Mean rSO2 Research Articles

Safety of perioperative cerebral oxygen saturation during debranching in patients with incomplete circle of Willis.

The consequences of common carotid artery (CCA) cross-clamping during debranching before thoracic endovascular aortic repair are unclear. We examined the safety of a simple CCA cross-clamping procedure under regional cerebral oxygen saturation monitoring (rSO2) in patients with a complete or incomplete circle of Willis (CoW) anatomy. Twenty-eight patients with thoracic aneurysm underwent elective debranching thoracic endovascular aortic repair with bilateral frontal rSO2 monitoring at our institution between January 2012 and October 2015. Before CCA cross-clamping, we maintained a systemic mean arterial pressure of >100 mm Hg with a vasopressor. We recorded the bilateral frontal rSO2 before, during and after CCA cross-clamping. The CoW was incomplete in 11 (39.3%) patients. Of these, 6 patients had a complication of ischaemic potential. The left frontal rSO2 was <50% in 3 patients but did not fall below 40%. Compared with baseline values (mean ± SD 64.6 ± 6.9%), the left frontal rSO2 showed no significant change perioperatively in those with a complete CoW on the left CCA cross-clamping (during: 61.0 ± 7.9%, P = 0.17; after: 65.1 ± 5.9%, P = 0.09). In patients with an incomplete CoW with ischaemic potential, the left frontal rSO2 did not change significantly after cross-clamping (baseline: 59.8 ± 3.2%, during: 55.5 ± 5.0%; P = 0.10) but increased significantly on declamping (62.8 ± 4.5%, P = 0.023). The extent of the changes in the mean left frontal rSO2 on clamping and declamping decreased and increased by 7.3% and 11.7%, respectively, in patients with an incomplete CoW, when compared with 5.3% and 5.8% in those with a complete CoW (P = 0.65 and 0.31, respectively). No perioperative cerebrovascular events were observed. Simple CCA cross-clamping during debranching was safe when arterial pressure was supported and rSO2 was monitored, even with an incomplete CoW and ischaemic potential.

Abstract 21060: The Association Between Post-Resusciation Cerebral Oxygenation and Survival With Favorable Neurological Outcomes: A Multicenter Study

Background: Cerebral ischemia/reperfusion injury in the post-resuscitation period contributes to morbidity and mortality following cardiac arrest (CA). Cerebral oximetry is a non-invasive system that uses near infrared spectroscopy to measure regional cerebral oxygenation level (rSO2) in the frontal lobe of the brain. Studies have shown that post-resuscitation rSO2 may be associated with survival and neurological outcomes in out-of-hospital cardiac arrest patients, however no studies have examined this in in-hospital cardiac arrest (IHCA) patients. Hypothesis: rSO2 changes following return of spontaneous circulation (ROSC) after IHCA are associated with survival with favorable neurological outcomes. Methods: A multi-site prospective study of consecutive day-time IHCA patients admitted to the ICU after ROSC at 7 sites. Continuous rSO2 monitoring (Equanox 7600, Nonin Medical, MN, USA) was applied for 48 hours after ROSC using a forehead sensor. Mean rSO2 was calculated hourly between 1-6 hrs. and at 6, 12, 18, 24, 48 hr. intervals. Demographic and data pertaining to possible confounding variables for rSO2 and survival with favorable neurological outcomes (cerebral performance scale [CPC] 1-2) vs death or severe neurological injury (CPC 3-5) at hospital discharge were collected. Results: Among 87 studied patients, 26 (29.9%) achieved CPC1-2. There were no differences in age, Charlson comorbidity index, APACHE II scores, and resuscitation duration, however, CPC 1-2 was higher in men vs. women (36.5% vs. 12.5%, p = 0.036). A significant difference in mean rSO2 was observed during hours 1-2 after ROSC in CPC 1-2 vs CPC3-5 (73.08 vs. 66.59, p = 0.031) but not at other time points. There were no differences in mean arterial pressure, PaO2, PaCO2, and hemoglobin levels, however subjects with CPC 1-2 had lower glucose (154.4mg/dL vs. 202.8mg/dL, p = 0.0054), lactate level (4.11 mmol/dL vs. 6.39 mmol/dL, p = 0.030), and higher Glasgow coma scale (9.42 vs. 5.96, p = 0.0026) within the first 24 hours. Conclusions: Changes in rSO2 as measured by cerebral oximetry in the first two hours after ROSC may predict survival with neurological outcomes after resuscitation following IHCA.

Cerebral and Limb Tissue Oxygenation During Peripheral Venoarterial Extracorporeal Life Support.

