Vascular density and distribution in neocortex

An amazingly wide range of complex behavior emerges from the cerebral cortex. Much of the information processing that leads to these behaviors is performed in neocortical circuits that span throughout the six layers of the cortex. Maintaining this circuit activity requires substantial quantities of oxygen and energy substrates, which are delivered by the complex yet well-organized and tightly-regulated vascular system. In this review, we provide a detailed characterization of the most relevant anatomical and functional features of the cortical vasculature. This includes a compilation of the available data on laminar variation of vascular density and the topological aspects of the microvascular system. We also review the spatio-temporal dynamics of cortical blood flow regulation and oxygenation, many aspects of which remain poorly understood. Finally, we discuss some of the important implications of vascular density, distribution, oxygenation and blood flow regulation for (laminar) fMRI.

Early-Onset Ventilator-Associated Pneumonia in Patients with Severe Traumatic Brain Injury: Incidence, Risk Factors, and Consequences in Cerebral Oxygenation and Outcome

BACKGROUND

Early-onset ventilator-associated pneumonia (EOVAP) occurs frequently in severe traumatic brain-injured patients, but potential consequences on cerebral oxygenation and outcome have been poorly studied. The objective of this study was to describe the incidence, risk factors for, and consequences on cerebral oxygenation and outcome of EOVAP after severe traumatic brain injury (TBI).

METHODS

We conducted a retrospective, observational study including all intubated TBI admitted in the trauma center. An EOVAP was defined as a clinical pulmonary infection score >6, and then confirmed by an invasive method. Patient characteristics, computed tomography (CT) scan results, and outcome were extracted from a prospective register of all intubated TBI admitted in the intensive care unit (ICU). Data concerning the cerebral oxygenation monitoring by PbtO2 and characteristics of EOVAP were retrieved from patient files. Multivariate logistic regression models were developed to determine the risk factors of EOVAP and to describe the factors independently associated with poor outcome at 1-year follow-up.

RESULTS

During 7 years, 175 patients with severe TBI were included. The overall incidence of EOVAP was 60.6% (47.4/1000 days of ventilation). Significant risk factors of EOVAP were: therapeutic hypothermia (OR 3.4; 95% CI [1.2-10.0]), thoracic AIS score ≥3 (OR 2.4; 95% CI [1.1-5.7]), and gastric aspiration (OR 5.2, 95% CI [1.7-15.9]). Prophylactic antibiotics administration was a protective factor against EOVAP (OR 0.3, 95% CI [0.1-0.8]). EOVAP had negative consequences on cerebral oxygenation. The PbtO2 was lower during EOVAP: 23.5 versus 26.4 mmHg (p <0.0001), and there were more brain hypoxia episodes: 32 versus 27% (p = 0.03). Finally, after adjusting for confounders, an EOVAP was an independent factor associated with unfavorable neurologic functional outcome at the 1-year follow-up (OR 2.71; 95% CI [1.01-7.25]).

CONCLUSIONS

EOVAP is frequent after a severe TBI (overall rate: 61%), with therapeutic hypothermia, severe thoracic lesion, and gastric aspiration as main risk factors. EOVAP had a negative impact on cerebral oxygenation measured by PbtO2 and was independently associated with unfavorable outcome at 1-year follow-up. This suggests that all precautions available should be taken to prevent EOVAP in this population.

Cerebral Near-Infrared Spectroscopy in Adult Patients Undergoing Veno-Arterial Extracorporeal Membrane Oxygenation

BACKGROUND

Acute cerebral complications (ACC) of veno-arterial extracorporeal membrane oxygenation (VA-ECMO) are associated with poor long-term neurologic outcome. We described the role of rSO2 monitoring in detecting ACC and desaturations and their relationship with poor outcome when employing VA-ECMO.

METHODS

Retrospective analysis of patients monitored by cerebral frontal near-infrared spectroscopy (NIRS) (CAS Medical Systems Inc., Branford, CT, USA) during VA-ECMO (November 2008-December 2015). ACC was defined as the presence of stroke and/or brain death, while cerebral desaturation as cortical oxygen tissue saturation (rSO2) < 60%.

RESULTS

Fifty-six of 159 VA-ECMO patients (age 55 [36-60] years) were included; 18 (32%) developed ACC and 36 died (64%). Cerebral desaturation occurred in 43 (74%) patients, who had a higher mortality than those without cerebral desaturation (74 vs. 31%). A high sequential organ failure assessment (SOFA) score on the first day of ECMO (OR 1.40 [95% CIs 1.06-1.84]) and the minimum ECMO blood flow during the first 4 days of therapy (OR 3.05 [1.01-9.17]) were independently associated with the occurrence of cerebral desaturation. Cerebral desaturation occurred more frequently in patients with ACC than others (94 vs. 68%); patients with ACC also had a lower minimal rSO2 over time (49 vs. 54%) and more frequently had high right-left rSO2 differences (33 vs. 8%), which were both independent predictors of ACC. The occurrence of cerebral desaturation (OR 7.93 [1.62-38.74]) and high lactate concentrations during the first 4 days of ECMO support (OR 1.22 [1.03-1.46]) was independently associated with hospital mortality.

CONCLUSIONS

Monitoring of rSO2 could be considered as an interesting tool to monitor the brain of patients on VA-ECMO.

