Correction to: Intraoperative cerebral oximetry-based management for optimizing perioperative outcomes: a meta-analysis of randomized controlled trials.

In the article entitled "Intraoperative cerebral oximetry-based management for optimizing perioperative outcomes: a meta-analysis of randomized controlled trials" Can J Anesth 2018; 65: 529-42, we wish to clarify the following items.

Intraoperative cerebral oximetry-based management for optimizing perioperative outcomes: a meta-analysis of randomized controlled trials.

PURPOSE: Although evidence from observational studies in a variety of clinical settings supports the utility of cerebral oximetry as a predictor of outcomes, prospective clinical trials thus far have reported conflicting results. This systematic review and meta-analysis was designed to evaluate the influence of management associated with intraoperative cerebral oximetry on postoperative outcomes. The primary outcome was postoperative cognitive dysfunction (POCD), with secondary outcomes that included postoperative delirium, length of intensive care unit (ICU) stay, and hospital length of stay (LOS). SOURCE: After searching the PubMed, EMBASE, Cochrane Library, Scopus, and Google Scholar databases, all randomized controlled trials (RCTs) assessing the impact of intraoperative cerebral oximetry-guided management on clinical outcomes following surgery were identified. PRINCIPAL FINDINGS: Fifteen RCTs comprising 2,057 patients (1,018 in the intervention group and 1,039 in control group) were included. Intraoperative management guided by the use of cerebral oximetry was associated with a reduction in the incidence of POCD (risk ratio [RR] 0.54; 95% confidence interval [CI], 0.33 to 0.90; P = 0.02; I2 = 85%) and a significantly shorter length of ICU stay (standardized mean difference [SMD], -0.21 hr; 95% CI, -0.37 to -0.05; P = 0.009; I2 = 48%). In addition, overall hospital LOS (SMD, -0.06 days; 95% CI, -0.18 to 0.06; P = 0.29; I2 = 0%) and incidence of postoperative delirium (RR, 0.69; 95% CI, 0.36 to 1.32; P = 0.27; I2 = 0%) were not impacted by the use of intraoperative cerebral oximetry. CONCLUSIONS: Intraoperative cerebral oximetry appears to be associated with a reduction in POCD, although this result should be interpreted with caution given the significant heterogeneity in the studies examined. Further large (ideally multicentre) RCTs are needed to clarify whether POCD can be favourably impacted by the use of cerebral oximetry-guided management.

Shoulder surgery in the beach chair position is associated with diminished cerebral autoregulation but no differences in postoperative cognition or brain injury biomarker levels compared with supine positioning: the anesthesia patient safety foundation beach chair study.

BACKGROUND: Although controversial, failing to consider the gravitational effects of head elevation on cerebral perfusion is speculated to increase susceptibility to rare, but devastating, neurologic complications after shoulder surgery in the beach chair position (BCP). We hypothesized that patients in the BCP have diminished cerebral blood flow autoregulation than those who undergo surgery in the lateral decubitus position (LDP). A secondary aim was to examine whether there is a relationship between patient positioning during surgery and postoperative cognition or serum brain injury biomarker levels. METHODS: Patients undergoing shoulder surgery in the BCP (n = 109) or LDP (n = 109) had mean arterial blood pressure (MAP) and regional cerebral oxygen saturation (rScO2) monitored with near-infrared spectroscopy. A continuous, moving Pearson correlation coefficient was calculated between MAP and rScO2, generating the variable cerebral oximetry index (COx). When MAP is in the autoregulated range, COx approaches zero because there is no correlation between cerebral blood flow and arterial blood pressure. In contrast, when MAP is below the limit of autoregulation, COx is higher because there is a direct relationship between lower arterial blood pressure and lower cerebral blood flow. Thus, diminished autoregulation would be manifest as higher COx. Psychometric testing was performed before surgery and then 7 to 10 days and 4 to 6 weeks after surgery. A composite cognitive outcome was determined as the Z-score. Serum S100ß, neuron-specific enolase, and glial fibrillary acidic protein were measured at baseline, after surgery, and on postoperative day 1. RESULTS: After adjusting for age and history of hypertension, COx (P = 0.035) was higher and rScO2 lower (P < 0.0001) in the BCP group than in the LDP group. After adjusting for baseline composite cognitive outcome, there was no difference in Z-score 7 to 10 days (P = 0.530) or 4 to 6 weeks (P = 0.202) after surgery between the BCP and the LDP groups. There was no difference in serum biomarker levels between the 2 position groups CONCLUSIONS: : Compared with patients in the LDP, patients undergoing shoulder surgery in the BCP are more likely to have higher COx indicating diminished cerebral autoregulation and lower rScO2. There were no differences in the composite cognitive outcome between the BCP and the LDP groups after surgery after accounting for baseline Z-score.

