Abstract
The no-reflow phenomenon (NRP) after cerebral ischemia has been proposed as a factor limiting brain recovery. However, there have been other reports which denied the occurrence of the NRP. The purpose of this study is to reinvestigate the presence or absence of the NRP after circulatory arrest by using strict quantitative analysis.
Nineteen adult mongrel dogs were used. Circulatory arrest was accomplished by occluding the ascending aorta for 15 minutes. The patency of cerebral microvasculature was assessed by carbon black perfusion study. The perfusion was performed without circulatory arrest (control; 6 dogs) and either immediately after releasing the circulatory arrest (group A; 7 dogs) or after reestablishment of normal blood pressure for 15 minutes (group B; 6 dogs).
In order to judge the presence or absence of the NRP quantitatively, a modification of Mitchell's point counting method was used. All the vessels under 10 μ in diameter were traced with × 125 magnification. Then, points counting screen tone, which had 500 points in 25 cm2 of areas, was overlied on the traced vessels. The number of points lying on vessels were counted. The ratio of the number to 500 was calculated and expressed as a percentage which was termed “The Density of Minute Blood Vessels (DMBV)” (Fig. 2). Samples for the calculation were taken from 15 regions as shown in Fig. 3. The calculation was made five times in each region. The results were compared in 3 groups.
In the control, it was shown quantitatively that the DMBV varied from one region to another over a wide range. The maximum DMBV was observed in the inferior colliculus. The minimum DMBV was recognized in the anterior hypothalamus. However, the standard deviation of the mean in the each region in the control was very small. Its value was 1.3 to 4.8% (average; 3.1%) (Fig. 5). The DMBV of the group A was significantly smaller than that of the control (p<0.01-0.05) (Fig. 6), but there was no difference of the DMBV between the control and the group B (Fig. 7). The MABP (mean arterial blood pressure) at the carbon black perfusion was 84 (±S.D. 24) mmHg in the control, 25 (±20) mmHg in the group A and 103 (±26) mmHg in the group B (Fig. 8).
On the basis of the above data, in order to discuss the presence or absence of the NRP using carbon black perfusion study, it is absolutely necessary to use quantitative method. And also the comparison must be made in the same region. By using this method, it was clarified that the NRP is present right after the circulatory arrest, but it is reversible if the sufficient recirculation is established within short period of time.
