Cerebral Tissue Oxygenation Research Articles

Near-Infrared Spectroscopy Monitoring of Cerebral Oxygenation and Influencing Factors in Neonates from High-Altitude Areas

Background: Accurate detection of cerebral oxygen saturation (rSO₂) may be useful for neonatal brain injury prevention, and the normal range of rSO₂ of neonates at high altitude remained unclear. Objective: To compare cerebral rSO₂ and cerebral fractional tissue oxygen extraction (cFTOE) at high-altitude and low-altitude areas in healthy neonates and neonates with underlying diseases. Methods: 515 neonates from low-altitude areas and 151 from Tibet were enrolled. These neonates were assigned into the normal group, hypoxic-ischemic encephalopathy (HIE) group, and other diseases group. Near-infrared spectroscopy was used to measure rSO₂ in neonates within 24 h after admission. The differences of rSO₂, pulse oxygen saturation (SpO₂), and cFTOE levels were compared between neonates from low- and high-altitude areas. Results: (1) The mean rSO₂ and cFTOE levels in normal neonates from Tibet were 55.0 ± 6.4% and 32.6 ± 8.5%, significantly lower than those from low-altitude areas (p < 0.05). (2) At high altitude, neonates with HIE, pneumonia (p < 0.05), anemia, and congenital heart disease (p < 0.05) have higher cFTOE than healthy neonates. (3) Compared with HIE neonates from plain areas, neonates with HIE at higher altitude had lower cFTOE (p < 0.05), while neonates with heart disease in plateau areas had higher cFTOE than those in plain areas (p < 0.05). Conclusions: The rSO₂ and cFTOE levels in normal neonates from high-altitude areas are lower than neonates from the low-altitude areas. Lower cFTOE is possibly because of an increase in blood flow to the brain, and this may be adversely affected by disease states which may increase the risk of brain injury.

Peaks and valleys: oscillatory cerebral blood flow at high altitude protects cerebral tissue oxygenation

Introduction. Oscillatory patterns in arterial pressure and blood flow (at ∼0.1 Hz) may protect tissue oxygenation during conditions of reduced cerebral perfusion and/or hypoxia. We hypothesized that inducing oscillations in arterial pressure and cerebral blood flow at 0.1 Hz would protect cerebral blood flow and cerebral tissue oxygen saturation during exposure to a combination of simulated hemorrhage and sustained hypobaric hypoxia. Methods. Eight healthy human subjects (4 male, 4 female; 30.1 ± 7.6 year) participated in two experiments at high altitude (White Mountain, California, USA; altitude, 3800 m) following rapid ascent and 5–7 d of acclimatization: (1) static lower body negative pressure (LBNP, control condition) was used to induce central hypovolemia by reducing chamber pressure to −60 mmHg for 10 min (0 Hz), and; (2) oscillatory LBNP where chamber pressure was reduced to −60 mmHg, then oscillated every 5 s between −30 mmHg and −90 mmHg for 10 min (0.1 Hz). Measurements included arterial pressure, internal carotid artery (ICA) blood flow, middle cerebral artery velocity (MCAv), and cerebral tissue oxygen saturation (ScO2). Results. Forced 0.1 Hz oscillations in mean arterial pressure and mean MCAv were accompanied by a protection of ScO2 (0.1 Hz: −0.67% ± 1.0%; 0 Hz: −4.07% ± 2.0%; P = 0.01). However, the 0.1 Hz profile did not protect against reductions in ICA blood flow (0.1 Hz: −32.5% ± 4.5%; 0 Hz: −19.9% ± 8.9%; P = 0.24) or mean MCAv (0.1 Hz: −18.5% ± 3.4%; 0 Hz: −15.3% ± 5.4%; P = 0.16). Conclusions. Induced oscillatory arterial pressure and cerebral blood flow led to protection of ScO2 during combined simulated hemorrhage and sustained hypoxia. This protection was not associated with the preservation of cerebral blood flow suggesting preservation of ScO2 may be due to mechanisms occurring within the microvasculature.

Monitoring of near-infrared spectrum values during packed red blood cell transfusion in pediatric intensive care unit.

