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- Open Access
Cross-correlation analysis of blood and microdialysis-assessed tissue lactate monitoring: a study in critically ill septic patients
© Ilias et al.; licensee BioMed Central Ltd. 2012
- Published: 20 March 2012
- Septic Shock
- Septic Patient
- Blood Lactate
- Septic Shock Patient
- Critical Care Setting
In the critical care setting, blood lactate (BL) concentration is measured to assess - albeit indirectly - tissue oxygenation. In addition, serial BL measurements are clinically useful since a drop in BL is a good prognostic finding, whereas persistent BL elevation portends poor outcome. Microdialysis (MD) enables direct monitoring of tissue metabolic changes. This study aimed to describe the dynamics of MD-assessed tissue lactate (TL) vis-à-vis BL in septic patients with and without shock.
We measured BL and thigh adipose tissue TL serially every 4 hours for 6 days in 88 patients with septic shock and 45 patients at various sepsis stages hospitalized in a tertiary-care hospital ICU. Analysis was done with measurement of the area under the curve (AUC) of lactate*hours, cross-approximate entropy (X-ApEn) and cross-correlation. Comparisons of septic shock versus nonseptic shock patients' results were done with t tests and z statistics.
BL and TL were higher in septic shock patients compared to nonseptic shock patients (AUCs of 276 vs. 176 and 355 vs. 273 mmol/l*hours, respectively; Welch's t test: P < 0.0001). X-ApEn for MDL/BL was lower in septic shock patients compared to those without septic shock (mean ± SD: 0.79 ± 0.12 vs. 1.14 ± 0.13, respectively; t test: P < 0.0001). Cross-correlation of TL versus BL was stronger in septic shock patients, with TL leading BL by 4 hours compared to TL versus BL with no lag time (r = +0.85, P < 0.0001 and r = +0.66, P < 0.0001, respectively) than in nonseptic shock patients (r = +0.58, P = 0.0003 with TL leading BL by 4 hours and r = +0.66, P < 0.0001 with no lag time; z statistic = 2.41 and P = 0.016 for leading BL compared to z statistic = 0.036, P = 0.971 for no lag time).
In septic shock patients, tissue lactate levels - measured by MD - are higher compared to nonseptic shock patients. Furthermore, TL is better correlated with and precedes - within 4 hours - BL in septic shock patients compared to nonseptic shock patients. Further studies are warranted to assess the clinical value of serial TL monitoring.
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.