Stereoscopic study on capillary density of early brain oedema in a dog postburn model.
BACKGROUND
After severe burn, the effective circulating blood volume decreases drastically due to massive body fluid loss, and blood redistribution occurs to maintain sufficient blood supply to vital organs. Blood perfusion of brain tissue changes and the permeability of the blood brain barrier increases due to ischaemia and hypoxia, which results in brain oedema. The goal of this study was to explore the changes of cerebral blood flow during the brain oedema at the early stage of severe burn.


METHODS
Twenty-six dogs were randomly divided into control and 6, 12, 18, and 24 PBH groups. The manifestation of MRI and histopathology, changes of brain water content were investigated; the shapes and distribution of the cerebral capillaries were observed with the endogenous AKP histochemical staining method and image analysis technique. The volume, surface, and length fractions of cerebral capillaries were tested and analysed with a stereographic method in each group, respectively.


RESULTS
The earliest changes of cerebral oedema were found at 12 PBH with MRI, which showed the brain swelling as characteristic of cerebral morphological changes. The decrease of SIR on T(1)WI was not observed until it was above 10%. Signal of T(2)WI increased for 8.29% at 24 PBH. Histological changes were observed as early as 6h after burn, accompanied by swelling of endothelial cells and peri-vascular astrocytes, vacuolation took place in neurons at 12h after burn, necrosis of different degrees in capillary endothelium, neurons, and axons. Increase in cerebral water content was noted at 6h postburn, and it was the most marked in 24 postburn group.The distributional density of capillaries became thicker at 6h and 12h postburn, the shapes were normal. The capillaries became sparser at 18h, and almost disappeared from view, only a few ends of capillaries in the shape of vine were seen at 24h postburn. The percentages of capillary volume, surface, and length fractions were increased at 6h and 12h, but decreased at 18h and reached the lowest point at 24h postburn (P<0.05).


CONCLUSIONS
We suggest that the changes of cerebral blood flow might play an important role in the pathogenesis of brain oedema in the early stage of severe burn.
Li
Hai-tao
HT
Department of Radiology, Southwesernt Hospital, Third Military Medical University, 30 Gao Tanyan Street, Chongqing, China. liihaitao@yahoo.com.cn
Ying
Da-jun
DJ
He
Xiao-chuan
XC
Sun
Jian-sen
JS
Chen
Lin
L
D000818:Animals; D001834:Body Water; D001921:Brain / Q000098:blood supply* / Q000473:pathology; D001923:Brain Chemistry; D001929:Brain Edema / Q000209:etiology / Q000473:pathology*; D002056:Burns / Q000150:complications*; D002196:Capillaries / Q000473:pathology; D002560:Cerebrovascular Circulation / Q000502:physiology; D004285:Dogs; D008279:Magnetic Resonance Imaging; D008297:Male