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Intracerebral microdialysis in neurointensive care : the use of urea as an endogenous reference compound

Ronne-Engström, E; Cesarini, K G; Enblad, P; Hesselager, G; Marklund, N LU ; Nilsson, P; Salci, K; Persson, L and Hillered, L (2001) In Journal of Neurosurgery 94(3). p.397-402
Abstract

OBJECT: When evaluating the results of intracerebral microdialysis, the in vivo performance of the microdialysis probe must be considered, because this determines the fraction of the interstitial concentration obtained in the microdialysis samples. The in vivo performance is dependent on several factors, for example, the interstitial compartment's diffusion characteristics, which may vary during the course of the acute brain injury process. In the present study the authors investigated the method of controlling the in vivo performance by using urea, which is evenly distributed in all body fluid compartments, as an endogenous reference compound and by comparing the urea levels in three compartments: the brain (CNS), abdominal... (More)

OBJECT: When evaluating the results of intracerebral microdialysis, the in vivo performance of the microdialysis probe must be considered, because this determines the fraction of the interstitial concentration obtained in the microdialysis samples. The in vivo performance is dependent on several factors, for example, the interstitial compartment's diffusion characteristics, which may vary during the course of the acute brain injury process. In the present study the authors investigated the method of controlling the in vivo performance by using urea, which is evenly distributed in all body fluid compartments, as an endogenous reference compound and by comparing the urea levels in three compartments: the brain (CNS), abdominal subcutaneous tissue (SC), and blood serum (BS).

METHODS: Sixty-nine patients with traumatic brain injury or cerebrovascular disease were included in the study. In 63 of these patients a CNS probe was used, an SC probe was used in 40, and both were used in 34. Urea was measured by enzymatic methods, at bedside for the microdialysis samples and in routine clinical laboratory studies for the BS samples, with the probe calibrated to give identical results. The correlation coefficient for CNS/SC urea was 0.88 (2414 samples), for CNS/BS urea it was 0.89 (180 samples), and for SC/BS urea it was 0.98 (112 samples).

CONCLUSIONS: Urea levels in the CNS, SC, and BS were highly correlated, which supports the assumption that urea is evenly distributed. The CNS/SC urea ratio can therefore be used for monitoring the CNS probe's in vivo performance. Fluctuations in other substances measured with microdialysis are probably caused by biological changes in the brain, as long as the CNS/SC urea ratio remains constant.

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author
publishing date
type
Contribution to journal
publication status
published
keywords
Adipose Tissue, Adult, Aged, Arterial Occlusive Diseases, Body Fluid Compartments, Brain Chemistry, Brain Injuries, Brain Ischemia, Cerebral Hemorrhage, Traumatic, Critical Care, Female, Humans, In Vitro Techniques, Linear Models, Male, Microdialysis, Middle Aged, Monitoring, Physiologic, Point-of-Care Systems, Reference Standards, Urea, Clinical Trial, Journal Article, Research Support, Non-U.S. Gov't
in
Journal of Neurosurgery
volume
94
issue
3
pages
6 pages
publisher
American Association of Neurosurgeons
external identifiers
  • scopus:0034859556
ISSN
0022-3085
DOI
10.3171/jns.2001.94.3.0397
language
English
LU publication?
no
id
d1cde7bf-5a5c-43ae-ba15-ac6923069dee
date added to LUP
2018-03-01 10:35:16
date last changed
2018-03-04 05:09:06
@article{d1cde7bf-5a5c-43ae-ba15-ac6923069dee,
  abstract     = {<p>OBJECT: When evaluating the results of intracerebral microdialysis, the in vivo performance of the microdialysis probe must be considered, because this determines the fraction of the interstitial concentration obtained in the microdialysis samples. The in vivo performance is dependent on several factors, for example, the interstitial compartment's diffusion characteristics, which may vary during the course of the acute brain injury process. In the present study the authors investigated the method of controlling the in vivo performance by using urea, which is evenly distributed in all body fluid compartments, as an endogenous reference compound and by comparing the urea levels in three compartments: the brain (CNS), abdominal subcutaneous tissue (SC), and blood serum (BS).</p><p>METHODS: Sixty-nine patients with traumatic brain injury or cerebrovascular disease were included in the study. In 63 of these patients a CNS probe was used, an SC probe was used in 40, and both were used in 34. Urea was measured by enzymatic methods, at bedside for the microdialysis samples and in routine clinical laboratory studies for the BS samples, with the probe calibrated to give identical results. The correlation coefficient for CNS/SC urea was 0.88 (2414 samples), for CNS/BS urea it was 0.89 (180 samples), and for SC/BS urea it was 0.98 (112 samples).</p><p>CONCLUSIONS: Urea levels in the CNS, SC, and BS were highly correlated, which supports the assumption that urea is evenly distributed. The CNS/SC urea ratio can therefore be used for monitoring the CNS probe's in vivo performance. Fluctuations in other substances measured with microdialysis are probably caused by biological changes in the brain, as long as the CNS/SC urea ratio remains constant.</p>},
  author       = {Ronne-Engström, E and Cesarini, K G and Enblad, P and Hesselager, G and Marklund, N and Nilsson, P and Salci, K and Persson, L and Hillered, L},
  issn         = {0022-3085},
  keyword      = {Adipose Tissue,Adult,Aged,Arterial Occlusive Diseases,Body Fluid Compartments,Brain Chemistry,Brain Injuries,Brain Ischemia,Cerebral Hemorrhage, Traumatic,Critical Care,Female,Humans,In Vitro Techniques,Linear Models,Male,Microdialysis,Middle Aged,Monitoring, Physiologic,Point-of-Care Systems,Reference Standards,Urea,Clinical Trial,Journal Article,Research Support, Non-U.S. Gov't},
  language     = {eng},
  number       = {3},
  pages        = {397--402},
  publisher    = {American Association of Neurosurgeons},
  series       = {Journal of Neurosurgery},
  title        = {Intracerebral microdialysis in neurointensive care : the use of urea as an endogenous reference compound},
  url          = {http://dx.doi.org/10.3171/jns.2001.94.3.0397},
  volume       = {94},
  year         = {2001},
}