Perioperative management of patients with left ventricular assist devices undergoing noncardiac procedures: a survey of current practices.

OBJECTIVES: To describe perioperative management of patients with left ventricular assist devices (LVAD) in noncardiac procedures. DESIGN: Survey of (1) respondent demographic characteristics, (2) anesthetic practices for LVAD patients having endoscopies, and (3) low-risk surgeries requiring general anesthesia. SETTING: Internet-based. PARTICIPANTS: Society of Cardiovascular Anesthesiologists membership. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Inpatient endoscopic procedures were done mainly in the endoscopy suite (71.7%) by a solo practitioner or 1:1 staffing ratio 59% of the time. LVAD-specific support personnel were present in more than 80% of all procedures. Both endoscopy and surgical patients used post-anesthesia recovery units and intensive care units for recovery; however, compared with endoscopy patients, surgical patients recovered in the ICU more frequently (45.5% v 29.1%, p<0.001). In addition, 18% of endoscopy patients recovered on site. Regarding patient monitoring, more than 90% of responders used electrocardiogram, pulse oximetry, end-tidal CO2, and blood pressure monitors on LVAD patients. Responders reported using arterial catheters to monitor blood pressure in 49% of endoscopy cases and 71% of surgical patients. The reported use of invasive monitors by individual clinicians was related inversely to institutional LVAD volume (p = 0.04 and p = 0.01 in endoscopy and surgical procedures, respectively). CONCLUSIONS: This survey found heterogeneity in hospital resource utilization for noncardiac LVAD procedures. There was a decrease in the use of invasive monitors with increased institutional LVAD volume in both endoscopy and surgical procedures.

Validation of a stand-alone near-infrared spectroscopy system for monitoring cerebral autoregulation during cardiac surgery.

BACKGROUND: Individualizing arterial blood pressure (ABP) targets during cardiopulmonary bypass (CPB) based on cerebral blood flow (CBF) autoregulation monitoring may provide a more effective means for preventing cerebral hypoperfusion than the current standard of care. Autoregulation can be monitored in real time with transcranial Doppler (TCD). We have previously demonstrated that near-infrared spectroscopy (NIRS)-derived regional cerebral oxygen saturation (rS(c)O(2)) provides a clinically suitable surrogate of CBF for autoregulation monitoring. The purpose of this study was to determine the accuracy of a stand-alone "plug-and-play" investigational system for autoregulation monitoring that uses a commercially available NIRS monitor with TCD methods. METHODS: TCD monitoring of middle cerebral artery CBF velocity and NIRS monitoring were performed in 70 patients during CPB. Indices of autoregulation were computed by both a personal computer-based system and an investigational prototype NIRS-based monitor. A moving linear correlation coefficient between slow waves of ABP and CBF velocity (mean velocity index [Mx]) and between ABP and rS(c)O(2) (cerebral oximetry index [COx]) were calculated. When CBF is autoregulated, there is no correlation between CBF and ABP; when CBF is dysregulated, Mx and COx approach 1 (i.e., CBF and ABP are correlated). Linear regression and bias analysis were performed between time-averaged values of Mx and COx derived from the personal computer-based system and from COx measured with the prototype monitor. Values for Mx and COx were categorized in 5 mm Hg bins of ABP for each patient. The lower limit of CBF autoregulation was defined as the ABP where Mx incrementally increased to ≥0.4. RESULTS: There was correlation and good agreement between COx derived from the prototype monitor and Mx (r = 0.510; 95% confidence interval, 0.414-0.595; P < 0.001; bias, -0.07 ± 0.19). The correlation and bias between the personal computer-based COx and the COx from the prototype NIRS monitor were r = 0.957 (95% confidence interval, 0.945-0.966; P < 0.001 and 0.06 ± 0.06, respectively). The average ABP at the lower limit of autoregulation was 63 ± 11 mm Hg (95% prediction interval, 52-74 mm Hg). Although the mean ABP at the COx-determined lower limit of autoregulation determined with the prototype monitor was statistically different from that determined by Mx (59 ± 9 mm Hg; 95% prediction interval, 50-68 mm Hg; P = 0.026), the difference was not likely clinically meaningful. CONCLUSIONS: Monitoring CBF autoregulation with an investigational stand-alone NIRS monitor is correlated and in good agreement with TCD-based methods. The availability of such a device would allow widespread autoregulation monitoring as a means of individualizing ABP targets during CPB.