Femoral access in extracorporeal life support (ECLS) has been associated with regional variations in arterial oxygen saturation, potentially predisposing the patient to ischemic tissue damage. Current monitoring techniques, however, are limited to intermittent bedside evaluation of capillary refill among other factors. The aim of this study was to assess whether cerebral and limb regional tissue oxygen saturation (rSO2) values reflect changes in various patient-related parameters during venoarterial ECLS (VA-ECLS). This retrospective observational study included adults assisted by femorofemoral VA-ECLS. Bifrontal cerebral and bilateral limb tissue oximetry was performed for the entire duration of support. Hemodynamic data were analyzed parallel to cerebral and limb rSO2. A total of 23 patients were included with a median ECLS duration of 5 [1-20] days. Cardiac arrhythmias were observed in 12 patients, which was associated with a decreased mean rSO2 from 61%±11% to 51%±10% during atrial fibrillation and 67%±9% to 58%±10% during ventricular fibrillation (P<0.001 for both). A presumably sudden increase in cardiac output due to myocardial recovery (n=8) resulted in a significant decrease in mean cerebral rSO2 from 73%±7% to 54%±6% and from 69%±9% to 53%±8% for the left and right cerebral hemisphere, respectively (P=0.012 for both hemispheres). Also, right radial artery partial gas pressure for oxygen decreased from 15.6±2.8 to 8.3±1.9 kPa (P=0.028). No differences were found in cerebral desaturation episodes between patients with and without neurologic complications. In six patients, limb rSO2 increased from on average 29.3±2.7 to 64.0±5.1 following insertion of a distal cannula in the femoral artery (P=0.027). Likewise, restoration of flow in a clotted distal cannula inserted in the femoral artery was necessary in four cases and resulted in increased limb rSO2 from 31.3±0.8 to 79.5±9.0; P=0.068. Non-invasive tissue oximetry adequately reflects events influencing cerebral and limb perfusion and can aid in monitoring tissue perfusion in patients assisted by ECLS.

Assessment of Mesenteric Tissue Saturation, Oxygen Saturation, and Heart Rate Pre- and Post-Blood Transfusion in Very Low-Birth-Weight Infants Using Abdominal Site Near-Infrared Spectroscopy.

Preterm infants often receive blood transfusions during hospitalization. Although transfusions are intended to enhance oxygen delivery, previous studies found decreases in tissue and mesenteric oxygen saturation during and after blood transfusions without changes in vital signs and hemoglobin oxygen saturation. To study the effect of blood transfusions on regional mesenteric tissue oxygen saturation (rSO2), hemoglobin saturation of oxygen (SpO2), and heart rate (HR) in premature infants. A prospective, observational, nonrandomized study using a repeated-measures design was done to evaluate changes in physiologic variables (HR, SpO2, rSO2) before, during, and after a blood transfusion in premature infants. A convenience sample of 30 infants with a mean gestational age of 25.5 (2.1) weeks was recruited. Repeated-measures analysis of variance found no significant differences in HR (P = .06) and SpO2 (P = .55) over time. However, significant differences occurred in rSO2 over the 3 time periods (P < .001). The rSO2 increased during the transfusion from 40.3% to 41.5%, but decreased to 34.9% in the posttransfusion period. Pairwise comparisons revealed statistically significant mean rSO2 differences between pretransfusion and posttransfusion (P < .001), and during transfusion to posttransfusion (P < .001) periods. This study supports previous findings of perfusion changes during blood transfusions in preterm infants. Measuring mesenteric tissue oxygenation during blood transfusion in very low-birth-weight infants can potentially add another physiologic parameter to guide further clinical assessment and interventions during transfusions.

The effect of the beach-chair position angle on cerebral oxygenation during shoulder surgery

Although the safety of the beach-chair position (BCP) is widely accepted, rare devastating neurologic complications have been reported and attributed to cerebral hypoperfusion. Cerebral oxygenation (regionaloxygensaturation [rSO2]) can be monitored noninvasively using near-infrared spectroscopy. The purpose of this study was to determine the effect of BCP angle on cerebral oxygenation in patients undergoing shoulder surgery in the BCP. Fifty patients undergoing shoulder arthroscopy were prospectively enrolled to participate. Following induction of general anesthesia, each patient's rSO2 was recorded at 0° of elevation and again at 30°, 45°, 60°, and 80° of elevation. Mean rSO2 values and mean differences in rSO2 were reported. An average total decrease of 5% in rSO2 was seen when comparing 0° with 80° (P < .001). There were statistically significant differences in rSO2 values at beach-chair angles of 0° versus 30° (P <.001), 30° versus 45° (P = .007), and 45° versus 60° (P <.001) but not between 60° and 80° (P = .12). The decrease in rSO2 was similar between each progressive increase in the beach-chair angle, leading to a linear decline in rSO2 as the BCP increased (regression slope of -0.060%/°, P <.001). No patient's cerebral oxygenation dropped greater than 20% from baseline. Neither body mass index nor American Society of Anesthesiologists score had a significant impact on the relation of rSO2 to BCP angle. The average drop in rSO2 is significantly less than the threshold of 20% used as an identifier for a cerebral deoxygenation event. This study illustrates the direct effect the BCP angle has on cerebral oxygenation.

