Skagen C L, Said A
Department of Medicine, University of Wisconsin, Madison, WI, USA.
Minerva Gastroenterol Dietol. 2010 Sep;56(3):279-96.
Liver transplantation is a challenging surgical operation performed in recipients with major hemodynamic perturbations related to portal hypertension. The pathophysiologic alterations in portal hypertension include a hyperdynamic circulation and decline in systemic vascular resistance and mean arterial pressure. Cardiac function can also be depressed due to cirrhosis related cardiomyopathy. These cirrhosis related changes often lead to a tenuous state in which organ perfusion is threatened and declines rapidly in the setting of many other insults including blood loss, infection, and use of medications which can cause a decline in blood pressure. This can result in renal failure as well as reduced perfusion of other organs. Additionally, direct consequences of portal hypertension include risk of bleeding from porto-systemic collaterals both in the gastrointestinal tract as well as during abdominal dissection in liver transplantation. In this milieu the management of hemodynamic alterations during liver transplant surgery is a daunting task. Recent approaches have utilized various vasoconstrictor therapies along with judicious use of intravenous fluids to maintain systemic pressures and organ perfusion. Added advantages of this approach include the potential for reducing portal pressure and thus the severity of intra-abdominal hemorrhage during surgery as well as potentially increasing renal blood flow and reducing mesenteric hyperemia. Avoidance of liberal fluid use to maintain systemic pressures also has the advantage of reducing the severity of pulmonary edema and risk of reintubation or prolonged intubation after surgery. Although these approaches utilizing vasoconstrictors are promising, many questions remain. Randomized controlled trials like those performed in the pretransplant population are sparse in the setting of liver transplantation. The optimal vasoconstrictors including combinations and doses have not been defined. Most of the benefits demonstrated thus far have been surrogate outcomes such as reduced transfusion requirement, decreased need for reintubation and improved systemic hemodynamics and reduced portal pressures during surgery. There may be different outcomes of these approaches in patients with varying severities of liver disease. The safety of minimization of fluids, along with vasoconstrictor therapy during liver transplantation has been questioned in patients with higher risk of renal failure including recipients with high MELD scores. Other factors besides disease severity, including organ quality and cold ischemia times, need to be accounted for in future trials. Optimal outcomes including postoperative patient and graft survival, hospital stay and renal function should also be incorporated in future trials of vasoconstrictor therapy during liver transplantation.
肝移植是一项具有挑战性的外科手术，针对的是伴有与门静脉高压相关的严重血流动力学紊乱的受体。门静脉高压的病理生理改变包括高动力循环、全身血管阻力下降和平均动脉压降低。由于肝硬化相关性心肌病，心脏功能也可能受到抑制。这些与肝硬化相关的变化常常导致一种脆弱状态，即器官灌注受到威胁，在失血、感染以及使用可导致血压下降的药物等许多其他损伤情况下，器官灌注会迅速下降。这可能导致肾衰竭以及其他器官灌注减少。此外，门静脉高压的直接后果包括在胃肠道以及肝移植腹部解剖过程中，门体侧支循环出血的风险。在这种情况下，肝移植手术期间血流动力学改变的管理是一项艰巨的任务。最近的方法采用了各种血管收缩剂疗法，并谨慎使用静脉输液以维持全身压力和器官灌注。这种方法的额外优点包括有可能降低门静脉压力，从而减轻手术期间腹腔内出血的严重程度，以及有可能增加肾血流量并减少肠系膜充血。避免大量使用液体来维持全身压力还有利于减轻肺水肿的严重程度以及降低术后再次插管或延长插管时间的风险。尽管这些使用血管收缩剂的方法很有前景，但仍存在许多问题。在肝移植背景下，像在移植前人群中进行的那些随机对照试验很少。包括联合用药和剂量在内的最佳血管收缩剂尚未确定。迄今为止所证明的大多数益处都是替代指标，如减少输血需求、减少再次插管的必要性、改善全身血流动力学以及降低手术期间的门静脉压力。在不同严重程度肝病患者中，这些方法可能会有不同的结果。在肾衰竭风险较高的患者（包括高MELD评分的受体）中，肝移植期间减少液体用量并联合血管收缩剂疗法的安全性受到了质疑。除了疾病严重程度外，其他因素，包括器官质量和冷缺血时间，在未来试验中也需要考虑。未来肝移植期间血管收缩剂疗法的试验还应纳入包括术后患者和移植物存活、住院时间和肾功能在内的最佳结果。
