脊髄血液量の自動調節能について—レーザードップラー法と水素クリアランス法による検討

Blood Flow, CO2 Response and Autoregulation in the Rat Spinal Cord by Laser-Doppler Flowmetry and Hydrogen Clearance

　ラットの脊髄血流における自動調節能および炭酸ガス反応性をhydrogen clearance method（HCと略す）およびlaster Doppler flowmetry（LDFと略す）を用い測定し，比較検討した。HCでは正常脊髄血流量は45.0±1.7ml／min／100gであった。HCによる脊髄血流量とLDFの値が正の相関を示し，直線回帰式によりLDFの血流絶対量を求めることが可能であった（Y＝14.2X−1.58，r＝0.78）。この式を用いた正常脊髄血流量は43.7±1.3ml／min／100gであった。炭酸ガス反応性はそれぞれHCでは，1.09ml／min／100g／mmHgで，LDFでは1.01ml／min／100g／mmHgでわずかにLDFが低値を示した。AutoregulationはHCとLDFいずれの方法も平均血圧が55-155mmHgで保たれた。しかしLDFでは脊髄血流絶対値の偏差が若干大きく，血流の変化率を見た相対評価を行うとさらに詳細な分析が可能であった。LDF法も小動物の脊髄血流の客観的な評価が可能であることが示された。

Spinal cord blood flow (SCBF) was measured simultaneously by laser Doppler flowmetry (LDF) and hydrogen clearance (HC) in the normal Wister rats. Under normal physiological condition, SCBF values by HC was 45.0±1.7ml/min/100 g at the level of Th-8. LDF values were well correlated (r= 0.78) to the SCBF measured by HC, where linear regression line was obtained as y=14.2x-1.58. Absolute SCBF values of LDF were also calculated as 43.7±1.3mg/min/100 g using this equation. CO2response of SCBF were 1.09ml/min/100 g/mmHg by HC and 1.01ml/min/100 g by LDF, respectively. Autoregulation of SCBF maintained at a range of 55 -155mmHg of mean arterial pressure in both methods. In conclusion, LDF is a useful technique for continuous SCBF monitoring. Since absolute SCBF value in LDF has some variance, the relative value is more suitable for accurate evaluation of SCBF during time course of an experiment.