Vascular occlusion in hepatic resections in cirrhotic rat livers: An experimental study in rats

The aim of this study was to evaluate the tolerance of normothermic liver ischemia with different degrees of hepatic function in cirrhotic rats. Liver cirrhosis was induced by administering carbon tetrachloride (CCl₄) in water solution to male Wistar rats. Hepatic function was graded using the plasma levels of antithrombin III, albumin, and bilirubin and the presence of ascites. Rats were distributed in four groups: noncirrhotic (control group), compensated cirrhosis (group A), decompensated cirrhosis (group B), and decompensated cirrhosis with ascites (group C). Groups A, B, and C were significantly different in all four parameters studied (P < .003). Subtotal liver ischemia was performed for periods of 0, 30, 45, 60, and 75 minutes. At the end of the procedure, the nonischemic lobes were resected. Postoperative evolution of alanine aminotransferase, aspartate aminotransferase, and bilirubin levels was also recorded. Survival rates after the same periods of ischemia were statistically different (P < .05): control group, 7 of 7 after 45 minutes (100%), 7 of 7 after 60 minutes (100%), and 4 of 9 after 75 minutes (44%); group A, 7 of 7 after 45 minutes (100%) and 1 of 7 after 60 minutes (14%); group B, 7 of 7 after 0 minutes (100%), 5 of 7 after 30 minutes (71%), and 1 of 7 after 45 minutes (14%); and group C, 0 of 5 after 0 minutes (0%) and 1 of 7 after 30 minutes (14%). No differences were found in the postoperative course of transaminases. However, bilirubin levels found 24 hours and 7 days after ischemia were significantly greater in cirrhotic rats, and this was directly related to the degree of hepatic insufficiency (P < .001). Histological examination of the livers exposed to CCl4 showed features of liver cirrhosis with ductal proliferation. The ischemia time tolerated by cirrhotic rat livers is shorter than the time tolerated by normal rats. Tolerance to hilar vascular occlusion depends on the degree of hepatic insufficiency. Rats with decompensated cirrhosis and ascites do not tolerate any surgical procedure. (Liver Transpl Surg 1997 Nov;3(6):617-23)     

Experimental study on the maintenance of sufficient hepatic circulation with arterial blood during the temporary occlusion of the hilar hepatic circulation

This study was performed to clarify the lowest limit of the blood flow volume to maintain the normal energy metabolism in the liver of mongrel dogs under the condition of total hilar clamping when the hepatic circulation was supplied only through the extracorporeal catheter bypass from the artery to the hepatic portal vein in flow control. The proper hepatic artery was ligated. The levels of adenosine triphosphate and total adenine nucleotide in the liver tissue were maintained as in the same level as the pre-bypass value during 120 minutes of this procedure even though the rate of bypass flow varied between 25% to 100% of normal total hepatic blood flow. When the bypass flow decreased below 10% of the normal flow, the hepatic energy metabolism was observed broken and the anaerobic glycolysis progressed within 30 minutes. Regional hepatic blood flow measured by the hydrogen clearance method was decreased slightly in the 25%-bypass flow and extremely in the 10%-flow after 30 minutes of the bypass. The lowest limit of the arterial blood inflow volume to maintain the hepatic function was confirmed to be in the range between 10% and 25% of the normal total hepatic blood flow volume.     

Peripheral nerve injection injury: an experimental study.

In an attempt to answer questions regarding nerve injection injuries, we injected 11 agents in current use and commonly administered by intramuscular injection into the sciatic nerves of adult Wistar rats. Equal volumes of normal saline were used as control. We harvested the sciatic nerves at various times after injection and examined them by both light and electron microscopy. We performed myelinated nerve fiber counts and constructed histograms. Any impairment of motor function was also noted. We gave injections to 79 animals a total of 158 times; 116 injections were directly into the nerve fascicle (intrafascicular) and 42 were into the epineural tissue (extrafascicular). The results revealed considerable variation in the degree of nerve fiber injury according to the agent injected. Minimal damage resulted from the injection of iron-dextran, meperidine, and cephalothin, and maximal nerve injury followed the injection of penicillin, diazepam, and chlorpromazine. The site of injection was crucial. Intrafascicular injection was invariably associated with severe nerve injury, but, with few exceptions, extrafascicular injection resulted in minimal damage. The quantity of drug injected was also important in determining the degree of injury. Large, heavily myelinated fibers were more susceptible to injection injury than smaller, thinly myelinated nerve fibers. The effect of the injected drug seemed to be related to injury of the nerve fiber unit--both the axon and the Schwann cell with its myelin sheath. Regeneration in damaged nerves was a constant finding; even the most severely injured nerves, with total axonal degeneration, underwent subsequent regeneration.     