Effect of Mild Hypercapnia on Lung Oxygenation in Sitting Position During Shoulder Arthroscopy Under General Anesthesia.

BackgroundMild hypercapnia is permitted during surgeries in sitting position under general anesthesia to maintain cerebral regional oxygen saturation (rSO2). However, since hypoventilation may cause gas exchange impairment, we evaluated effects of mild hypercapnia on lung oxygenation during shoulder arthroscopy in sitting position.Material/MethodsForty patients were randomly allocated to a normocapnia group (ETCO2 35 mmHg, n=20) or a hypercapnia group (45 mmHg, n=20). The mean arterial pressure (MAP), heart rate (HR), and rSO2 were measured 5 min after intubation in supine position (T0), and at 2, 4, 6, 8, 10, 20, 30, 40, 50, and 60 min of remaining in sitting position (T1–10). Arterial blood gas was analyzed at T0 and T5. The oxygenation index (PaO2/FiO2) and dead-space ventilation ratio (Vd/Vt) were calculated.ResultsThere were no differences in PaO2/FiO2 at T0 and T5 between the 2 groups. At T5, the Vd/Vt was higher in the normocapnia group than in the hypercapnia group (p=0.04). The Vd/Vt at T5 increased from T0 in the normocapnia group. The incidence of cerebral desaturation in the hypercapnia group (0/20) was lower than in the normocapnia group (5/20) (p=0.047). Among rSO2, MAP, and HR, only changes in rSO2 over time between the 2 groups differed significantly (p=0.048).ConclusionsMild hypercapnia did not decrease lung oxygenation in sitting position, probably due to attenuation of the increase in dead-space ventilation ratio. Since hypercapnia maintained rSO2 without changes in oxygenation index and hemodynamic parameters, mild hypercapnia should be maintained during shoulder arthroscopy in sitting position under general anesthesia.

Comparison of the Effects of Different Positive End-Expiratory Pressure Levels on Cerebral Oxygen Saturation With Near Infrared Spectroscopy During Laparoscopic Cholecystectomy

Although positive end-expiratory pressure (PEEP) is commonly used to improve respiratory mechanics and oxygenation during pneumoperitoneum (PP), the effect of PEEP on cerebral homeostasis during carbon dioxide PP remains uncertain. This study investigated the changes in regional cerebral oxygen saturation (rSO2) associated with 0, 5, and 10 cm H2O PEEP during PP while undergoing laparoscopic cholecystectomy under sevoflurane anesthesia. In total, 105 patients between the ages of 18 to 60 years, scheduled to undergo laparoscopic cholecystectomy under general anesthesia, were studied. The patients were randomized, into 3 groups: group I (n=35) with no external PEEP, group II (n=35) with external PEEP of 5 cm H2O, group III (n=35) with external PEEP of 10 cm H2O. Heart rate, mean blood pressure, oxygen saturation, and rSO2 values were continuously recorded from awake status to tracheal extubation. The measurements of hemodynamic parameters were statistically similar between 3 groups (P>0.05). rSO2 values were statistically similar between 3 groups (P>0.05). We consider that both 5 and 10 cm H2O PEEP levels can be safely used during PP applied during laparoscopic surgery, without affecting hemodynamics, and without causing a decline in rSO2.

Changes in cerebral oxygen saturation during transcatheter aortic valve replacement.

