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.