Ultrastructural alterations in myocardial, pulmonary and cerebral tissues after resuscitation by closed chest cardiopulmonary bypass (CPB)

Objective

To observe ultrastructural changes in myocardial, pulmonary and hippocampal tissues after resuscitation by closed chest CPB with mild and deep hypothermia following 15 min cardiac arrest in dogs.

Methods

After 15 min cardiac arrest by KCl-induced 10 dogs were resuscitated with the use of mild hypothermia (33–34°C) chest closed CPB in group 1 (n = 5) and with deep hypothermia (26–27°C) in group 2 (n = 5). The mean arteral pressures were maintained higher than 80 mmHg during CPB. The hippocampal, myocardial and pulmonary tissues were studied by light and electromicroscopy after 3 hours of CPB in group 1 and in group 2, in group 3 (n = 3) which was controlled after 15 min cardiac arrest.

Results

There are no significantly pathological injury in group 3. The numbers of oligodendrocytes at the light microscopy level were 4.6 ± 0.9 in group 1, less than 13.6 ± 5.2 in group 2 (P < 0.01) and 8.3 ± 4.7 in group 3. The average diameters of nuclei of oligodendrocytes at electromicroscopy were 4.563 ± 1.035 μm in group 3, more than 3.944 ± 0.90 μm in group 2 (P < 0.05) and less than 5.086 ± 0.80 μm in group 1 (P < 0.05), in group 1 more than in group 2 (P < 0.01).

In group 1, the broken cell membranes, the swollen nuclei and mitochondria in oligodendrocytes were found by electromicroscopy, whereas the cell membranes and nuclei were intact in group 2. In group 2, intra-aoveolar pulmonary surfactants showed by electromicroscopy were increased, whereas in group 1 were decreased. The swollen endoplasmic reticulum in type II pulmonary epithelial cells were found, and pulmonary vascular endothelium were showed weak intercellular connections in group 1, but in group 2 were closed. In group 2, the smaller and structurally altered mitochondrial, the thinned and fragmentation of myogenic fibrils, decrease of content in glycogen granules in the swollen myocardial cell were found, but in group 1 were no significantly pathological future.

Conclusions

The pathological changes were found during reperfusion after 15 min cardiac arrest in dogs. The ultrastructure changes of reperfusion injury in pulmonary and hippocampal tissues was more severe by mild hypothermia CPB than by deep hypothermia CPB, but in myocardial tissues were no significantly injury. This suggests that resuscitation by mild hypothermia CPB with head deep hypothermia or by deep hypothermia CPB with myocardial protection may be more effective after prolong cardiac arrest.