**3. Surgical strategies and ECLS setup**

Many centers reported their experience in PEA, focusing on perioperative ECLS: there is no consensus on the best strategy, because of multiple possible indications and approaches, but many authors recommend a prompt, aggressive treatment with ECLS before severe end-stage organ hypoperfusion, possibly with a tailored approach [15, 18].

**Table 1** summarizes the most relevant series in the last two decades.

ECLS can be set up as veno-venous (VV) or veno-arterial (VA) support. Isolated potentially reversible respiratory failure requiring VV-ECLS is an infrequent scenario, because of the aforementioned vitious circles triggered by complications after PEA: often respiratory failure (hypoxia), high PVR and increased lung stiffness offers an excessive hemodynamic barrage to RV, leading to heart failure.

The group of San Diego advocates the use of VV-ECLS in selected patients because of its technical advantages (physiologic flow and no influence on ventricular pre- and after-load, simple and quick implantation; peripheral and percutaneous access, avoiding redo-sternotomy; on the other side, it is burdened by a significant risk of bleeding, infectious and thromboembolic complications if support is

*The Role of Extracorporeal Membrane Oxygenation Support after Pulmonary… DOI: http://dx.doi.org/10.5772/intechopen.108472*


#### **Table 1.**

*Literature reports on type of strategy.*

prolonged) [14]. Standard VV-ECLS is achieved through bi-femoral or jugulo-femoral cannulation; the use of dual lumen cannula (Avalon Elite, Avalon Laboratories, Rancho Dominguez, CA, USA) reduces invasiveness and further simplifies the procedure.

Particular care must be taken in titrating pump flow in order to increase oxygen delivery without any recirculation between the drainage and reinfusion cannulas.

VA-ECLS is preferred by many centers because it provides efficient RV unloading, and reduces transpulmonary flow, parenchymal edema, and/or bleeding. Furthermore, the increased afterload due to arterial inflow improves the filling and diastolic performance of the left ventricle, as well as preventing RV distension and leftward septal shift. But there are some drawbacks, especially in case of peripheral setting, such as unphysiological retrograde perfusion that is at high risk of stroke, "Harlequin syndrome" and limb ischemia [9–11, 24].

Cannulation could be peripheral or central. The standard peripheral setting involves femoro-femoral cannulation, but other cannulation sites such as the subclavian artery can be a viable option: an upper extremity configuration allows mobility and even re-habilitation, especially in case of BTT strategy. Technically, femorofemoral approach is a straightforward procedure that can be easily done in stable conditions while CPB is already ongoing. If feasible, the chest can be definitively closed, reducing the risk of infection and supporting recovery in more physiological conditions. Moreover, cannulas can be removed in the ICU. Of course, troubles with lower limb ischemia or other vascular complications may occur and periodically checked and eventually treated with distal reperfusion [9, 10].

Furthermore, considering flows ranging from 2.5–4 L/min, external oxygenator allows reduction of the mechanical ventilation protecting impaired alveolo-capillary units from barotrauma or high oxygen exposure.

If ECLS is started in the operating room for impossible weaning from CPB, some authors suggest central VA configuration, because it decreases RV afterload, and ensures a pulsatile blood flow into the lung vessels, avoiding overflow episodes during the early postoperative period. Preventive VA-ECMO should be a reasonable BTR strategy that mitigates the negative effects of both critical pulmonary reperfusion syndrome and severe RVF, after PEA procedures [11, 15].

In summary, VV-ECLS should be the treatment of choice for pulmonary reperfusion injury, manifested as pulmonary edema with preserved right heart function, particularly if it occurs in the intensive care unit after PEA. For persistent residual PH and ongoing RV failure, central VA ECLS was excellent providing both oxygenation and effective unloading of the right heart and pulmonary vessels [15].

Regardless of the management strategy, unfortunately, ECLS is burdened by bleeding, infective, and thromboembolic complications, thus patients must be weaned from ECLS as soon as possible.

### **4. Results and outcomes**

The need for postoperative ECLS ranges between 1 and 19%; incidence tends to decrease with experience and in high-volume centers. Mean support time ranges between 4 and 5 days. Successful weaning rate range between 43 and 100% [10, 11, 14, 15, 18, 19, 24, 25].

The main risk factor for ECLS was high PVR often associated with distal thromboembolic disease (Jamieson type 4), while predictors of mortality after ECLS were elder age, high PVR, RV failure, reperfusion injuries, and parenchymal bleeding [9–11, 14, 15].

Considering postoperative hemodynamics, PVR was significantly better in non-ECLS patients [9, 24, 25].

Only two studies reported postoperative BTT strategy: in these cases, survival was about 50% and, according to Boulate and colleagues, survival was similar in BTT and BTR strategies [9, 11].

In general, in comparison with patients not requiring ECLS, long-term survival was significantly lower in ECLS patients [9].

On the other side, early hemodynamic improvement in patients with successful BTR-ECLS persisted in the midterm, confirming the benefit of PEA also in patients with severe CTEPH. This observation is consistent with microvascular disease reversal within a few weeks after PEA as previously suggested in human and animal models [11].

Interestingly, in case of parenchymal bleeding Guth and colleagues tailored the approach to reaching excellent results with 100% of successful weaning: prompt institution of ECLS systems with heparin-coated circuits instead of conventional extracorporeal circulatory support during PEA surgery allows complete restoration of blood coagulation with protamine with a minimal risk of clot formation inside the oxygenator: the majority of patients were treated in the operating theater with very short term support and avoiding long-term complications.

In our experience, ECLS was needed in 12.3% of patients who underwent PEA. The duration of ECMO was 11 ± 8 days and successful weaning was achieved in 52.6% *The Role of Extracorporeal Membrane Oxygenation Support after Pulmonary… DOI: http://dx.doi.org/10.5772/intechopen.108472*

of cases, of these 70% were discharged. Also, in our experience, high PVR was associated with a high risk of ECLS. Surprisingly, the PAPs were lower in the nonsurvivor group: this could be a flag of RV dysfunction function, not able to produce adequate pulmonary flow and pulsatility [10].
