| Objectives:Use the posterior vertebral column resection(PVCR)to establish L3 whole spine removed animal models of spinal shortening with the beagle dogs.In animal models,appling laser doppler blood flow monitor(LDF)measures the change of the exposed spinal cord blood flow(SCBF)in the process of operation period.Based on different degrees of segmental vascular ligation and different degrees of spinal cord shortening,the content of Oxide(Nitric Oxide,NO)and endothelin-1(Endothelin-1,ET-1)in the exposed spinal cord were measured by radioimmunoassay,and immunohistochemical method was used to evaluate the expression of heme oxygenase-1(Heme Oxygenase-1,HO-1)in the exposed spinal cord.On the basis of this study,the changes of blood flow in the spinal cord were studied in different degrees of segmental vascular ligation,total vertebral column resection and different degrees of spinal shortening.At the same time,the changes of nitric oxide(NO),endothelin-1(ET-1)and the expression of heme oxygenase-1(HO-1)in the expored spinal cord of different degrees of segmental vascular ligation and different degrees of spinal shortening were observed.To study the effect of safety range of ligation of segmental vessels,spinal cord shorting and different surgical procedures on the blood flow of spinal cord in order to provide a reference for the clinical practice of PVCR.Methods:The Beagle dogs(mean weight:10.36kg)provided by the Department of animal science of Kunming Medical University were selected as the experimental animals.In the course of the experiment,there were two experimental dogs who failed to make the model(one cases died of anesthetic accident,and one case died of bleeding in operation).All of the animals were completed,and the final experiment was completed in 48 dogs.48 healthy beagle dogs(No.1-48)were randomly divided into A,B,C,D,E,F,G,H eight groups by ligation of the segmental vessels pairs 5 6 beagle dogs each group(body weight,body length,body temperature,preoperative blood pressure,preoperative heart rate,operation time,blood loss,urine volume,fluid volume were recorded).Group A:L3 bilateral 0x0 segmental vascular ligation(ligation of 0x0)(sham operation group);group B:bilateral L3 segmental vascular ligation(ligation 1x1 pairs);group C:L2/L3 bilateral segmental vascular ligation(ligation of 2x2);group D:bilateral L2/L3/L4 segmental vascular ligation(ligation 3x3 pairs);group E:the ligation of one side segment vessels of L2/L3 and the contralateral L1/L2/L3/L4 segment vessels(2x4 ligation)(measure the side that segmental vascular ligation of L2/L3);group F:the ligation of one side segment vessels of L2/L3 and the contralateral L1/L2/L3/L4 segment vessels(4x2 ligation)(measure the side that segmental vascular ligation of L1/L2/L3/L4);group G:L 1/L2/L3/L4 bilateral segmental vascular ligation(ligation of 4x4);group H:L1/L2/L3/L4/L5 bilateral segmental vascular ligation(ligation of 5x5).Based on ligation of segmental vessels,then each group were randomly divided into spinal no shortening group(followed by A0,B0,C0,D0,E0,F0,G0,H0),group 1/3 spinal shortening(followed by A1,B1,C1,D1,E1,F1,G1,H1)and group 2/3 spinal shortening(followed by A2,B2,C2,D2,E2,F2,G2,H2).Each sub group contained 2 beagle dogs.The degree of shortening of the spinal cord was the 1/3 and 2/3 of the gap formed after the resection of the vertebral body.The height of the gap should be the height of the L3 vertebral body and the thickness of the intervertebral disc.After induction of anesthesia,tracheal intubation was performed after anesthesia,and the whole somatosensory evoked potential(SEP)was monitored.Completed posteriorly exposure of L1-L5 spinal posterior structure,L3 laminectomy and exposure of dorsal spinal cord,then applied laser Doppler flowmetry to measure the spinal cord blood flow PU(Laser Doppler flowmetry probes take exposure of spinal cord after midpoint midline of the 2-3mm lateral measurement of the relative value of spinal cord blood flow.Measurement should try to take the same position,and avoid visible in the spinal cord of large vessels branch).According to the grouping plan,as the center of the L3 vertebral body exposure and ligation 0 pairs,1 pairs,2 pairs,3 pairs,2x4 pairs,4x2 pairs,4 pairs,5paris segment vascular that adjacent to L3 vertebral body.After ligation,use laser doppler flowmetry measures spinal cord blood flowPU(The measurement method of the same).Apply bipolar coagulation blockade epidural vessels of L3,then use laser doppler flowmetry to measure spinal cord blood flow PU value.AfterL3 total spondylectomy,use laser doppler flowmetry to measure spinal cord blood flow PU value.The PU values of spinal cord blood flow in A0-H2 group after spinal cord shortening operation were recorded,and then repeated in 5min and 30min.(After every step of the operation was finished,monitor the spinal cord blood flow,and carried on somatosensory evoked potential monitoring as while.Set the peak delay greater than or equal to 10%,and the decrease of amplitude greater than or equal to 50%as the warning value,then we thought spinal cord function was significantly impaired).The experimental animals in each subgroup were subjected to spinal cord perfusion,fixed and sampling,respectively.The levels of-1(NO)and endothelin(ET-1)were measured by radioimmunoassay.The expression of heme oxygenase-1(HO-1)was evaluated by immunohistochemistry.Results:(1).Between the A,B,C,D,E,F,G,Height groups of experimental animals,body weight,body length,body temperature,operation time,fluid volume,urine volume,blood loss,preoperative blood pressure,preoperative heart rate difference was not statistically significant(P>0.05);After laminectomy,eight groups of the experimental animal spinal cord blood flow PU were no significant difference(P>0.05),and the monitoring results of SSEP did not reach the warning value;Ligation of 0x0,1x1,2x2,3X3,2x4(measure