VV-ECMO and surgical technique
Most patients on VV-ECMO as a BTT were awake throughout the period before the transplant and participated in regular physical therapy. At our institution, awake and ambulatory ECMO protocols have been implemented in order to provide rehabilitation, physical therapy, and minimization of sedation prior to LTx. Whenever feasible, VV-ECMO cannulation was performed with the patient awake in the presence of two experienced operators, using short-acting agents to provide anxiolysis and relying on local anesthetic to maintain patient comfort. The VV-ECMO circuit consisted of a conventional centrifugal pump (Levitronix CentriMagTM, Thoratec, Pleasanton, CA, USA or Cardiohelp, Maquet, Rastatt, Germany) combined with an oxygenator. Our preferred cannulation strategies were a dual-site (femoro-femoral or femoro-jugular) or single-site dual-lumen cannula through the right internal jugular vein (Avalon Elite® bi-caval dual-lumen catheter, Maquet, Rastatt, Germany). In the case of femoro-femoral configuration, a 25Fr Bio-MedicusTMmulti-stage cannula (Medtronic) for drainage and a 23Fr single-stage cannula were used. Continuous intravenous infusion of unfractionated heparin was administered and regularly monitored by measuring activated partial thromboplastin time (aPTT, target range 60-80 sec) and/or anti-Xa (target range 0.30-0.50).
Surgical technique of LTx was described by our group in earlier reports.16 Intraoperative mechanical circulatory support was considered in the case of severe pulmonary hypertension, inability to tolerate one-lung ventilation, and hemodynamic instability after pulmonary artery clamping. Most commonly, patients who were bridged to transplantation with VV-ECMO were transplanted on VV-ECMO; however, in some cases, intraoperative conversion to veno-arterial (VA) ECMO was required. While ECMO was our preferred method of intraoperative support, cardiopulmonary bypass (CPB) has been used depending on the surgeon’s preference, and in the case of severe hemodynamic instability or uncontrolled intraoperative bleeding. Intraoperative VA-ECMO was used to support patients who developed primary graft dysfunction, protamine sulphate-related right ventricular failure, or profound vasoplegia. In these cases, our preference was the use of central cannulation.
If CPB was required, full heparinization (300 IU/kg) was provided before initiation of CPB to maintain an activated clotting time (ACT) greater than 400 seconds during the period of CPB. After discontinuation of the CPB, protamine sulphate was administered to reverse the effect of heparin. On the other hand, when ECMO was used, an initial bolus of 5,000 IU intravenous heparin was given and ACT was maintained between 180 to 250 seconds. Protamine sulphate administration was considered after decannulation only in cases of significant bleeding. Postoperatively, VV-ECMO was used to facilitate the improvement of gas exchange when required, while VA-ECMO was used in the case of severe pulmonary hypertension to protect the new lungs from hyperperfusion or for additional hemodynamic support.