Lactate in rat skeletal muscle after hemorrhage measured by microdialysis probe calibrated in situ

Monitoring systems and quantitative measurement of biomolecules for the management of trauma

Continued high morbidity and complications due to trauma related hemorrhage underscores the fact that our understanding of the detailed molecular events of trauma are inadequate to bring life-saving changes to practice. The current state of efficacy and advances in biomedical microdevice technology for trauma diagnostics concerning hemorrhage and hemorrhagic shock was considered with respect to vital signs and metabolic biomarkers. Tachycardia and hypotension are markers of hemorrhagic shock in decompensated trauma patients. Base deficit has been predicative of injury severity at hospital admission. Tissue oxygen saturation has been predicative of onset of multiple organ dysfunction syndrome. Blood potassium levels increase with onset of hemorrhagic shock. Lactate is a surrogate for tissue hypoxia and its clearance predicts mortality. Triage glucose measurements have been shown to be specific in predicting major injuries. No vital sign has yet to be proven effective as an independent predictor of trauma severity. Point of care (POC) devices allow for rapid results, easy sample preparation and processing, small sample volumes, small footprint, multifunctional analysis, and low cost. Advances in the field of in-vivo biosensors has provided a much needed platform by which trauma related metabolites can be monitored easily, rapidly and continuously. Multi-analyte monitoring biosensors have the potential to explore areas still undiscovered in the realm of trauma physiology.

Overview of brain microdialysis

The technique of microdialysis enables sampling and collecting of small-molecular-weight substances from the interstitial space. It is a widely used method in neuroscience and is one of the few techniques available that permits quantification of neurotransmitters, peptides, and hormones in the behaving animal. More recently, it has been used in tissue preparations for quantification of neurotransmitter release. This unit provides a brief review of the history of microdialysis and its general application in the neurosciences. The authors review the theoretical principles underlying the microdialysis process, methods available for estimating extracellular concentration from dialysis samples (i.e., relative recovery), the various factors that affect the estimate of in vivo relative recovery, and the importance of determining in vivo relative recovery to data interpretation. Several areas of special note, including impact of tissue trauma on the interpretation of microdialysis results, are discussed. Step-by-step instructions for the planning and execution of conventional and quantitative microdialysis experiments are provided.

Overview of microdialysis

The technique of microdialysis enables the monitoring of neurotransmitters and other molecules in the extracellular environment. This method has undergone several modifications and is now widely used for sampling and quantitating neurotransmitters, neuropeptides, and hormones in the brain and periphery. This unit describes the principles of conventional and quantitative microdialysis as well as strategies in designing a dialysis experiment. It establishes the groundwork for the basic techniques of preparation, conduct, and analysis of dialysis experiments in rodents and subhuman primates. Although the methods described are those used for monitoring CNS function, they can be easily applied with minor modification to other organ systems.