Artikel
Temperature gradient between brain tissue and arterial blood can reflect imbalances between cerebral blood flow, brain tissue oxygenation and brain metabolism
Temperaturdifferenz zwischen Hirngewebe und arteriellem Blut ist Indikator für Imbalance zwischen dem regionalen zerebralen Blutfluss, regionaler Hirngewebsoxygenierung und -metabolismus
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Autoren
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J. Soukup
- Klinik für Anästhesiologie und Operative Intensivmedizin, Martin-Luther-Universität Halle-Wittenberg, Halle/Saale, Deutschland
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A. Rieger
- Kliniken für Anästhesiologie und Neurochirurgie, Klinikum Wolfsburg, Deutschland
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C. Holz
- Klinik für Neurochirurgie, Martin-Luther-Universität Halle-Wittenberg, Halle/Saale, Deutschland
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I. Miko
- Department of Operative Techniques and Surgical Research, University of Debrecen Medical and Health Science Center, Debrecen, Hungary
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N. Nemeth
- Department of Operative Techniques and Surgical Research, University of Debrecen Medical and Health Science Center, Debrecen, Hungary
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M. Menzel
- Kliniken für Anästhesiologie und Neurochirurgie, Klinikum Wolfsburg, Deutschland
| Veröffentlicht: | 11. April 2007 |
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Gliederung
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Objective: The purpose of the present experimental study was to determine the impact of variations of cerebral perfusion pressure (CPP) and concomitant changes of the regional cerebral blood flow (rCBF) on brain temperature (Tbr) and the difference between brain temperature and arterial blood temperature (ΔTbr-a) during periods below the lower autoregulation threshold.
Methods: Nine anaesthetized pigs were subjected to controlled CPP-decrease to assess the lower cerebral autoregulation threshold. A parenchymal ICP-sensor combined with a microthermistor for temperature measurement, a miniaturized Clark-type electrode measuring brain tissue oxygenation (ptiO2), a small flexible intraparenchymal thermodilution probe for measuring rCBF and cerebral microdialysis were inserted carefully in the frontal white matter.
Results: We found a decline of ΔTbr-a starting at CPP below 40 mmHg (rCBF of 20 mL/100g/min; R2=0.696) with mean ΔTbr-a of -0.18±0.06°C followed by a rapid decrease below 20 mmHg CPP (rCBF 10 mL/100g/min; R2=0.11) with a mean ΔTbr-a of -0.40±0.14°C and a negative maximum of -0.88°C. Analyzing the CPP-ptiO2 relationship we found a significant first drop of ptiO2 at CPP 40mmHg (rCBF of 20mL/100g/min; R2=0.845), corresponding to a ptiO2 of about 17.5mmHg. A second break was determined at a CPP below 20mmHg (rCBF 10 mL/100g/min R2=0.276), corresponding to a ptiO2 lower than 4mmHg. A controlled CPP-decrease <20 mmHg lead to a significant increase of the mean extracellular fluid (ECF) lactate (2.4 ±0.7 mmol/l, +90%; p<0.0001). Furthermore, the calculated lactate/pyruvate ratio increased from 18.0±12.0 (baseline) up to 84.0±59 at a CPP below 20 mmHg (p<0.0001).
Conclusions: Analyzing the ptiO2 during controlled CPP-decrease, we found significant breakpoints at a CPP of 40mmHg and 20mmHg, related to an rCBF of 20mL/100g/min and about 10mL/100g/min. Similarly the breakpoints of the temperature difference DTbr-a, inidicated a characteristic increase of DTbr-a in the negative direction up to more than -0.30 °C. The metabolic constellation reflects the process of an anaerobic metabolism as well. DTbr-a can estimate the individual lower cerebral autoregulation threshold and provides further special information about the regional flow metabolism-relationship.
