Rapid cold hardening delays the onset of anoxia-induced coma via an octopaminergic pathway in Locusta migratoria.

Rapid cold hardening (RCH) is a short-term hormesis that occurs in many invertebrate species, especially in insects. Although RCH is best known as enhancing cold tolerance, it can also enhance anoxic tolerance. When exposed to prolonged anoxia, insects enter a reversible coma, which is associated with spreading depolarization (SD) in the central nervous system (CNS). In this study, we investigated the effects of RCH and octopamine (OA) on anoxia-induced SD in L. migratoria. OA is an insect stress hormone that has roles in many physiological processes. Thus, we hypothesized that OA is involved in the mechanism of RCH. First, we found that RCH affects the K+ sensitivity of the locust blood brain barrier (BBB) in a way similar to the previously described effects of OA. Next, using SD as an indicator of anoxia-induced coma, we took a pharmacological approach to investigate the effects of OA and epinastine (EP), an octopaminergic receptor (OctR) antagonist. We found that OA mimics, whereas EP blocks, the effect of RCH on anoxia-induced SD. This study demonstrates that OA is involved in the mechanism of RCH in delaying the onset of anoxia-induced locust coma and contributes to determining the mechanism of RCH that modulates insect stress tolerances.

Inhibition of ATP-sensitive potassium channels exacerbates anoxic coma in Locusta migratoria.

Under extreme environmental conditions, many insects enter a protective coma associated with a spreading depolarization (SD) of neurons and glia in the central nervous system (CNS). Recovery depends on the restoration of ion gradients by mechanisms that are not well understood. We investigated the effects of glybenclamide, an ATP-sensitive K+ (KATP) channel inhibitor, and pinacidil, a KATP activator, on the mechanisms involved in anoxic coma induction and recovery in Locusta migratoria. KATP channels allow for the efflux of K+ when activated, thereby linking cellular metabolic state to membrane potential. In intact locusts, we measured the time to enter a coma after water immersion and the time to recover the righting reflex after returning to normoxia. In semi-intact preparations, we measured the time to SD in the metathoracic ganglion after flooding the preparation with saline or exposing it to 100% N2 gas, and the time for the transperineurial potential to recover after removal of the saline or return to air. Glybenclamide decreased the time to coma induction, whereas pinacidil increased induction times. Glybenclamide also lengthened the time to recovery and decreased the rate of recovery of transperineurial potential after SD. These results were not the same as the effects of 10-2 M ouabain on N2-induced SD. We conclude that glybenclamide affects the CNS response to anoxia via inhibition of KATP channels and not an effect on the Na+/K+-ATPase.NEW & NOTEWORTHY We demonstrate the involvement of ATP-sensitive K+ (KATP) channels during recovery from spreading depolarization (SD) induced via anoxic coma in locusts. KATP inhibition using glybenclamide impaired ion homeostasis across the blood-brain barrier resulting in a longer time to recovery of transperineurial potential following SD. Comparison with ouabain indicates that the effects of glybenclamide are not mediated by the Na+/K+-ATPase but are a result of KATP channel inhibition.

Lateral Brain Displacement and Cerebral Autoregulation in Acutely Comatose Patients.

OBJECTIVES: Lateral displacement and impaired cerebral autoregulation are associated with worse outcomes following acute brain injury, but their effect on long-term clinical outcomes remains unclear. We assessed the relationship between lateral displacement, disturbances to cerebral autoregulation, and clinical outcomes in acutely comatose patients. DESIGN: Retrospective analysis of prospectively collected data. SETTING: Neurocritical care unit of the Johns Hopkins Hospital. PATIENTS: Acutely comatose patients (Glasgow Coma Score ≤ 8). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Cerebral oximetry index, derived from near-infrared spectroscopy multimodal monitoring, was used to evaluate cerebral autoregulation. Associations between lateral brain displacement, global cerebral autoregulation, and interhemispheric cerebral autoregulation asymmetry were assessed using mixed random effects models with random intercept. Patients were grouped by functional outcome, determined by the modified Rankin Scale. Associations between outcome group, lateral displacement, and cerebral oximetry index were assessed using multivariate linear regression. Increasing lateral brain displacement was associated with worsening global cerebral autoregulation (p = 0.01 septum; p = 0.05 pineal) and cerebral autoregulation asymmetry (both p < 0.001). Maximum lateral displacement during the first 3 days of coma was significantly different between functional outcome groups at hospital discharge (p = 0.019 pineal; p = 0.008 septum), 3 months (p = 0.026; p = 0.007), 6 months (p = 0.018; p = 0.010), and 12 months (p = 0.022; p = 0.012). Global cerebral oximetry index was associated with functional outcomes at 3 months (p = 0.019) and 6 months (p = 0.013). CONCLUSIONS: During the first 3 days of acute coma, increasing lateral brain displacement is associated with worsening global cerebral autoregulation and cerebral autoregulation asymmetry, and poor long-term clinical outcomes in acutely comatose patients. The impact of acute interventions on outcome needs to be explored.

