Evaluating Common Anticoagulation Laboratory Values in Single Ventricle Patients following Cardiac Surgery

Objectives: We evaluated common laboratory values such as platelet levels, activated partial thromboplastin time (aPTT), and antifactor Xa (anti-FXa) levels monitoring coagulation therapy in single ventricle (SV) patients after congenital heart surgery. We tested the hypothesis that low platelet levels are associated with bleeding events in this population.

Methods: This was a prospective, single-center, observational study conducted at the Boston Children’s Hospital following SV patients in the cardiac intensive care unit (CICU) after congenital heart surgery between November 2016 and February 2018. Bleeding events remote from surgery and independent of interventional procedures served as outcome. Median anti-FXa, aPTT, and platelet levels were compared among bleeding and nonbleeding patients using Mann–Whitney’s U test. Multivariate binary logistic regression including age group and three different platelet categories (cat.) (cat. 1 = < 200 × 10³/µL, cat. 2 = 200–400 × 10³/µL, cat. 3= >400 × 10³/µL) was performed to identify the association with bleeding among the different groups. Group allocation was retrospectively based on the lowest (platelet) and highest (aPTT and anti-FXa) levels measured 1 day prior to the event in bleeding patients, and on the lowest/highest level ever measured during their CICU stay in nonbleeding patients.

Results: A total of 270 patients were followed up during their postoperative CICU stay (median age = 364 days, IQR: 123–1,285). At least one bleeding was observed in 51 patients (18.9%). No association between aPTT or anti-FXa levels and bleeding was found in this population (p = 0.526 and 0.202). Out of 119, 34 patients (28.6%) in platelet cat. 1 developed a bleeding. Out of 45, 34 bleeding patients (75.6%) had a platelet count of < 200 × 10³/µL 1 day prior to the event. Median lowest platelet counts were 112 × 10³/µL (IQR: 93–196) in bleeding and 225 × 10³/µL (IQR: 161–341) in nonbleeding patients (p < 0.001). In our multivariate regression model platelet, cat. 1 was associated with significantly more bleedings compared with cat. 3 (OR: 13.713, CI: 2.803–67.080, p = 0.001) after adjusting for age group. There was no significant difference noted in bleeding rates between platelet cat. 2 and cat. 3 (p = 0.292).

Conclusion: Platelet levels of < 200 × 10³/µL are associated with significantly increased bleeding rates in SV patients. Laboratory ranges for this patient population should be reassessed to optimize clinical care accordingly.