**2. Weaning process**

#### **2.1 Factors of successful weaning**

#### *2.1.1 Hemodynamics parameters*

The most easily obtained signal of when to start the ECMO weaning process is the patient's blood pressure. ECMO weaning can be considered if the patient's blood pressure and pulse pressure begin to increase even after applying the same ECMO flow and using the same inotropic medications. When the patient's blood pressure increases, the minimum mean arterial pressure is maintained at about 60 mmHg, and inotropes are gradually reduced or rarely used [2].

Substantial hemodynamic assessments may be needed during the weaning trial for critically ill patient monitoring. If the patient has a pulmonary arterial catheter, the pulmonary arterial catheter measurements provide key information regarding the right ventricle (RV) and left ventricle (LV) pre-loads [3]. To consider a patient for VA ECMO weaning, the hemodynamic variables with the pump off should be as follows: cardiac index >2.4 L/min/m2, mean blood pressure > 60 mmHg, pulmonary capillary wedge pressure < 18 mm Hg, and central venous pressure < 18 mmHg.

#### *2.1.2 Laboratory findings*

When considering ECMO weaning, laboratory findings should also be referred to, including blood tests for B-type natriuretic peptide, cardiac enzymes, lactate, liver function tests, and kidney function tests. A decreasing trend in these values rather than absolute values should be seen after ECMO support is withdrawn [4]. A few studies recommended that lactate and lactate clearance could aid for ECMO weaning [3].

#### *2.1.3 Echocardiographic parameters*

Echocardiography is a critical tool used to determine the recovery of both left ventricle and right ventricle function [5]. During ECMO support, performing echocardiography is recommended at least once a day as much as possible.

In several reports, ECMO weaning is likely when the following findings are observed [3, 4, 6, 7].


Both LV and RV size and function should be estimated during weaning of extracorporeal support and if distension and impending failure of either ventricle is noted, they may warrant termination of the weaning trial [6].

*How to Do Weaning and Decannulation in Adult Cardiac DOI: http://dx.doi.org/10.5772/intechopen.108074*

*2.1.4 Other findings*

In addition to myocardial recovery, end-organ recovery is essential. Pulmonary function should also not be compromised and pulmonary edema should be reduced as much as possible. A PaO2/FiO2 of ≥200, an oxygen fraction delivered by the extracorporeal circuit of 25%, and an oxygen fraction delivered by the ventilator circuit of 60% are rational for weaning trials. These measurements should be made with VA-ECMO blood flow at 1 ~ 1.5 L/min and a sweep gas flow rate of ≤1 L/min. Of note, if the patient


**Figure 1.** *VA ECMO weaning protocol.* experiences persistent pulmonary compromise but sufficient myocardial recovery could be achieved, switching to a veno-venous (VV)-ECMO should be considered [4].

If the findings listed above are observed, ECMO weaning is initiated.

#### **2.2 Weaning trial**

As mentioned earlier, there is no absolute way to determine the time for ECMO weaning. Each center or each person in charge has set and applied algorithms or protocols based on their own experience and knowledge. The patient should have estimated hemodynamic stability in the absence of or at low doses of vasoactive agents and pulsatile arterial waveform maintained for several hours. The ECMO flow is decreased to 60–70% of the initial flow rate for several minutes. It is then decreased to 30–40% for several minutes. Depending on the patient's condition, the ECMO weaning process may end within a day, or it may take several days. If the patient is stable in such a flow, it can be decreased to a minimum of 1–1.5 L/min and FiO2 in gas blender of <50–60% for several minutes. If no particular problem occurs during this process, ECMO removal can be considered. If mean blood pressure falls significantly and is continuously <50–60 mmHg during the trial, ECMO flow was returned to 100% of the initial flow and the trial is stopped. We propose the strategy we are using in our center in **Figure 1**.

#### *2.2.1 The pump-controlled retrograde trial off (PCRTO)*

Pump speed is steadily reduced in a controlled manner until circuit flow becomes retrograde, ensuring adequate RV filling and proper assessment of RV function. Since the circuit becomes an arteriovenous shunt, the revolving pump head acts as a resistor, preventing a significant drop in systemic vascular resistance during PCRTO. Patients can be considered ready for decannulation if the hemodynamic and echocardiographic criteria are met after a few minutes or hours [8]. Some researchers reported PCRTO to be a safe, simple, and reproducible approach for enabling a trial period while preserving the circuit during weaning from VA ECMO [9, 10]. In stable patients, PCRTO seems reasonable even if it is tested for 5–10 minutes without additional heparin or decannulation. However, in patients with low blood pressure or high vasoactive drugs with low ECMO flow, sufficient time spent on testing and removal will reduce the possibility of reinsertion.

### **3. Decannulation**

Once the decision has been made to terminate ECMO, the cannulas are removed. Hemostasis can be achieved by extraction of the venous cannula from the femoral vein using a mattress suture and manual compression. Decannulation of arterial ECMO may be achieved by open surgical repair or *via* manual compression or using closing devices.

