Regional Cerebral Blood Flow and Brain Edema Responses to Continuous Versus Intermittent Brain Retraction

Cho, Byeong Il; Koo, Jung Chul; Lee, Sang Won; Park, Young Sup; Kim, Young; Park, Chun Kun; Kim, Moon Chan; Youn, Suck Hoon; Kang, Joon Ki; Song, Jin Un; Chang, Sang Keun

Abstract

Retraction of any part of the brain may damage the cortex as well as the parenchyma, so it is advisable to retract the brain with the least force necessary and for the shortest time as possible. The purpose of this study was to examine in cats the damage caused by retraction of the brain by measuring the regional blood flow and brain edema, and to determine which of two methods, continuous or intermittent brain retraction, is less harmful to the brain. Twenty five adult cats weighting 2.5 to 4.0Kg, were used in this study. The twenty five cats were divided into three groups ; control (n=5), continuous retraction (n=10) and intermittent retraction groups (n=10) respectively. The brain retraction was produced by applying the lead weight with the stainless retractor on the right frontal lobe through a craniectomy at the right frontal bone. The weight (20g) was supported throught the pulley so that its long axis was perpendicular to the cortical surface. In the continuous retraction group, the brain was retracted for 180 min with a retraction force of 20g and in the intermittent retraction group, a 15 min period of retraction was applied, followed by a 5 min release, repeated nine times. The regional cerebral blood flow (rCBF) and brain specific gravity measurements were carried out in each animal before and immediately after brain retraction, at the 30th min, 60th min, 90th min, 120th min, 150th min and 180th min after retraction. The rCBF was measured by hydrogen clearance method and the brain edema was measured by gravimetric technique. The results were as follows : 1) After the brain retraction, there were rise in blood pressure and bradycardia in 60 min. 2) Normal control cerebral blood flow (rCBF, ml/100g/min) were 38.7+/-1.9 in right frontal, 38.7+/-1.7 in left frontal, 38.6+/-2.3 in right parietal and 38.2+/-2,3 in left parietal lobes. 3) A considerable reduction in rCBF at the retraction site, has been demonstrated with continuous brain retraction in 60 min after retraction. A reduction in rCBF to 30% of control (RF ; 28.2+/-2.1ml/100g/min) in 180 min after continuous retraction of the right frontal lobe, however, intermittent retraction resulted in a reduction of flow to 12% of control(RF ; 37.5+/-2.9ml/100g/min) at retraction site in 180 min after retraction. 4) The changes of brain specific gravity relatively began to notice at rCBF less than 23.0ml/100g/min. It might be inferred from these that intermittent retraction was less harmful to the brain, which indicate adequate arterial blood flow under the retractor was vital for the preservation and return of the neuronal function following brain retraction.