Hemodynamic antecedents of peri/intraventricular hemorrhage in very preterm neonates

Novel hemodynamic monitoring technologies have contributed to the understanding of developmental cardiovascular physiology and pathophysiology in general, and of developmental hemodynamics in particular. Hemodynamic disturbances play a significant role in the pathogenesis of peri/intraventricular hemorrhage (P/IVH) in preterm infants. Immaturity of the myocardium, delayed and incomplete cardiopulmonary transition, sustained patency of the ductus arteriosus, and unintended consequences of respiratory and cardiovascular supportive care are all likely to be involved in the presentation of low cardiac output syndrome and decreased organ blood flow in a large number of very preterm neonates (gestational age ≤28 weeks). Forebrain vessels in very preterm infants may not have achieved a "high-priority vasculature" status at the time of delivery; in these patients, forebrain perfusion is not protected during the compensated phase of shock. Reperfusion may be attenuated by the careful use of medications decreasing cerebrovascular reactivity, thus providing a potential target for the development of careful pharmacological support of transitional hemodynamics in selected patients at high risk for the development of P/IVH.

Cerebral oxygenation after birth - a comparison of INVOS(®) and FORE-SIGHT™ near-infrared spectroscopy oximeters

Aim

To compare absolute values of regional cerebral tissue oxygenation (cStO₂) during haemodynamic transition after birth and repeatability during steady state for two commercial near‐infrared spectroscopy (NIRS) devices.

Methods

In a prospective observational study, the INVOS 5100C and FORE‐SIGHT were compared on 12 term newborns delivered by elective caesarean section. During the 10 min following umbilical cord clamping, cStO₂ was measured simultaneously with the neonatal sensors from each device. Repeated measurements were taken the following day.

Results

Three and 8 min after clamping, the mean cStO₂ value increased from 53.4% (CI 36.8–69.9%) to 86.0% (CI 80.2–91.7%) for INVOS and from 61.6% (CI 55.4–67.8%) to 82.2% (CI 77.7–86.7%) for FORE‐SIGHT. The Bland–Altman plot revealed decreasing difference (INVOS minus FORE‐SIGHT) (D) in absolute values (A) with increasing cStO2 (D = 0.5A – 38.19 p = <0.001). The mean steady‐state value on day two was 78.4% (CI 74.6–82.2%) and 86.2% (CI 85.0–87.4%) for INVOS and FORE‐SIGHT, respectively. The within‐subject standard deviation during steady‐state repeated measurements was 4.8% ± 0.86 for INVOS and 2.8% ± 0.5 for FORE‐SIGHT.

Conclusion

The INVOS and FORE‐SIGHT cStO₂ estimates showed oxygenation‐level‐dependent difference during birth transition. The better repeatability of FORE‐SIGHT could be due to the lower response to change in saturation.

Pushing to the limits: the dynamics of cognitive control during exhausting exercise

This study aimed at investigating concurrent changes in cognitive control and cerebral oxygenation (Cox) during steady intense exercise to volitional exhaustion. Fifteen participants were monitored using prefrontal near-infrared spectroscopy and electromyography of the thumb muscles during the completion of an Eriksen flanker task completed either at rest (control condition) or while cycling at a strenuous intensity until exhaustion (exercise condition). Two time windows were matched between the conditions to distinguish a potential exercise-induced evolutive cognitive effect: an initial period and a terminal period. In the initial period, Cox remained unaltered and, contrary to theoretical predictions, exercise did not induce any deficit in selective response inhibition. Rather, the drop-off of the delta curve as reaction time lengthened suggested enhanced efficiency of cognitive processes in the first part of the exercise bout. Shortly before exhaustion, Cox values were severely reduced - though not characteristic of a hypofrontality state - while no sign of deficit in selective response inhibition was observed. Despite this, individual's susceptibility to making fast impulsive errors increased and less efficient online correction of incorrect activation was observed near exhaustion. A negative correlation between Cox values and error rate was observed and is discussed in terms of cerebral resources redistribution.

Early cerebral and intestinal oxygenation in the risk assessment of necrotizing enterocolitis in preterm infants

BACKGROUND AND AIM

Predicting necrotizing enterocolitis (NEC) might help in preventing its devastating consequences. We aimed to investigate whether early cerebral and intestinal tissue oxygen saturation (rSO₂) and fractional tissue oxygen extraction (FTOE) predict the onset of NEC.

STUDY DESIGN

Prospective observational case-control study.

SUBJECTS

Infants with gestational age (GA) <32 weeks were included. For every NEC case we matched two controls based on GA, birth weight (BW), and a patent ductus arteriosus.

OUTCOME MEASURES

Cerebral oxygenation and intestinal oxygenation were prospectively monitored two-hours daily during the first five days after birth and once a week thereafter until five weeks after birth or until NEC developed. We used Kaplan-Meier analyses to determine the ability of near-infrared spectroscopy (NIRS) measurements, including their variability, to predict the development of NEC.

RESULTS

We included ten infants (median (range) GA 27.1 (24.6-29.4) weeks, BW 903 (560-1630) grams) who developed NEC at median postnatal day 13 (range: 4-43 days), and 20 matched controls. Infants with cerebral rSO₂ <70% within the first 48 h after birth developed NEC significantly more often than infants with cerebral rSO₂ ≥70% (odds ratio 9.00 (95% CI 1.33-61.14). Intestinal FTOE was higher in infants who developed NEC compared to controls during the last NIRS measurement at median 2 days (range: 1-7) before NEC onset (median 0.65 vs. 0.44).

