Contributing factors to heparin resistance during cardiopulmonary bypass.

Since the risk factors for heparin resistance (HR) before cardiopulmonary bypass (CPB) have not been fully clarified, this study investigated the contributing factors for HR after the initial unfractionated heparin (UFH) dose of 500 IU/kg. We retrospectively analyzed the data of 371 patients who underwent CPB surgery, with the initial UFH dose of 500 IU/kg, between May 2017 and December 2021. We defined HR as the failure to achieve activated clotting time (ACT) of > 480 s after the initial UFH dose of 500 IU/kg. HR was observed in 36 patients (9.7%) (HR group), while HR was not observed in 335 patients (control group). The HR group included significantly more patients with preoperative use of UFH, with significantly higher white blood cell counts, fibrinogen, fibrinogen degradation products, D-dimer, and C-reactive protein, and lower hemoglobin and albumin. The multivariable logistic regression analysis identified albumin (OR: 3.09, 95% CI 1.3504-7.0845, p = 0.0075) and fibrinogen (OR: 0.99, 95% CI 0.9869-0.9963, p = 0.0003) as independent predictors for HR. Using the Youden index, the cutoffs of albumin and fibrinogen were calculated as 3.8 g/dL and 303 mg/dL, respectively. The receiver operating characteristic curves showed the predictive performance of albumin (area under the curve (AUC): 0.78, sensitivity: 65%, specificity: 81%) and fibrinogen (AUC: 0.77, sensitivity: 56%, specificity: 88%). The incidence of HR after the initial UFH dose of 500 IU/kg was 9.7%. The preoperative albumin < 3.8 g/dL and fibrinogen > 303 mg/dL were independent predictors for HR.

Abnormal stenosis of a drainage cannula due to excessive negative pressure during venovenous extracorporeal membrane oxygenation management: a case report.

We report a case in which excessive negative pressure may have been applied to the proximal side hole of a drainage cannula during venovenous extracorporeal membrane oxygenation (V-V ECMO), resulting in abnormal stenosis of the drainage cannula. V-V ECMO was introduced in a 71-year-old male patient who was transferred from another hospital for severe respiratory failure associated with varicella pneumonia and acute respiratory distress syndrome. Drainage was performed using a PCKC-V™ 24Fr (MERA, Japan) cannula via the right femoral vein with the tip of the cannula near the level of the diaphragm under fluoroscopy. Reinfusion was performed via the right internal jugular vein. Due to poor systemic oxygenation, the drainage cannula was withdrawn caudally and refixed to reduce the effect of recirculation. Two days later, drainage pressure dropped rapidly, and frequent ECMO flow interruption occurred due to poor drainage. An abdominal X-ray revealed abnormal stenosis of the proximal side hole site of the drainage cannula. We diagnosed that the drainage cannula was damaged, and it was replaced with another, namely a Medtronic Bio-Medicus™ 25 Fr (GETINGE, Sweden) cannula. However, the removed drainage cannula was not damaged, suggesting that the cannula was temporarily stenosed by momentary excessive negative pressure. In a multi-stage drainage cannula, the main drainage site is the proximal side hole, with little negative pressure applied at the apical foramen in a mock experimental ex vivo drainage test in a water tank. Hence, improvement of a multi-stage drainage cannula is recommended, such as adequate reinforcement of the side hole site with a wire.