Glycated Hemoglobin is Associated with Glycemic Control and 6-Month Neurologic Outcome in Cardiac Arrest Survivors Undergoing Therapeutic Hypothermia.

BACKGROUND: Glucose control status after cardiac arrest depending on chronic glycemic status and the association between chronic glycemic status and outcome in cardiac arrest survivors are not well known. We investigated the association between glycated hemoglobin (HbA1c) and 6-month neurologic outcome in cardiac arrest survivors undergoing therapeutic hypothermia (TH) and whether mean glucose, area under curve (AUC) of glucose during TH, and neuron-specific enolase (NSE) are different between normal and high HbA1c groups. METHODS: This retrospective single-center study included adult comatose cardiac arrest survivors who underwent TH from September 2011 to December 2017. HbA1c and glucose were measured after return of spontaneous circulation (ROSC), and normal or high HbA1c was defined using cutoff value of 6.4% of HbA1c. Blood glucose was measured at least every 4 h and treated with a written protocol to maintain the range of 80-200 mg/dL. Hypoglycemia and hyperglycemia were defined with glucose < 70 or > 180 mg/dL. Mean glucose during induction and rewarming phase and AUC of glucose during every 6 h of maintenance were calculated, and NSE at 48 h after cardiac arrest was recorded. The primary outcome was unfavorable neurologic outcome, defined as Glasgow Pittsburgh Cerebral Performance Category scale 3-5 at 6 months after cardiac arrest. RESULTS: Of 384 included patients, 81 (21.1%) had high HbA1c and 247 (64.3%) had an unfavorable neurologic outcome. Patients with high HbA1c were more common in the unfavorable group than in favorable group (27.5% vs 9.5%, p < 0.001), and the unfavorable group had significantly higher HbA1c level (5.8% [5.4-6.8%] vs 5.6% [5.3-6.0%], p = 0.007). HbA1c level was independently associated with worse neurologic outcome (odds ratio 1.414; 95% confidence interval 1.051-1.903). High HbA1c group had higher glucose after ROSC, glucose AUC during maintenance, and rewarming phase than normal HbA1c group. High HbA1c group had significantly higher incidence of hyperglycemia throughout the TH, while normal HbA1c group had significantly higher incidence of normoglycemia. However, no glucose parameter remained as an independent predictor of neurologic outcome after adjustment, irrespective of HbA1c level. NSE showed good prognostic performance (area under curve 0.892; cutoff value 26.3 ng/mL). Although NSE level was not different between HbA1c groups, high HbA1c group had higher proportion of patient having NSE over cutoff. CONCLUSIONS: Higher HbA1c was independently associated with unfavorable neurologic outcome. Glycemic status during TH was different between normal and high HbA1c groups.

A clinical trial of enteral Levetiracetam for acute seizures in pediatric cerebral malaria.

