每日一题_2022.06.20

A 72-year-old man is postoperative day two (hospitalization day four) after a three- vessel, on-pump coronary artery bypass graft. His medical history includes coronary artery disease, hypertension, hyperlipidemia, and asthma. His platelet count has decreased from a preoperative value of 130 x 109/L to 78 x 109/L this morning. His hemoglobin remains the same, and white blood cell count is 14.2 x 109/L, up from a preoperative value of 8.6 x 109/L. Vital signs remain stable, and he is without complaints. On physical examination, there are no signs of bleeding, rash, or extremity swelling.

Which of the following is the most appropriate next step in management?

A. Continue heparin, but discontinue aspirin

B. Continue both aspirin and subcutaneous heparin.

C. Continue aspirin, but switch heparin to argatroban.

D. Discontinue both aspirin and heparin until platelet count normalizes. ​

E. Transfuse platelets.

答案解析：

肝素诱导的血小板减少症(HIT)Ⅱ型的首要原因是肝素-血小板因子4抗体的产生，体外循环(CPB)患者术中暴露于大剂量肝素推注，但CPB患者发生HIT的比例不足3%。心脏手术后血小板减少主要是由于旁路回路上血小板的机械破坏，以及旁路时发生的血液稀释。CPB后血小板最低值为术后2-3天，这是该患者的表现。接受CPB的患者血小板计数通常下降30%。根据降低的时间和程度，血小板计数降低最可能的原因是CPB。必须考虑HIT，但这不太可能，因为他的血小板计数下降不是50%或更多。在HIT患者中，血小板计数降低通常在开始肝素治疗后5-14天开始。此外，没有血栓形成的迹象。无需停用阿司匹林，因为没有出血的临床体征。该患者没有输注血小板的指征。

在接受CPB的患者中，HIT的诊断较为困难；已努力确定HIT诊断的简单标准。制定了辅助诊断的评分，该评分来自对84例接受CPB患者的回顾性审查。评分要素为血小板减少模式（血小板计数双相与线性下降）、CPB时间大于或等于118 min、间隔时间大于或等于5d。该评分对排除HIT诊断的阴性预测值为97%。HIT对心脏手术患者的诊断很重要，因为它与死亡率增加50%和发病率显著增加相关。

正确答案：B