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Changes in oxygen metabolism during orthotopic liver transplantation without veno－venous bypass

黄素琴 祝胜美 吴健 何慧梁 陈益忠 冯智英 陈庆廉

HUANG Su－qin，ZHU Sheng－mei，WU Jian，et al.Department of Anesthesia，First Affiliated Hospital，Medical College，Zhejiang University，Hangzhou 310003，China

Abstract

　　Objective：To investigate the changes in oxygen metabolism during orthotopic liver transplantation（OLR）without veno－venous bypass since dramatic circulatory changes may take place during operation.

　　Methods：Twenty－one patients with end－stage liver disease（18 males，3 females）aged 20－61 yrs weighing 44－86 kg undergoing OLT without venous bypass under general anesthesia were enroUed in this study.S－G catheter was placed in the pulmonary artery via right internal‘jugular vein and both right and left radial artery were cannated. ECG，Sp0₂，Prr C0₂ and naso－pharyngeal temperature were continuously monitored during surgery. Anesthesia Was induced with midazolam 0.1 mg/kg，etomidate 0.2－0.3 mg/kg，fentanyl 5－10 μg/kg and vecuronium 0.08－0.1 mg/kg，After tracheal intubation anesthesia Was maintained with isoflurane inhalation（0.5％－1.0％）and continuous infusion of propofol at 2－4 mg/kg/h supplemented with intermittent i.v.boluses of midazolam，fentanyl and vecuronium.A 14F naso－gastric TRIP－NGS tube was inserted in the stomach for measurement of gastric mucosal pH （pHi）.Blood samples were taken from radial and pulmonary artery for blood gas unalysis. Hemodynam icparameters，blod gases（arterial and mixed venous） and Psc0₂ were recorded and oxygen delivery （DO₂），oxygen consumption（VO₂）and pHi were calculated at 30 min after induction（T₀，baseline），when inferior vena cava and portal vein were clamped（T₁），5 min after unclam ping of inferior verla cava and portal vein（T₂），90 min after graft reperfusion（T₃）and at the end of operation（T₄）.

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讨 论

　　原位肝移植术患者病情危重，手术操作复杂，术中有大量的血液丢失和相应的容量置换，采用非转流术式时，无肝期内脏器官及下肢淤血。门静脉和下腔静脉开放后，肝脏和其它内脏器官再灌注可导致血液动力学不稳定，引起全身和局部组织氧代谢异常。在本研究中血液动力学表现为无肝期SVI、CO、CI、CVP、PAP和PAWP急剧下降，这是由于回心血量急剧减少所致。同时，HR和SVRI增加，MAP基本保持稳定，这与使用肾上腺素有关；f－1静脉和下腔静脉开放后，CO和各压力指标均增加，这是由于回心血量骤增所致。随着时间推移血液动力学状态逐渐得到改善并与无肝前期相近。Carmichael^[2]等的研究结果与本研究的一致。

　　DO₂、VO₂作为全身组织氧代谢监测的指标，可作为评价危重患者机体功能改善的重要标志^[3，4]，被认为是肝移植术中一个重要的监测指标^[5，6]。

　　本研究显示，门静脉和下腔静脉阻断即刻DO₂显著下降。这是由于回心血量减少和CO降低的结果。由于无肝期全身VO₂并不减少^[2，7]，因此ERO₂增加，以保证有充足的氧维持重要器官的有氧代谢。本组患者在门静脉阻断前即开始持续应用肾上腺素，使HR明显增快，MAP维持相对稳定，在一定程度上阻止了DO₂的过度降低，使得门腔静脉阻断对全身的影响降低。门静脉开放后的Do₂基本恢复至无肝前期水平，是CO增加和血液动力学改善的结果。新肝后期（关腹时）随着新肝血流的再灌注和肝功能的逐渐恢复，以及原来在无肝期因缺血、淤血而处于低灌注、低氧代谢的组织器官血供恢复后有氧代谢增强，导致了氧耗量增加。

　　DO₂、VO₂作为机体氧代谢监测的指标，反映的是全身微循环和氧代谢状态。Steib等^[8]观察到肝移植时尽管维持足够的全身DO₂和灌注压，仍存在组织氧合受损的情况。胃肠粘膜是缺氧时最容易和最先被累及的部位，因而pHi值是较敏感的局部组织氧代谢指标，能够及时反映内脏器官灌注及氧合状态，有助于较早的发现内脏微循环灌注不足及缺氧。本研究发现无肝期的PgCO₂升高、pHi下降，其原因是门腔静脉阻断导致胃肠道血流减少、局部粘膜缺血缺氧；新肝期PsCO₂、Pg－aCO₂迅速恢复至无肝前期水平但，phi仍较低，提示胃肠粘膜仍存在代谢性酸中毒。其可能与以下因素有关：尽管门静脉开放后D0₂、VO₂已恢复至无肝前期水平，但胃肠道血流分布不均仍存在^[9]；无肝期胃肠道形成的氧债的偿还有一个过程；肾上腺素使内脏血流减少，对组织氧合产生不利影响^[10，11]。Welte等^[9]的研究结果与此一致。

　　综上所述，非转流下原位肝移植术患者无肝期后存在明显氧代谢障碍，其对手术预后的影响值得进一步研究。

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