BACKGROUND: Acute seizures are common in pediatric cerebral malaria (CM), but usual care with phenobarbital risks respiratory suppression. We undertook studies of enteral levetiracetam (eLVT) to evaluate pharmacokinetics (PK), safety and efficacy including an open-label, randomized controlled trial (RCT) comparing eLVT to phenobarbital. METHODS: Children 24-83 months old with CM were enrolled in an eLVT dose-finding study starting with standard dose (40 mg/kg load, then 30 mg/kg Q12 hours) titrated upward until seizure freedom was attained in 75% of subjects. The RCT that followed randomized children to eLVT vs. phenobarbital for acute seizures and compared the groups on minutes with seizures based upon continuous electroencephalogram. Due to safety concerns, midway through the study children allocated to phenobarbital received the drug only if they continued to have seizures (either clinically or electrographically) after benzodiazepine treatment. Secondary outcomes were treatment failure requiring cross over, coma duration and neurologic sequelae at discharge. PK and safety assessments were also undertaken. RESULTS: Among 30 comatose CM children, eLVT was rapidly absorbed and well-tolerated. eLVT clearance was lower in patients with higher admission serum creatinine (SCr), but overall PK parameters were similar to prior pediatric PK studies. Within 4 h of the first dose, 90% reached therapeutic levels (> 20 µg/mL) and all were above 6 µg/mL. 7/7 children achieved seizure freedom on the initial eLVT dose. Comparing 23 eLVT to 21 phenobarbital patients among whom 15/21 received phenobarbital, no differences were seen for minutes with seizure, seizure freedom, coma duration, neurologic sequelae or death, but eLVT was safer (p = 0.019). Phenobarbital was discontinued in 3/15 due to respiratory side effects. CONCLUSION: Enteral LVT offers an affordable option for seizure control in pediatric CM and is safer than phenobarbital. TRIAL REGISTRATION: NCT01660672 . NCT01982812 .

Antidotal Effects of the Phenothiazine Chromophore Methylene Blue Following Cyanide Intoxication.

Our study was aimed at (1) determining the efficacy of the dye methylene blue (MB), following a rapidly lethal cyanide (CN) intoxication in un-sedated rats; (2) clarifying some of the mechanisms responsible for the antidotal properties produced by this potent cyclic redox dye. Sixty-nine awake rats acutely intoxicated by CN (IP, KCN 7 mg/kg) received saline, MB (20 mg/kg) or hydroxocobalamin (HyCo, 150 mg/kg) when in deep coma. Survival in this model was very low, reaching 9% at 60 min without any treatment. Methylene blue significantly increased survival (59%, p < .001) at 60 min, versus 37% with HyCo (p < .01). In addition, 8 urethane-anesthetized rats were exposed to a sublethal CN intoxication (KCN, 0.75 mg/kg/min IV for 4 min); they received MB (20 mg/kg, IV) or saline, 5 min after the end of CN exposure. All MB-treated rats displayed a significant reduction in hyperlactacidemia, a restoration of pyruvate/lactate ratio-a marker of NAD/NADH ratio-and an increase in CO2 production, a marker of the activity of the TCA cycle. These changes were also associated with a 2-fold increase in the pool of CN in red cells. Based on series of in vitro experiments, looking at the effects of MB on NADH, as well as the redox effects of MB on hemoglobin and cytochrome c, we hypothesize that the antidotal properties of MB can in large part be accounted for by its ability to readily restore NAD/NADH ratio and to cyclically re-oxidize then reduce the iron in hemoglobin and the electron chain complexes. All of these effects can account for the rapid antidotal properties of this dye following CN poisoning.

Recurrent moderate hypoglycemia exacerbates oxidative damage and neuronal death leading to cognitive dysfunction after the hypoglycemic coma.

Moderate recurrent hypoglycemia (RH) is frequent in Type 1 diabetes mellitus (TIDM) patients who are under intensive insulin therapy increasing the risk for severe hypoglycemia (SH). The consequences of RH are not well understood and its repercussions on neuronal damage and cognitive function after a subsequent episode of SH have been poorly investigated. In the current study, we have addressed this question and observed that previous RH during seven consecutive days exacerbated oxidative damage and neuronal death induced by a subsequent episode of SH accompanied by a short period of coma, in the parietal cortex, the striatum and mainly in the hippocampus. These changes correlated with a severe decrease in reduced glutathione content (GSH), and a significant spatial and contextual memory deficit. Administration of the antioxidant, N-acetyl-L-cysteine, (NAC) reduced neuronal death and prevented cognitive impairment. These results demonstrate that previous RH enhances brain vulnerability to acute hypoglycemia and suggests that this effect is mediated by the decline in the antioxidant defense and oxidative damage. The present results highlight the importance of an adequate control of moderate hypoglycemic episodes in TIDM.

Clinical and Biological Predictors of Plasma Levels of Soluble RAGE in Critically Ill Patients: Secondary Analysis of a Prospective Multicenter Observational Study.