Cerebral oxygen saturation (rSO2) is a non-invasive monitor used to monitor cerebral oxygen balance and perfusion. Decreases in rSO2 >20% from baseline have been associated with cerebral ischemia and increased perioperative morbidity. During transcatheter aortic valve replacement (TAVR), hemodynamic manipulation with ventricular pacing up to 180 beats per minute is necessary for valve deployment. The magnitude and duration of rSO2 change during this manipulation is unclear. In this small case series, changes in rSO2 in patients undergoing TAVR are investigated. Ten ASA IV patients undergoing TAVR with general anesthesia at a university hospital were prospectively observed. Cerebral oximetry values were analyzed at four points: pre-procedure (baseline), after tracheal intubation, during valve deployment, and at procedure end. Baseline rSO2 values were 54.5±6.9%. After induction of general anesthesia, rSO2 increased to a mean of 66.0±6.7%. During valve deployment, the mean rSO2 decreased <20% below baseline to 48.5±13.4%. In two patients, rSO2 decreased >20% of baseline. Cerebral oxygenation returned to post-induction values in all patients 13±10min after valve deployment. At procedure end, the mean rSO2 was 67.6±8.1%. As expected, rapid ventricular pacing resulting in the desired decrease in cardiac output during valve deployment was associated with a significant decrease in rSO2 compared to post-induction values. However, despite increased post-induction values in all patients, whether related to increased inspired oxygen fraction or reduced cerebral oxygen consumption under anesthesia, two patients experienced a significant decrease in rSO2 compared to baseline. Recovery to baseline was not immediate, and took up to 20min in three patients. Furthermore, baseline rSO2 in this population was at the lower limit of the published normal range. Significant cerebral desaturation during valve deployment may potentially be limited by maximizing rSO2 after anesthetic induction. Future studies should attempt to correlate recovery in rSO2 with recovery of hemodynamics and cardiac function, provide detailed neurological assessments pre and post procedure, determine the most effective method of maximizing rSO2 prior to hemodynamic manipulation, and provide the most rapid method of recovery of rSO2 following valve deployment.

Retrospective evaluation of the effect of carotid artery stenosis on cerebral oxygen saturation during off-pump coronary artery bypasses grafting in adult patients.

BackgroundIt is unknown whether cerebral oxygenation in patients with carotid artery stenosis (CAS) undergoing off-pump coronary artery bypass grafting (CABG) differs from that in patients without CAS. Thus, the effect of the presence of CAS ≥ 50 % on cerebral oxygenation during off-pump CABG in adult patients was evaluated retrospectively.MethodsEleven patients with CAS ≥ 50 % and 14 patients without CAS ≥ 50 % were enrolled. Regional cerebral tissue oxygen saturation (rSO2) was quantified using near-infrared spectroscopy. Mean arterial pressure, cardiac index, central venous pressure (CVP), and rSO2 at specific points were collected, and significant changes in each parameter were detected using repeated analysis of variance. Mean rSO2 and minimum rSO2 during anastomosis were analyzed by one-way analysis of variance. Multiple logistic regression analysis was used to estimate the odds ratio (OR) with 95 % confidence interval (CI) for cerebral desaturation (a decrease in rSO2 ≥ 10 % from preoperative value).ResultsTwo patients with CAS ≥ 50 % who received complete carotid artery stenting preoperatively were excluded from the analyses. In both patients with and without CAS, a decrease in rSO2 and cardiac index and an increase in CVP were observed during anastomosis. Mean (SD) maximum decrease in rSO2 from preoperative value was 9.2 (12.7) % on the left side and 8.1 (11.7) % on the right side in patients with CAS ≥ 50 %, and 13.5 (11.3) % on the left side and 16.1 (9.8) % on the right side in patients without CAS ≥ 50 % (p = 0.316). Neurological complications were not identified in both patients with and without CAS ≥ 50 %. In multiple logistic regression analysis, CAS ≥ 50 % was not associated with an increased risk of cerebral desaturation (OR 0.160, 95 % CI 0.036–0.707, p = 0.016), and rSO2 decreased with decreasing cardiac index < 2.0 l/min/m2 (OR 3.287, 95 % CI 2.218–5.076, p < 0.001).ConclusionsCAS ≥ 50 % was not an independent risk factor of cerebral desaturation during off-pump CABG. Our results suggest that maintaining cardiac output can prevent a decrease in cerebral oxygenation in both patients with and without CAS ≥ 50 %.

Increase in cerebral oxygenation during advanced life support in out-of-hospital patients is associated with return of spontaneous circulation.

IntroductionBy maintaining sufficient cerebral blood flow and oxygenation, the goal of cardiopulmonary resuscitation (CPR) is to preserve the pre-arrest neurological state. To date, cerebral monitoring abilities during CPR have been limited. Therefore, we investigated the time-course of cerebral oxygen saturation values (rSO2) during advanced life support in out-of-hospital cardiac arrest. Our primary aim was to compare rSO2 values during advanced life support from patients with return of spontaneous circulation (ROSC) to patients who did not achieve ROSC.MethodsWe performed an observational study to measure rSO2 using Equanox™ (Nonin, Plymouth, MI) from the start of advanced life support in the pre-hospital setting.ResultsrSO2 of 49 consecutive out-of-hospital cardiac arrest patients were analyzed. The total increase from initial rSO2 value until two minutes before ROSC or end of advanced life support efforts was significantly larger in the group with ROSC 16% (9 to 36) compared to the patients without ROSC 10% (4 to 15) (P = 0.02). Mean rSO2 from the start of measurement until two minutes before ROSC or until termination of advanced life support was higher in patients with ROSC than in those without, namely 39% ± 7 and 31% ± 4 (P = 0.05) respectively.ConclusionsDuring pre-hospital advanced life support, higher increases in rSO2 are observed in patients attaining ROSC, even before ROSC was clinically determined. Our findings suggest that rSO2 could be used in the future to guide patient tailored treatment during cardiac arrest and could therefore be a surrogate marker of the systemic oxygenation state of the patient.