Packed red blood cell (PRBC) transfusion is one of the most common treatment options in pediatric intensive care unit (PICU) which targets a better cerebral oxygenation. This study aimed to show the cerebral near-infrared spectroscopy (cNIRS) changes during PRBC transfusions in PICU. In this prospective observational study, changes in regional cerebral tissue oxygen saturation (rSO2) in pediatric patients, who required PRBC transfusion were monitored. All the cNIRS and related values were classified as baseline values. The same values were measured and calculated at the end of transfusion and named as 4th-hour values. Further measurements and calculations were made three hours later and named as 7th-hour values. Changes in cNIRS, cerebral tissue fractional oxygen extraction (CTFOE), cNIRS variability index (cNIRS-VI) were compared using Friedman test. A total of 53 PRBC transfusions were monitored. Baseline haemoglobin increased from 6.3 (5.9, 6.7) gr/dL to 8.6 (8.4, 9) gr/dL at the 7th-hour. cNIRS values improved during transfusion (P=0.012), with a concomitant decrease in cNIRS-VI and CTFOE values (P<0.001 and P=0.017 consecutively) CONCLUSION: Our study revealed that there is an increase in cNIRS and related values after transfusion compared to baseline values in critically ill children admitted to a PICU. Age of PRBC did not have an effect on delta-cNIRS or post-transfusion hemoglobin values. There is a moderate correlation between the baseline cNIRS values and delta-cNIRS value after the transfusion.

Glyceryl trinitrate for the treatment of ischaemic stroke: Determining efficacy in rodent and ovine species for enhanced clinical translation

Hypertension is a leading risk factor for death and dependency after ischaemic stroke. However, administering anti-hypertensive medications post-stroke remains contentious with concerns regarding deleterious effects on cerebral blood flow and infarct expansion. This study sought to determine the effect of glyceryl trinitrate (GTN) treatment in both lissencephalic and gyrencephalic pre-clinical stroke models. Merino sheep underwent middle cerebral artery occlusion (MCAO) followed by GTN or control patch administration (0.2 mg/h). Monitoring of numerous physiologically relevant measures over 24 h showed that GTN administration was associated with decreased intracranial pressure, infarct volume, cerebral oedema and midline shift compared to vehicle treatment (p < 0.05). No significant changes in blood pressure or cerebral perfusion pressure were observed. Using optical imaging spectroscopy and laser speckle imaging, the effect of varying doses of GTN (0.69–50 µg/h) on cerebral blood flow and tissue oxygenation was examined in mice. No consistent effect was found. Additional mice undergoing MCAO followed by GTN administration (doses varying from 0–60 µg/h) also showed no improvement in infarct volume or neurological score within 24 h post-stroke. GTN administration significantly improved numerous stroke-related physiological outcomes in sheep but was ineffective in mice. This suggests that, whilst GTN administration could potentially benefit patients, further research into mechanisms of action are required.

Impact of bradycardia and hypoxemia on oxygenation in preterm infants requiring respiratory support at birth

Aim of the studyAnalysis of the impact of bradycardia and hypoxemia on the course of cerebral and peripheral oxygenation parameters in preterm infants in need for respiratory support during foetal-to-neonatal transition. MethodsThe first 15 min after birth of 150 preterm neonates in need for respiratory support born at the Division of Neonatology, Graz (Austria) were analyzed. Infants were divided into different groups according to duration of bradycardia exposure (no Bradycardia, brief bradycardia <2 min, and prolonged bradycardia ≥2 min) and to systemic oxygen saturation (SpO2) value at 5 min of life (<80% or ≥80%). Analysis was performed considering the degree of bradycardia alone (step 1) and in association with the presence of hypoxemia (step 2). ResultsIn step 1, courses of SpO2 differed significantly between bradycardia groups (p = 0.002), while courses of cerebral regional oxygen saturation (crStO2) and cerebral fractional tissue oxygen extraction (cFTOE) were not influenced (p = 0.382 and p = 0.878). In step 2, the additional presence of hypoxemia had a significant impact on the courses of SpO2 (p < 0.001), crStO2 (p < 0.001) and cFTOE (p = 0.045). ConclusionOur study shows that the degree of bradycardia has a significant impact on the course of SpO2 only, but when associated with the additional presence of hypoxemia a significant impact on cerebral oxygenation parameters was seen (crStO2, cFTOE). Furthermore, the additional presence of hypoxemia has a significant impact on FiO2 delivered. Our study emphasizes the importance of HR and SpO2 during neonatal resuscitation, underlining the relevance of hypoxemia during the early transitional phase.