RATIONALE: Although soluble forms of the receptor for advanced glycation end products (RAGE) have been recently proposed as biomarkers in multiple acute or chronic diseases, few studies evaluated the influence of usual clinical and biological parameters, or of patient characteristics and comorbidities, on circulating levels of soluble RAGE in the intensive care unit (ICU) setting. OBJECTIVES: To determine, among clinical and biological parameters that are usually recorded upon ICU admission, which variables, if any, could be associated with plasma levels of soluble RAGE. METHODS: Data for this ancillary study were prospectively obtained from adult patients with at least one ARDS risk factor upon ICU admission enrolled in a large multicenter observational study. At ICU admission, plasma levels of total soluble RAGE (sRAGE) and endogenous secretory (es)RAGE were measured by duplicate ELISA and baseline patient characteristics, comorbidities, and usual clinical and biological indices were recorded. After univariate analyses, significant variables were used in multivariate, multidimensional analyses. MEASUREMENTS AND MAIN RESULTS: 294 patients were included in this ancillary study, among whom 62% were admitted for medical reasons, including septic shock (11%), coma (11%), and pneumonia (6%). Although some variables were associated with plasma levels of RAGE soluble forms in univariate analysis, multidimensional analyses showed no significant association between admission parameters and baseline plasma sRAGE or esRAGE. CONCLUSIONS: We found no obvious association between circulating levels of soluble RAGE and clinical and biological indices that are usually recorded upon ICU admission. This trial is registered with NCT02070536.

The Glucagon-Like Peptide-1 Analog Exenatide Increases Blood Glucose Clearance, Lactate Clearance, and Heart Rate in Comatose Patients After Out-of-Hospital Cardiac Arrest.

OBJECTIVES: To investigate the effects of the glucagon-like peptide-1 analog exenatide on blood glucose, lactate clearance, and hemodynamic variables in comatose, resuscitated out-of-hospital cardiac arrest patients. DESIGN: Predefined post hoc analyzes from a double-blind, randomized clinical trial. SETTING: The ICU of a tertiary heart center. PATIENTS: Consecutive sample of adult, comatose patients undergoing targeted temperature management after out-of-hospital cardiac arrest from a presumed cardiac cause, irrespective of the initial cardiac rhythm. INTERVENTIONS: Patients were randomized 1:1 to receive 6 hours and 15 minutes of infusion of either 17.4 µg of the glucagon-like peptide-1 analog exenatide (Byetta; Lilly) or placebo within 4 hours from sustained return of spontaneous circulation. The effects of exenatide were examined on the following prespecified covariates within the first 6 hours from study drug initiation: lactate level, blood glucose level, heart rate, mean arterial pressure, and combined dosage of norepinephrine and dopamine. MEASUREMENTS AND MAIN RESULTS: The population consisted of 106 patients receiving either exenatide or placebo. During the first 6 hours from study drug initiation, the levels of blood glucose and lactate decreased 17% (95% CI, 8.9-25%; p = 0.0004) and 21% (95% CI, 6.0-33%; p = 0.02) faster in patients receiving exenatide versus placebo, respectively. Exenatide increased heart rate by approximately 10 beats per minute compared to placebo (p < 0.0001). There was no effect of exenatide on other hemodynamic variables. CONCLUSIONS: In comatose out-of-hospital cardiac arrest patients, infusion with exenatide lowered blood glucose and resulted in increased clearance of lactate as well as increased heart rate. The clinical importance of these physiologic effects remains to be investigated.

Analysis of Risk Factors for Hypoglycemic Coma in 194 Patients with Type 2 Diabetes.

BACKGROUND The present study was conducted to analyze possible risk factors in patients with type 2 diabetes who are in hypoglycemic coma. MATERIAL AND METHODS A total of 194 patients with type 2 diabetic hypoglycemic coma who were admitted to our hospital between January 2010 and January 2016 were included. The patients were all in coma on admission, and their blood glucose levels were lower than 2.8 mmol/L. None of the patients had type I diabetes, specific types of diabetes, or gestational diabetes. Multiple linear regression analysis was used to determine possible factors associated with hypoglycemic coma. RESULTS Among the patients, 82 were male and 112 were female (mean age, 66.88±10.62 years). In addition, 72 patients lived in urban areas and 122 lived in rural areas. Occurrence of hypoglycemic coma was correlated with difference between urban and rural residence, glycosylated hemoglobin (HbA1c) level, combined hypertension, and combined neural complications. Self-purchased drugs resulted in significantly lower blood glucose level at the onset of hypoglycemic coma than insulin, secretagogue, or non-secretagogue drugs. Blood glucose level at onset was correlated with season. Patients living in rural areas or with combined macrovascular or microvascular complications had prolonged hospital stay and poor prognosis. CONCLUSIONS Our results demonstrate that rural residence, higher HbA1c level, combined hypertension, and combined neural complications increase the incidence of hypoglycemic coma. Use of self-purchased drugs and colder seasons may result in lower blood glucose levels in patients with hypoglycemic coma.

