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第四节 术中变化和监护
肝移手术复杂，术中必须密切注意病人的血压、脉搏、呼吸、体温、心电图、中心静脉压及尿量的变化，并准确记录，同时应抽血查血糖、尿素氮、肌酐、钾、钠、氯、钙、红细胞计数、血红蛋白、血细胞比容、凝血机制和血气分析。
肝移植手术的整个手术过程可以分为3期：病肝切除期、无肝期和肝脏再灌注期。
病肝切除期是从病肝分离至门静脉、肝动脉及下腔静脉切断为止；无肝期是指从门静脉、肝动脉和下腔静脉切断至门静脉和肝上下腔静脉开放、肝脏血流部分恢复为止；再灌注期是门静脉和肝上下腔静脉开放、肝脏血流部分恢复至手术完成为止。这3期均会明显影响受体的血流动力学和机体代谢状态，应根据各期不同的变化，做好充分准备，及时防治。
（1）病肝切除期：由于受体往往合并有肝硬化，存在粘连和丰富的侧支循环，在分离病肝时容易出血和渗血，这一期容易出现低血容量的休克，应密切注意观察失血量，动脉压、中心静脉压和尿量，根据情况补充液体和全血，并要注意钙离子的补充。我们的第1例病人由于术中失血过多出现动脉压下降，经补充血容量后动脉压恢复正常。
（2）无肝期：由于病肝的切除，这一期可能出现高血糖、低血钾、酸中毒、心律紊乱、凝血功能障碍及低体温等。所以要注意病人的血压、血糖、生化指标、心电图、血气和体温的观测。出现低血压昌可以给予多巴胺维持血压；出现酸中毒时，可以用5%的碳酸氢钠纠正；无肝期血糖往往偏高，但随着新肝功能的建立，糖利用增加，血糖水平可以逐渐下降，这也是新肝具有代谢活性的一个标志；无肝期体温往往下降，可以降至33℃以下，可用电热毯、热水袋和输液装置加温等方法来保持体温。由于回流血量的减少，这一期中心静脉压（CVP）、肺动脉楔压（PCWP）、平均动脉压（MAP）均可以轻度下降，同时体循环阻力（SVR）升高而肺循环阻力（PVR）降低。
（3）再灌注期：这一期由于淤血胃肠道内大量酸性代谢产物和肠道内毒性物质进入体循环，可能出现高血钾、酸中毒、凝血功能障碍和心律失常等，要严密观测，高血钾是再灌注早期的一个重要现象，平均可以升高1.5-2mmol/L，是手术过程中影响血流动力学稳定和抑制心肌功能的潜在因素。如果血钾过高，可以注射氯化钙或葡萄糖酸钙；可用5%的碳酸氢的钠纠正酸中毒。随着回流血量的恢复，这一期中心静脉压（CVP），肺动脉楔压（PCWP）、平均动脉压（MAP）、体循环阻力（SVR）和肺循环阻力（PVR）均逐渐恢复正常。
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