Effect of aging on cerebral tissue oxygenation in relation to reflex syncope

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The Swedish Heart and Lung Foundation, The Swedish Heart and Lung Association, ALF funds, Skåne University Hospital Funds, The Crafoord Foundation. Background There is an increased susceptibility to syncope with aging attributed to age-related physiological impairments. Cerebral oximetry non-invasively measures cerebral tissue oxygenation (SctO2) and has been shown to be valuable in syncope evaluation. SctO2 has been found to decrease with aging but it is unknown whether the decrease in SctO2 is related to increased susceptibility to syncope during orthostatic provocation. By measuring SctO2 during head up tilt test (HUT) we can study age-related differences in SctO2 and their impact on developing reflex syncope. Purpose To investigate the effect of age on the cerebral tissue oxygenation threshold for syncope and presyncope among patients with vasovagal syncope. Methods Non-invasive haemodynamic monitoring and near-infrared spectroscopy (NIRS) were applied during head-up tilt (HUT) in 139 vasovagal syncope patients (mean [SD] 45[17] years, 60% female), and 82 control patients with a normal response to HUT (45[18] years, 61% female). Group differences in SctO2 and systolic blood pressure (SBP) during HUT in supine position, after 3 and 10 min of HUT, 30 seconds prior to syncope ("presyncopal phase") and during syncope in different age groups (&amp;lt;30, 30-60 and &amp;gt;60 years) were compared using one-way ANOVA and Tukey"s multiple comparison test. Associations between age and SctO2 were studied using linear regression models adjusted for sex and concurrent SBP. Results Lower SctO2 in supine position was associated with increasing age among controls (B=-0.085, p = 0.010) but not among VVS patients (B=-0.036, p = 0.114). No age-related differences in SctO2 were found after 3 and 10 minutes of HUT and during syncope. Mean SctO2 (%) during the presyncopal phase decreased over the advancing age groups (&amp;lt;30: 66.9 ± 6.2, 30-60: 64.5 ± 6.1, &amp;gt;60: 62.2 ± 5.8; p = 0.009 for inter-group comparison). In contrast, mean SBP during the presyncopal phase did not differ by age groups (&amp;lt;30: 85.6 ± 21.8, 30-60: 77.6 ± 19.7, &amp;gt;60: 77.6 ± 20.8 mmHg, p = 0.133). Age was associated with lower SctO2 during the presyncopal phase after adjusting for sex and SBP (B = 0.096, p = 0.001). Conclusion Older VVS patients have lower cerebral tissue oxygenation in the presyncopal phase compared with younger patients independently of systolic blood pressure. These results suggest either that with imminent reflex syncope cerebral tissue oxygenation diminishes more with advancing age or that cerebral deoxygenation is better tolerated by older reflex syncope patients. Abstract Figure.

Cardiac Output and Cerebral Oxygenation in Term Neonates during Neonatal Transition.

The immediate transition from foetus to neonate includes substantial changes, especially concerning the cardiovascular system. Furthermore, the brain is one of the most vulnerable organs to hypoxia during this period. According to current guidelines for postnatal stabilization, the recommended parameters for monitoring are heart rate (HR) and arterial oxygen saturation (SpO2). Recently, there is a growing interest in advanced monitoring of the cardio-circulatory system and the brain to get further objective information about the neonate’s condition during the immediate postnatal transition after birth. The aim of the present study was to combine cardiac output (CO) and brain oxygenation monitoring in term neonates after caesarean section in order to analyse the potential influence of CO on cerebral oxygenation during neonatal transition. This was a monocentric, prospective, observational study. For non-invasive cardiac output measurements, the electrical velocimetry (EV) method (Aesculon Monitor, Osypka Medical, CA, USA) was used. The pulse oximeter probe for SpO2 and HR measurements was placed on the right hand or wrist. The cerebral tissue oxygen index (cTOI) was measured using a NIRO-200NX monitor with the near-infrared spectroscopy (NIRS) transducer on the right frontoparietal head. Monitoring started at minute 1 and was continued until minute 15 after birth. At minutes 5, 10, and 15 after birth, mean CO was calculated from six 10 s periods (with beat-to-beat analysis). During the study period, 99 term neonates were enrolled. Data from neonates with uncomplicated transitions were analysed. CO showed a tendency to decrease until minute 10. During the complete observational period, there was no significant correlation between CO and cTOI. The present study was the first to investigate a possible correlation between CO and cerebral oxygenation in term infants during the immediate neonatal transition. In term infants with uncomplicated neonatal transition after caesarean section, CO did not correlate with cerebral oxygenation.