the ligation 2 segmental vessels side)group of animal spinal cord blood flow compared with after laminectomy spinal cord blood flow decreased slightly,and the difference was not statistically significant(P>0.05).There was no significant difference between the groups of blood flow signal(P>0.05),and SSEP monitoring results did not reach the warning value;but the ligation of 2x4(measurement 4 ligation side),4x4,5x5 on experimental animal spinal cord,the blood flow was decreased significantly after laminectomy(P<0.01),the monitoring results of SSEP reached the warning value,suggesting that the function of spinal cord damage.After epidural vascular occlusion,the blood flow of the spinal cord decreased slightly compared with the segmental ligation,and the difference was not statistically significant(P>0.05).Each group SSEP monitoring results showed the same with experimental animal after laminectomy.After establish L3 whole spine removed,there was no significant difference in the blood flow of the spinal cord of each group compared with that of epidural vessels occlusion,and the difference was not statistically significant(P>0.05).The SSEP monitoring of the experimental animals in each group showed the same results as that of epidural vascular occlusion.When the spinal cord was shortened by 1/3 or 2/3,the PU value of the spinal cord in the 1/3 shorting group was slightly higher than that of the spinal cord without shortening group,and there was no significant difference(P>0.05).However,the PU value of the spinal cord of the shortened 2/3 group was significantly lower than that in the spinal cord without shortening group and the shortened 1/3 group,and the difference was statistically significant(P<0.01).The monitoring results of the SSEP of the shortened 2/3 group of the experimental animals were all up to the warning value that prompt the spinal cord function was damaged.The NO content,ET-1 content and HO-1 expression in the spinal cord tissue of the eight groups of experimental animals increased with the increase of the ligation of the segmental vessels.Especially when the ligation of the vessels was greater than 3 pairs,the NO content,ET-1 content and HO-1 expression in the spinal cord tissue of the eight groups of experimental animals increased significantly(P<0.05).(7).The NO content,ET-1 content and HO-1 expression in the spinal cord of the 1/3 shorting group of the eight groups of the experimental animals were significantly increased compared with that of the spinal cord without shortening subgroup,and the difference was not statistically significant(P>0.05).However,the content of NO,ET-1 and HO-1 expression in the spinal cord of the 2/3 shorting group of the eight groups of experimental animals were significantly higher than that of 1/3 shorting group and no shorting group,and the difference was statistically significant(P<0.01).Conclusions:In the construction of beagle L3 total spondylectomy and spinal shortening model,ligation of the segmental vessels will affect the spinal cord blood flow.When the ligation of segmental vessels was Less than or equal to 3pairs,there will be a slight decrease in the blood supply of the spinal cord,and spinal cord blood flow can be compensated;When the ligation of segmental vessels was more than 3 pairs,spinal cord blood significantly reduced,and spinal cord blood loss compensation.Blockade of spinal epidural vascular network will affect the spinal cord blood flow.In the model with ligation of less than or equal to 3pairs segmental vascular,blocking the surface of dural vascular network will further reduce the spinal cord blood supply,but the spinal cord blood flow in the spinal cord is still tolerable.3.After L3 total spondylectomy and circumferential decompression of spinal cord,spinal cord blood flow increased.In models of segmental vascular ligation less than or equal to 3pairs,L3 total spondylectomy and circumferential spinal cord decompression will increase the the spinal cord blood supply of spinal cord to a certain extent that will improve the tolerability of spinal cord and reduce the possibility of spinal cord injury.Ligation of more than 3 pairs of segmental vascular experimental animals,even if L3 total spondylectomy and circumferential decompression of spinal cord,the degree of spinal cord ischemia were still serious,and the possibility of ischemic injury of spinal cord was greatly increased.4.After L3 total spondylectomy,shorten the gap that formate after resection of L3 vertebral body(L3 plus the upper and lower vertebral height of intervertebral disc thickness).When the short gap is less than or equal to 1/3,the spinal cord blood flow increases slightly,which can increase the tolerance of spinal cord ischemia and reduce the degree of spinal cord injury;when shortening the gap is greater than or equal to 2/3,spinal cord blood flow was significantly reduced and spinal cord injury aggravated.5.With the increasing of ligation of the segmental vessels,spinal cord injury related factors(NO content,ET-1 content and HO-1 expression)increased in exposed spinal cord tissues.Especially when the ligation of the segmental vessels were more than 3 pairs,spinal cord injury related factors increased significantly,and spinal cord ischemia/hypoxia induced damage was significantly increased.6.When proper spinal shortening(? 1/3),spinal cord injury related factors involved in the exposure spinal cord tissues(NO content,ET-1 content and HO-1 expression)slightly increased,and the degree of spinal cord injury did not obvious aggravate;However,when too much short spinal cord(? 2/3),the related factors after spinal cord injury in spinal cord injury(involved in the regulation of NO content,ET-1 content and HO-1 expression)significantly increased,and the degree of spinal cord injury significantly aggravated. |
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