Severe morphologic changes in the central nervous system (CNS) have been recognized in aucte carbon monoxide (CO) poisoning. These have been usually located in globus pallidus, hippocampus, substantia nigra, cerebral white matter, cortical gray
mattr,
and cerebellum. It is well known that lesions in the CAN are shown both in the globus pallidus and cerebral white matter on neuroradiologic studies using CT or MRI. However we recently experienced two patients of aucte CO poisoning with residual
neurologic sequelae, showing the bilateral lesions in the globus pallidus and substantia nigra on MRI performed 10 to 11 days after acute CO poisoning.
Experimental studies were performed to investigate the correlation between the physiological data, such as duration of CO exposure, change of blood pressure, and terminal carboxyhemoglobin (HbCO) concentration in the blood, and the severities of
pallidal and nigral lesions in acute CO-exposured cats.
Twelve mature cats, weighing 2.7-3.8kg, were exposured to 0.3% CO gas for 95-215 min. using artificial ventilation. The systemic blood pressure and electrocardiogram were monitored continuously during CO exposure. HbCO concentration in the blood
was
analyzed immediatelly when CO exposure was terminated. One to 12 days after CO poisoning, animals were killed and the brain was examined morphologically. Then the correlation between the physiological data and the severities of ischemic change in
the
globus pallidus and substantia nigra was examined. The results were summerized as follows;
1. The duration of CO exposure was ranged from 95 to 215 minutes, and the degree of BP-drop from 14 to 76%. There were various kinds of abnormalities, such as cardiac arrhythmia and ischemic pattern on EKG, and terminal HbCO concentration in the
blood
was ranged from 36 to 79.3%.
2. Morphologically, there was focal necrosis with intense infiltration of macrophages in the globus pallidus pallidus of the remaining 11 cats, the severity of ischemic change was 27.3 to 95.6%. In the substantia nigra of 12 cats, the severity
of
ischemic change was 6 to 88.2%.
3. The severity of ischemic change in the globus pallidus did significantly correlate with the degree of blood pressure drop (r=0.77, p<0.05), but did not correlate with other factors, such as duration of CO exposure and HbCO concentration in
the
blood.
4. The severity of ischemic change in the substantia nigra did significantly correlate with the degree of blood pressure drop (r=0.76, p<0.05), but did not correlate with other factors, such as duration of CO expsure and HbCO concentration in
the
blood.
In this study, it is suggested that systemic hypotenison associated with hypoxia are the main pathogenic mechanism of pallidal and nigral lesions after acute CO poisoning. In the furture, combined with the serial MRI studies, the effects of the
new
therapeutic modalities, such as calcium channel bloing agent and iron chelating agent, may be evaluated with this animal model.
|