Neurovascular coupling (NVC) in newborns using processed EEG versus amplitude-EEG

There is a critical need for development of real time physiological biomarkers for birth asphyxia that constitutes a major global public health burden. Our recent study (Scientific Reports, V10:9183, 2020) established a novel non-invasive neurovascular coupling (NVC) assessment in newborns using dynamic wavelet transform coherence (WTC) analysis irrespective of different aEEG algorithms. As an extended study, the current paper examines whether the variability in processed EEG and amplitude-EEG (aEEG) outputs would impact the determination of NVC in newborns with encephalopathy. Concurrent processed EEG tracings and regional near infrared spectroscopy (NIRS)-based cerebral tissue oxygen saturation (SctO2) readings during a period of twenty hours in their first day of life were selected and processed in this study. After bandpass-filtered in 2–15 Hz, rectified, and down-sampled at 0.21 Hz, the processed EEG tracings along with NIRS-SctO2 (0.21 Hz) were used to perform WTC analysis, followed by comparison of WTC-metrics between SctO2-processed EEG coherence and SctO2-aEEG coherence using Bland–Altman statistics. Our results demonstrated high and significant correlation (R2 = 0.96, p < 0.001) between NVC assessments by SctO2-processed EEG and SctO2-aEEG coherence, confirming that band-passed, rectified, and down-sampled processed EEG, or aEEG, can be paired with NIRS-SctO2 to assess NVC in newborns with encephalopathy. Findings indicate the feasibility of a simpler approach to NVC in neonates by using directly processed EEG, instead of aEEG.

Nocturnal cerebral tissue oxygenation in lowlanders with chronic obstructive pulmonary disease travelling to an altitude of 2,590m: Data from a randomised trial.

Altitude exposure induces hypoxaemia in patients with chronic obstructive pulmonary disease (COPD), particularly during sleep. The present study tested the hypothesis in patients with COPD staying overnight at high altitude that nocturnal arterial hypoxaemia is associated with impaired cerebral tissue oxygenation (CTO). A total of 35 patients with moderate-to-severe COPD, living at <800m (mean [SD] age 62.4[12.3]years, forced expiratory volume in 1s [FEV1 ] 61[16]% predicted, awake pulse oximetry ≥92%) underwent continuous overnight monitoring of pulse oximetry (oxygen saturation [SpO2 ]) and near-infrared spectroscopy of prefrontal CTO, respectively, at 490m and 2,590m. Regression analysis was used to evaluate whether nocturnal arterial desaturation (COPDDesat , SpO2 <90% for >30% of night-time) at 490m predicted CTO at 2,590m when controlling for baseline variables. At 2,590m, mean nocturnal SpO2 and CTO were decreased versus 490m, mean change -8.8% (95% confidence interval [CI] -10.0 to -7.6) and -3.6% (95% CI -5.7 to -1.6), difference in change ΔCTO-ΔSpO2 5.2% (95% CI 3.0 to 7.3; p<.001). Moreover, frequent cyclic desaturations (≥4% dips/hr) occurred in SpO2 and CTO, mean change from 490m 35.3/hr (95% CI 24.9 to 45.7) and 3.4/hr (95% CI 1.4 to 5.3), difference in change ΔCTO-ΔSpO2 -32.8/hr (95% CI -43.8 to -21.8; p<.001). Regression analysis confirmed an association of COPDDesat with lower CTO at 2,590m (coefficient -7.6%, 95% CI -13.2 to -2.0; p=.007) when controlling for several confounders. We conclude that lowlanders with COPD staying overnight at 2,590m experience altitude-induced hypoxaemia and periodic breathing in association with sustained and intermittent cerebral deoxygenation. Although less pronounced than the arterial deoxygenation, the altitude-induced cerebral tissue deoxygenation may represent a risk of brain dysfunction, especially in patients with COPD with nocturnal hypoxaemia at low altitude.

Neonatal Music Therapy and Cerebral Oxygenation in Extremely and Very Preterm Infants: a Pilot Study

Music therapy is a novel intervention that may minimize neonatal stress. The mechanism of action is still largely unknown. We hypothesized that one mechanism of action regards altered brain oxygenation (either due to altered cerebral perfusion or altered cerebral oxygen consumption). We measured cerebral oxygenation before, during and after music therapy sessions using Near-Infrared Spectroscopy (NIRS). We extracted data on cerebral oxygen saturation (rcSO2) and calculated cerebral fractional tissue oxygen extraction (cFTOE). In addition, we measured heart rate. We included 20 infants, receiving 44 music therapy sessions. Median gestational age was 27 weeks, the majority were males. We identified two distinct reactions: in one group rcSO2 increased and cFTOE decreased during therapy compared with before therapy, whereas in the other group rcSO2 decreased and cFTOE increased during therapy compared with before therapy. The first may indicate a sedative effect, whereas the second may reflect a hyperalert state. The observed changes in heart rate may contribute to these observations through altered cerebral perfusion. The clinical significance of these two distinct reactions for music processing and (future) neurological functioning in these infants warrants further investigation.

