人為的低血圧の中枢神経組織に与える影響についての研究 : -第1報,脳微小循環の形態学的研究-

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There is little information as to the safety margin of degree and duration of controlled hypotension. The present study was designed to observe microvascular impairment after profound hypotension induced by sodium nitro-prusside (SNP).Twenty nine adult mongrel dogs were used. All the dogs were anesthetized with halothane, nitrous oxide and oxygen. With the exception of six dogs (control group), the mean arterial blood pressure (MABP) was acutely reduced to 36(±S.D.4)mmHg and was maintained at this level for one hour by infusing SNP.The patency of cerebral microvasculature was assessed by carbon black perfusion study via the thoracic aorta at a pressure of 150 mmHg. The perfusion was performed either after halothane anesthesia alone (6 dogs, control group) or after reestablishment of MABP values for periods of 0〜5 minutes (9 dogs, group-A), of 90 minutes(8 dogs,group-B) and of 7 days (6 dogs, group-C).Symmetrical distribution of grayish-black coloration was apparent macroscopically (Fig.1). However, marked difference in small vessels density in various structures was observed microscopically.In order to measure these differences quantitatively, a modification of Mitchell and Cranston's point counting method was used. All small vessels under 10 μ in diameter were traced with Visopan projecting microscope under × 125 magnification (Fig. 2). Then, points counting screen tone, which has 500 points in 25 cm^2 of area, was overlied on the traced small vessels. The number of points lying on small vessels were counted, and the ratio of points on small vessels to 500 points was calculated and expressed as a percentage which was termed "the frequency distribution of small vessels (FDSV)."The FDSV was calculated at the same 15 structures in the 4 groups mentioned above (Fig.3).Results ;1) The FDSV in the control group varied from one structure to another over a wide range. But the standard deviation of the mean for the same structure in this group was small (Fig.4).2) The FDSV of the hypotensive groups (group-A,B,C) was not lower than that of the control group (Fig. 5a,b,c).Conclusions;1) To discuss whether the impaired filling of microvasculature was seen or not after the cerebral ischemia using carbon black perfusion study, the FDSV of the control group and that of the ischemic group must be compared quantitatively by objecting the same structure.2) In adult mongrel dogs, SNP induced hypotension under the halothane anesthesia to a MABP of 36(±S.D.4)mmHg for one hour does not alter the cerebral microcirculation as judged by the present method.
日本脳神経外科学会の論文
1978-07-15

人為的低血圧の中枢神経組織に与える影響についての研究 : -第1報,脳微小循環の形態学的研究-

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