Malapati Harsha, Hanwright Philip J, Tuffaha Sami H
Department of Plastic and Reconstructive Surgery, Johns Hopkins University School of Medicine, Baltimore, Md.
Plast Reconstr Surg Glob Open. 2021 Aug 12;9(8):e3769. doi: 10.1097/GOX.0000000000003769. eCollection 2021 Aug.
Flap thrombosis is a rare but devastating complication in microsurgery. Preoperative identification of patients at increased risk for microvascular thrombosis remains challenging. Viscoelastic testing (VET) provides a comprehensive evaluation of the clotting process and can effectively identify hypercoagulability. However, the utility of VET in microvascular reconstruction remains unclear.
A systematic review of the association between VET and pedicle thrombosis and free flap loss was performed in accordance with Preferred Reporting Items for Systematic Reviews (PRISMA) guidelines. Identified studies were reviewed independently by two authors for pertinent data.
Six studies met inclusion criteria. Heterogenous study design and outcome reporting complicated direct comparisons and precluded a formal meta-analysis. Four studies found a statistically significant relationship between VET results and flap thrombosis or flap loss. The maximum clot strength and the fibrinogen-to-platelet ratio (FPR) were key viscoelastic parameters in these studies, both representing a measure of maximal clot strength. Specifically, an elevated FPR (>42%) generated a sensitivity and specificity for flap loss ranging from 57% to 75% and 60% to 82%, respectively. Notably, the negative predictive value for flap failure with a normal preoperative FPR was greater than 90% in all studies reporting a correlation. The remaining two studies reported no predictive value for VET with respect to flap failure or pedicle thrombosis.
The results of this review suggest that VET, particularly parameters relating to clot strength, may help clinicians identify patients at risk for flap thrombosis. However, uncontrolled and heterogenous reporting limit definitive conclusions, and high-quality diagnostic studies are needed to better determine the clinical utility of viscoelastic testing for free flap patients.
皮瓣血栓形成是显微外科手术中一种罕见但极具破坏性的并发症。术前识别微血管血栓形成风险增加的患者仍然具有挑战性。粘弹性测试（VET）可对凝血过程进行全面评估，并能有效识别高凝状态。然而，VET在微血管重建中的作用仍不明确。
根据系统评价的首选报告项目（PRISMA）指南，对VET与蒂部血栓形成及游离皮瓣丢失之间的关联进行系统评价。两位作者独立审查纳入研究以获取相关数据。
六项研究符合纳入标准。研究设计和结果报告的异质性使得直接比较变得复杂，无法进行正式的荟萃分析。四项研究发现VET结果与皮瓣血栓形成或皮瓣丢失之间存在统计学显著关系。最大凝血强度和纤维蛋白原与血小板比值（FPR）是这些研究中的关键粘弹性参数，均代表最大凝血强度的一种度量。具体而言，FPR升高（>42%）对皮瓣丢失的敏感性和特异性分别为57%至75%和60%至82%。值得注意的是，在所有报告有相关性的研究中，术前FPR正常时皮瓣失败的阴性预测值均大于90%。其余两项研究报告VET对皮瓣失败或蒂部血栓形成无预测价值。
本综述结果表明，VET，尤其是与凝血强度相关的参数，可能有助于临床医生识别有皮瓣血栓形成风险的患者。然而，研究的非对照性和报告的异质性限制了确定性结论的得出，需要高质量的诊断性研究来更好地确定粘弹性测试对游离皮瓣患者的临床应用价值。
