总钙水平测定不适用于肝移植术中高钙血症和低钙血症的诊断

Total calcium is not suitable for diagnosis of hyper- and hypo-calcemia in liver transplantation

目的观察肝移植术中离子钙和总钙浓度的变化，探讨监测总钙是否适用于钙紊乱的诊断。方法20例肝移植患者，全身麻醉下行改良背驮式肝移植，分别于术前、无肝前期、无肝期30min以及下腔静脉开放后5、30、120min时采集动脉血，测定离子钙和总钙水平，并按公式（离子钙=总钙×0．48）依据总钙计算出离子钙水平。结果所有患者均完成手术，术中输液总量为3500～10000ml，包括晶体、白蛋白、新鲜冰冻血浆、冷沉淀和红细胞，补氯化钙3．5～8．0g。检测所得离子钙和计算得出的离子钙，除术前外，差异有统计学意义（P〈0．01）。若依据总钙浓度判断，术前12例血钙正常，而以测定的离子钙来判断，则其中4例是低钙血症（假阴性）；在无肝前期，依据总钙浓度判断，4例血钙正常，其余16例均为高钙血症，但是若以离子钙作为诊断标准，血钙正常的4例均为低钙血症，而诊断为高钙血症的16例，仅有3例是高钙血症，余下的13例中有7例是低钙血症；无肝30min时及移植肝恢复血流30min时的情况和无肝前期类似；移植肝恢复血流120min时，依据总钙水平，所有患者均为高钙血症，但离子钙测定提示7例血钙正常。无肝前期之后，依据总钙水平诊断术中各期高钙血症、低钙血症的特异性或敏感性较低。结论肝移植术中总钙及离子钙浓度变化明显，相对于总钙水平，肝移植术中离子钙水平的变化能更真实反映机体的钙紊乱。

Objective To evaluate whether total calcium can be used to monitor calcium hemoestasis in orthotopic liver transplantation （OLT） patients. Methods Twenty ASA Ⅱ-Ⅴ patients with end-stage liver diseases underwent OLT. Anesthesia was induced with midazolam 0. 1 mg/kg, fentanyl 3 μg/kg, propofol 0. 5-1.5 mg/kg, vecoronium 0. 1 mg/kg and maintained with isoflurance inhalation and intermittent i.v. boluses of fentanyl, vcoronium. The patients were mechanically ventilated after tracheal intubation. Swan-ganz catheter was inserted via right internal jugular vein and radial artery was carmulated. MAP, ECG, CVP, cardiac output （CO）, SpO2, PetCO2 and core temperature were continuously monitored during operation. Artery blood samples were taken before induction of anesthesia, preanhepatic, anhepatic, neohepatic 5 min, neohepatic 30 min and neohepatic 120 min for ionized calcium and total calcium, and formula ionized calcium was calculated using the following formula.. Ionized calcium= total calcium 0. 48. Results Total calcium levels and ionized calcium levels changed significantly throughout OLT, especially during the preanhepatic, anhepatic, neohepatic 5 min, neohepatic 30 min and neohepatic 120 min periods. Between ionized calcium concentrations and formula ionized calcium concentrations there were significant changes during the procedure except before induction of anesthesia. Among 12 of 20 patients, normal calcium was diagnosed based on total calcium concentration, while 4 patients had low ionized calcium （false negative） before induction of anesthesia. Whatever, there were many patients with hypercalcemia diagnosed according to total calcium concentration with normal ionized calcium even with low ionized during the other periods （false positive）. Conclusion Plasma calcium concentration changed significantly during liver transplantation. Total calcium is not suitable for diagnosis of hyper- or hytx^calcemia in those patients and should be replaced by measurement of ionized calcium.