Brain temperature regulation in poor-grade subarachnoid hemorrhage patients – A multimodal neuromonitoring study

Elevated body temperature (Tcore) is associated with poor outcome after subarachnoid hemorrhage (SAH). Brain temperature (Tbrain) is usually higher than Tcore. However, the implication of this difference (Tdelta) remains unclear. We aimed to study factors associated with higher Tdelta and its association with outcome. We included 46 SAH patients undergoing multimodal neuromonitoring, for a total of 7879 h of averaged data of Tcore, Tbrain, cerebral blood flow, cerebral perfusion pressure, intracranial pressure and cerebral metabolism (CMD). Three-months good functional outcome was defined as modified Rankin Scale ≤2. Tbrain was tightly correlated with Tcore (r = 0.948, p < 0.01), and was higher in 73.7% of neuromonitoring time (Tdelta +0.18°C, IQR −0.01 – 0.37°C). A higher Tdelta was associated with better metabolic state, indicated by lower CMD-glutamate ( p = 0.003) and CMD-lactate ( p < 0.001), and lower risk of mitochondrial dysfunction (MD) (OR = 0.2, p < 0.001). During MD, Tdelta was significantly lower (0°C, IQR −0.2 – 0.1; p < 0.001). A higher Tdelta was associated with improved outcome (OR = 7.7, p = 0.002). Our study suggests that Tbrain is associated with brain metabolic activity and exceeds Tcore when mitochondrial function is preserved. Further studies are needed to understand how Tdelta may serve as a surrogate marker for brain function and predict clinical course and outcome after SAH

Brain Temperature Influences Intracranial Pressure and Cerebral Perfusion Pressure After Traumatic Brain Injury: A CENTER-TBI Study.

Funder: Università degli Studi di MilanoBACKGROUND: After traumatic brain injury (TBI), fever is frequent. Brain temperature (BT), which is directly linked to body temperature, may influence brain physiology. Increased body and/or BT may cause secondary brain damage, with deleterious effects on intracranial pressure (ICP), cerebral perfusion pressure (CPP), and outcome. METHODS: Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI), a prospective multicenter longitudinal study on TBI in Europe and Israel, includes a high resolution cohort of patients with data sampled at a high frequency (from 100 to 500 Hz). In this study, simultaneous BT, ICP, and CPP recordings were investigated. A mixed-effects linear model was used to examine the association between different BT levels and ICP. We additionally focused on changes in ICP and CPP during the episodes of BT changes (Δ BT ≥ 0.5 °C lasting from 15 min to 3 h) up or downward. The significance of ICP and CPP variations was estimated with the paired samples Wilcoxon test (also known as Wilcoxon signed-rank test). RESULTS: Twenty-one patients with 2,435 h of simultaneous BT and ICP monitoring were studied. All patients reached a BT of 38 °C and experienced at least one episode of ICP above 20 mm Hg. The linear mixed-effects model revealed an association between BT above 37.5 °C and higher ICP levels that was not confirmed for lower BT. We identified 149 episodes of BT changes. During BT elevations (n = 79) ICP increased, whereas CPP was reduced; opposite ICP and CPP variations occurred during episodes of BT reduction (n = 70). All these changes were of moderate clinical relevance (increase of ICP of 4.5 and CPP decrease of 7.5 mm Hg for BT rise, and ICP reduction of 1.7 and CPP elevation of 3.7 mm Hg during BT defervescence), even if statistically significant (p  38 °C soon after the injury. BT may influence brain physiology, as reflected by ICP and CPP. An association between BT exceeding 37.5 °C and a higher ICP was identified but not confirmed for lower BT ranges. The relationship between BT, ICP, and CPP become clearer during rapid temperature changes. During episodes of temperature elevation, BT seems to have a significant impact on ICP and CPP