Predicting the limits of cerebral autoregulation during cardiopulmonary bypass.

BACKGROUND: Mean arterial blood pressure (MAP) targets are empirically chosen during cardiopulmonary bypass (CPB). We have previously shown that near-infrared spectroscopy (NIRS) can be used clinically for monitoring cerebral blood flow autoregulation. The hypothesis of this study was that real-time autoregulation monitoring using NIRS-based methods is more accurate for delineating the MAP at the lower limit of autoregulation (LLA) during CPB than empiric determinations based on age, preoperative history, and preoperative blood pressure. METHODS: Two hundred thirty-two patients undergoing coronary artery bypass graft and/or valve surgery with CPB underwent transcranial Doppler monitoring of the middle cerebral arteries and NIRS monitoring. A continuous, moving Pearson correlation coefficient was calculated between MAP and cerebral blood flow velocity and between MAP and NIRS data to generate mean velocity index and cerebral oximeter index. When autoregulated, there is no correlation between cerebral blood flow and MAP (i.e., mean velocity and cerebral oximetry indices approach 0); when MAP is below the LLA, mean velocity and cerebral oximetry indices approach 1. The LLA was defined as the MAP at which mean velocity index increased with declining MAP to ≥ 0.4. Linear regression was performed to assess the relation between preoperative systolic blood pressure, MAP, MAP in 10% decrements from baseline, and average cerebral oximetry index with MAP at the LLA. RESULTS: The MAP at the LLA was 66 mm Hg (95% prediction interval, 43 to 90 mm Hg) for the 225 patients in which this limit was observed. There was no relationship between preoperative MAP and the LLA (P = 0.829) after adjusting for age, gender, prior stroke, diabetes, and hypertension, but a cerebral oximetry index value of >0.5 was associated with the LLA (P = 0.022). The LLA could be identified with cerebral oximetry index in 219 (94.4%) patients. The mean difference in the LLA for mean velocity index versus cerebral oximetry index was -0.2 ± 10.2 mm Hg (95% CI, -1.5 to 1.2 mm Hg). Preoperative systolic blood pressure was associated with a higher LLA (P = 0.046) but only for those with systolic blood pressure ≤ 160 mm Hg. CONCLUSIONS: There is a wide range of MAP at the LLA in patients during CPB, making estimation of this target difficult. Real-time monitoring of autoregulation with cerebral oximetry index may provide a more rational means for individualizing MAP during CPB.

Cerebral blood flow autoregulation is preserved after continuous-flow left ventricular assist device implantation.