Level of systemic inflammation and endothelial injury is associated with cardiovascular dysfunction and vasopressor support in post-cardiac arrest patients.

AIM: Post-cardiac arrest syndrome (PCAS) is characterized by a sepsis-like inflammatory response and hemodynamic instability. We investigated the associations between systemic inflammation, endothelial damage and hemodynamic parameters including vasopressor support in patients with out-of-hospital cardiac arrest (OHCA). METHODS: In this post-hoc study, we analysed data from 163 comatose patients included at a single center in the Target Temperature Management (TTM) trial, randomly assigned to TTM at 33°C or 36°C for 24h. Inflammatory biomarkers (interleukin (IL)-6, IL-10, procalcitonin and Tumor Necrosis Factor-α (TNF-α)) and endothelial biomarkers (thrombomodulin, sE-selectin, syndecan-1 and VE-cadherin) were measured at randomization and 24, 48 and 72h after OHCA. Corresponding hemodynamic status, heart rate (HR), mean arterial pressure (MAP) and Cumulative Vasopressor Index (CVI) was reported. RESULTS: At randomization, level of IL-6 correlated negatively with MAP (r=-0.19, p=0.03) and positively with HR (r=0.29, p=0.0002). Serial IL-6 levels correlated consistently with CVI at 24h: (r=0.19, p=0.02) 48h: (r=0.31, p=0.0001) and 72h: (r=0.39, p<0.0001). Thrombomodulin (r=0.23, p=0.004) and syndecan-1 (r=0.27, p=0.001) correlated with CVI at 48h. All inflammatory markers excerpt IL-10 and all endothelial markers correlated with CVI at 72h. Multivariable regression models adjusting for potential confounders confirmed that IL-6 (ß=0.2 (95% CI: 0.06-0.3), p=0.004) and TTM-group (TTM36: ß=-0.5 (95% CI: -0.9 to 0.1), p=0.01) were associated with CVI at 48h. At 72h after OHCA, IL-6 (ß=0.3 (95% CI: 0.03-0.6), p<0.0001), TNF-α (ß=-0.4 (95% CI:- 0.5 to 0.2), p<0.0001) and TTM-group (TTM36: ß=-0.4 (95% CI: -0.8 to 0.1), p=0.008) were associated with CVI. An overall two-fold increase in levels of IL-6 (ß=0.2 (95% CI: 0.1-0.3), p<0.0001) and IL-10 (ß=-0.2 (95% CI: -0.3 to 0.06), p=0.005) within 72h after OHCA were significantly associated with CVI. TTM-group modified the interaction between CVI and IL-6 (pinteraction=0.008), but not with IL-10 (pinteraction=0.23). CONCLUSIONS: In comatose survivors after OHCA, increasing systemic inflammation and endothelial injury was associated with increased need of vasopressor support. Systemic inflammation, in particular IL-6, was consistently associated with vasopressor support, however endothelial injury may also play a role in PCAS associated cardiovascular dysfunction after OHCA.

Traumatic axonal injury, a clinical-pathological correlation.

Traumatic axonal injury (TAI) is a distinct clinicopathological entity that can cause serious impairment of the brain function and can sometimes be found as a concrete cause of death. It has been discussed from the perspective of its biomechanical importance, and also from the standpoint of certain criteria for the pathological diagnosis of TAI. However, since the time when DAI (diffuse axonal injury) was initially described, there have been few, if any, discussions about the clinical-pathological correlation in TAI. This paper is an attempt to address this issue. For the purpose of certain pathological diagnoses of TAI, 63 cases with closed head injuries have been subjected to the complete forensic-neuropathological examination, involving immunohistochemistry with antibody against ß-APP. In the diagnosis of TAI strict criteria have been followed. Then, retrograde analysis of the clinical parameters has been performed in order to determine some clinical-pathological correlation. The following two most reliable parameters of the impairment of the brain function have been analyzed: the impairment of the consciousness and the time of survival. Comparing the two groups, the one with TAI and the other without TAI, and using appropriate statistical evaluation, our results show that TAI is not a significant contributing factor to the lethal outcome in the early post injury period (24 h), but it is undoubtedly a contributing factor for the severe impairment of the brain function indicated through the status of the consciousness.

