Mean CBF Research Articles

29: Cerebral metabolism during starvation in infant and adult rats and the effect of int'rauterine growth retardation (IUG-R)

Cerebral blood flow (CBP) was measured with radioactive microspheres in 20 days old IUGR rats, normal littermates and adult rats. Cerebral a-v diff. of acetoacetate (AcAc), D-β-hydroxybutyrate (βHBA), glucose, lactate, oxygen and brain DNA content were determined in other corresponding groups of similarly treated animals. Mean CBF values of 0.48±0.04 and 0.62±0.07 ml/gxmin(± SEM) in infant and adult rats resp. were not sign. diff. CBF was unaffected by starvation and was not diff. between IUGR and normal littermates. Cerebral uptake of ketone bodies (umol/mg DNAxmin) was higher in infant than adult rats during starvation. Cerebral uptake ofβHBA was higher in controls than in IUGR rats after 48 h. of starvation. Uptake of glucose was not diff. between infant and adult rats or between IUGR and normal, littermates. Arterial blood glucose was sign, lower in 48 h. starved IUGR rats than controls. Cerebral uptake of oxygen was lower in infant than adult rats and also lower in IUGR than normal littermates during starvation. The average percentage of the total cerebral uptake of substrate (mmol/min) accounted for by ketone bodies was 15.2, 25.7 and 41.0 % resp. in adult rats, 20 days old IUGR and normal littermates. Conclusion: l) Ketone bodies are more important substrates for the brain in 20 days old than adult rats during starvation. 2) Cerebral utilization of ketone bodies is reduced in 20 day IUGR rats compared to normal littermates suggesting greater sensitivity to starvation.

Whole-brain blood flow and oxygen metabolism in the rat after halothane anesthesia.

A recent modification of the Kety-Schmidt wash-out technique for 133xenon was used to measure whole-brain blood flow (CBF) and oxygen consumption (CMRO2) 1 to 4 hours after termination of halothane anesthesia in 15 Wistar rats. In this 3-hour experimental period, mean CBF and CMRO2 were reduced to 29 and 43% of control values, respectively. CBF and CMRO2 determined at the beginning and end of the experimental period were not significantly different from each other. Cerebral venous O2 tension was significantly higher than in the control group, supporting recent suggestions of a primary, intrinsic effect of halothane on the homeostatic control of this variable. It is concluded that halothane is not useful for cerebral metabolic studies in the rat.

Cerebral autoregulation in man.

Autoregulation was tested by regional blood flow (rCBF) and cardiohemodynamic measurements before and after induced systemic arterial hypertension in 16 patients with varying neurological disorders. Hypertension was induced by increasing the arterial blood pressure by an intravenous infusion of Aramine. Seven (Group 1) of the patients had a mean increase in mean arterial pressure (MAP) of 32 mm Hg and had preserved autoregulation while nine (Group 2) with a 56 mm Hg increase in MAP showed complete or mixed loss of autoregulation. Group 1 had a higher baseline mean CBF than did the group with loss of autoregulation. The group with loss of autoregulation also generally had more severe involvement on the cerebral angiogram than did the other. Baseline cardiac index and cardiac work were lower in the group with loss of autoregulation. During Aramine infusion the MAP was increased by 38% in Group 1 and 59% in Group 2. The mean CBF was essentially unchanged in Group 1 but increased 24% in Group 2. When autoregulation is lost, rCBF may increase homogeneously or heterogeneously with some areas increasing while others remained unchanged or even decreased. In four instances there was an intracerebral steal during induced hypertension with a fall in rCBF. Whether or not autoregulation is preserved could be related to: (1) the greater induced increase in MAP in Group 2 than Group 1, (2) greater angiographical involvement with a lower baseline in CBF in Group 2 than in Group 1 or (3) a direct or indirect influence of various cardiovascular factors.

Regional Cerebral Blood Flow in Patients With Hypertensive Intracerebral Hemorrhage

Regional cerebral blood flow was measured by 183 Xe clearance method in 44 patients with hypertensive intracerebral hemorrhage (HIH) within three weeks from attack. Mean CBF in cases with the more disturbed consciousness was the lower value. There was no definite relationship between mean CBF and the duration from last stroke to measurement. In 44 cases, 35 showed hematoma of so-called "lateral type" and nine showed a "mesial type." There was no difference of mean CBF between these two groups. In the group with lateral-type hematoma, 14 cases were thought to show large space-occupying signs, and their mean CBF was significantly lower than that of the other 21 cases. In 16 cases, relative hyperemic regions were observed in both the focal and nonfocal areas. In seven cases, relative ischemic regions were frequently in nonfocus rather than focus. Response of hyperemic region to carbon dioxide was good in seven and poor in three regions in focal area, and was good in eight and poor in one region in nonfocal area. Reactivity of ischemic region to 5% CO 2 inhalation was good in three and poor in zero regions in focus, and was good in three and poor in two regions in nonfocus. Early venous filling (EVF) was observed in 13 cases and all of them were with lateral-type hematomas. Only four out of 13 cases showed good correlation between angiographical findings and cerebral circulation.

