Microdialysis in the management of hepatic encephalopathy

Multimodal brain monitoring following traumatic brain injury: A primer for intensive care practitioners

Traumatic brain injury (TBI) is common and potentially devastating. Traditional examination-based patient monitoring following TBI may be inadequate for frontline clinicians to reduce secondary brain injury through individualized therapy. Multimodal neurologic monitoring (MMM) offers great potential for detecting early injury and improving outcomes. By assessing cerebral oxygenation, autoregulation and metabolism, clinicians may be able to understand neurophysiology during acute brain injury, and offer therapies better suited to each patient and each stage of injury. Hence, we offer this primer on brain tissue oxygen monitoring, pressure reactivity index monitoring and cerebral microdialysis. This narrative review serves as an introductory guide to the latest clinically-relevant evidence regarding key neuromonitoring techniques.

Cerebral microdialysis reflects the neuroprotective effect of fractionated plasma separation and adsorption in acute liver failure better and earlier than intracranial pressure: a controlled study in pigs

BACKGROUND

Cerebral edema is a well-recognized and potentially fatal complication of acute liver failure (ALF). The effectiveness of treatments that address intracranial hypertension is generally assessed by measuring intracranial pressure (ICP). The aim of this study was to determine the role of cerebral microdialysis in monitoring the efficacy of fractionated plasma separation and adsorption (FPSA) treatment for ALF. We hypothesized that in ALF cerebral microdialysis reflects the benefits of FPSA treatment on cerebral edema before ICP.

METHODS

A surgical resection model of ALF was used in 21 pigs. We measured plasma ammonia concentration, brain concentrations of glucose, lactate, pyruvate, glutamate and glutamine, and ICP. Animals were randomized into three groups: in one group eight animals received 6 hours of FPSA treatment 2 hours after induction of ALF; in another group 10 animals received supportive treatment for ALF only; and in the final group three underwent sham surgery.

RESULTS

The ICP was significantly higher in the ALF group than in the FPSA group 9 hours after surgery. The lactate/pyruvate (L/P) ratio was significantly lower in the FPSA group than the ALF group 5 hours after surgery, before any significant difference in ICP was detected. Indeed, significant changes in the L/P ratio could be observed within 1 hour of treatment. Glutamine levels were significantly lower in the FPSA group than the ALF group between 6 hours and 10 hours after surgery.

CONCLUSIONS

Brain lactate/pyruvate ratio and concentration of glutamine measured by cerebral microdialysis reflected the beneficial effects of FPSA treatment on cerebral metabolism more precisely and rapidly than ICP in pigs with fulminant ALF. The role of glutamine as a marker of the efficacy of FPSA treatment for ALF appears promising, but needs further evaluation.

Analytical methods for brain targeted delivery system in vivo: perspectives on imaging modalities and microdialysis

Since the introduction of microdialysis in 1974, the semi-invasive analytical method has grown exponentially. Microdialysis is one of the most potential analysis technologies of pharmacological drug delivery to the brain. In recent decades, analysis of chemicals targeting the brain has led to many improvements. It seems likely that fluorescence imaging was limited to ex vivo and in vitro applications with the exception of several intravital microscopy and photographic imaging approaches. X-ray computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) have been commonly utilized for visualization of distribution and therapeutic effects of drugs. The efficient analytical methods for studies of brain-targeting delivery system is a major challenge in detecting the disposition as well as the variances of the factors that regulate the substances delivery into the brain. In this review, we highlight some of the ongoing trends in imaging modalities and the most recent developments in the field of microdialysis of live animals and present insights into exploiting brain disease for therapeutic and diagnostics purpose.

Improving the recovery of S100B protein in cerebral microdialysis: implications for multimodal monitoring in neurocritical care

INTRODUCTION

Cerebral microdialysis is an established research tool that is used by an increasing number of neurocritical care units as a component of bedside multimodality monitoring. Body fluid biomarkers are an emerging tool for the assessment of brain injury. The correct interpretation of body fluid biomarker levels depends on the degree of recovery, i.e. relative recovery and the accuracy of the analytical technique.

METHODS

In vitro recovery experiments were performed on 100mL volumes of cerebrospinal fluid and solutions of S100B, glucose, lactate and pyruvate comparing relative recoveries using commercially available 20 kDa (CMA70) and 100 kDa (CMA71) microdialysis catheters. We also compared the CMA 600 microdialysis analyzer with a YSI 2003 STAT Plus analyzer for glucose and lactate to determine its reliability.

RESULTS

Significantly, we demonstrate the improved recovery of the protein S100B using a larger molecular weight (MW) cut-off catheter (20 kDa range: 0.1-9%; 100 kDa range: 1.7-18.3%) while maintaining comparable performance for the conventional markers glucose, lactate and pyruvate. Additionally we found that the CMA 600 analyzer may be prone to overestimation of lactate readings at higher concentration with implications for clinical decision-making.

CONCLUSION

Our data demonstrates that the 100 kDa MW cut-off catheter allows for the improved recovery of macromolecules in cerebral microdialysis research while maintaining the value of existing MD data for routine clinical use.