Blood-Brain Barrier and Cognitive Function

The blood-brain barrier (BBB) is the highly specialized and selective crossing area between blood and brain, essential for brain homeostasis and functioning, formed by the endothelial cells of the cerebral microvasculature in a rich and intimate cooperation with the neighboring cells and local signaling factors from both the brain and blood sides. Its distribution throughout the brain is following the brain cytoarchitectonic patterns, each capillary serving the adjacent neurons in a privileged neurovascular interplay that ultimately responds to the manifestation of brain functions, scaled from the cellular to the system level. At the edge of our understanding, cognition stands for what makes us humans and needs the cooperation of the entire body functioning to assist homeostatic favorable conditions for its manifestation. The cerebral endothelial system is operating at this interfacing point, modulating its own phenotype in accordance with various conditions to which the organism and brain are exposed, responding with changes in its permeability and signaling processes. In this chapter we will briefly describe the multicellular assembly of the neurovascular unit from which the BBB emerges, and its contribution to the brain homeostasis by dynamic neurovascular and neurometabolic coupling processes. Further, we will refer to the principal morphologic and functional features of the BBB from which its specific properties arise, making it not just a physical selective barrier, but also a metabolic, neuroimmune and endocrine interface. We will touch on the physiological implications of BBB and neurovascular coupling on high brain functions and cognition, in normal or disease-associated conditions

Neuronal Transmembrane Chloride Transport Has a Time-Dependent Influence on Survival of Hippocampal Cultures to Oxygen-Glucose Deprivation

Neuronal ischemia results in chloride gradient alterations which impact the excitatory&ndash;inhibitory balance, volume regulation, and neuronal survival. Thus, the Na+/K+/Cl&minus; co-transporter (NKCC1), the K+/ Cl&minus; co-transporter (KCC2), and the gamma-aminobutyric acid A (GABAA) receptor may represent therapeutic targets in stroke, but a time-dependent effect on neuronal viability could influence the outcome. We, therefore, successively blocked NKCC1, KCC2, and GABAA (with bumetanide, DIOA, and gabazine, respectively) or activated GABAA (with isoguvacine) either during or after oxygen-glucose deprivation (OGD). Primary hippocampal cultures were exposed to a 2-h OGD or sham normoxia treatment, and viability was determined using the resazurin assay. Neuronal viability was significantly reduced after OGD, and was further decreased by DIOA treatment applied during OGD (p &lt; 0.01) and by gabazine applied after OGD (p &lt; 0.05). Bumetanide treatment during OGD increased viability (p &lt; 0.05), while isoguvacine applied either during or after OGD did not influence viability. Our data suggests that NKCC1 and KCC2 function has an important impact on neuronal viability during the acute ischemic episode, while the GABAA receptor plays a role during the subsequent recovery period. These findings suggest that pharmacological modulation of transmembrane chloride transport could be a promising approach during stroke and highlight the importance of the timing of treatment application in relation to ischemia-reoxygenation

Brain Temperature Influences Intracranial Pressure and Cerebral Perfusion Pressure After Traumatic Brain Injury: A CENTER-TBI Study

Background: After traumatic brain injury (TBI), fever is frequent. Brain temperature (BT), which is directly linked to body temperature, may influence brain physiology. Increased body and/or BT may cause secondary brain damage, with deleterious effects on intracranial pressure (ICP), cerebral perfusion pressure (CPP), and outcome. Methods: Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI), a prospective multicenter longitudinal study on TBI in Europe and Israel, includes a high resolution cohort of patients with data sampled at a high frequency (from 100 to 500 Hz). In this study, simultaneous BT, ICP, and CPP recordings were investigated. A mixed-effects linear model was used to examine the association between different BT levels and ICP. We additionally focused on changes in ICP and CPP during the episodes of BT changes (Δ BT ≥ 0.5 °C lasting from 15 min to 3 h) up or downward. The significance of ICP and CPP variations was estimated with the paired samples Wilcoxon test (also known as Wilcoxon signed-rank test). Results: Twenty-one patients with 2,435 h of simultaneous BT and ICP monitoring were studied. All patients reached a BT of 38 °C and experienced at least one episode of ICP above 20 mm Hg. The linear mixed-effects model revealed an association between BT above 37.5 °C and higher ICP levels that was not confirmed for lower BT. We identified 149 episodes of BT changes. During BT elevations (n = 79) ICP increased, whereas CPP was reduced; opposite ICP and CPP variations occurred during episodes of BT reduction (n = 70). All these changes were of moderate clinical relevance (increase of ICP of 4.5 and CPP decrease of 7.5 mm Hg for BT rise, and ICP reduction of 1.7 and CPP elevation of 3.7 mm Hg during BT defervescence), even if statistically significant (p 38 °C soon after the injury. BT may influence brain physiology, as reflected by ICP and CPP. An association between BT exceeding 37.5 °C and a higher ICP was identified but not confirmed for lower BT ranges. The relationship between BT, ICP, and CPP become clearer during rapid temperature changes. During episodes of temperature elevation, BT seems to have a significant impact on ICP and CPP

