Recently, it is recommended to keep activated clotting time (ACT) more than 480 seconds during cardiopulmonary bypass (CPB) according to the guideline of American Society of ExtraCorporeal Technology (AmSECT). However, it is not rare than ACT does not exceed 480 seconds after administration of unfractionated heparin (UFH). We retrospectively investigated parameters which influenced heparin reactivity in 137 patients out of 272 patients who underwent cardiovascular surgery with CPB from May 2017 to December 2018. One hundred thirty-five patients were excluded to remove influences of initial UFH dose. Heparin reactivity decrease was recognized in 41 (30%) patients. Between patients with decreased heparin reactivity (Low group) and others(Hi group), there were significant differences in age, aortic regurgitation (AR), Hb, TP, ALB/TP, preoperative ACT (PreACT), total UFH dose, and antithrombin (AT) dose. In multivariate analysis, Alb and PreACT were identified as independent parameters influencing decreased heparin reactivity. The evaluation of the suitability of parameters obtained from ROC curve suggested decreased heparin reactivity might be observed when the albumin concentration is 3.8g/dL (cutoff value) or less.
During the Modified Ultrafiltration (MUF), negative pressure may arise in the oxygenator and air may be sent into the patient. Therefore, we added a flow path with a check valve to the conventional A-V MUF flow path. An experimental study was conducted on the effect of A-V MUF efficiency and measures to prevent air intake from the oxygenator.
These experiments on the impact of reduced A-V MUF efficiency due to the addition of a check valve showed no significant impact. An experimental measures to prevent air intake from the oxygenator is although all the pressures became negative, the flow rate of the check valve did not differ much from that of the MUF pump. On the other hands but there was a difference in the time for drawing air due to fluctuations in the MUF pump flow rate. With additional experiments, we found that we could adjust the oxygenator so that it could retain air inside it. Until the air is drawn into the secondary side of the oxygenator air could be retained inside the oxygenator by the surface tension arised in the arterial filter pores. The self-vent technology can remove air from hollow fiber and prevent misfeeding of air. The use of an oxygenator with a check valve and bubble retention function can enhance the safety of MUF.