微泡空化效应对大鼠骨骼肌微循环的影响

目的观察治疗剂量超声介导的微泡造影剂破坏产生的空化效应对大鼠骨骼肌微循环的影响。方法将30只SD大鼠随机均分为对照组、微泡组、超声组(超声能量为1.5W·cm-2)、高能量超声加微泡组(超声能量为1.5W·cm-2)及低能量超声加微泡组(超声能量为0.75W·cm-2),每组6只,按Gray法制备大鼠脊斜肌活体微循环观察标本,分别在处理前、处理后不同时间测量平均动脉压,用红细胞跟踪相关仪和电视测微仪测量微动静脉口径和血流流速,并用电镜观察大鼠脊斜肌组织结构的变化。结果微泡空化效应对大鼠平均动脉血压和微血管口径无显著变化(P>0.05);微血管血流速度减慢,血流量降低(P<0.05)。微循环血流速度和血流量下降和恢复的程度与超声能量有关,低能量组静脉血流速度及血流量15min左右可明显恢复,动脉血流速度及血流量1h左右可明显恢复,而高能量组2h微动静脉血流速度及血流量均未完全恢复。微泡空化效应能使毛细血管内皮细胞破裂,内皮间隙增宽,红细胞溢出于毛细血管外;2h后未发现内皮破口。结论微泡空化效应对局部微循环及微血管产生损伤跟超声的能量有关,能量越小产生损伤越轻,局部微循环修复的速度越快。

Effect of microbubble cavitation on microcirculation of rat skeletal muscle

Objective To investigate the effect of therapeutic ultrasound-induced microbubble destruction on the microcirculation of rat skeletal muscle.Methods Thirty SD rats were randomized into 5 groups(n=6),namely normal saline,microbubble,ultrasound,high-energy ultrasound microbubble and low-energy ultrasound microbubble groups.Before and after the treatments,the diameter and blood flow velocity in the microvessels in the skeletal muscle were measured,and the structural changes of the injured microvessels observed by electron microscopy.Results Microbubble cavitation did not produce significant effect on the mean arterial pressure and diameter of microvessels in rat skeletal muscle(P>0.05),but the blood flow velocity was obviously lowered and blood flow volume reduced in the microvessels.The reduction of the flow velocity and blood flow volume and their subsequent recovery were associated with ultrasound energy,and in the low ultrasound energy group,the flow velocity and blood flow volume in the of venules recovered obviously after about 15 min,which,however,took approximately 1 h for the arterioles.In contrast,recovery of the flow velocity and blood flow volume in the microvessels took more than 2 h in the high ultrasound energy group.Cavitation resulted in endothelium cell rupture,widening of the endothelial interspace and entry of the red blood cells into the extravascular tissues as revealed by electron microscopy,but no rupture of the lining endothelium was observed 2 h after the treatment.Conclusions Endothelium cell rupture induced by microbubble cavitation may affect the local microcirculation,and lower ultrasound energy exposure is associated with milder endothelial injury and more rapid recovery.