Detection of metabolic pattern following decompressive craniectomy in severe traumatic brain injury: A microdialysis study

Brain Regional Energy Metabolism in Patients with Traumatic Brain Injury: A Cerebral Microdialysis Guided Study

BACKGROUND

In traumatic brain injuries (TBI), cerebral microdialysis (CMD)-derived parameters, especially the lactate to pyruvate ratio (LP ratio), have been utilized for cerebral perfusion optimization. The objectives were to identify cerebral ischemia as measured by CMD in TBI patients requiring decompressive craniectomy and to observe the correlation between cerebral perfusion pressure (CPP), intracranial pressure (ICP), and CMD variables in these patients. Our secondary aim was to observe the effect of CPP augmentation on ischemia biomarkers.

METHODS

After the Institute Ethics Committee approvals, seven adult patients requiring decompressive craniectomy following TBI were enrolled and CMD data were obtained prospectively for 72 h. CPP was augmented by 20% with noradrenaline infusion if LP ratio >40. Correlations were done with bootstrapping (n = 500) to obtain the confidence intervals (CI) due to the small sample size.

RESULTS

One patient had cerebral ischemia (median LP ratio of 265.5 and median pyruvate of 38 μmol/L), while another patient had non-ischemic mitochondrial dysfunction (median LP ratio 40.7 and median pyruvate 278.5). The coefficients of correlation between the LP ratio with CPP and ICP were r = -0.05 (CI = -0.14-0.03) and r = 0.09 (CI = -0.03-0.24), respectively. The coefficient of correlation between cerebral and blood glucose was r = 0.38, (CI - 0.35-0.14). Only two patients needed CPP augmentation, however, postaugmentation cerebral biochemistry did not change appreciably.

CONCLUSION

CMD can identify cerebral ischemia, however, no correlations were observed between the LP ratio and CPP or ICP. CPP augmentation did not improve cerebral biochemistry. More studies are required to understand and treat cerebral metabolism in TBI.

Prolonged course of brain edema and neurological recovery in a translational model of decompressive craniectomy after closed head injury in mice

Background

The use of decompressive craniectomy in traumatic brain injury (TBI) remains a matter of debate. According to the DECRA trial, craniectomy may have a negative impact on functional outcome, while the RescueICP trial revealed a positive effect of surgical decompression, which is evolving over time. This ambivalence of craniectomy has not been studied extensively in controlled laboratory experiments.

Objective

The goal of the current study was to investigate the prolonged effects of decompressive craniectomy (both positive and negative) in an animal model.

Methods

Male mice were assigned to the following groups: sham, decompressive craniectomy, TBI and TBI followed by craniectomy. The analysis of functional outcome was performed at time points 3d, 7d, 14d and 28d post trauma according to the Neurological Severity Score and Beam Balance Score. At the same time points, magnetic resonance imaging was performed, and brain edema was analyzed.

Results

Animals subjected to both trauma and craniectomy presented the exacerbation of the neurological impairment that was apparent mostly in the early course (up to 7d) after injury. Decompressive craniectomy also caused a significant increase in brain edema volume (initially cytotoxic with a secondary shift to vasogenic edema and gliosis). Notably, delayed edema plus gliosis appeared also after decompression even without preceding trauma.

Conclusion

In prolonged outcomes, craniectomy applied after closed head injury in mice aggravates posttraumatic brain edema, leading to additional functional impairment. This effect is, however, transient. Treatment options that reduce brain swelling after decompression may accelerate neurological recovery and should be explored in future experiments.

Management Strategies Based on Multi-Modality Neuromonitoring in Severe Traumatic Brain Injury