CONCLUSIONS

Cerebral oxygenation monitoring early after birth might be valuable in the risk assessment of NEC development. Additionally, our results suggest that intestinal oxygenation is impaired before the onset of clinical NEC.

Early effects of ventilatory rescue therapies on systemic and cerebral oxygenation in mechanically ventilated COVID-19 patients with acute respiratory distress syndrome: a prospective observational study

BACKGROUND

In COVID-19 patients with acute respiratory distress syndrome (ARDS), the effectiveness of ventilatory rescue strategies remains uncertain, with controversial efficacy on systemic oxygenation and no data available regarding cerebral oxygenation and hemodynamics.

METHODS

This is a prospective observational study conducted at San Martino Policlinico Hospital, Genoa, Italy. We included adult COVID-19 patients who underwent at least one of the following rescue therapies: recruitment maneuvers (RMs), prone positioning (PP), inhaled nitric oxide (iNO), and extracorporeal carbon dioxide (CO2) removal (ECCO2R). Arterial blood gas values (oxygen saturation [SpO2], partial pressure of oxygen [PaO2] and of carbon dioxide [PaCO2]) and cerebral oxygenation (rSO2) were analyzed before (T0) and after (T1) the use of any of the aforementioned rescue therapies. The primary aim was to assess the early effects of different ventilatory rescue therapies on systemic and cerebral oxygenation. The secondary aim was to evaluate the correlation between systemic and cerebral oxygenation in COVID-19 patients.

RESULTS

Forty-five rescue therapies were performed in 22 patients. The median [interquartile range] age of the population was 62 [57-69] years, and 18/22 [82%] were male. After RMs, no significant changes were observed in systemic PaO2 and PaCO2 values, but cerebral oxygenation decreased significantly (52 [51-54]% vs. 49 [47-50]%, p < 0.001). After PP, a significant increase was observed in PaO2 (from 62 [56-71] to 82 [76-87] mmHg, p = 0.005) and rSO2 (from 53 [52-54]% to 60 [59-64]%, p = 0.005). The use of iNO increased PaO2 (from 65 [67-73] to 72 [67-73] mmHg, p = 0.015) and rSO2 (from 53 [51-56]% to 57 [55-59]%, p = 0.007). The use of ECCO2R decreased PaO2 (from 75 [75-79] to 64 [60-70] mmHg, p = 0.009), with reduction of rSO2 values (59 [56-65]% vs. 56 [53-62]%, p = 0.002). In the whole population, a significant relationship was found between SpO2 and rSO2 (R = 0.62, p < 0.001) and between PaO2 and rSO2 (R0 0.54, p < 0.001).

CONCLUSIONS

Rescue therapies exert specific pathophysiological mechanisms, resulting in different effects on systemic and cerebral oxygenation in critically ill COVID-19 patients with ARDS. Cerebral and systemic oxygenation are correlated. The choice of rescue strategy to be adopted should take into account both lung and brain needs. Registration The study protocol was approved by the ethics review board (Comitato Etico Regione Liguria, protocol n. CER Liguria: 23/2020).

Partial MCT1 invalidation protects against diet-induced non-alcoholic fatty liver disease and the associated brain dysfunction

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) has been associated with mild cerebral dysfunction and cognitive decline, although the exact pathophysiological mechanism remains ambiguous. Using a diet-induced model of NAFLD and monocarboxylate transporter-1 (Mct1^+/-) haploinsufficient mice, which resist high-fat diet-induced hepatic steatosis, we investigated the hypothesis that NAFLD leads to an encephalopathy by altering cognition, behaviour, and cerebral physiology. We also proposed that global MCT1 downregulation offers cerebral protection.

METHODS

Behavioural tests were performed in mice following 16 weeks of control diet (normal chow) or high-fat diet with high fructose/glucose in water. Tissue oxygenation, cerebrovascular reactivity, and cerebral blood volume were monitored under anaesthesia by multispectral optoacoustic tomography and optical fluorescence. Cortical mitochondrial oxygen consumption and respiratory capacities were measured using ex vivo high-resolution respirometry. Microglial and astrocytic changes were evaluated by immunofluorescence and 3D reconstructions. Body composition was assessed using EchoMRI, and liver steatosis was confirmed by histology.

RESULTS

NAFLD concomitant with obesity is associated with anxiety- and depression-related behaviour. Low-grade brain tissue hypoxia was observed, likely attributed to the low-grade brain inflammation and decreased cerebral blood volume. It is also accompanied by microglial and astrocytic morphological and metabolic alterations (higher oxygen consumption), suggesting the early stages of an obesogenic diet-induced encephalopathy. Mct1 haploinsufficient mice, despite fat accumulation in adipose tissue, were protected from NAFLD and associated cerebral alterations.

CONCLUSIONS

This study provides evidence of compromised brain health in obesity and NAFLD, emphasising the importance of the liver-brain axis. The protective effect of Mct1 haploinsufficiency points to this protein as a novel therapeutic target for preventing and/or treating NAFLD and the associated brain dysfunction.