OBJECTIVE: To compare cerebral blood flow (CBF) autoregulation in patients undergoing continuous-flow left ventricular assist device (LVAD) implantation with that in patients undergoing coronary artery bypass grafting (CABG). DESIGN: Prospective, observational, controlled study. SETTING: Academic medical center. PARTICIPANTS: Fifteen patients undergoing LVAD insertion and 10 patients undergoing CABG. MEASUREMENTS AND MAIN RESULTS: Cerebral autoregulation was monitored with transcranial Doppler and near-infrared spectroscopy. A continuous Pearson correlation coefficient was calculated between mean arterial pressure (MAP) and CBF velocity and between MAP and near-infrared spectroscopic data, rendering the variables mean velocity index (Mx) and cerebral oximetry index (COx), respectively. Mx and COx approach 0 when autoregulation is intact (no correlation between CBF and MAP), but approach 1 when autoregulation is impaired. Mx was lower during and immediately after cardiopulmonary bypass in the LVAD group than in the CABG group, indicating better-preserved autoregulation. Based on COx monitoring, autoregulation tended to be better preserved in the LVAD group than in the CABG group immediately after surgery (p = 0.0906). On postoperative day 1, COx was lower in the LVAD group than in the CABG group, indicating preserved CBF autoregulation (p = 0.0410). Based on COx monitoring, 3 patients (30%) in the CABG group had abnormal autoregulation (COx ≥0.3) on the first postoperative day but no patient in the LVAD group had this abnormality (p = 0.037). CONCLUSIONS: These data suggest that CBF autoregulation is preserved during and immediately after surgery in patients undergoing LVAD insertion.

Review article: implications of vascular aging.

Chronological age is a well-established risk factor for the development of cardiovascular diseases. The changes that accumulate in the vasculature with age, however, are highly variable. It is now increasingly recognized that indices of vascular health are more reliable than age per se in predicting adverse cardiovascular outcomes. The variation in the accrual of these age-related vascular changes is a function of multiple genetic and environmental factors. In this review, we highlight some of the pathophysiological mechanisms that characterize the vascular aging phenotype. Furthermore, we provide an overview of the key outcome studies that address the value of these vascular health indices in general and discuss potential effects on perioperative cardiovascular outcomes.

Emergency cardiac surgery in patients with acute coronary syndromes: a review of the evidence and perioperative implications of medical and mechanical therapeutics.

Patients with acute coronary syndromes who require emergency cardiac surgery present complex management challenges. The early administration of antiplatelet and antithrombotic drugs has improved overall survival for patients with acute myocardial infarction, but to achieve maximal benefit, these drugs are given before coronary anatomy is known and before the decision to perform percutaneous coronary interventions or surgical revascularization has been made. A major bleeding event secondary to these drugs is associated with a high rate of death in medically treated patients with acute coronary syndrome possibly because of subsequent withholding of antiplatelet and antithrombotic therapies that otherwise reduce the rate of death, stroke, or recurrent myocardial infarction. Whether the added risk of bleeding and blood transfusion in cardiac surgical patients receiving such potent antiplatelet or antithrombotic therapy before surgery specifically for acute coronary syndromes affects long-term mortality has not been clearly established. For patients who do proceed to surgery, strategies to minimize bleeding include stopping the anticoagulation therapy and considering platelet and/or coagulation factor transfusion and possibly recombinant-activated factor VIIa administration for refractory bleeding. Mechanical hemodynamic support has emerged as an important option for patients with acute coronary syndromes in cardiogenic shock. For these patients, perioperative considerations include maintaining appropriate anticoagulation, ensuring suitable device flow, and periodically verifying correct device placement. Data supporting the use of these devices are derived from small trials that did not address long-term postoperative outcomes. Future directions of research will seek to optimize the balance between reducing myocardial ischemic risk with antiplatelet and antithrombotics versus the higher rate perioperative bleeding by better risk stratifying surgical candidates and by assessing the effectiveness of newer reversible drugs. The effects of mechanical hemodynamic support on long-term patient outcomes need more stringent analysis.

Real-time continuous monitoring of cerebral blood flow autoregulation using near-infrared spectroscopy in patients undergoing cardiopulmonary bypass.