Secondary brain injury after neurotrauma is comprised of a host of distinct, potentially concurrent and interacting mechanisms that may exacerbate primary brain insult. Multimodality neuromonitoring is a method of measuring multiple aspects of the brain in order to understand the signatures of these different pathomechanisms and to detect, treat, or prevent potentially reversible secondary brain injuries. The most studied invasive parameters include intracranial pressure (ICP), cerebral perfusion pressure (CPP), autoregulatory indices, brain tissue partial oxygen tension, and tissue energy and metabolism measures such as the lactate pyruvate ratio. Understanding the local metabolic state of brain tissue in order to infer pathology and develop appropriate management strategies is an area of active investigation. Several clinical trials are underway to define the role of brain tissue oxygenation monitoring and electrocorticography in conjunction with other multimodal neuromonitoring information, including ICP and CPP monitoring. Identifying an optimal CPP to guide individualized management of blood pressure and ICP has been shown to be feasible, but definitive clinical trial evidence is still needed. Future work is still needed to define and clinically correlate patterns that emerge from integrated measurements of metabolism, pressure, flow, oxygenation, and electrophysiology. Pathophysiologic targets and precise critical care management strategies to address their underlying causes promise to mitigate secondary injuries and hold the potential to improve patient outcome. Advancements in clinical trial design are poised to establish new standards for the use of multimodality neuromonitoring to guide individualized clinical care.

Prolonged and intense neuroinflammation after severe traumatic brain injury assessed by cerebral microdialysis with 300 kDa membranes

BACKGROUND

A neuroinflammatory response that may lead to edema and secondary brain damage is elicited in severe traumatic brain injury (TBI). Previous studies using microdialysis (MD) membranes with 100 k Dalton (kDa) cut-off found a transient intracerebral release of cytokines and chemokines without significant correlations to clinical course, intracranial pressure (ICP) or metabolites. In this study, a (300 kDa) MD probe was used to measure the levels of cytokines and chemokines in relation to ICP and metabolites.

METHODS

Seven patients with severe TBI received 2 MD catheters. In four patients sufficient dialysate could be retrieved for analysis from both catheters. MD samples were analyzed bedside, then frozen and analyzed for chemokines and cytokines using a multiplex assay (Mesoscale Discovery).

RESULTS

MD sampling was performed from 9 to 350 h. In total, 17 chemokines and cytokines were detected. Of these, IL-6, IL-8, IP-10, MCP-1 and MIP-1β were consistently elevated, and investigated further in relation to metabolites, and ICP. Levels of chemokines and cytokines were higher than previously reported from TBI patients, and partially higher than those reported in patients with cytokine release syndrome. There were no significant differences between the two catheters regarding cytokine/chemokine concentrations, except for IL-6 which was higher in the peri-contusional area. No correlation with metabolites and ICP was observed. No significant increase or decline of chemokine or cytokine secretion was observed during the study period.

CONCLUSION

Our data suggest that cytokine and chemokine levels reflect a perpetual, potent and pan-cerebebral inflammatory response that persists beyond 15 days following TBI.

Lamellar perfusion and energy metabolism in a preferential weight bearing model

BACKGROUND

Supporting limb laminitis (SLL) is suspected to be caused by lamellar ischaemia as a consequence of increased mechanical load.

OBJECTIVES

Examine the effects of prolonged preferential weight bearing (PWB) on lamellar perfusion and metabolism.

STUDY DESIGN

In vivo experiment.

METHODS

Microdialysis probes were inserted in the lamellar and sublamellar dermis of one forelimb in 13 Standardbred horses. In six horses, a platform shoe (contralateral forelimb) was used to induce increased load on the microdialysis-instrumented forelimb (PWB). The remaining seven horses were controls (CON). All horses were housed in stocks with limb weight distribution logged continuously for 92 hours. Microdialysate was collected and analysed every 4 hours for glucose, lactate, pyruvate, and lactate to pyruvate ratio (L:P). Microdialysis urea clearance was used to estimate lamellar perfusion. Data were analysed using a mixed-effects linear regression model.

RESULTS

Median [IQR] load on the microdialysis-instrumented limb was equivalent to 38.7% bwt. [37.3-40.3] in PWB and 27.3% bwt. [26.6-28] in CON. Limb offloading frequency increased in CON (P < .001) but not PWB (P = .2). Lamellar microdialysate glucose decreased in PWB (P < .001) and CON (P = .004), however, the rate of decrease was higher in PWB (P = .007). Lamellar L:P increased in PWB (P < .001) and peaked at 196 [79-656], whereas L:P did not change over time in CON (P = .6) and peaked at 42 [41-49]. Lamellar urea clearance decreased in PWB (P < .001) but not in CON (P = .3). Sublamellar L:P and urea clearance did not change over time in either group (P > .05).

MAIN LIMITATIONS

The PWB model may not be representative of naturally occurring SLL.