Recovery from Coma Post-Cardiac Arrest Is Dependent on the Orexin Pathway.

Cardiac arrest (CA) affects >550,000 people annually in the United States whereas 80-90% of survivors suffer from a comatose state. Arousal from coma is critical for recovery, but mechanisms of arousal are undefined. Orexin-A, a hypothalamic excitatory neuropeptide, has been linked to arousal deficits in various brain injuries. We investigated the orexinergic system's role in recovery from CA-related neurological impairments, including arousal deficits. Using an asphyxial CA and resuscitation model in rats, we examine neurological recovery post-resuscitation in conjunction with changes in orexin-A levels in cerebrospinal fluid (CSF) and orexin-expressing neurons. We also conduct pharmacological inhibition of orexin post-resuscitation. We show that recovery from neurological deficits begins between 4 and 24 h post-resuscitation, with additional recovery by 72 h post-resuscitation. Orexin-A levels in the CSF are lowest during periods of poorest arousal post-resuscitation (4 h) and recover to control levels by 24 h. Immunostaining revealed that the number of orexin-A immunoreactive neurons declined at 4 h post-resuscitation, but increased to near normal levels by 24 h. There were no significant changes in the number of neurons expressing melanin-concentrating hormone, another neuropeptide localized in similar hypothalamus regions. Last, administration of the dual orexin receptor antagonist, suvorexant, during the initial 24 h post-resuscitation, led to sustained neurological deficits. The orexin pathway is critical during early phases of neurological recovery post-CA. Blocking this early action leads to persistent neurological deficits. This is of considerable clinical interest given that suvorexant recently received U.S. Food and Drug Administration approval for insomnia treatment.

Characterization of mitochondrial injury after cardiac arrest (COMICA).

INTRODUCTION: Mitochondrial injury post-cardiac arrest has been described in pre-clinical settings but the extent to which this injury occurs in humans remains largely unknown. We hypothesized that increased levels of mitochondrial biomarkers would be associated with mortality and neurological morbidity in post-cardiac arrest subjects. METHODS: We performed a prospective multicenter study of post-cardiac arrest subjects. Inclusion criteria were comatose adults who suffered an out-of-hospital cardiac arrest. Mitochondrial biomarkers were measured at 0, 12, 24, 36 and 48h after return of spontaneous circulation as well as in healthy controls. RESULTS: Out of 111 subjects enrolled, 102 had evaluable samples at 0h. Cardiac arrest subjects had higher baseline cytochrome c levels compared to controls (2.18ng/mL [0.74, 7.74] vs. 0.16ng/mL [0.03, 0.91], p<0.001), and subjects who died had higher 0h cytochrome c levels compared to survivors (3.66ng/mL [1.40, 14.9] vs. 1.27ng/mL [0.16, 2.37], p<0.001). There were significantly higher Ribonuclease P (RNaseP) (3.3 [1.2, 5.7] vs. 1.2 [0.8, 1.2], p<0.001) and Beta-2microglobulin (B2M) (12.0 [1.0, 22.9], vs. 0.6 [0.6, 1.3], p<0.001) levels in cardiac arrest subjects at baseline compared to the control subjects. There were no differences between survivors and non-survivors for mitochondrial DNA, nuclear DNA, or cell free DNA. CONCLUSIONS: Cytochrome c was increased in post- cardiac arrest subjects compared to controls, and in post-cardiac arrest non-survivors compared to survivors. Nuclear DNA and cell free DNA was increased in plasma of post-cardiac arrest subjects. There were no differences in mitochondrial DNA, nuclear DNA, or cell free DNA between survivors and non-survivors. Mitochondrial injury markers showed mixed results in the post-cardiac arrest period. Future research needs to investigate these differences.

Simultaneous monitoring of potassium, glucose and lactate during spreading depolarization in the injured human brain - Proof of principle of a novel real-time neurochemical analysis system, continuous online microdialysis.