BACKGROUND AND PURPOSE: Individualizing mean arterial blood pressure targets to a patient's cerebral blood flow autoregulatory range might prevent brain ischemia for patients undergoing cardiopulmonary bypass (CPB). This study compares the accuracy of real-time cerebral blood flow autoregulation monitoring using near-infrared spectroscopy with that of transcranial Doppler. METHODS: Sixty adult patients undergoing CPB had transcranial Doppler monitoring of middle cerebral artery blood flow velocity and near-infrared spectroscopy monitoring. The mean velocity index (Mx) was calculated as a moving, linear correlation coefficient between slow waves of middle cerebral artery blood flow velocity and mean arterial blood pressure. The cerebral oximetry index was calculated as a similar coefficient between slow waves of cerebral oximetry and mean arterial blood pressure. When cerebral blood flow is autoregulated, Mx and cerebral oximetry index vary around zero. Loss of autoregulation results in progressively more positive Mx and cerebral oximetry index. RESULTS: Mx and cerebral oximetry index showed significant correlation (r=0.55, P<0.0001) and good agreement (bias, 0.08+/-0.18, 95% limits of agreement: -0.27 to 0.43) during CPB. Autoregulation was disturbed in this cohort during CPB (average Mx 0.38, 95% CI 0.34 to 0.43). The lower cerebral blood flow autoregulatory threshold (defined as incremental increase in Mx >0.45) during CPB ranged from 45 to 80 mm Hg. CONCLUSIONS: Cerebral blood flow autoregulation can be monitored continuously with near-infrared spectroscopy in adult patients undergoing CPB. Real-time autoregulation monitoring may have a role in preventing injurious hypotension during CPB. Clinical Trials Registration- at www.clinicaltrials.gov (NCT00769691).

Impaired autoregulation of cerebral blood flow during rewarming from hypothermic cardiopulmonary bypass and its potential association with stroke.

BACKGROUND: Patient rewarming after hypothermic cardiopulmonary bypass (CPB) has been linked to brain injury after cardiac surgery. In this study, we evaluated whether cooling and then rewarming of body temperature during CPB in adult patients is associated with alterations in cerebral blood flow (CBF)-blood pressure autoregulation. METHODS: One hundred twenty-seven adult patients undergoing CPB during cardiac surgery had transcranial Doppler monitoring of the right and left middle cerebral artery blood flow velocity. Eleven patients undergoing CPB who had arterial inflow maintained at >35 degrees C served as controls. The mean velocity index (Mx) was calculated as a moving, linear correlation coefficient between slow waves of middle cerebral artery blood flow velocity and mean arterial blood pressure. Intact CBF-blood pressure autoregulation is associated with an Mx that approaches 0. Impaired autoregulation results in an increasing Mx approaching 1.0. Comparisons of time-averaged Mx values were made between the following periods: before CPB (baseline), during the cooling and rewarming phases of CPB, and after CPB. The number of patients in each phase of CPB with an Mx >4.0, indicative of impaired CBF autoregulation, was determined. RESULTS: During cooling, Mx (left, 0.29 +/- 0.18; right, 0.28 +/- 0.18 [mean +/- SD]) was greater than that at baseline (left, 0.17 +/- 0.21; right, 0.17 +/- 0.20; P or=0.4 during the cooling phase of CPB and 68 (53%) had an average Mx >or=0.4 during rewarming. Nine of the 11 warm controls had an average Mx >or=0.4 during the entire CPB period. There were 7 strokes and 1 TIA after surgery. All strokes were in patients with Mx >or= 0.4 during rewarming (P = 0.015). The unadjusted odds ratio for any neurologic event (stroke or transient ischemic attack) for patients with Mx >or= 0.4 during rewarming was 6.57 (95% confidence interval, 0.79 to 55.0, P < 0.08). CONCLUSIONS: Hypothermic CPB is associated with abnormal CBF-blood pressure autoregulation that is worsened with rewarming. We found a high rate of strokes in patients with evidence of impaired CBF autoregulation. Whether a pressure-passive CBF state during rewarming is associated with risk for ischemic brain injury requires further investigation.

Bioprosthetic valve thrombosis in carcinoid heart disease.

Tricuspid regurgitation in carcinoid syndrome leads to significant morbidity and mortality that may warrant a tricuspid valve replacement. However, for patients with high serotonin levels and known hypercoagulable risks, the optimum timing for surgery and postoperative anticoagulation approaches remain unclear. High serotonin-triggered hypercoagulability makes prosthetic valves susceptible to thrombosis. Despite appropriate management with a somatostatin analog, some patients continue to have high markers of serotonin that causes platelet aggregation and rapid clot formation. In severely symptomatic patients who require valve surgery, it may not be feasible to postpone surgery until these metabolites are normalized, which may add a substantial risk for postoperative valve thrombosis to an otherwise uneventful procedure. In some, there is a significant need to predict and prevent bioprosthetic valve thrombosis in carcinoid heart disease and to identify best anticoagulation practices across a spectrum of its complex coagulation dynamics and clinical presentation.