Safety of cystic duct clipping in healthy and cirrhotic livers: a cadaveric study.

BACKGROUND AND OBJECTIVES: Biliary leakage through the cystic duct stump due to clip dislodgement has been a concern since the advent of the laparoscopic cholecystectomy. The authors proposed a cadaveric model to test the safety of cystic duct clipping in a hypertensive biliary tract in healthy and cirrhotic livers. METHODS: Twenty fresh cadavers were studied (5 cirrhotic, 15 healthy). Open cholecystectomy was performed and the cystic duct clipped with commercially available titanium clips. The distal common bile duct was catheterized to allow infusion of water and pressure measurement. RESULTS: Increased pressure in the bile duct resulted in back diffusion into the liver, preventing reaching high-pressure levels. Only 1 clip was dislodged in this situation, in a cirrhotic liver with a large cystic duct. As a second experiment, the hepatic hilum was clamped to allow higher pressures of the biliary tree (500 mm Hg). In this situation, no clip was dislodged. CONCLUSIONS: We have established the safety of cystic duct clipping in healthy and cirrhotic livers; however, bigger clips or alternative methods to seal the duct may be necessary in larger ducts.     

Ischemic preconditioning of free muscle flaps: an experimental study

The aim of this study was to apply the hypothesis of ischemic preconditioning (IP) on free skeletal muscle (rat thigh flap). Five groups of Sprague-Dawley rats (n = 6) were used. In group A (control group), standard free autologous flap transfers were performed. Flaps in groups B and C underwent 4 and 6 h, respectively, of ischemia before transfer. In groups D and E, muscle flaps were preconditioned (3 x 10 min ischemia interrupted by 10 min of reperfusion, clip applied on the dissected artery of the flap) and subjected to 4 and 6 h, respectively, of ischemia before transfer. After 48 h of reperfusion, the muscle flaps were evaluated macroscopically as well as by histological and immunohystochemical staining. In group A, the viability was 100%, whereas in groups D and E the viability was 83.3% and 100%, respectively. Groups B and C had undergone macroscopically parceled to total necrosis, further confirmed by histological findings (fragmentation and disappearance of muscle striations, combined with tissue necrosis and intravascular thrombosis). The beneficial effect of IP demonstrated in the heart, liver, and small bowel extends to skeletal muscle, which can be used in free-flap transfers, if the transfer includes a long period of predictable ischemia.     

门腔静脉侧仙分流加肝动脉强化灌注对肝硬变肝脏影响的实验研究

目的 门腔分流术严重影响肝脏血循环,为改善术后肝供血,设计并进行了门腔分流加肝动脉强化灌注术的实验研究。方法 ４８只Ｗｉｓｔａｒ大鼠被随机均分为：正常对照组（Ⅰ组）,肝硬变对照组（Ⅱ组）,肝硬变分流组（Ⅲ组）,肝硬变分流加肝动脉强化灌注组（Ⅳ组）;行肝功能检查,肝活检及核素动态肝胆显像。结果 Ⅳ组较Ⅲ组肝功能明显改善（Ｐ〈０．０５）。核素显像：高峰时间提前（Ｐ〈０．０５）;排泄率增高（Ｐ〈０．０１     