Spreading depolarizations occur spontaneously and frequently in injured human brain. They propagate slowly through injured tissue often cycling around a local area of damage. Tissue recovery after an spreading depolarization requires greatly augmented energy utilisation to normalise ionic gradients from a virtually complete loss of membrane potential. In the injured brain, this is difficult because local blood flow is often low and unreactive. In this study, we use a new variant of microdialysis, continuous on-line microdialysis, to observe the effects of spreading depolarizations on brain metabolism. The neurochemical changes are dynamic and take place on the timescale of the passage of an spreading depolarization past the microdialysis probe. Dialysate potassium levels provide an ionic correlate of cellular depolarization and show a clear transient increase. Dialysate glucose levels reflect a balance between local tissue glucose supply and utilisation. These show a clear transient decrease of variable magnitude and duration. Dialysate lactate levels indicate non-oxidative metabolism of glucose and show a transient increase. Preliminary data suggest that the transient changes recover more slowly after the passage of a sequence of multiple spreading depolarizations giving rise to a decrease in basal dialysate glucose and an increase in basal dialysate potassium and lactate levels.

Influence of core body temperature on Tryptophan metabolism, kynurenines, and estimated IDO activity in critically ill patients receiving target temperature management following cardiac arrest.

BACKGROUND/AIMS: Temperature control improves neurological prognosis in comatose cardiac arrest (CA) survivors. Previous reports demonstrate that most affected patients show signs of significant systemic inflammation. In an effort to better characterize potential temperature-related effects on key inflammatory pathways, we investigate the course of Tryptophan (Trp) levels, Tryptophan catabolites (including kynurenines) and indoleamine-2,3-dioxygenase (IDO)-activity in post CA patients. MATERIAL/METHODS: In an observational blinded endpoint analysis, a total of n=270 serial samples from 20 post CA patients (63.1±16.6 yrs., 45% shockable rhythm, mean time to return of spontaneous circulation (ROSC) 26.6±16.0min) treated with target temperature management (TTM) were analyzed. Core body temperatures, course of Trp, Trp catabolites (incl. kynurenines), and estimated IDO-activity were followed up for a maximum of 7 days after ROSC. Patients were followed up until hospital discharge or death and functional outcome was recorded. RESULTS: Over the 7-day observational interval, marked changes in Trp serum levels and IDO-activity were noted. In general, Trp serum levels but not IDO-activity seemed to parallel with the course of core body temperature. In explorative analyses, a correlation of Trp (rho=0.271 (95%-CI: 0.16-0.38, p<0.0001) and IDO-activity (rho=-0.155, 95%-CI: -0.27 to -0.037, p=0.01) with core body temperature was observed. Linear mixed effect models revealed a positive significant association of core body temperature with Trp serum levels (Likelihood ratio test χ(2)=6.35, p=0.012). In patients with good (vs. unfavorable) outcome, a tendency toward higher Trp serum levels, lower IDO-activity, and lower Kynurenic acid levels was noted. CONCLUSIONS: We observed significant changes in Trp catabolism and IDO-activity that appeared temperature associated in post CA patients. Under hypothermia, decreased serum levels of Trp and increased IDO-activity were noted. We speculate from our data that IDO-induction during hypothermia contributes to the previously described increased susceptibility to infection or sepsis under reduced temperatures.

Endothelial activation/injury and associations with severity of post-cardiac arrest syndrome and mortality after out-of-hospital cardiac arrest.