Regional cerebral blood flow in patients with hypertensive intracerebral hemorrhage.

Regional cerebral blood flow was measured by 133 Xe clearance method in 44 patients with hypertensive intracerebral hemorrhage (HIH) within three weeks from attack. Mean CBF in cases with the more disturbed consciousness was the lower value. There was no definite relationship between mean CBF and the duration from last stroke to measurement. In 44 cases, 35 showed hematoma of so-called "lateral type" and nine showed a "mesial type." There was no difference of mean CBF between these two groups. In the group with lateral-type hematoma, 14 cases were thought to show large space-occupying signs, and their mean CBF was significantly lower than that of the other 21 cases. In 16 cases, relative hyperemic regions were observed in both the focal and nonfocal areas. In seven cases, relative ischemic regions were frequently in nonfocus rather than focus. Response of hyperemic region to carbon dioxide was good in seven and poor in three regions in focal area, and was good in eight and poor in one region in nonfocal area. Reactivity of ischemic region to 5% CO 2 inhalation was good in three and poor in zero regions in focus, and was good in three and poor in two regions in nonfocus. Early venous filling (EVF) was observed in 13 cases and all of them were with lateral-type hematomas. Only four out of 13 cases showed good correlation between angiographical findings and cerebral circulation.

CORRECTION

An error appeared in the abstract of the article "The Relationship of Regional Cerebrovascular CO 2 Reactivity to Blood Pressure and Regional Resting Flow" by Robert H. Ackerman, M.D., which appeared in STROKE, volume 4, page 725 (September-October) 1973. The following is the corrected abstract. Cerebrovascular CO 2 reactivity (the change in cerebral blood flow per mm Hg change in Pa CO CO 2 ) is shown to be directly related to resting flow and inversely related to blood pressure for regional as well as for mean CBF data. Both regional and mean CO 2 reactivity therefore are proportional to the ratio resting flow/blood pressure. This ratio is the reciprocal of resistance and may be called conductance . When regional CO 2 reactivity for 428 cerebral areas is plotted against an approximation of regional conductance, the data describe positive linear relationships similar to those found when mean CO 2 reactivity is plotted against mean conductance. These relationships can be demonstrated whether CO 2 reactivity is calculated with specific or percent change in flow. The data suggest that under physiological conditions CO 2 reactivity is related to the basal tone of the cerebrovascular bed. The way in which CO 2 reactivity relates to conductance, therefore, may be a more reliable index of the integrity of the cerebrovascular CO 2 response than the CBF change per se. Analysis of CO 2 reactivity as a function of conductance may facilitate the interpretation of mean and regional CO 2 reactivity and may provide a more meaningful basis for comparison of the CO 2 response between individuals.

The relationship of regional cerebrovascular CO2 reactivity to blood pressure and regional resting flow.

Cerebrovascular CO 2 reactivity (the change in cerebral blood flow per mm Hg change in Pa co co 2 ) is shown to be directly related to resting flow and inversely related to blood pressure for regional as well as for mean CBF data. Both regional and mean CO 2 reactivity therefore are proportional to the ratio resting flow/blood pressure. This ratio is the reciprocal of resistance and may be called conductance . When regional CO 2 reactivity for 428 cerebral areas is plotted against an approximation of regional conductance, the data describe positive linear relationships similar to those found when mean CO 2 , reactivity is plotted against mean conductance. These relationships can be demonstrated whether CO 2 reactivity is calculated with specific or percent change in flow, the data describe positive linear lerationships similar to those found when mean CO 2 basal tone of the cerebrovascular bed. The way in which CO 2 reactivity relates to conductance, therefore, may be a more reliable index of the integrity of the cerebrovascular CO 2 response than the CBF change per se. Analysis of CO 2 reactivity as a function of conductance may facilitate the interpretation of mean and regional CO 2 reactivity and may provide a more meaningful basis for comparison of the CO 2 response between individuals.