肝硬变大鼠肝脏缺血再灌注损伤

为比较硬化肝与正常肝在缺血再灌注损伤时的差异和意义。作者采用四氯化碳复制大鼠肝硬变模型,通过大鼠肝脏缺血再灌注损伤模型,检查不同时限大鼠门静脉血内毒素、肝静脉血一氧化氮。结果显示：肝硬变大鼠再灌注时门静脉内毒素水平更高;肝脏ＮＯ合成释放显著增加。作者认为肝硬变时对缺血再灌注损伤反应与正常大鼠不同,可能是肝硬变时对缺血再灌注损伤更敏感,更易发生肝功能衰竭的重要原因。     

Neuropathological changes in vibration injury: an experimental study

Vibration syndrome, a clinical condition arising from chronic use of vibrating tools, is associated with a spectrum of neurovascular symptoms. To date, only its vascular pathology has been extensively studied; we sought to determine what direct neurologic injury, if any, is caused by vibration. Hindlimbs of anesthetized rats were affixed to a vibrating platform 4 h a day for 7 days. Study animals were vibrated with set parameters for frequency, acceleration, velocity, and amplitude; control animals were not vibrated. On day 7, nerves were studied by light and electron microscopy. While light microscopy showed minimal histologic differences between vibrated (n=12) and control (n=12) nerves, electron microscopic changes were dramatic. Splitting of the myelin sheath and axonal damage (e.g., myelin balls and "finger ring") were consistently seen in both myelinated and nonmyelinated axons. Despite relatively short vibration, definite pathology was demonstrated, suggesting that vibration syndrome has a direct neurologic component.     

猪肝脏灌注异常现象的相关机制

目的通过对猪正常肝脏建立灌注异常模型,探讨肝灌注异常的发生因素。方法9头实验用小型猪进入研究,随机平均分为A、B、C3组,分别采用明胶海绵碎屑进行肝内门静脉、肝动脉、肝静脉分支栓塞,术后即刻及1周后进行CT增强扫描,观察是否存在肝灌注异常现象。结果术后即刻CT扫描,全部研究对象出现肝灌注异常现象,表现为动脉期肝实质内出现楔形或不规则形一过性强化,门静脉期恢复正常。A组出现灌注异常的部位与栓塞血管所在肝段、叶一致;B组栓塞区出现低灌注区,非栓塞区出现一过性强化现象。C组2头出现灌注异常的部位与栓塞区域一致,1头比栓塞区域大。1周时CT复查,除C组存在部分灌注异常现象外,A、B组灌注异常现象消失。结论肝内门静脉、肝动脉、肝静脉分支堵塞是造成肝灌注异常现象的因素。     

Duplex ultrasonography versus arteriography in the diagnosis of arterial injury: an experimental study.

Duplex ultrasonography (DUS) and arteriography (ART) were evaluated using an experimental model of arterial trauma in order to determine the accuracy of DUS compared with ART and to define the characteristic ultrasonographic features of arterial injuries. Occlusions (n = 19), blunt injuries (n = 24), lacerations (n = 25), arteriovenous fistulae (n = 13), or no injuries (sham, n = 19) were surgically created in the femoral and carotid arteries of 25 dogs. Following closure of the incisions, DUS was performed and interpreted by a staff vascular surgeon without knowledge of the presence or type of injury. Biplane selective ART was evaluated by an independent staff radiologist. Although DUS and ART were equally accurate in evaluating arterial injuries, DUS was more sensitive (90.1% +/- 3.3% versus 80.2% +/- 4.4%, p = 0.002) and better at identifying lacerated arteries (p = 0.01). However, ART had greater specificity (94.7% +/- 5.1% versus 68.4% +/- 10.7%, p = 0.04) and was more accurate for identifying normal arteries (p = 0.04). The validity of DUS increased in the latter half of the study, thus demonstrating a learning curve. Duplex ultrasonography was a more sensitive screening modality than ART for evaluating arterial injuries in our experimental model, thereby supporting its use in clinical trials to evaluate its accuracy, reliability, and cost effectiveness in the trauma setting. Furthermore, management decisions can be based on the specific type of injury, pathologic condition of the arterial wall, and hemodynamic factors identified by DUS. Clinically occult arterial injuries can be followed by repeat DUS to define the natural history of these injuries.