IMPACT AND IMPLICATIONS

This study is focused on unravelling the pathophysiological mechanism by which cerebral dysfunction and cognitive decline occurs during NAFLD and exploring the potential of monocarboxylate transporter-1 (MCT1) as a novel preventive or therapeutic target. Our findings point to NAFLD as a serious health risk and its adverse impact on the brain as a potential global health system and economic burden. These results highlight the utility of Mct1 transgenic mice as a model for NAFLD and associated brain dysfunction and call for systematic screening by physicians for early signs of psychological symptoms, and an awareness by individuals at risk of these potential neurological effects. This study is expected to bring attention to the need for early diagnosis and treatment of NAFLD, while having a direct impact on policies worldwide regarding the health risk associated with NAFLD, and its prevention and treatment.

Pathophysiology and Management of Intracranial Hypertension and Tissular Brain Hypoxia After Severe Traumatic Brain Injury: An Integrative Approach

Monitoring intracranial pressure in comatose patients with severe traumatic brain injury (TBI) is considered necessary by most experts. Acute intracranial hypertension (IHT), when severe and sustained, is a life-threatening complication that demands emergency treatment. Yet, secondary anoxic-ischemic injury after brain trauma can occur in the absence of IHT. In such cases, adding other monitoring modalities can alert clinicians when the patient is in a state of energy failure. This article reviews the mechanisms, diagnosis, and treatment of IHT and brain hypoxia after TBI, emphasizing the need to develop a physiologically integrative approach to the management of these complex situations.

Growth restriction and gender influence cerebral oxygenation in preterm neonates

OBJECTIVE

To investigate the effect of fetal growth restriction and gender on cerebral oxygenation in preterm neonates during the first 3 days of life.

DESIGN

Case-control study.

SETTING

Neonatal Intensive Care Unit of the Wilhelmina Children's Hospital, The Netherlands.

PATIENTS

68 (41 males) small for gestational age (SGA) (birth weight <10th percentile) and 136 (82 males) appropriate for gestational age (AGA) (birth weight 20th-80th percentile) neonates, matched for gender, gestational age, ventilatory and blood pressure support.

METHODS

Regional cerebral oxygen saturation (rScO2) and cerebral fractional tissue oxygen extraction (cFTOE) as measured by near-infrared spectroscopy throughout the first 72 h of life were compared between SGA and AGA neonates. The effect of gender was also explored within these comparisons.

RESULTS

SGA neonates demonstrated higher rScO2 (71% SEM 0.2 vs 68% SEM 0.2) and lower cFTOE (0.25 SEM 0.002 vs 0.29 SEM 0.002) than AGA neonates. There was an independent effect of gender on rScO2 and cFTOE, resulting in the finding that SGA males displayed highest rScO2 and lowest cFTOE (73% SEM 0.3 respectively 0.24 SEM 0.003). AGA males and SGA females showed comparable rScO2 (69% SEM 0.2 vs 69% SEM 0.4) and cFTOE (0.28 SEM 0.002 vs 0.28 SEM 0.004). AGA females showed lowest rScO2 and highest cFTOE (66% SEM 0.2 respectively 0.30 SEM 0.002).

CONCLUSIONS

Growth restriction and gender influence cerebral oxygenation and oxygen extraction in preterm neonates throughout the first 3 days of life.

A Combined EEG-fNIRS Study Investigating Mechanisms Underlying the Association between Aerobic Fitness and Inhibitory Control in Young Adults

The current evidence suggests that aerobic fitness is associated with inhibitory control of executive functioning in children and older adults. However, the relative contributions of different neurophysiological mechanisms to this relation remain unclear and have not yet been examined in young adults. The present study aimed to compare inhibitory control between high and low-fit young adult men, and to investigate a possible mediation of fitness effects by conflict monitoring (N450 component of event-related potentials) and lateralized oxygenation difference (LOD) in the DLPFC. For the present cross-sectional study, participants with different physical activity levels were recruited and divided into low-fit and high-fit participants based on relative power on the PWC170. A Stroop Color-Word task was administered and combined EEG-fNIRS was simultaneously utilized to assess the N450 and LOD, because these parameters are linked with behavioral performance. The results of the statistical analysis showed that high-fitcompared to low-fit participants showed less Stroop interference and lower negativity of the N450, whereas no difference was found for LOD. Path-analyses further revealed that the relation between aerobic fitness levels and Stroop interference was indirect and mediated by N450. In contrast, LOD was inversely correlated with Stroop interference, but did not explain the relation of aerobic fitness with behavioral performance. The present findings indicate that greater inhibitory control in high- compared to low-fit young men can be explained by more effective conflict monitoring. Moreover, young adults with left-lateralizedDLPFC oxygenation also show higher inhibitory control, but this oxygenation pattern is not influenced by aerobic fitness.

Cerebral regional tissue Oxygen Saturation to Guide Oxygen Delivery in preterm neonates during immediate transition after birth (COSGOD III): an investigator-initiated, randomized, multi-center, multi-national, clinical trial on additional cerebral tissue oxygen saturation monitoring combined with defined treatment guidelines versus standard monitoring and treatment as usual in premature infants during immediate transition: study protocol for a randomized controlled trial

BACKGROUND

Transition immediately after birth is a complex physiological process. The neonate has to establish sufficient ventilation to ensure significant changes from intra-uterine to extra-uterine circulation. If hypoxia or bradycardia or both occur, as commonly happens during immediate transition in preterm neonates, cerebral hypoxia-ischemia may cause perinatal brain injury. The primary objective of the COSGOD phase III trial is to investigate whether it is possible to increase survival without cerebral injury in preterm neonates of less than 32 weeks of gestation by targeting cerebral tissue oxygen saturation (crSO2) using specified clinical treatment guidelines during the immediate transition period after birth (the first 15 min) in addition to the routine monitoring of arterial oxygen saturation (SpO2) and heart rate (HR).