Determinants and significance of cerebral oximetry after cardiac arrest: A prospective cohort study

Aim of the studyTo study the determinants and the evolution of cerebral oximetry determined by near-infrared spectroscopy after out-of-hospital cardiac arrest of cardiac origin during therapeutic hypothermia and rewarming, and to compare cerebral oximetry values between patients with good and bad prognosis. MethodsIn this prospective, non-interventional, single center study, all consecutive patients between 18 and 80 years admitted for out-of-hospital cardiac arrest (OHCA) with a no flow less than 10min, a low flow of less than 50min and a persistent coma after ROSC with Glasgow score equal or less than seven at baseline were included. ResultsBetween February 2012 and January 2013, 43 patients were admitted for OHCA in our ICU. Twenty-two patients (51%) were discharged with no or minimal neurologic complications (CPC 1–2). Mortality rate in the ICU was 46.5%. Cerebral oximetry (rSO2) was correlated with temperature, heart rhythm, PaO2, hemoglobin, and mean arterial pressure. Mean rSO2 during the 48 first hours was not different between patients with good and bad neurologic outcomes, respectively, 61.8 (5.9) vs. 58.1 (8.8), P=0.13, as during the period of hypothermia. The minimal value of rSO2 during the first 48h was significantly different between patients with good prognosis and those with bad prognosis, respectively, 45.0 (6.8) vs. 31.7 (15.0), P=0.0009. ConclusionsIn this prospective cohort of OHCA patients, main determinants of rSO2 were systemic variables. Monitoring of rSO2 does not allow discriminating patients with good or bad outcome, but could be useful for identifying vulnerable periods for the development of neurologic injury.

Abstract 15899: The Effect of Cerebral Oxygenation on Cardiac Arrest Outcomes: A Multicenter Pilot Observational Study

Background: Cardiac arrest (CA) is associated with morbidity and mortality due to cerebral ischemia. We therefore tested the hypothesis that higher regional cerebral oxygenation (rSO2) during resuscitation is associated with improved return of spontaneous circulation (ROSC), survival and neurological outcomes at hospital discharge. We further examined the validity of rSO2 as a test to predict these outcomes. Methods: Multicenter prospective study of in-hospital CA (IHCA). Inclusion criteria: IHCA, age≥18 years, Prolonged CPR≥5 minutes. Patients were recruited consecutively during working hours between 08/2011-09/2014. Survival with a favorable neurological outcome was defined as a Cerebral Performance Category (CPC)1-2. Results: Among 504 IHCA events, 183 (36%) met inclusion criteria. Overall 62/183 (33.9%) achieved ROSC, while 13/183(7.1%) achieved CPC1-2 at discharge. Higher mean±SD rSO2 was associated with ROSC vs. no ROSC (51.8±11.2% vs. 40.9±12.3%) and CPC1-2 vs. CPC3-5 (56.1±10.0% vs. 43.8±12.8%), both P&lt;0.001). Mean rSO2 during the last 5 minutes of CPR best predicted ROSC (AUC=0.76:95% CI:0.69-0.83); rSO2≥25% provided 100% sensitivity (95%CI:94%-100%), 100% negative predictive value (NPV) (95%CI:79%-100%); rSO2 ≥65% provided: 99% specificity (95%CI:95%-100%), 93% positive predictive value (PPV) (95%CI:66%-100%) for ROSC. Time with rSO2&gt;50% during CPR best predicted CPC1-2 (AUC=0.79: 95%CI:0.70-0.88). Specifically, ≥60% CPR time with rSO2&gt;50% provided 77% sensitivity (95%CI:46%-95%), 72% specificity (95%CI:65%-79%) and 98% NPV (95%CI: 93%-100%) for CPC1-2. Conclusions: Cerebral oximetry allows real-time non-invasive cerebral oxygenation monitoring during CPR. Higher cerebral oxygenation during CPR is associated with ROSC and neurologically favorable survival to hospital discharge. Achieving higher rSO2 during resuscitation may optimize the chances of CA favorable outcomes.

