Microdialysis-assessed adipose tissue metabolism in critically ill patients

Background: Microdialysis is a minimally invasive technique that allows direct in situ and in vivo sampling, studies and manipulations of the interstitial/extracellular fluid/space. It has been shown to be of use mainly in acute brain injury/neurocritical care. Methods: Microdialysis has been used to study obesity, diabetes mellitus, inflammation and pharmacokinetics at the adipose tissue level. In critically ill patients (and particularly in those with sepsis or septic shock), within days to weeks, adipose tissue shows profound alterations; under such conditions, the implementation of microdialysis can provide researchers with interesting findings. Results: The well-known association between lipolysis and cortisol has been verified at the tissue level with microdialysis. Specific metabolic aberrations in critically ill patients with septic shock have been noted in adipose tissue-assessed with microdialysis before becoming evident in the systemic circulation. Measurement of the lactate to pyruvate ratio in adipose tissue-also assessed with microdialysis-in patients with septic shock has prognostic value equal to that of universally accepted clinical severity scores. Conclusion: Microneedle arrays have been already used to assess interstitial fluid glucose. Possibly, the implementation of microneedle and lab-on-a-chip technology, might complement the current use of microdialysis in the study of the interstitial space/adipose tissue metabolism in health and disease.