METHODS/DESIGN

COSGOD III is an investigator-initiated, randomized, multi-center, multi-national, phase III clinical trial. Inclusion criteria are neonates of less than 32 weeks of gestation, decision to provide full life support, and parental informed consent. Exclusion criteria are severe congenital malformations of brain, heart, lung, or prenatal cerebral injury or a combination of these. The premature infants will be randomly assigned to study or control groups. Both groups will have a near-infrared spectroscopy (NIRS) device (left frontal), pulse oximeter (right palm/wrist), and electrocardiogram placed immediately after birth. In the study group, the crSO2, SpO2, and HR readings are visible, and the infant will receive treatment in accordance with defined treatment guidelines. In the control group, only SpO2 and HR will be visible, and the infant will receive routine treatment. The intervention period will last for the first 15 min after birth during the immediate transition period and resuscitation. Thereafter, each neonate will be followed up for primary outcome to term date or discharge. The primary outcome is mortality or cerebral injury (or both) defined as any intra-ventricular bleeding or cystic periventricular leukomalacia (or both). Secondary outcomes are neonatal morbidities.

DISCUSSION

crSO2 monitoring during immediate transition has been proven to be feasible and improve cerebral oxygenation during immediate transition. The additional monitoring of crSO2 with dedicated interventions may improve outcome of preterm neonates as evidenced by increased survival without cerebral injury.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03166722 . Registered March 5, 2017.

Age-related alterations in phase synchronization of oxyhemoglobin concentration changes in prefrontal tissues as measured by near-infrared spectroscopy signals

The prefrontal cortex plays an important role in planning complex cognitive behavior, personality expression, and decision making. This study aims to assess the phase synchronization of signals of the oxyhemoglobin concentration changes (Δ[HbO2]) in the left and right prefrontal tissues through near-infrared spectroscopy (NIRS) with wavelet phase coherence (WPCO) method. The NIRS signals were continuously recorded from the left and right prefrontal lobes in 43 healthy elderly subjects (age: 69.6 ± 8.4 years) and 40 young healthy subjects (age: 24.5 ± 1.7 years) during the resting state. Phase synchronization between the left and right prefrontal oscillations in six frequency intervals (I, 0.6-2 Hz; II, 0.145-0.6 Hz; III, 0.052-0.145 Hz; IV, 0.021-0.052 Hz; V, 0.0095-0.021 Hz; and VI, 0.005-0.0095 Hz) was analyzed using the WPCO method. The WPCO values of elderly subjects were significantly lower in frequency intervals I (F=7.376, p=0.010) and III (F=6.418, p=0.016) than those of the young subjects. Low phase coherence in intervals I and III indicates reduced synchronization of cardiac activity in the prefrontal area and weakened prefrontal functional connectivity, respectively.

Low Cerebral Oxygenation Is Associated with Cognitive Impairment in Chronic Hemodialysis Patients

BACKGROUND/AIMS

High rates of cognitive impairment (CI) are an alarming problem in patients undergoing chronic hemodialysis (HD). Its pathophysiology remains unclear and there are indications that brain ischemia might be one of the key causes. Cerebral tissue oxygenation, as measured by near-infrared spectroscopy, is known to be decreased in HD patients. However, it is unknown whether CI is associated or not associated with lower cerebral oxygenation in these patients. The primary aim of our study was to probe this possible association. Our secondary aim was to assess other factors possibly related to cerebral ischemia and CI.

METHODS

Thirty-nine patients treated by chronic HD were included in this cross-sectional study. All measurements were performed before the initiation of an HD session. The Montreal Cognitive Assessment (MoCA) was administered according to published recommendations. Regional saturation of oxygen (rSO2) of the left frontal lobe was measured using the INVOS 5100C device. Basic medical history and laboratory data were recorded, and handgrip strength was analyzed. We used the unpaired t test to compare the rSO2 and other variables between cognitively normal patients (MoCA score ≥26) and those who displayed CI (MoCA score <26). Multiple linear regression analysis was used to adjust for principal confounders.

RESULTS

Cognitively impaired patients had lower brain rSO2 values compared to cognitively normal patients (48 ± 9 vs. 57 ± 10%, p = 0.01). Among other variables, higher red cell distribution width (15.8 ± 1.9 vs. 13.8 ± 1.6%, p = 0.01) and lower hand grip strength (49.2 ± 23.3 vs. 99.3 ± 31.4 lbs, p < 0.001) also displayed a significant association with CI. The relation between rSO2 and MoCA score was significant after adjustment for age and gender (p = 0.007).

CONCLUSION

Decreased brain oxygenation is associated with weaker cognitive performance in patients undergoing chronic HD. Further understanding the causes of cerebral ischemia in HD patients could lead to the prevention of cognitive decline in this population.

The beach chair position for shoulder surgery in intravenous general anesthesia and controlled hypotension: Impact on cerebral oxygenation, cerebral blood flow and neurobehavioral outcome

STUDY OBJECTIVES

The aim of this study was to assess the impact of intravenous general anesthesia and controlled hypotension on cerebral saturation (rScO₂), cerebral blood flow measured as middle cerebral artery blood flow velocity (Vmax MCA) and neurobehavioral outcome in patients scheduled for shoulder surgery in beach chair position.