Comparison of renal region, cerebral and peripheral oxygenation for predicting postoperative renal impairment after CABG

Patients undergoing coronary artery bypass grafting (CABG) are at risk of developing postoperative renal impairment, amongst others caused by renal ischemia and hypoxia. Intra-operative monitoring of renal region tissue oxygenation (SrtO2) might be a useful tool to detect renal hypoxia and predict postoperative renal impairment. Therefore, the aim of this study was to assess the ability of intra-operative SrtO2 to predict postoperative renal impairment, defined as an increase of serum creatinine concentrations of > 10% from individual baseline, and compare this with the predictive abilities of peripheral and cerebral tissue oxygenation (SptO2 and SctO2, respectively) and renal specific tissue deoxygenation. Forty-one patients undergoing elective CABG were included. Near-infrared spectroscopy (NIRS) was used to measure renal region, peripheral (thenar muscle) and cerebral tissue oxygenation during surgery. Renal region specific tissue deoxygenation was defined as a proportionally larger decrease in SrtO2 than SptO2. ROC analyses were used to compare predictive abilities. We did not observe an association between tissue oxygenation measured in the renal region and cerebral oxygenation and postoperative renal impairment in this small retrospective study. In contrast, SptO2 decrease > 10% from baseline was a reasonable predictor with an AUROC of 0.767 (95%CI 0.619 to 0.14; p = 0.010). Tissue oxygenation of the renal region, although non-invasively and continuously available, cannot be used in adults to predict postoperative renal impairment after CABG. Instead, peripheral tissue deoxygenation was able to predict postoperative renal impairment, suggesting that SptO2 provides a better indication of ‘general’ tissue oxygenation status.Registered at ClinicalTrials.gov: NCT01347827, first submitted April 27, 2011.

Cerebral Oxygenation and Perfusion when Positioning Preterm Infants: Clinical Implications

To evaluate cerebral tissue oxygenation (cTOI) and cerebral perfusion in preterm infants in supine vs prone positions. Sixty preterm infants, born before 32weeks of gestation, were enrolled; 30 had bronchopulmonary dysplasia (BPD, defined as the need for respiratory support and/or supplemental oxygen at 36weeks of postmenstrual age). Cerebral perfusion, cTOI, and polysomnography were measured in both the supine and prone position with the initial position being randomized. Infants with a major intraventricular hemorrhage or major congenital abnormality were excluded. Cerebral perfusion was unaffected by position or BPD status. In the BPD group, the mean cTOI was higher in the prone position compared with the supine position by a difference of 3.27% (P=.03; 95% CI 6.28-0.25) with no difference seen in the no-BPD group. For the BPD group, the burden of cerebral hypoxemia (cumulative time spent with cTOI <55%) was significantly lower in the prone position (23%) compared with the supine position (29%) (P<.001). In those without BPD, position had no effect on cTOI. In preterm infants with BPD, the prone position improved cerebral oxygenation and reduced cerebral hypoxemia. These findings may have implications for positioning practices. Further research will establish the impact of position on short- and long-term developmental outcomes.

The Antiedematous Effect of Exogenous Lactate Therapy in Traumatic Brain Injury: A Physiological and Mechanistic Approach

BackgroundSodium lactate (SL) has been described as an efficient therapy in treating raised intracranial pressure (ICP). However, the precise mechanism by which SL reduces intracranial hypertension is not well defined. An antiedematous effect has been proposed but never demonstrated. In this context, the involvement of chloride channels, aquaporins, or K–Cl cotransporters has also been suggested, but these mechanisms have never been assessed when using SL.MethodsIn a rat model of traumatic brain injury (TBI), we compared the effect of SL versus mannitol 20% on ICP, cerebral tissue oxygen pressure, and brain water content. We attempted to clarify the involvement of chloride channels in the antiedematous effects associated with lactate therapy in TBI.ResultsAn equimolar single bolus of SL and mannitol significantly reduced brain water content and ICP and improved cerebral tissue oxygen pressure 4 h after severe TBI. The effect of SL on brain water content was much longer than that of mannitol and persisted at 24 h post TBI. Western blot and immunofluorescence staining analyses performed 24 h after TBI revealed that SL infusion is associated with an upregulation of aquaporin 4 and K–Cl cotransporter 2.ConclusionsSL is an effective therapy for treating brain edema after TBI. This study suggests, for the first time, the potential role of chloride channels in the antiedematous effect induced by exogenous SL.