Regional cerebral oxygen saturation monitoring for predicting interventional outcomes in patients following out-of-hospital cardiac arrest of presumed cardiac cause: A prospective, observational, multicentre study

AimThis study investigated the value of regional cerebral oxygen saturation (rSO2) monitoring upon arrival at the hospital for predicting post-cardiac arrest intervention outcomes. MethodsWe enrolled 1195 patients with out-of-hospital cardiac arrest of presumed cardiac cause from the Japan-Prediction of Neurological Outcomes in Patients Post-cardiac Arrest Registry. The primary endpoint was a good neurologic outcome (cerebral performance categories 1 or 2 [CPC1/2]) 90 days post-event. ResultsA total of 68 patients (6%) had good neurologic outcomes. We found a mean rSO2 of 21%±13%. A receiver operating characteristic curve analysis indicated an optimal rSO2 cut-off of ≥40% for good neurologic outcomes (area under the curve 0.92, sensitivity 0.81, specificity 0.96). Good neurologic outcomes were observed in 53% (55/103) and 1% (13/1092) of patients with high (≥40%) and low (<40%) rSO2, respectively. Even without return of spontaneous circulation (ROSC) upon arrival at the hospital, 30% (9/30) of patients with high rSO2 had good neurologic outcomes. Furthermore, 16 patients demonstrating ROSC upon arrival at the hospital and low rSO2 had poor neurologic outcomes. Multivariate analyses indicated that high rSO2 was independently associated with good neurologic outcomes (odds ratio=14.07, P<0.001). Patients with high rSO2 showed favourable neurologic prognoses if they had undergone therapeutic hypothermia or coronary angiography (CPC1/2, 69% [54/78]). However, 24% (25/103) of those with high rSO2 did not undergo these procedures and exhibited unfavourable neurologic prognoses (CPC1/2, 4% [1/25]). ConclusionrSO2 is a good indicator of 90-day neurologic outcomes for post-cardiac arrest intervention patients.

The Effects of Limb Elevation on Muscle Oxygen Saturation: A Near-Infrared Spectroscopy Study in Humans

BackgroundOrthopaedic and rehabilitation physicians often instruct patients to elevate a traumatized or postoperative lower extremity. Elevation is thought to improve patient comfort, as well as decrease swelling, wound complications, and the risk of compartment syndrome. Elevating a limb with increased compartment pressures, however, has been shown to reduce perfusion pressure and contribute to tissue ischemia. This investigation aims to advance our understanding of the tissue effects of limb elevation using a healthy patient model. ObjectiveTo quantify the effects of elevation, experimentally induced ischemia, and immobilization on muscle oxygen saturation in the human leg using near-infrared spectroscopy (NIRS). DesignExperimental crossover study. SettingOrthopaedic Surgery research laboratory, Stanford Hospitals & Clinics. Patients for ParticipationTwenty-six healthy volunteers. MethodsUsing transcutaneous sensors, we measured muscle oxygen saturation of the anterior compartment of the left (control) leg at 0, 15, and 30 cm of elevation relative to the heart using NIRS. A standardized short leg splint and a thigh tourniquet inflated to 50 mmHg were then applied to the right (experimental) leg to simulate a traumatized state. NIRS measurements were then repeated, again at 0, 15, and 30 cm of elevation. Muscle oxygen saturation values at various degrees of elevation of the control and experimental limb were then compared and analyzed by the use of a crossover study design and mixed-effects regression. Main Outcome MeasurementsMuscle oxygen saturation at varying levels of elevation in both the (1) control leg and (2) experimental leg in a simulated traumatic state. ResultsMale (18) males and female (8) patients between 22 and 62 years of age (mean 29.8 years) were enrolled. Mean regional muscle oxygen saturation (rSO2) of the control limbs at 0, 15 and, 30 cm of elevation were 74.2%, 72.5%, and 70.6%, respectively, whereas mean rSO2 of the experimental limbs were 66.3%, 65.0%, and 63.3%. A statistically significant decrease of rSO2 was observed (mean 7.65%) in the experimental limbs compared with the control limbs. As elevation increased, there was a statistically significant decrease in rSO2 of 0.12% per centimeter of elevation. Elevation did not decrease the rSO2 in the experimental limb to a greater degree than in the control limb. ConclusionIncreasing levels of elevation in a human limb results in progressively compromised muscle oxygen saturation as measured by NIR.

Corticospinal excitability changes to anodal tDCS elucidated with NIRS-EEG joint-imaging: An ischemic stroke study.

