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Metabolic crisis in severely head-injured patients: is ischemia just the tip of the iceberg?

ABSTRACT: Ischemia and metabolic crisis are frequent post-traumatic secondary brain insults that negatively influence outcome. Clinicians commonly mix up these two types of insults, mainly because high lactate/pyruvate ratio (LPR) is the common marker for both ischemia and metabolic crisis. However, LPR elevations during ischemia and metabolic crisis reflect two different energetic imbalances: ischemia (Type 1 LPR elevations with low oxygenation) is characterized by a drastic deprivation of energetic substrates, whereas metabolic crisis (Type 2 LPR elevations with normal or high oxygenation) is associated with profound mitochondrial dysfunction but normal supply of energetic substrates. The discrimination between ischemia and metabolic crisis is crucial because conventional recommendations against ischemia may be detrimental for patients with metabolic crisis. Multimodal monitoring, including microdialysis and brain tissue oxygen monitoring, allows such discrimination, but these techniques are not easily accessible to all head-injured patients. Thus, a new "gold standard" and adapted medical education are required to optimize the management of patients with metabolic crisis.

SUBMITTER: Carre E

PROVIDER: S-EPMC3795329 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature

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Metabolic crisis in severely head-injured patients: is ischemia just the tip of the iceberg?

Carre Emilie E Ogier Michael M Boret Henry H Montcriol Ambroise A Bourdon Lionel L Jean-Jacques Risso R

Frontiers in neurology 20131011

Ischemia and metabolic crisis are frequent post-traumatic secondary brain insults that negatively influence outcome. Clinicians commonly mix up these two types of insults, mainly because high lactate/pyruvate ratio (LPR) is the common marker for both ischemia and metabolic crisis. However, LPR elevations during ischemia and metabolic crisis reflect two different energetic imbalances: ischemia (Type 1 LPR elevations with low oxygenation) is characterized by a drastic deprivation of energetic subs ...[more]

PMID: 24130548

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Project description:Initially underestimated as platelet dust, extracellular vesicles are continuously gaining interest in the field of inflammation. Various studies addressing inflammatory diseases have shown that microvesicles (MVs) originating from different cell types are systemic transport vehicles carrying distinct cargoes to modulate immune responses. In this study, we focused on the clinical setting of multiple trauma, which is characterized by activation and dysfunction of both, the fluid-phase and the cellular component of innate immunity. Given the sensitivity of neutrophils for the complement anaphylatoxin C5a, we hypothesized that increased C5a production induces alterations in MV shedding of neutrophils resulting in neutrophil dysfunction that fuels posttraumatic inflammation. In a mono-centered prospective clinical study with polytraumatized patients, we found significantly increased granulocyte-derived MVs containing the C5a receptor (C5aR1, CD88) on their surface. This finding was accompanied by a concomitant loss of C5aR1 on granulocytes indicative of an impaired cellular chemotactic and pro-inflammatory neutrophil functions. Furthermore, in vitro exposure of human neutrophils (from healthy volunteers) to C5a significantly increased MV shedding and C5aR1 loss on neutrophils, which could be blocked using the C5aR1 antagonist PMX53. Mechanistic analyses revealed that the interaction between C5aR1 signaling and the small GTPase Arf6 acts as a molecular switch for MV shedding. When neutrophil derived, C5a-induced MV were exposed to a complex ex vivo whole blood model significant pro-inflammatory properties (NADPH activity, ROS and MPO generation) of the MVs became evident. C5a-induced MVs activated resting neutrophils and significantly induced IL-6 secretion. These data suggest a novel role of the C5a-C5aR1 axis: C5a-induced MV shedding from neutrophils results in decreased C5aR1 surface expression on the one hand, on the other hand it leads to profound inflammatory signals which likely are both key drivers of the neutrophil dysfunction which is regularly observed in patients suffering from multiple traumatic injuries.

Project description:BackgroundChoosing the appropriate endpoint for a trauma hemorrhage control trial can determine the likelihood of its success. Recent Phase 3 trials and observational studies have used 24-h and/or 30-day all-cause mortality as the primary endpoint and some have not used exception from informed consent (EFIC), resulting in multiple failed trials. Five recent high-quality prospective studies among 4,064 hemorrhaging trauma patients provide new evidence to support earlier primary endpoints.MethodsThe goal of this project was to determine the optimal endpoint for hemorrhage control trials using existing literature and new analyses of previously published data.ResultsRecent studies among bleeding trauma patients show that hemorrhagic deaths occur rapidly, at a high rate, and in a consistent pattern. Early preventable deaths among trauma patients are largely due to hemorrhage and the median time to hemorrhagic death from admission is 2.0 to 2.6 h. Approximately 85% of hemorrhagic deaths occur within 6 h. The hourly mortality rate due to traumatic injury decreases rapidly after enrollment from 4.6% per hour at 1 hour postenrollment to 1% per hour at 6 h to <0.1% per hour by 9 h and thereafter. Early primary endpoints (within 6 h) have critically important benefits for hemorrhage control trials, including being congruent with the median time to hemorrhagic death, biologic plausibility, and enabling the use of all-cause mortality, which is definitive and objective.ConclusionsPrimary endpoints should be congruent with the timing of the disease process. Therefore, if a resuscitation/hemorrhage control intervention is under study, a primary endpoint of all-cause mortality evaluated within the first 6 h is appropriate. Before choosing the timing of the primary endpoint for a large multicenter trial, we recommend performing a Phase 2 trial under EFIC to better understand the effects of the hemorrhage control intervention and distribution of time to death. When early primary endpoints are used, patients should be monitored for multiple subsequent secondary safety endpoints, including 24 h and 30-day all-cause mortality as well as the customary safety endpoints.

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Metabolic crisis in severely head-injured patients: is ischemia just the tip of the iceberg?

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Metabolic crisis in severely head-injured patients: is ischemia just the tip of the iceberg?

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