Neurologic Assessment of the Neurocritical Care Patient.

Sedation is a ubiquitous practice in ICUs and NCCUs. It has the benefit of reducing cerebral energy demands, but also precludes an accurate neurologic assessment. Because of this, sedation is intermittently stopped for the purposes of a neurologic assessment, which is termed a neurologic wake-up test (NWT). NWTs are considered to be the gold-standard in continued assessment of brain-injured patients under sedation. NWTs also produce an acute stress response that is accompanied by elevations in blood pressure, respiratory rate, heart rate, and ICP. Utilization of cerebral microdialysis and brain tissue oxygen monitoring in small cohorts of brain-injured patients suggests that this is not mirrored by alterations in cerebral metabolism, and seldom affects oxygenation. The hard contraindications for the NWT are preexisting intracranial hypertension, barbiturate treatment, status epilepticus, and hyperthermia. However, hemodynamic instability, sedative use for primary ICP control, and sedative use for severe agitation or respiratory distress are considered significant safety concerns. Despite ubiquitous recommendation, it is not clear if additional clinically relevant information is gleaned through its use, especially with the contemporaneous utilization of multimodality monitoring. Various monitoring modalities provide unique and pertinent information about neurologic function, however, their role in improving patient outcomes and guiding treatment plans has not been fully elucidated. There is a paucity of information pertaining to the optimal frequency of NWTs, and if it differs based on type of injury. Only one concrete recommendation was found in the literature, exemplifying the uncertainty surrounding its utility. The most common sedative used and recommended is propofol because of its rapid onset, short duration, and reduction of cerebral energy requirements. Dexmedetomidine may be employed to facilitate serial NWTs, and should always be used in the non-intubated patient or if propofol infusion syndrome (PRIS) develops. Midazolam is not recommended due to tissue accumulation and residual sedation confounding a reliable NWT. Thus, NWTs are well-tolerated in selected patients and remain recommended as the gold-standard for continued neuromonitoring. Predicated upon one expert panel, they should be performed at least one time per day. Propofol or dexmedetomidine are the main sedative choices, both enabling a rapid awakening and consistent NWT.

Association Between Cerebral Desaturation and Postoperative Delirium in Thoracotomy With One-Lung Ventilation: A Prospective Cohort Study.

The association between cerebral desaturation and postoperative delirium in thoracotomy with one-lung ventilation (OLV) has not been specifically studied. A prospective observational study performed in thoracic surgical patients. Cerebral tissue oxygen saturation (Scto2) was monitored on the left and right foreheads using a near-infrared spectroscopy oximeter. Baseline Scto2 was measured with patients awake and breathing room air. The minimum Scto2 was the lowest measurement at any time during surgery. Cerebral desaturation and hypersaturation were an episode of Scto2 below and above a given threshold for ≥15 seconds during surgery, respectively. The thresholds based on relative changes by referring to the baseline measurement were <80%, <85%, <90%, <95%, and <100% baseline for desaturation and >105%, >110%, >115%, and >120% baseline for hypersaturation. The thresholds based on absolute values were <50%, <55%, <60%, <65%, and <70% for desaturation and >75%, >80%, >85%, and >90% for hypersaturation. The given area under the threshold (AUT)/area above the threshold (AAT) was analyzed. Delirium was assessed until postoperative day 5. The primary analysis was the association between the minimum Scto2 and delirium using multivariable logistic regression controlled for confounders (age, OLV time, use of midazolam, occurrence of hypotension, and severity of pain). The secondary analysis was the association between cerebral desaturation/hypersaturation and delirium, and between the AUT/AAT and delirium using multivariable logistic regression controlled for the same confounders. Multiple testing was corrected using the Holm-Bonferroni method. We additionally monitored somatic tissue oxygen saturation on the forearm and upper thigh. Delirium occurred in 35 (20%) of 175 patients (65 ± 6 years old). The minimum left or right Scto2 was not associated with delirium. Cerebral desaturation defined by <90% baseline for left Scto2 (odds ratio [OR], 5.82; 95% confidence interval [CI], 2.12-19.2; corrected P =.008) and <85% baseline for right Scto2 (OR, 4.27; 95% CI, 1.77-11.0; corrected P =.01) was associated with an increased risk of delirium. Cerebral desaturation defined by other thresholds, cerebral hypersaturation, the AUT/AAT, and somatic desaturation and hypersaturation were all not associated with delirium. Cerebral desaturation defined by <90% baseline for left Scto2 and <85% baseline for right Scto2, but not the minimum Scto2, may be associated with an increased risk of postthoracotomy delirium. The validity of these thresholds needs to be tested by randomized controlled trials.