Transcranial direct current stimulation (tDCS) has been shown to modulate corticospinal excitability. We used near-infrared spectroscopy (NIRS)-electroencephalography (EEG) joint-imaging during and after anodal tDCS to measure changes in mean cerebral haemoglobin oxygen saturation (rSO2) along with changes in the log-transformed mean-power of EEG within 0.5 Hz-11.25 Hz. In two separate studies, we investigated local post-tDCS alterations from baseline at the site of anodal tDCS using NIRS-EEG/tDCS joint-imaging as well as local post-tDCS alterations in motor evoked potentials (MEP)-measure of corticospinal excitability. In the first study, we found that post-tDCS changes in the mean rSO2 from baseline mostly correlated with the corresponding post-tDCS change in log-transformed mean-power of EEG within 0.5 Hz-11.25 Hz. Moreover, a decrease in log-transformed mean-power of EEG within 0.5 Hz-11.25 Hz corresponded with an increase in the MEP-measure of corticospinal excitability--found in the second study. Therefore, we propose to combine NIRS-EEG/tDCS joint-imaging with corticospinal excitability investigation in a single study to confirm these finding. Furthermore, we postulate that the innovative technologies for portable NIRS-EEG neuroimaging may be leveraged to objectively quantify the progress (e.g., corticospinal excitability alterations) and dose tDCS intervention as an adjuvant treatment during neurorehabilitation.

Anterior temporal artery tap to identify systemic interference using short-separation NIRS measurements: A NIRS/EEG-tDCS study.

Transcranial direct current stimulation (tDCS) has been shown to modulate neural activity. Neural activity has been shown to be closely related, spatially and temporally, to cerebral blood flow (CBF) that supplies glucose via neurovascular coupling. Therefore, noninvasive and continuous monitoring of neural activity is possible with a measure of cerebral hemoglobin oxygenation using near-infrared spectroscopy (NIRS). In principal accordance, NIRS can capture the hemodynamic response to tDCS but the challenge remains in removing the systemic interference occurring in the superficial layers of the head that are also affected by tDCS. An approach may be to use short optode separations to measure systemic hemodynamic fluctuations occurring in the superficial layers which can then be used as regressors to remove the systemic contamination. Here, we demonstrate that temporal artery tap may be used to better identify systemic interference using this short-separation NIRS. Moreover, NIRS-EEG joint-imaging during anodal tDCS was used to measure changes in mean cerebral haemoglobin oxygen saturation (rSO2) along with changes in the log-transformed mean-power of EEG within 0.5 Hz-11.25 Hz. We found that percent change in the mean rSO2 better correlated with the corresponding percent change in log-transformed mean-power of EEG within 0.5 Hz-11.25 Hz frequency band after removing the systemic contamination using the temporal artery tap method. Based on our findings, we propose that anterior temporal artery tap technique presented in this paper may be able to classify carotid stenosis, external carotid artery stenosis, and internal carotid artery stenosis patients using the laterality in the hemodynamic response evoked by anodal tDCS both at the brain as well as at the superficial layers. These findings may have important implications for both prognosis and rehabilitation of patients with intracranial stenosis.

Phenobarbital and neonatal seizures affect cerebral oxygen metabolism: a near-infrared spectroscopy study.

BackgroundNear-infrared spectroscopy (NIRS) measures oxygen metabolism and is increasingly used for monitoring critically-ill neonates. The implications of NIRS-recorded data in this population are poorly understood. We evaluated NIRS monitoring for neonates with seizures.MethodsIn neonates monitored with video-EEG, NIRS-measured cerebral regional oxygen saturation (rSO2) and systemic O2 saturation were recorded every 5 seconds. Mean rSO2 was extracted for 1-hour blocks before, during, and after phenobarbital doses. For each electrographic seizure, mean rSO2 was extracted for a period of 3-times the duration of the seizure before and after the ictal pattern, and during the seizure. Linear mixed models were developed to assess the impact of phenobarbital administration and of seizures on rSO2 and fractional tissue oxygen extraction (FTOE).ResultsFor 20 neonates (EGA 39.6±1.5 weeks), 61 phenobarbital doses and 40 seizures were analyzed. Cerebral rSO2 rose (p=0.005), and FTOE declined (p=0.018) with increasing phenobarbital doses. rSO2 declined during seizures, compared with baseline and post-ictal phases (baseline 81.2 vs. ictal 77.7 vs. post-ictal 79.4; p=0.004). FTOE was highest during seizures (p=0.002).ConclusionsCerebral oxygen metabolism decreases after phenobarbital administration and increases during seizures. These small, but clear, changes in cerebral oxygen metabolism merit assessment for potential clinical impact.