DESIGN

Prospective, assessor-blinded observational study.

SETTING

University hospital, shoulder surgery operating room.

PATIENTS

Forty ASA I-II patients scheduled for shoulder surgery in beach chair position and controlled hypotension.

INTERVENTIONS

Neurological and neurobehavioral tests were performed prior and the day after surgery. The baseline data for near-infrared spectroscopy, bispectral index, cerebral blood flow, PaCO₂ and invasive blood pressure (radial artery) were taken prior anesthesia and after anesthesia induction, after beach chair positioning and all 20 min after surgery start until discharge of the patient.

MEASUREMENTS

Neurological and neurobehavioral tests, cerebral saturation (rScO₂) using near-infrared spectroscopy, BIS, cerebral blood flow using Doppler of the middle cerebral artery (Vmax MCA), PaCO₂ and invasive blood pressure assessed at heart and at the external acoustic meatus level.

MAIN RESULTS

The incidence of cerebral desaturation events (CDEs) was 25%. The blood pressure drop 5 min after beach chair position measured at the acoustic meatus level in the CDE group was higher compared to patients without CDEs (p = 0.009) as was the rScO₂ (p = 0.039) and the Vmax MCA (p = 0.002). There were no neurological deficits but patients with CDEs showed a greater negative impact on neurobehavioral tests 24 h after surgery compared to patients without CDEs (p = 0.001).

CONCLUSIONS

In ASA I-II patients intravenous general anesthesia and controlled hypotension in the beach chair position affects cerebral blood flow and cerebral oxygenation with impact on the neurobehavioral outcome.

Near-infrared spectroscopy after out-of-hospital cardiac arrest

Background

Cerebral hypoperfusion may aggravate neurological damage after cardiac arrest. Near-infrared spectroscopy (NIRS) provides information on cerebral oxygenation but its relevance during post-resuscitation care is undefined. We investigated whether cerebral oxygen saturation (rSO₂) measured with NIRS correlates with the serum concentration of neuron-specific enolase (NSE), a marker of neurological injury, and with clinical outcome in out-of-hospital cardiac arrest (OHCA) patients.

Methods

We performed a post hoc analysis of a randomised clinical trial (COMACARE, NCT02698917) comparing two different levels of carbon dioxide, oxygen and arterial pressure after resuscitation from OHCA with ventricular fibrillation as the initial rhythm. We measured rSO₂ in 118 OHCA patients with NIRS during the first 36 h of intensive care. We determined the NSE concentrations from serum samples at 48 h after cardiac arrest and assessed neurological outcome with the Cerebral Performance Category (CPC) scale at 6 months. We evaluated the association between rSO₂ and serum NSE concentrations and the association between rSO₂ and good (CPC 1–2) and poor (CPC 3–5) neurological outcome.

Results

The median (inter-quartile range (IQR)) NSE concentration at 48 h was 17.5 (13.4–25.0) μg/l in patients with good neurological outcome and 35.2 (22.6–95.8) μg/l in those with poor outcome, p < 0.001. We found no significant correlation between median rSO₂ and NSE at 48 h, r_s = − 0.08, p = 0.392. The median (IQR) rSO₂ during the first 36 h of intensive care was 70.0% (63.5–77.0%) in patients with good outcome and 71.8% (63.3–74.0%) in patients with poor outcome, p = 0.943. There was no significant association between rSO₂ over time and neurological outcome. In a binary logistic regression model, rSO₂ was not a statistically significant predictor of good neurological outcome (odds ratio 0.99, 95% confidence interval 0.94–1.04, p = 0.635).

Conclusions

We found no association between cerebral oxygenation measured with NIRS and NSE concentrations or outcome in patients resuscitated from OHCA.

Trial registration

ClinicalTrials.gov, NCT02698917. Registered on 26 January 2016.

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2428-3) contains supplementary material, which is available to authorized users.

Postoperative cognitive dysfunction after liver transplantation

OBJECTIVE

Postoperative cognitive dysfunction (POCD) in liver transplant (LT) recipients is defined as a "more than expected" postoperative deterioration in cognitive domains, including short-term and long-term memory, mood, consciousness and circadian rhythm. It is diagnosed, after exclusion of other neurological complications, by using specific neuropsychological tests that need preoperative baseline. The aim of this systematic review was to assess the prevalence of POCD after LT and to analyze patients' symptoms, type and timing of assessment used.

METHODS

PubMed, MEDLINE and The Cochrane Li-brary were searched up from January 1986 to August 2014. Study eligibility criteria are as follows: prospective and retrospective studies on human adult subjects describing prevalence of POCD and/or its sequelae after LT episodes were included.

RESULTS

Eighteen studies were identified. The timing of testing for POCD may vary between different studies and within the single study, ranging from 0.5 to 32 weeks. POCD occurs in up to 50% of LT recipient.

CONCLUSION

Future studies should be focused on detecting preoperative and intraoperative factors associated to POCD in order to carry out appropriate strategies aimed at reducing this disabling health condition. Relationship between POCD and long-term outcome needs to be investigated.

