Refaai Majed A, Wright Rick W, Parvin Curtis A, Gronowski Ann M, Scott Mitchell G, Eby Charles S
Division of Laboratory Medicine, Department of Pathology and Immunology, Washington University School of Medicine, 660 South Euclid Avenue, Box 8118, Saint Louis, MO 63110, United States.
Clin Chim Acta. 2006 Apr;366(1-2):264-8. doi: 10.1016/j.cca.2005.10.020. Epub 2005 Dec 7.
Ischemia can alter the ability of albumin to bind free metal atoms. Based on these biochemical changes, methods to quantify ischemia modified albumin (IMA) were developed to assist in the evaluation of patients with symptoms of cardiac ischemia. Since ischemia can occur in any vascular bed, the specificity of IMA for cardiac muscle ischemia is unclear and requires further investigation.
We evaluated the specificity of an IMA test in patients with skeletal muscle ischemia during arthroscopic knee surgery. A pressurized thigh cuff was continuously inflated to 300 mm Hg on the operative leg, in order to arrest blood flow during the procedure. Samples were collected before surgery, 15 min after surgery, and prior to discharge.
Twenty-three patients were enrolled in the study. Median tourniquet time was 29 min (range 19-108). Median pre-operative IMA was 90.2 KU/l (range 77-101.6). Statistically significant (p<0.05) increases in IMA and myoglobin concentrations, and decreases in albumin concentrations were observed following tourniquet release and before discharge.
Post-operative myoglobin elevations indicated that skeletal muscle ischemia was sufficient to produce detectable myocyte necrosis. Post-operative IMA increases are consistent with ischemic modification of albumin during exposure to ischemic conditions in skeletal muscle during and /or immediately after tourniquet application. However, the negative correlations between IMA and albumin results suggest that increases in IMA were in part due to lower post-operative albumin concentrations resulting in decreased cobalt binding.
缺血可改变白蛋白结合游离金属原子的能力。基于这些生化变化，人们开发了定量缺血修饰白蛋白（IMA）的方法，以辅助评估有心脏缺血症状的患者。由于任何血管床都可能发生缺血，IMA对心肌缺血的特异性尚不清楚，需要进一步研究。
我们评估了IMA检测在膝关节镜手术期间骨骼肌缺血患者中的特异性。对手术侧腿部的大腿袖带持续充气至300毫米汞柱，以便在手术过程中阻止血流。在手术前、手术后15分钟和出院前采集样本。
23名患者纳入本研究。止血带中位使用时间为29分钟（范围19 - 108分钟）。术前IMA中位数为90.2KU/L（范围77 - 101.6）。在止血带松开后和出院前，观察到IMA和肌红蛋白浓度有统计学意义的升高（p<0.05），白蛋白浓度降低。
术后肌红蛋白升高表明骨骼肌缺血足以导致可检测到的心肌细胞坏死。术后IMA升高与在止血带应用期间和/或之后立即暴露于缺血条件下骨骼肌中白蛋白的缺血修饰一致。然而，IMA与白蛋白结果之间的负相关表明，IMA升高部分是由于术后白蛋白浓度降低导致钴结合减少。