Difference in cerebral saturation during cardiopulmonary resuscitation between survivors with favorable neurological outcome and compromised neurological outcome at hospital discharge

During out-of-hospital cardiac arrest (OHCA) monitoring possibilities are limited. Recently, the role of cerebral oximetry, using near-infrared spectroscopy, during ALS was investigated. In this study we determined whether the magnitude of increase in cerebral saturation (rSO2) or mean rSO2 during prehospital ALS was associated with good neurological outcome at hospital discharge (Cerebral Performance Category (CPC) 1 or 2).

The relationship between carotid artery colour Doppler finding and cerebral oximetry.

Background:In some cases, permanent reduction in cerebral functioning affects a high percentage of patients undergoing cardiovascular surgery. We studied the relationship between the results of preoperative bilateral carotid artery colour Doppler sonography and regional cerebral oxygen saturation (rSO2) during coronary artery bypass graft surgery (CABG).Materials and Methods:This study was a cross-sectional analytical study conducted with 96 candidates for off-pump CABG. This study determined the percentage of the correlation of rSO2 with demographic information, diabetes, hyperlipidemia, hypertension, myocardial infraction (MI), and smoking, and also provided information on the presence and type of plaque, intima-media thickness (IMT), and percentage of stenosis of carotid artery detected through colour Doppler sonography. Data were analyzed by the t-test, the Chi-square test, and simple linear regression.Results:In this study, the mean value of rSO2 increased after intubation compared to the mean before intubation, the difference being statistically significant (P = 0.005). A comparison of the mean rSO2 of the right side of the brain and the percentage of right carotid obstruction (stenosis of less than 50% vs. stenosis with a range of 50-69%) revealed that the mean rSO2 at the time of the partial-clamp between carotid stenosis less than 50% and carotid stenosis with a range of 50-69% was statistically significant (P = 0.043).Conclusions:There is no statistically significant correlation between rSO2 and percentage of carotid artery stenosis less than 70%. It is advised that rSO2 and carotid stenosis of greater than 70% be studied in future.

Near-infrared spectroscopy measurement of abdominal tissue oxygenation is a useful indicator of intestinal ischemia in neonates

Introduction. Neonatal intestinal ischemia is a frequent pathology, but unfortunately, often underdiagnosed. Current technique allows non-invasive investigation of splanchnic circulation, being capable of detecting early perfusion changes that occur at this level. Objectives. The aim of this study was to determine the clinical value of infrared spectroscopy (NIRS) in early detection of ischemic bowel modifications in newborns from neonatal intensive care unit. Material and methods. We performed a prospective observational study over a period of 18 months, on a group of 15 newborns with gestational age between 25-38 weeks. All infants included in the study had one or more clinical signs of digestive pathology. Starting non-invasive continuous monitoring by cerebral and abdominal NIRS was performed according to the appearance of the first digestive changes between day 3 and 21 of life. Oxygen saturation was measured in the cerebral and abdominal regions (rSO2-C and rSO2-A) and cerebro-splanchnic oxygenation ratio (CSOR) was carried out. Meanwhile infants were monitored by biological and hemodynamic methods. The monitoring period was variable, being between 1-5 days, the period required for establish the causal diagnosis. Statistical significance was determined using statistical t-test. “p” was calculated for confidence interval of 95% (statistical significance p &lt; 0.05). Also was evaluated the area under the receiver operating characteristic (ROC) curve to determine the suitability of this technique as a diagnostic tool. Results. The study group included: 3 neonates with congenital heart disease(CHD) with significant decrease in aortic blood flow, 4 neonates with necrotizing enterocolitis (NEC) stage II, 3 patients with intrauterine growth retardation (IUGR) severe form, 1 newborn with intestinal atresia and secondary peritonitis, 1 newborn with Rh incompatibility anemia with placental anasarca and 3 patients with sepsis and associated gastrointestinal pathology without NEC criteria. In all 15 patients, NIRS measurement values were significantly lower compared to the normal range, with different values depending on the severity of the condition. Mean rSO2 -A value was 41.85 (interquartile range15-85) compared to an average value, considered normal. Also the average value of the CSOR ratio was significantly lower compared to the normal. The lowest values of rSO2-A at the beginning of symptoms has had the group of patients with CHD followed by those with NEC. The area under the ROC curve was 0.95 (95% CI 0.88 to 1.02) for the CSOR ratio. Considering a limit value of ROCS for prediction of intestinal ischemia &lt; 0.75, this ratio proves to be an excellent indicator of changes in bowel circulation. Conclusion. NIRS method has the potential to detect the occurrence of alterations in intestinal oxygenation and perfusion, allowing early detection of bowel ischemia, just before the modification of other hemodynamic parameters. NIRS is a non-invasive, highly accurate method, to follow in evolution the changes in tissue perfusion under the treatment instituted, also being able to guide treatment, proving helpful in clinical practice.