Comparison of electroencephalography and cerebral oximetry to determine the need for in-line arterial shunting in patients undergoing carotid endarterectomy.

OBJECTIVE: To compare cerebral near-infrared regional spectroscopy (NIRS) with the 12-lead electroencephalogram for the detection of ischemia during carotid artery clamping for carotid endarterectomy (CEA). DESIGN: Prospective, observational. SETTING: Single, tertiary care center. PARTICIPANTS: Ninety patients older than 18 undergoing elective, unilateral CEA. INTERVENTIONS: In addition to EEG monitoring, all patients underwent continuous blinded NIRS monitoring with sensors placed bilaterally above the supraorbital ridge. MEASUREMENTS AND MAIN RESULTS: Seventeen patients were excluded, leaving 73 patients available for evaluation. Four patients (5.5%) required shunting based on EEG findings. Changes in cerebral oxygen saturation (rSO2) were assessed on the operative side using the average value for the 1 minute prior to cross-clamp and the lowest rSO2 value the first 5 minutes postclamp. Each 1% absolute decrease and each 1% relative decrease from baseline conferred a 50% increase in the need for shunt placement (OR 1.5; 95% CI (1.03-2.26); p = 0.03 and OR 1.4; 95% CI (1.02-1.81); p = 0.04 respectively). Sensitivity, specificity, and positive and negative predictive values were determined using significant cutoffs of≥5% absolute change or≥10% relative change. Positive predictive value was low (<25%) for both absolute and relative changes. CONCLUSIONS: A decrease in rSO2 during carotid cross-clamping for CEA is associated with EEG-determined need for shunting, but the positive predictive value is low. Using the above cutoffs in the current series would have resulted in an increase in the shunt rate by approximately 20% when it was not indicated by EEG.

Development and validation of a cerebral oximeter capable of absolute accuracy.

OBJECTIVE: Cerebral oximetry may be a valuable monitor, but few validation data are available, and most report the change from baseline rather than absolute accuracy, which may be affected by individuals whose oximetric values are outside the expected range. The authors sought to develop and validate a cerebral oximeter capable of absolute accuracy. DESIGN: An in vivo research study. SETTING: A university human physiology laboratory. PARTICIPANTS: Healthy human volunteers were enrolled in calibration and validation studies of 2 cerebral oximetric sensors, the Nonin 8000CA and 8004CA. The 8000CA validation study identified 5 individuals with atypical cerebral oxygenation values; their data were used to design the 8004CA sensor, which subsequently underwent calibration and validation. INTERVENTIONS: Volunteers were taken through a stepwise hypoxia protocol to a minimum saturation of peripheral oxygen. Arteriovenous saturation (70% jugular bulb venous saturation and 30% arterial saturation) at 6 hypoxic plateaus was used as the reference value for the cerebral oximeter. Absolute accuracy was defined using a combination of the bias and precision of the paired saturations (A(RMS)). MEASUREMENTS AND MAIN RESULTS: In the validation study for the 8000CA sensor (n = 9, 106 plateaus), relative accuracy was an A(RMS) of 2.7, with an absolute accuracy of 8.1, meeting the criteria for a relative (trend) monitor, but not an absolute monitor. In the validation study for the 8004CA sensor (n = 11, 119 plateaus), the A(RMS) of the 8004CA was 4.1, meeting the prespecified success criterion of <5.0. CONCLUSIONS: The Nonin cerebral oximeter using the 8004CA sensor can provide absolute data on regional cerebral saturation compared with arteriovenous saturation, even in subjects previously shown to have values outside the normal population distribution curves.

Cerebral oximetry during cardiac surgery: the association between cerebral oxygen saturation and perioperative patient variables.