Brain Oxygenation Monitoring

A mismatch between cerebral oxygen supply and demand can lead to cerebral hypoxia/ischemia and deleterious outcomes. Cerebral oxygenation monitoring is an important aspect of multimodality neuromonitoring. It is increasingly deployed whenever intracranial pressure monitoring is indicated. Although there is a large body of evidence demonstrating an association between cerebral hypoxia/ischemia and poor outcomes, it remains to be determined whether restoring cerebral oxygenation leads to improved outcomes. Randomized prospective studies are required to address uncertainties about cerebral oxygenation monitoring and management. This article describes the different methods of monitoring cerebral oxygenation, their indications, evidence base, limitations, and future perspectives.

Assessment of risk factors for cerebral oxygen desaturation during neonatal and infant general anesthesia: an observational, prospective study

Background

Cerebral oxygen saturation (rSO₂c) decrease from baseline greater than 20 % during infant cardiac surgery was associated with postoperative neurologic changes and neurodevelopmental impairment at 1 year of age. So far, there is no sufficient evidence to support the routine monitoring of rSO₂c during general surgical procedures in children. We aimed to find out the frequency of cerebral desaturation 20 % or more from baseline and to identify possible predictors of change in cerebral oxygen saturation during neonatal and infant general surgery.

Methods

Forty-four infants up to 3 months of age were recruited. Before induction of anesthesia, two pediatric cerebral sensors were placed bilaterally to the forehead region and monitoring of regional cerebral saturation of oxygen was started and continued throughout the surgery. Simultaneously, mean arterial blood pressure (MAP), pulse oximetry (SpO₂), heart rate (HR), endtidal CO₂, expired fraction of sevoflurane and rectal temperature were recorded. The main outcome measure was rSO₂c value drop-off ≥20 % from baseline. Mann-Whitney U-test, chi-squared test, simple and multiple linear regression models were used for statistical analysis.

Results

Forty-three infants were analyzed. Drop-off ≥20 % in rSO₂c from baseline occurred in 8 (18.6 %) patients. There were no differences in basal rSO₂c, SpO₂, HR, endtidal CO₂, expired fraction of sevoflurane and rectal temperature between patients with and without desaturation 20 % or more from baseline. But the two groups differed with regard to gestation, preoperative mechanical ventilation and the use of vasoactive medications and red blood cell transfusions during surgery. Simple linear regression model showed, that gestation, age, preoperative mechanical ventilation and mean arterial pressure corresponding to minimal rSO₂c value during anesthesia (MAP_minrSO2c) were associated with a change in rSO₂c values. Multiple regression model including all above mentioned variables, revealed that only MAP_minrSO2c was predictive for a change in rSO₂c values (β (95 % confidence interval) -0.28 (−0.52–(−0.04)) p = 0.02).

Conclusions

Cerebral oxygen desaturation ≥20 % from baseline occurred in almost one fifth of patients. Although different perioperative factors can predispose to cerebral oxygenation changes, arterial blood pressure seems to be the most important. Gestation as another possible risk factor needs further investigation.

Trial registration

The international registration number NCT02423369. Retrospectively registered on April 2015.

Electronic supplementary material

The online version of this article (doi:10.1186/s12871-016-0274-2) contains supplementary material, which is available to authorized users.

Incidence of hyperoxia and factors associated with cerebral oxygenation during cardiopulmonary resuscitation

BACKGROUND

High oxygen levels may worsen cardiac arrest reperfusion injury. We determined the incidence of hyperoxia during and immediately after successful cardiopulmonary resuscitation and identified factors associated with intra-arrest cerebral oxygenation measured with near-infrared spectroscopy (NIRS).

METHODS

A prospective observational study of out-of-hospital cardiac arrest patients treated by a physician-staffed helicopter unit. Collected data included intra-arrest brain regional oxygen saturation (rSO₂) with NIRS, invasive blood pressures, end-tidal CO₂ (etCO₂) and arterial blood gas samples. Moderate and severe hyperoxia were defined as arterial oxygen partial pressure (paO₂) 20.0-39.9 and ≥40 kPa, respectively. Intra-arrest factors correlated with the NIRS value, rSO_2, were assessed with the Spearman's correlation test.

RESULTS

Of 80 recruited patients, 73 (91%) patients had rSO₂ recorded during CPR, and 46 had an intra-arrest paO₂ analysed. ROSC was achieved in 28 patients, of whom 20 had paO₂ analysed. Moderate hyperoxia was seen in one patient during CPR and in four patients (20%, 95% CI 7-42%) after ROSC. None had severe hyperoxia during CPR, and one patient (5%, 95% 0-25%) immediately after ROSC. The rSO₂ during CPR was correlated with intra-arrest systolic (r = 0.28, p < 0.001) and diastolic blood pressure (p = 0.32, p < 0.001) but not with paO₂ (r = 0.13, p = 0.41), paCO₂ (r = 0.18, p = 0.22) or etCO₂ (r = 0.008, p = 0.9).

CONCLUSION

Hyperoxia during or immediately after CPR is rare in patients treated by physician-staffed helicopter units. Cerebral oxygenation during CPR appears more dependent, albeit weakly, on hemodynamics than arterial oxygen concentration.

Clinical and Technical Limitations of Cerebral and Somatic Near-Infrared Spectroscopy as an Oxygenation Monitor

Cerebral and somatic near-infrared spectroscopy monitors are commonly used to detect tissue oxygenation in various circumstances. This form of monitoring is based on tissue infrared absorption and can be influenced by several physiological and non-physiological factors that can induce error in the interpretation. This narrative review explores those clinical and technical limitations and proposes solutions and alternatives in order to avoid some of those pitfalls.

