光電法による局所脳血液量測定の試み

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The cerebral blood volume (CBV) is considered to be an important parameter in the regulation of the cerebral hemodynamics. However, methodological difficulty in measurement of CBV has not clarified how CBV is changed in pathological condition of the brain. We have devised photoelectric method to measure regional CBV. The sensor of the apparatus consists of three gadgets ; microlamp, photodiode to which infra-red filter is attached, and poly-ethylene catheter with its tip open for intracranial pressure (ICP) measurement. They are pasted with silicon rubber. The sensor is applied on the brain surface to measure the intensity of the optical absorption (OA) of hemoglobin in the brain tissue. OA remained nearly constant despite various degrees of change of cerebral blood flow (CBF) and blood gases.Both GA and ICP increased during vasodilatation induced either by CO_2 inhalation, compression of jugular vein, or intravenous injection of papaverine. In contrast, both of them decreased during vasoconstriction induced either by hyperventilation or severe arterial hypotension.From these results we can conclude that OA may demonstrate changes of CBV.Disadvantages of this method are that absolute CBV and CBV in the depth of the brain tissue are not measured and that the operative field should be kept dark. However, this method has several advantages as the following;1) Regional CBV is continuously measured without radionuclide or specific indicators.2) This method does not require skilled technique.3) This sensor also measured ICP simultaneously.4) The cerebral transit time is measurable by injection of saline or indicators into the right brachial artery.This method will be useful in measurement of CBV which is one of the important factors in pathological condition.By increasing ICP stepwisely on six dogs, CBV was measured continuously by the photoelectric method and CBF by the heat clearance method. CO_2 reactivity was also obtained from changing of CBV following inhalationof 10% CO_2. ICP was gradually elevated up to 130 mmHg by saline infusion through a tube introduced into the cisterna magna.While ICP was below 50 mmHg, neither CBV nor CBF showed any changes. However, when ICP was increased from 50 mmHg to 130 mmHg, CBV showed continuous increase while CBF showed continuous decrease. On the other hand, CO_2 reactivity was completely lost when ICP was more than 110 mmHg, which was thought to be due to vasoparalysis.
日本脳神経外科学会の論文
1978-10-15

光電法による局所脳血液量測定の試み

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