Near-Infrared Spectroscopy Monitoring in Pediatric Anesthesiology: A Pro-Con Discussion.

Near-infrared spectroscopy (NIRS) has been increasingly used as a non-invasive measurement of cerebral tissue oxygen saturation. The aim of this short review is to discuss the benefits and drawbacks of its use in the pediatric anesthesia population. In the context of cardiac surgery, lower intraoperative NIRS values have shown a modest association with neurodevelopmental outcomes while lower neonatal intensive care unit NIRS values have been correlated with reduced neurodevelopment in children. However, it is still unclear if management aimed at increasing cerebral tissue oxygenation would have any benefit on these outcomes. Without prospective research looking into the effects of intervention given proper thresholds, the true benefit of NIRS use is still up for debate. Even with current research gaps, its use in the clinical setting continues.

Anemia of prematurity: how low is too low?

Anemia of prematurity (AOP) is a common condition with a well-described chronology, nadir hemoglobin levels, and timeline of recovery. However, the underlying pathophysiology and impact of prolonged exposure of the developing infant to low levels of hemoglobin remains unclear. Phlebotomy losses exacerbate the gradual decline of hemoglobin levels which is insidious in presentation, often without any clinical signs. Progressive anemia in preterm infants is associated with poor weight gain, inability to take oral feeds, tachycardia and exacerbation of apneic, and bradycardic events. There remains a lack of consensus on treatment thresholds for RBC transfusion which vary considerably. This review elaborates on the current state of the problem, its implication for the premature infant including association with subphysiologic cerebral tissue oxygenation, necrotizing enterocolitis, and retinopathy of prematurity. It outlines the impact of prophylaxis and treatment of anemia of prematurity and offers suggestions on improving monitoring and management of the condition.

Cerebral Oxygenation in Very Preterm Newborn Neonates Measured During the First Three Days of Life: Correlation with the Index of Arterial Blood Gas

Background: Very premature infants with cerebral hemorrhage often have decreased cerebral oxygenation (CrSO2) monitored by near-infrared spectroscopy (NIRS) in the first few days after birth. This study aimed to analyze the correlation between NIRS data of very premature infants monitored in the first 72 hours of life and clinical data, as well as their impact on cerebral oxygenation and cerebral fractional tissue oxygen extraction ( cFTOE ) Methods: From July 2017 to June 2019, neonates of gestation age between 28 to 31 weeks were recruited from the Seventh medical center of Chinese PLA general hospital, Beijing, China. While arterial blood gas(ABG) analysis was monitored from neonates' admission to 72 hours after birth, data such as CrSO2, transcutaneous arterial oxygen saturation (SpO2), oxygen saturation (SaO2), heart rate(HR), and mean arterial blood pressure (MABP) were collected simultaneously. cFTOE was calculated as follows: cFTOE = [(SpO2 - CrSO2)/SpO2]. Head ultrasounds were generally obtained at 6–48 hours, 1week, and 1month of age. The linear mixed model was used to analyze the blood gas value, CrSO2, cFTOE, and other system signals. Findings: 145 newborns were included in this study. CrSO2 was significantly related to partial pressure of oxygen (PaO2), glucose (Glu) within 72 hours after birth (F=6·53 and 5·82, respectively, P<0·05). Compared with intraventricular hemorrhage (IVH) infants, CrSO2 was decreased and cFTOE was increased over time at three days old neonates without IVH. In contrast, infants with IVH had gradually increased CrSO2 and decreased cFTOE within 72 hours after birth, and compared to infants without IVH they had lower mean CrSO2 (P<0·05) and higher mean cFTOE (P<0·05). Interpretation: Newborns with lower CrSO2 and higher cFTOE, who were prone to occur hypoperfusion or hypoglycemia. Neonates with IVH had lower CrSO2 and higher cFTOE within 72 hours after birth, and the change trends of them were opposed to the infants without IVH. Funding: National Natural Science Foundation of China supported this study(81471492). Declaration of Interests: The authors declare no conflicts of interest. Ethics Approval Statement: This study was a prospective cohort study and the protocol was approved by the ethics committee of Seventh medical center of Chinese PLA general hospital.