Optimal blood pressure during cardiopulmonary bypass defined by cerebral autoregulation monitoring.

OBJECTIVES: We sought to define the lower and upper limits of cerebral blood flow autoregulation and the optimal blood pressure during cardiopulmonary bypass. We further sought to identify variables predictive of these autoregulation end points. METHODS: Cerebral autoregulation was monitored continuously with transcranial Doppler in 614 patients during cardiopulmonary bypass enrolled in 3 investigations. A moving Pearson's correlation coefficient was calculated between cerebral blood flow velocity and mean arterial pressure to generate the variable mean velocity index. Optimal mean arterial pressure was defined as the mean arterial pressure with the lowest mean velocity index indicating the best autoregulation. The lower and upper limits of cerebral blood flow autoregulation were defined as the mean arterial pressure at which mean velocity index was increasingly pressure passive (ie, mean velocity index ≥0.4) with declining or increasing blood pressure, respectively. RESULTS: The mean (± standard deviation) lower and upper limits of cerebral blood flow autoregulation, and optimal mean arterial pressure were 65 ± 12 mm Hg, 84 ± 11 mm Hg, and 78 ± 11 mm Hg, respectively, after adjusting for study enrollment. In 17% of patients, though, the lower limit of cerebral autoregulation was above this optimal mean arterial pressure, whereas in 29% of patients the upper limit of autoregulation was below the population optimal mean arterial pressure. Variables associated with optimal mean arterial pressure based on multivariate regression analysis were nonwhite race (increased 2.7 mm Hg; P = .034), diuretics use (decreased 1.9 mm Hg; P = .049), prior carotid endarterectomy (decreased 5.5 mm Hg; P = .019), and duration of cardiopulmonary bypass (decreased 1.28 per 60 minutes of cardiopulmonary bypass). The product of the duration and magnitude that mean arterial pressure during cardiopulmonary bypass was below the lower limit of cerebral autoregulation was associated with the risk for stroke (P = .02). CONCLUSIONS: Real-time monitoring of autoregulation may improve individualizing mean arterial pressure during cardiopulmonary bypass and improving patient outcomes.

Continuous cerebrovascular reactivity monitoring and autoregulation monitoring identify similar lower limits of autoregulation in patients undergoing cardiopulmonary bypass.

OBJECTIVES: Cerebrovascular autoregulation can be monitored with a moving linear correlation of blood pressure to cerebral blood flow velocity (mean velocity index, Mx) during cardiopulmonary bypass (CPB). Vascular reactivity can be monitored with a moving linear correlation of blood pressure to cerebral blood volume trended with near-infrared spectroscopy (hemoglobin volume index, HVx). We hypothesized that the lower limits of autoregulation (LLA) and the optimal blood pressure (ABPopt) associated with the most active autoregulation could be determined by HVx in patients undergoing CPB. METHODS: Adult patients (n = 109) who underwent CPB for cardiac surgery had monitoring of both autoregulation (Mx) and vascular reactivity (HVx). Individual curves of Mx and HVx were constructed by placing each in 5 mmHg bins. The LLA and ABPopt for each subject were then identified by both methods and compared for agreement by correlation analysis and Bland-Altman. RESULTS: The average LLA defined by Mx compared to HVx were comparable (66±13 and 66±12 mmHg). Correlation between the LLA defined by Mx and HVx was significant (Pearson r = 0.2867; P = 0.0068). The average ABPopt with the most robust autoregulation by Mx was comparable to HVx (75±11 and 74±13 mmHg) with significant correlation (Pearson r = 0.5915; P < or =0.0001). DISCUSSION: Autoregulation and vascular reactivity monitoring are expected to be distinct, as flow and volume have different phasic relationships to pressure when cerebrovascular autoregulation is active. However, the two metrics have good agreement when identifying the LLA and optimal blood pressure in patients during CPB.