BACKGROUND: Post-cardiac arrest syndrome (PCAS) is characterized by whole-body ischemia triggering systemic inflammation and damage of the endothelium. This study investigated the relationship between systemic inflammation, endothelial damage and severity of PCAS and the association between endothelial damage and outcome after out-of-hospital cardiac arrest (OHCA). METHODS: In this post hoc study, we analyzed 163 comatose patients included at a single center in the target temperature management (TTM) trial, randomly assigned to TTM at 33°C or 36°C for 24h. Endothelial biomarkers (syndecan-1, thrombomodulin, sE-selectin, sVE-cadherin) and the inflammatory biomarker interleukin-6 (IL-6) were measured at admission (baseline) and 24, 48 and 72h after OHCA. Severity of PCAS was assessed by Sequential Organ Failure Assessment score. Mortality at 30-days was evaluated by Cox regression analysis. RESULTS: By linear regression, baseline IL-6 levels (two-fold) was independently associated with glycocalyx damage (syndecan-1 (10.3ng/ml (p=0.01))), endothelial activation (sE-selectin (2.0ng/ml (p=0.03))) and endothelial damage (thrombomodulin 0.7ng/ml (p=0.0005)) at 24h after OHCA. Adjusted for baseline IL-6, a two-fold increase in thrombomodulin from baseline to 48h (1.7 (0.9-2.4), p<0.0001) and 72h (1.5 (0.6-2.3), p<0.0007) was more closely associated with severity of PCAS than IL-6. Levels of syndecan-1, thrombomodulin and sVE-cadherin was not influenced by level of target temperature but levels of sE-selectin was significantly lower in the 36°C group (-55ng/ml (95%CI: -53 to -58ng/ml), p=0.005) compared to the 33°C group. High levels of thrombomodulin at 24h (HR=2.1 (1.3-3.3), p=0.001) and 48h (HR=1.75 (1.0-2.8), p=0.02) were associated with increased 30-day mortality in univariate analysis, but not in multivariable analyses. CONCLUSION: In comatose survivors after OHCA treated with TTM, systemic inflammation was associated with endothelial activation and endothelial damage. Sustained endothelial damage was independently associated with severity of PCAS, adjusted for level of systemic inflammation. TTM at 36°C compared to 33°C after OHCA was associated with lower endothelial activation, but not endothelial damage. CLINICAL TRIAL REGISTRATION: URL: clinicaltrials.gov/ct2/show/NCT01020916. Unique identifier: NCT01020916.

Neurological prognostication of outcome in patients in coma after cardiac arrest.

Management of coma after cardiac arrest has improved during the past decade, allowing an increasing proportion of patients to survive, thus prognostication has become an integral part of post-resuscitation care. Neurologists are increasingly confronted with raised expectations of next of kin and the necessity to provide early predictions of long-term prognosis. During the past decade, as technology and clinical evidence have evolved, post-cardiac arrest prognostication has moved towards a multimodal paradigm combining clinical examination with additional methods, consisting of electrophysiology, blood biomarkers, and brain imaging, to optimise prognostic accuracy. Prognostication should never be based on a single indicator; although some variables have very low false positive rates for poor outcome, multimodal assessment provides resassurance about the reliability of a prognostic estimate by offering concordant evidence.

Effects of Experimental Coma on the Expression of Bcl-2 Protein and Caspases 3 and 9 in Rat Brain.

We performed immunohistochemical analysis of the expression of caspases 3, 9 and bcl-2 protein in rat brain at various terms after administration of LD50 of sodium thiopental. Expression of the specified apoptosis markers was found in the sensorimotor cortex and hippocampus (dentate gyrus and CA2 region).

Disruption of posteromedial large-scale neural communication predicts recovery from coma.

OBJECTIVE: We hypothesize that the major consciousness deficit observed in coma is due to the breakdown of long-range neuronal communication supported by precuneus and posterior cingulate cortex (PCC), and that prognosis depends on a specific connectivity pattern in these networks. METHODS: We compared 27 prospectively recruited comatose patients who had severe brain injury (Glasgow Coma Scale score <8; 14 traumatic and 13 anoxic cases) with 14 age-matched healthy participants. Standardized clinical assessment and fMRI were performed on average 4 ± 2 days after withdrawal of sedation. Analysis of resting-state fMRI connectivity involved a hypothesis-driven, region of interest-based strategy. We assessed patient outcome after 3 months using the Coma Recovery Scale-Revised (CRS-R). RESULTS: Patients who were comatose showed a significant disruption of functional connectivity of brain areas spontaneously synchronized with PCC, globally notwithstanding etiology. The functional connectivity strength between PCC and medial prefrontal cortex (mPFC) was significantly different between comatose patients who went on to recover and those who eventually scored an unfavorable outcome 3 months after brain injury (Kruskal-Wallis test, p < 0.001; linear regression between CRS-R and PCC-mPFC activity coupling at rest, Spearman ρ = 0.93, p < 0.003). CONCLUSION: In both etiology groups (traumatic and anoxic), changes in the connectivity of PCC-centered, spontaneously synchronized, large-scale networks account for the loss of external and internal self-centered awareness observed during coma. Sparing of functional connectivity between PCC and mPFC may predict patient outcome, and further studies are needed to substantiate this potential prognosis biomarker.