Factors affecting intraoperative changes in regional cerebral tissue oxygen saturation in elderly patients undergoing laparoscopic hysterectomy

Objective: To explore the factors that affect the fluctuation of intraoperative regional cerebral oxygen saturation (rSctO2) in elderly patients undergoing laparoscopic hysterectomy. Methods: A retrospective analysis of 39 elderly patients undergoing elective laparoscopic hysterectomy in Yale New Haven Hospital from October 2016 to February 2017 was performed. Factors including patients' demographic data, past medical history, intraoperative monitoring index and rSctO2 index (baseline, maximum, minimum, maximum-baseline, baseline-minimum) were recorded. Pearson correlation analysis was used to analyze the correlation between rSctO2 indexes and preoperative and intraoperative factors. Independent sample t-test was used to compare the differences of rSctO2 indexes between hypertension group and the group without hypertension, as well as diabetes group and the group without diabetes. Taking diabetes as the stratification factor, the relationship between rSctO2and factors including age, body mass index, hypertension were analyzed using multivariate analysis. Results: The age of the patients was (67.6±5.6) years old. The baseline value of rSctO2 was (71.2±3.9)% in the left frontal lobe and (70.8±4.1)% in the right frontal lobe. Results from univariate analysis showed that the left and right maximum-baseline value of rSctO2 were (12.9±4.5)% and (12.8±4.4)%, which were significantly lower than (16.3±4.2)% and (16.2±4.9)% in the group without hypertension (t=2.329, 2.266, all P<0.05). The right baseline-minimum in the group with hypertension was (5.3±3.7)%, which was significantly higher than (2.7±4.2)% in the group without hypertension (t=-2.061, P<0.05). The left minimum value of rSctO2 in diabetic group was (64.4±4.2)%, and the maximum value of rSctO2on the left and right sides were (81.7±4.0)% and (81.9±4.5)%, which were lower than (68.4±4.1)%, (86.7±4.2)% and (86.0±3.7)% in the group without diabetes (t=2.623, 3.297, 2.850, all P<0.05). The results of multivariate analysis showed the influence of age (t=2.866, P<0.05) and hypertension on left maximum-baseline (t=-4.530, P<0.01) was statistically significant. The influence of hypertension on right maximum-baseline was statistically significant (t=-4.629,P<0.01). Conclusion: Preoperative diabetes and hypertension are factors significantly affecting the intraoperative rSctO2 of elderly patients with laparoscopic hysterectomy.

Cerebral autoregulation in infants during sevoflurane anesthesia for craniofacial surgery.

Data on cerebral pressure-flow autoregulation in the youngest children are scarce. We studied the correlation between mean arterial pressure and cerebral tissue oxygen saturation (rSO2 ) by near-infrared spectroscopy (NIRS) in patients undergoing nose, lip, and palate surgery. We tested the hypothesis that cerebral pressure-flow autoregulation is impaired in children less than 1year undergoing surgery and general anesthesia with sevoflurane under controlled mechanical ventilation. After approval from the Ethical board, 15 children aged <1year were included. Before anesthesia induction, a NIRS sensor (INVOSTM , Medtronic, Minneapolis, USA) was placed over the cerebral frontal lobe. Frontal rSO2 , a surrogate for cerebral perfusion, mean arterial pressure, end-tidal CO2 - and sevoflurane concentration, and arterial oxygen saturation were sampled every minute after the induction. A repeated measures correlation analysis was performed to study correlation between mean arterial pressure and cerebral rSO2 , and the repeated measures correlation coefficient (rrm ) was calculated. Fifteen patients, aged 7.7±1.9months, were studied. rSO2 showed a positive correlation with mean arterial pressure ([95% CI: 9.0-12.1], P<0.001) with a moderate to large effect size (rrm =0.462), indicating an impaired cerebral pressure-flow autoregulation. The slopes of the rSO2 -mean arterial pressure correlations were steeper in patients who were hypotensive (mean arterial pressure <50mm Hg) compared to patients having a mean arterial pressure ≥50mm Hg, indicating that at lower mean arterial pressure, the cerebral pressure dependence of cerebral oxygenation is even more pronounced. During sevoflurane anesthesia in the youngest pediatric patients, cerebral perfusion is pressure-dependent, suggesting that the efficiency of the cerebral blood flow autoregulation is limited.