic monitors for use during congenital heart surgery. After review of the basic principles of each monitoring modality, we discuss their uses during pediatric heart surgery. We present evidence that multimodal neurological monitoring in conjunction with a treatment algorithm may improve neurological outcome for patients undergoing congenital heart surgery and present one such algorithm.

Intraoperative transcranial ultrasonic monitoring for cardiac and vascular surgery.

The brain is the only organ not routinely monitored by any direct method during the administration of anesthesia. Anesthesiologists rely primarily on indirect physiologic evidence provided by blood pressure, peripheral pulse oximetry, heart rate, and respiratory and anesthetic gas concentrations to determine that brain blood flow and oxygenation are adequate. The reasons for this practice are that: (1) after millions of anesthetics significant numbers of adverse neurologic outcomes have not occurred, (2) the interpretation of transcranial Doppler, electroencephalogram, and near-infrared cerebral oximetry requires experienced personnel, and (3) the evidence of cost-benefit to support monitoring is limited. Brain monitoring generally has been confined to procedures where the brain is exposed to unique insults and risks specific to the procedures and where reliance on indirect physiologic evidence of cerebral integrity has been proven to be unreliable. Transcranial Doppler monitoring is valuable in the assessment of established surgical techniques, refinement of recent surgical techniques, and development of new techniques and instrumentation. Brain monitoring with transcranial Doppler is of particular value when deviations from established surgical or anesthetic techniques may place the brain at risk for cerebral hyper- or hypoperfusion, gaseous or particulate embolization, or their combined effects. This paper discusses applications of transcranial Doppler in coronary artery bypass surgery, aortic arch procedures, pediatric cardiac surgery, carotid endarterectomy, and a few other special cases. The insight into cerebral physiology is unique to the continuous window on the brain that transcranial Doppler provides.

Cerebral function monitoring during carotid endarterectomy:clinical comparison between near-infrared cerebral oximetry and electroencephalography

s and Programme: European Society of Anaesthesiologists; 9th Annual Meeting with the Swedish Society of Anaesthesiology; Gothenburg, Sweden, 7-10 April 2001: Neurosciences: Monitoring Equipment and Computers

Arterial and venous contributions to near-infrared cerebral oximetry.

Cerebral oximetry is a noninvasive bedside technology using near-infrared light to monitor cerebral oxygen saturation (Sco2) in an uncertain mixture of arteries, capillaries, and veins. The present study used frequency domain near-infrared spectroscopy to determine the ratio of arterial and venous blood monitored by cerebral oximetry during normoxia, hypoxia, and hypocapnia. Twenty anesthetized children aged < 8 yr with congenital heart disease of varying arterial oxygen saturation (Sao2) were studied during cardiac catheterization. Sco2, Sao2, and jugular bulb oxygen saturation (Sjo2) were measured by frequency domain near-infrared spectroscopy and blood oximetry at normocapnia room air, normocapnia 100% inspired O2, and hypocapnia room air. Among subject conditions, Sao2 ranged from 68% to 100%, Sjo2 from 27% to 96%, and Sco2 from 29% to 92%. Sco2 was significantly related to Sao2 (y = 0. 85 x -17, r = 0.47), Sjo2 (y = 0.77 x +13, r = 0.70), and the combination (Sco2 = 0.46 Sao2 + 0.56 Sjo2 - 17, R = 0.71). The arterial and venous contribution to cerebral oximetry was 16 +/- 21% and 84 +/- 21%, respectively (where Sco2 = alpha Sao2 + beta Sjo2 with alpha and beta being arterial and venous contributions). The contribution was similar among conditions but differed significantly among subjects (range, approximately 40:60 to approximately 0:100, arterial:venous). Cerebral oximetry monitors an arterial/venous ratio of 16:84, similar in normoxia, hypoxia, and hypocapnia. Because of biologic variation in cerebral arterial/venous ratios, use of a fixed ratio is not a good method to validate the technology.