CONCLUSIONS

Evidence of lamellar ischaemia (increased L:P and decreased urea clearance) was detected exclusively in the lamellar dermis of PWB feet subjected to persistently increased load. Lamellar ischaemia is a consequence of increased mechanical load and likely contributes to the development of SLL.

Lamellar energy metabolism and perfusion in the euglycaemic hyperinsulinaemic clamp model of equine laminitis

BACKGROUND

Hyperinsulinaemia is associated with the development of endocrinopathic laminitis; however, the mechanisms remain unclear.

OBJECTIVES

Evaluate the effects of hyperinsulinaemia on lamellar energy metabolism and perfusion during laminitis development.

STUDY DESIGN

In vivo experiment.

METHODS

Eight Standardbred horses were instrumented with a microdialysis probe in the lamellae of a forelimb. A 24 hours baseline period (BASELINE) was followed by 48 hours of a continuous euglycaemic hyperinsulinaemic clamp (EHC) from 24 to 72 hours (CLAMP). Microdialysate was collected every 6 hours and analysed for glucose, lactate and pyruvate concentrations and lactate-to-pyruvate ratio (L:P). Microdialysis urea clearance was used to estimate lamellar tissue perfusion. Archived microdialysis samples from six identically instrumented Standardbred horses served as controls (CON). Variables were compared over time and between EHC and CON horses using a mixed-effects linear regression model.

RESULTS

Glucose concentration decreased during the CLAMP period in CON and EHC horses (P < .001), but there was no difference between CON and EHC (P > .9). Lactate concentration increased during the CLAMP period in CON and EHC horses (P < .001), however, the rate of increase was significantly higher in EHC horses relative to CON (P = .014). There was a relative increase in pyruvate concentration in EHC horses compared with CON during the CLAMP period (P = .03). L:P increased significantly in CON horses during the CLAMP period (P < .001) but not in EHC (P = .1). Urea clearance did not change in CON (P = .9) or EHC (P = .05) during the CLAMP, but did increase in EHC relative to CON (P = .02).

MAIN LIMITATIONS

The effects of microdialysis probe implantation on perfusion and metabolism remain unclear. The EHC model may not mimic natural endocrinopathic laminitis.

CONCLUSIONS

Laminitis developed without evidence of lamellar hypoperfusion or energy stress. Therapies to improve perfusion are unlikely to affect the initial development of endocrinopathic laminitis.

Decompressive Craniectomy for Traumatic Brain Injury: Postoperative TCD Cerebral Hemodynamic Evaluation

Background: There are no studies describing the cerebral hemodynamic patterns that can occur in traumatic brain injury (TBI) patients following decompressive craniectomy (DC). Such data have potentially clinical importance for guiding the treatment. The objective of this study was to investigate the postoperative cerebral hemodynamic patterns, using transcranial Doppler (TCD) ultrasonography, in patients who underwent DC. The relationship between the cerebral circulatory patterns and the patients' outcome was also analyzed. Methods: Nineteen TBI patients with uncontrolled brain swelling were prospectively studied. Cerebral blood circulation was evaluated by TCD ultrasonography. Patients and their cerebral hemispheres were categorized based on TCD-hemodynamic patterns. The data were correlated with neurological status, midline shift on CT scan, and Glasgow outcome scale scores at 6 months after injury. Results: Different cerebral hemodynamic patterns were observed. One patient (5.3%) presented with cerebral oligoemia, 4 patients (21%) with cerebral hyperemia, and 3 patients (15.8%) with cerebral vasospasm. One patient (5.3%) had hyperemia in one cerebral hemisphere and vasospasm in the other hemisphere. Ten patients (52.6%) had nonspecific circulatory pattern. Abnormal TCD-circulatory patterns were found in 9 patients (47.4%). There was no association between TCD-cerebral hemodynamic findings and outcome. Conclusion: There is a wide heterogeneity of postoperative cerebral hemodynamic findings among TBI patients who underwent DC, including hemodynamic heterogeneity between their cerebral hemispheres. DC was proved to be effective for the treatment of cerebral oligoemia. Our data support the concept of heterogeneous nature of the pathophysiology of the TBI and suggest that DC as the sole treatment modality is insufficient.