The effect of temperature increases on brain tissue oxygen tension in patients with traumatic brain injury: a Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury substudy

Fever may aggravate secondary brain injury after traumatic brain injury (TBI). The aim of this study was to identify episodes of temperature increases through visual plot analysis and algorithm supported detection, and to describe associated patterns of changes in on brain tissue oxygen tension (PbtO2). Data derive from the high-resolution cohort of the multicenter prospective Collaborative European NeuroTrauma Effectiveness Research in TBI (CENTER-TBI) study. Temperature increases (≥0.5°C) were visually identified in 33 patients within the first 11 days of monitoring. Generalized estimating equations were used to detect significant changes of systemic and neuromonitoring parameters from baseline to the highest temperature. Patients were median 50 (interquartile range [IQR], 35-62) years old, and presented with a Glasgow Coma Scale (GCS) of 8 (IQR, 4-10). In 202 episodes of temperature increases, mean temperature rose by 1.0°C ± 0.5°C within 4 hours. Overall, PbtO2 slightly increased (ΔPbtO2 = 0.9 ± 6.1 mmHg, p = 0.022) during temperature increases. PbtO2 increased in 35% (p < 0.001), was stable in 49% (p = 0.852), and decreased in 16% (p < 0.001) of episodes. During episodes of temperature increases and simultaneous drops in PbtO2, cerebral perfusion pressure (CPP) decreased (ΔCPP -6.3 ± 11.5 mmHg; p < 0.001). Brain tissue hypoxia (PbtO2 <20 mmHg) developed during 27/164 (17%) episodes of effervescences, in the remaining 38/202 episodes baseline PbtO2 was already <20 mmHg. Comparable results were found when using algorithm-supported detection of temperature increases. In conclusion, during effervescences, PbtO2 was mostly stable or slightly increased. A decrease of PbtO2 was observed in every sixth episode, where it was associated with a decrease in CPP. Our data highlight the need for special attention to CPP monitoring and maintenance during episodes of fever

The effect of the volemic and cardiac status on brain oxygenation in patients with subarachnoid hemorrhage: a bi-center cohort study

Background: Fluid management in patients after subarachnoid hemorrhage (SAH) aims at the optimization of cerebral blood flow and brain oxygenation. In this study, we investigated the effects of hemodynamic management on brain oxygenation by integrating advanced hemodynamic and invasive neuromonitoring. Methods: This observational cohort bi-center study included data of consecutive poor-grade SAH patients who underwent pulse contour cardiac output (PiCCO) monitoring and invasive neuromonitoring. Fluid management was guided by the transpulmonary thermodilution system and aimed at euvolemia (cardiac index, CI ≥ 3.0 L/min/m2; global end-diastolic index, GEDI 680–800 mL/m2; stroke volume variation, SVV < 10%). Patients were managed using a brain tissue oxygenation (PbtO2) targeted protocol to prevent brain tissue hypoxia (BTH, PbtO2 < 20 mmHg). To assess the association between CI and PbtO2 and the effect of fluid challenges on CI and PbtO2, we used generalized estimating equations to account for repeated measurements. Results: Among a total of 60 included patients (median age 56 [IQRs 47–65] years), BTH occurred in 23% of the monitoring time during the first 10 days since admission. Overall, mean CI was within normal ranges (ranging from 3.1 ± 1.3 on day 0 to 4.1 ± 1.1 L/min/m2 on day 4). Higher CI levels were associated with higher PbtO2 levels (Wald = 14.2; p < 0.001). Neither daily fluid input nor fluid balance was associated with absolute PbtO2 levels (p = 0.94 and p = 0.85, respectively) or the occurrence of BTH (p = 0.68 and p = 0.71, respectively). PbtO2 levels were not significantly different in preload dependent patients compared to episodes of euvolemia. PbtO2 increased as a response to fluid boluses only if BTH was present at baseline (from 13 ± 6 to 16 ± 11 mmHg, OR = 13.3 [95% CI 2.6–67.4], p = 0.002), but not when all boluses were considered (p = 0.154). Conclusions: In this study a moderate association between increased cardiac output and brain oxygenation was observed. Fluid challenges may improve PbtO2 only in the presence of baseline BTH. Individualized hemodynamic management requires advanced cardiac and brain monitoring in critically ill SAH patients.SCOPUS: ar.jinfo:eu-repo/semantics/publishe