Executive function after exhaustive exercise

PURPOSE

Findings concerning the effects of exhaustive exercise on cognitive function are somewhat equivocal. The purpose of this study was to identify physiological factors that determine executive function after exhaustive exercise.

METHODS

Thirty-two participants completed the cognitive tasks before and after an incremental exercise until exhaustion (exercise group: N = 18) or resting period (control group N = 14). The cognitive task was a combination of a Spatial Delayed-Response (Spatial DR) task and a Go/No-Go task, which requires executive function. Cerebral oxygenation and skin blood flow were monitored during the cognitive task over the prefrontal cortex. Venous blood samples were collected before and after the exercise or resting period, and blood catecholamines, serum brain-derived neurotrophic factor, insulin-like growth hormone factor 1, and blood lactate concentrations were analyzed.

RESULTS

In the exercise group, exhaustive exercise did not alter reaction time (RT) in the Go/No-Go task (pre: 861 ± 299 ms vs. post: 775 ± 168 ms) and the number of error trials in the Go/No-Go task (pre: 0.9 ± 0.7 vs. post: 1.8 ± 1.8) and the Spatial DR task (pre: 0.3 ± 0.5 vs. post: 0.8 ± 1.2). However, ΔRT was negatively correlated with Δcerebral oxygenation (r = -0.64, P = 0.004). Other physiological parameters were not correlated with cognitive performance. Venous blood samples were not directly associated with cognitive function after exhaustive exercise.

CONCLUSION

The present results suggest that recovery of regional cerebral oxygenation affects executive function after exhaustive exercise.

Neonatal brain oxygenation during thoracoscopic correction of esophageal atresia

Background

Little is known about the effects of carbon dioxide (CO₂) insufflation on cerebral oxygenation during thoracoscopy in neonates. Near-infrared spectroscopy can measure perioperative brain oxygenation [regional cerebral oxygen saturation (rScO₂)].

Aims

To evaluate the effects of CO₂ insufflation on rScO₂ during thoracoscopic esophageal atresia (EA) repair.

Methods

This is an observational study during thoracoscopic EA repair with 5 mmHg CO₂ insufflation pressure. Mean arterial blood pressure (MABP), arterial oxygen saturation (SaO₂), partial pressure of arterial carbon dioxide (paCO₂), pH, and rScO₂ were monitored in 15 neonates at seven time points: baseline (T0), after anesthesia induction (T1), after CO₂-insufflation (T2), before CO₂-exsufflation (T3), and postoperatively at 6 (T4), 12 (T5), and 24 h (T6).

Results

MABP remained stable. SaO₂ decreased from T0 to T2 [97 ± 3–90 ± 6 % (p < 0.01)]. PaCO₂ increased from T0 to T2 [41 ± 6–54 ± 15 mmHg (p < 0.01)]. pH decreased from T0 to T2 [7.33 ± 0.04–7.25 ± 0.11 (p < 0.05)]. All parameters recovered during the surgical course. Mean rScO₂ was significantly higher at T1 compared to T2 [77 ± 10–73 ± 7 % (p < 0.05)]. Mean rScO₂ levels never dropped below a safety threshold of 55 %.

Conclusion

The impact of neonatal thoracoscopic repair of EA with insufflation of CO₂ at 5 mmHg was studied. Intrathoracic CO₂ insufflation caused a reversible decrease in SaO₂ and pH and an increase in paCO₂. The rScO₂ was higher at anesthesia induction but remained stable and within normal limits during and after the CO₂ pneumothorax, which suggest no hampering of cerebral oxygenation by the thoracoscopic intervention. Future studies will focus on the long-term effects of this surgery on the developing brain.

Effect on cerebral oxygenation of paracetamol for patent ductus arteriosus in preterm infants

Paracetamol seems to have similar success rates compared with indomethacin and ibuprofen in closing patent ductus arteriosus (PDA) in preterm infants, but with a better safety profile. The aim of our study was to evaluate the possible effects of paracetamol on cerebral oxygenation and cerebral blood flow velocity (CBFV). Infants with gestational age < 32 weeks with hemodynamically significant PDA (hsPDA) were prospectively studied by near infrared spectroscopy (NIRS) after the first dose of paracetamol (15 mg/kg) or ibuprofen (10 mg/kg). Cerebral regional oxygenation (rSO₂C) and fractional oxygen extraction ratio (FOEC) were recorded 30 min before (T₀) and 60 ± 20 min (T₁), 180 ± 30 min (T₂), and 360 ± 30 min (T₃) after the beginning of drug infusion. Moreover, mean flow velocity (Vmean) and resistance index (RI = PSV-DV/PSV) measured with Doppler ultrasound in pericallosal artery were recorded at the same times. Significant changes in rSO₂C and FOEC were not found during the study period within and between the groups. Similarly, Vmean did not vary in infants treated with paracetamol or ibuprofen, while RI decreased in the ibuprofen group.

CONCLUSION

The treatment of hsPDA with paracetamol does not affect cerebral oxygenation in very preterm infants; there were no differences in cerebral oxygenation in infants treated with paracetamol or ibuprofen, although in the ibuprofen group, the possible closure progression of PDA was associated to changes of RI. What is Known: • Paracetamol has similar success rates to indomethacin and ibuprofen in closing PDA with a better safety profile since previous studies did not report adverse effects. What is New: • Paracetamol does not affect cerebral oxygenation and perfusion in very preterm infants with PDA and this confirms its good safety profile.