Norihiko Mizukawa

Postoperative hemodynamic and metabolic changes in patients with subarachnoid hemorrhage.

Positron emission tomography was performed using an oxygen-15 gas inhalation technique to measure regional cerebral blood flow, metabolic rate for oxygen, oxygen extraction fraction, and cerebral blood volume in 13 patients with subarachnoid hemorrhage during the period of delayed vasospasm after surgery as well as in 10 volunteers as controls. Compared with the controls, the patients showed decreased hemoglobin concentration and decreased total arterial oxygen content due to postoperative hemodilution. Global reductions in the metabolic rate for oxygen and in the tissue oxygen supply were noted even in the apparently normal cortex of the patients in spite of adequate blood flow and adequate oxygen extraction fraction. In addition, regional reductions in blood flow and in perfusion reserve were seen in the cortical territory corresponding to cerebral vasospasm. Our results indicate that two processes are involved in the pathophysiology of cerebral vasospasm: 1) generalized impairment of oxygen metabolism with a reduced tissue oxygen supply, even in the apparently normal cortex, and 2) additional impairment of regional perfusion in the territory of vasospasm.

Effect of hemodilution on cerebral hemodynamics and oxygen metabolism.

Background and Purpose To evaluate the effects of hemodilution on cerebral hemodynamics and oxygen metabolism in the normal human brain, we measured regional cerebral blood flow, oxygen extraction fraction, oxygen metabolic rate, and regional cerebral blood volume in eight normal volunteers before and after hemodilution using positron emission tomography and oxygen-15–labeled gas inhalation technique. Summary of Report Hemodilution was accomplished by phlebotomy of 400 ml and drip infusion of 500 ml low molecular weight dextran, which reduced hematocrit from 42.5% to 37.2% and arterial oxygen content from 19.1 to 16.9 ml/dl (both p < 0.005). It also increased mean cerebral blood flow from 45.2 to 47.7 ml/100 ml/min (p < 0.025), but decreased tissue oxygen delivery from 8.7 to 8.0 ml/100 ml/min (p < 0.05) and cerebral blood volume from 4.9% to 4.6% (p < 0.025) in the overall cortical gray matter. Conclusions Our results indicate that hemodilution in the tested range does not improve oxygen transport or tissue oxygenation in the normal human brain, although it increases cerebral blood flow.

Positron emission tomographic studies on cerebral hemodynamics in patients with cerebral contusion.

Positron emission tomography is currently one of the most useful methods for measurements of cerebral hemodynamics and oxygen metabolism, because it facilitates accurate analysis of the local cerebral circulation in three-dimensional quantitative images. In this study, we performed positron emission tomography studies to measure cerebral circulation in a total of 11 patients who sustained head injuries with contusion. Several parameters were measured including regional cerebral blood flow, regional cerebral blood volume, permeability, and regional cerebral metabolic rate for oxygen. Data from brains both with and without contusion were analyzed for chronological changes, in the subacute stage from the 8th to 29th day and in the chronic stage until 360 days after the injury and compared with similar data in a group of normal subjects. It was concluded that in the subacute stage, regional cerebral blood flow decreased (26 +/- 7 and 39 +/- 10 ml/100 g/min) and regional cerebral blood volume increased (5.6 +/- 1.8 and 5.4 +/- 0.9 ml/100 g) both in areas of cerebral contusion and in areas remote from cerebral contusion and that permeability increased in areas of contusion but not in remote brain areas. In the chronic stage, these parameters showed a tendency for recovery.

Thiobarbituric acid reactive substances and vitamin E in serum and cerebrospinal fluid from patients with cerebral apoplexy

Thiobarbituric acid (TBA) reactive substances in serum and cerebrospinal fluid from patients with cerebral apoplexy were determined and their relationship to this disease was studied. TBA reactants in serum were elevated in patients with cerebral apoplexy, but there was no difference between patients with brain tumor or other neurological disease and healthy persons. TBA reactants in cerebrospinal fluid in patients with cerebral aneurysm, cerebral arterial and venous anomalies or intracerebral hematoma, and its levels in patients with cerebral infarction or brain tumor were also higher than in healthy persons. Serum alpha-tocopherol levels were elevated in patients with cerebral infarction, but were relatively low in patients with cerebral aneurysm, cerebral arterial and venous anomalies or intracerebral hematoma. The reverse was the case with cerebrospinal fluid levels of alpha-tocopherol. That is, the sequence of decreasing level of alpha-tocopherol in cerebrospinal fluid was intracerebral hematoma, cerebral aneurysm, cerebral arterial and venous anomalies, and cerebral infarction. The levels of TBA reactive substances in patients with cerebral apoplexy showed a positive correlation between serum and cerebrospinal fluid, and the levels of alpha-tocopherol showed a similar correlation.

Hemodynamic and Metabolic Studies of Patients with Normal Pressure Hydrocephalus Using Positron Emission Tomography

We performed positron emission tomography (PET) to investigate the pathophysiology of cerebral dysfunction in 5 preoperative patients with normal pressure hydrocephalus (NPH) and ascertain hemodynamic and/or metabolic parameters which predict surgical outcome. Regional cerebral blood flow (CBF), oxygen extraction fraction (OEF), oxygen metabolic rate (CMRO2) and regional blood volume throughout the cortex and in the periventricular white matter were measured using oxygen-15 labelled gas inhalation technique. All patients subsequently underwent ventriculo-peritoneal shunting, but only three improved after shunting.

Causal Factors of Shunt Revisions: With special reference to frequent and immediate revisions

In our institution, 50 children with nontumoral hydrocephalus received ventriculoperitoneal shunt between January 1970 and June 1987. Among them, 38 children received 75 revisions. We analysed the causal factors of the shunt revisions, which were performed in the short Open image in new window period (within 6 months) after preceding operations and were performed frequently (more than 4 times).

Causal Factors of Shunt Revision in Nontumoral Hydrocephalus

Although ventriculoperitoneal shunt is common as the surgical procedures for hydrocephalus, shunt revisions due to their malfunctions and/or complications are frequent. We analysed the causal factors of shunt revision for nontumoral hydrocephalus in our institution. From 1970 to 1985, 73 children with nontumoral and tumoral hydrocephalus received cerebrospinal fluid shunt operation in which 37 cases (50.7%) had shunt revisions. As to nontumoral hydrocephalus, 31 cases (73.8%) of 42 had shunt revisions, of which the total was 63.

腎血流量と糸球体ろ過率: C15O, 68Ga-ethylenediaminetetraacetic acid (EDTA) による検討

68Ga-EDTA (ethylenediaminetetraacetic acid) is simply and economically obtained without a cyclotron. We used renal blood volume (RBV) values obtained by C15O studies for blood activity subtraction on renal time activity curves using a positron emission tomography for the determination of the glomerular filtration rate (GFR) by intravenous 68Ga-EDTA administration. Positive correlation was revealed between the GFR and RBV values, where the ratio of blood activity in whole renal activity increased relatively as GFR value decreased. The estimation using a correction equation derived from the correlation curve was possible without a C15O study.