ECMO decannulation is related to the high risks of complications, such as bleeding, hematoma, pseudoaneurysm, thrombosis, and arterial-venous fistula. Bleeding complications occur after removal in 2%, with vascular complications generally up to 18% [11]. Frank Bidar et al. reported cannula-associated deep vein thrombosis occurred in 44 patients (41%), and arterial complications occurred in 15 (14%) (9 with acute leg ischemia, 1 with arteriovenous femoral fistula, and 5 with late femoral stenosis).

Vascular complications after ECMO decannulation can lead to prolong hospitalization and increase medical costs. Therefore, decannulation should be performed carefully and the patient's condition should be closely examined after cannula removal.

The selection of the cannula removal method is applied differently according to the condition of each center, the responsible person, and patient. The discontinuation of heparin infusion before cannula removal is also implemented differently depending on each center and the responsible person. Careful patient selection for the hemostasis method used and a proper method are needed for successful hemostasis following ECMO decannulation.

#### **3.1 Manual or mechanical compression**

All venous cannulas can be removed using a simple aseptic method. The operator must be aware of the danger of air embolism. This situation can be prevented by the application of Valsalva maneuver. The area around the venous cannula should be infiltrated with local anesthetic, and a horizontal mattress suture can be helpful to the hemostasis.

For percutaneous ECMO establishment, the artery was manually compressed after decannulation for 30–60 minutes. In case of persistent bleeding, a surgical correction was done. In the absence of any bleeding, only a standard pressure bandage or mechanical compressor was applied.

For a more definite hemostasis, prior to manual compression, if possible, modifiable coagulopathy factors such as activated coagulation time (ACT), activated partial thromboplastin time (aPTT), prothrombin time (PT), and platelet activation should be corrected. Yeo et al. reported the use of dual antiplatelet drugs and a higher aPTT can lead to an increased risk of postprocedural vascular complications. Therefore, manual compression should be applied cautiously after the correction of coagulopathy factors such as ACT, aPTT, and platelets counts [12].

Manual compression does not require movement of the patient and can be performed relatively easily without any special device. However, it may be difficult to obtain consistent results using this method, depending on the person applying compression. If a large cannula is used, the patient has severe calcification of the blood vessels, or long ECMO duration, is obese, or coagulopathy is not well corrected, it would be better to consider other methods. Further studies are necessary to evaluate the efficacy and safety of manual or mechanical compression in patients with ECMO.

#### **3.2 Surgical repair**

Peripheral or central cannulas inserted surgically should be removed surgically. If the arterial thrombosis was detected before ECMO weaning, the thrombosis can be removed together with surgical cannula removal.

Surgical removal has the advantage of visualizing blood vessels directly, removing the cannula, and stopping bleeding. Surgical removal can cause problems such as infection or poor healing of the wound and bleeding or lymphatic leakage. There is also a limitation in that it is possible only when a patient is moved to an operating room and surgical equipment is moved, or an operator is required.

Although more research is needed, surgical removal is thought to reduce the side effects if applied when large cannula is used, ECMO application period is long, and vascular calcification is severe.

#### **3.3 The vascular closure device**

In an effort to reduce the rates of vascular complications at the time of VA-ECMO decannulation and avoid the need for traditional surgical vascular repair, percutaneous techniques for closure of arterial cannulation sites utilizing several vascular closure systems have been employed by a number of centers [13].

Chandel et al. reported the use of a pre-closure technique was associated with a significant decrease in limb complications and bleeding events with an estimated 81% and 79% decreased likelihood of these complications, respectively, compared with surgical removal [13]. Data from prior cohorts have documented the utility of this technique in the removal of arterial sheaths of sizes ranging from 5 Fr to 24 Fr [13]. The main benefit of using this technique is the avoidance of a groin incision, which may be susceptible to wound infection, poor healing, and lymph leakage [14]. The procedure time is shorter than that of other methods.

This method also has disadvantages such as technical failure, thromboembolism, pseudoaneurysm, and stenosis, and is more expensive than other methods. If hemostasis is difficult or has failed, manual compression must be applied or conversion to surgery must be undertaken, which may cause a large amount of bleeding. After applying a closure device, it is necessary to closely monitor the occurrence of complications.

Some centers use closure devices for distal perfusion catheter removal [14].

However, as experience is accumulated with this technique, it may be possible to accomplish arterial ECMO decannulation at the bedside without the use of general anesthesia.

### **4. Conclusion**

VA ECMO is an influential life support tool. Weaning from VA ECMO remains a challenging decision. In addition to cardiac function, overall patient evaluation should be done accurately to achieve successful ECMO weaning. It is especially important that the ECMO is not weaned while the patient is still recovering from the conditions that required the VA ECMO implantation.

Weaning strategies are based on institutional standards and individual experiences. Different weaning algorithms are used and none have reached dominance yet. Experienced VA ECMO centers should elaborate standardized weaning algorithms and consensus documents. A systematic weaning protocol will be able to lower the weaning failure rate.

Cannula removal should be selected well according to the patient's condition and the experience of the centers. It is also important to reduce complications by closely observing the patient after cannula removal.

Larger randomized trials are needed to confirm our findings and generate a new standard for VA-ECMO decannulation.

### **Acknowledgements**

Thanks go to Asan Medical Center for having the experience and knowledge of ECMO.

*How to Do Weaning and Decannulation in Adult Cardiac DOI: http://dx.doi.org/10.5772/intechopen.108074*