OBJECTIVE: This "real-world" study was designed to assess the patterns of regional cerebral oxygen saturation (rSO(2)) change during adult cardiac surgery. A secondary objective was to determine any relation between perioperative rSO(2) (baseline and during surgery) and patient characteristics or intraoperative variables. DESIGN: Prospective, observational, multicenter, nonrandomized clinical study. SETTING: Cardiac operating rooms at 3 academic medical centers. PARTICIPANTS: Ninety consecutive adult patients presenting for cardiac surgery with or without cardiopulmonary bypass. INTERVENTIONS: Patients received standard care at each institution plus bilateral forehead recordings of cerebral oxygen saturation with the 7600 Regional Oximeter System (Nonin Medical, Plymouth, MN). MEASUREMENTS AND MAIN RESULTS: The average baseline (before induction) rSO(2) was 63.9 ± 8.8% (range 41%-95%); preoperative hematocrit correlated with baseline rSO(2) (0.48% increase for each 1% increase in hematocrit, p = 0.008). The average nadir (lowest recorded rSO(2) for any given patient) was 54.9 ± 6.6% and was correlated with on-pump surgery, baseline rSO(2), and height. Baseline rSO(2) was found to be an independent predictor of length of stay (hazard ratio 1.044, confidence interval 1.02-1.07, for each percentage of baseline rSO(2)). CONCLUSIONS: In cardiac surgical patients, lower baseline rSO(2) value, on-pump surgery, and height were significant predictors of nadir rSO(2), whereas only baseline rSO(2) was a predictor of postoperative length of stay. These findings support previous research on the predictive value of baseline rSO(2) on length of stay and emphasize the need for further research regarding the clinical relevance of baseline rSO(2) and intraoperative changes.

Berlin Heart EXCOR Pediatric ventricular assist device Investigational Device Exemption study: study design and rationale.

BACKGROUND: Currently, there are no Food and Drug Administration-approved devices available that can provide long-term mechanical circulatory support to smaller children with severe heart failure as a bridge to heart transplant (HT). In recent years, the Berlin Heart EXCOR Pediatric ventricular assist device (VAD) has emerged as a potential treatment option. Systematic data on the safety and efficacy of the EXCOR are limited. METHODS: The Investigational Device Exemption (IDE) clinical study is designed to evaluate the safety and probable benefit of the EXCOR to support regulatory review of the device under the Humanitarian Device Exemption regulation. The study design and rationale are reviewed in light of the well-described challenges inherent in small population studies. RESULTS: The Berlin Heart EXCOR IDE clinical study is a prospective, multicenter, single-arm, clinical cohort study. Children aged 0 to 16 years with severe heart failure (Interagency Registry for Mechanically Assisted Circulatory Support profile 1 or 2) due to 2-ventricle heart disease and actively listed for HT comprise the primary study cohort. The control population is a propensity-matched retrospective cohort of children supported with extracorporeal membrane oxygenation, the only bridge device available to smaller children before the EXCOR. The primary efficacy end point is survival to heart transplantation or recovery. The primary safety end point is the incidence of serious adverse events as defined by pediatric Interagency Registry for Mechanically Assisted Circulatory Support criteria. The study will enroll a total of 48 subjects in 2 cohorts based on body surface area (cohort 1 <0.7 m(2), cohort 2 0.7-1.5 m(2)) and is powered to show safety superiority to a prespecified performance goal of 0.25 serious adverse events per day of support. Children ineligible for the primary cohort will still have access to the device in a third compassionate-use cohort where adverse event data will be collected for additional safety characterization of the device. CONCLUSION: The Berlin Heart IDE clinical study will be the first bridge-to-HT VAD study designed exclusively for children. It is anticipated that the study will provide important information on the safety and efficacy of the Berlin Heart EXCOR Pediatric in children while providing valuable lessons into the design and conduct of future VAD studies in children.

Wearable Pulse Oximetry Measurements on the Torso, Arms, and Legs: A Proof of Concept.

For decades pulse oximeters designed for use on the head, hands, or feet have provided invaluable estimates of oxygen saturation to medical personal attending to combat casualties. However, traditional placement sites are not ideal for the relatively new paradigm of continuous battlefield telemonitoring. To assess the feasibility of oximetry on nontraditional body sites, 42 healthy volunteers were enrolled, consented, and underwent an industry standard induced-hypoxia study. During the study volunteers used prototype wearable oximeters, designed for the torso, arms, and legs. Subsets (size n) of the volunteers had the wearables placed at the following body sites, and achieved accuracies (ARMS, root-mean-square difference) of the following: calf 1.7% (n = 26); bicep 3.1% (n = 12); forearm 3.4% (n = 11); pectoral 2.9% (n = 42); sternum 2.9% (n = 13). In keeping with regulatory guidance calibrations with an ARMS of less than 3.5% are acceptable for potential future development. Additionally, a new method was developed to enable accurate reporting of respiration rate from the pectoral oximeter, ARMS of 1.1 breaths per minute (n = 10). This study demonstrates the feasibility of monitoring oxygen saturation and respiration rate from nontraditional sites via a wearable pulse oximeter.