Troubleshooting for the Empowered ECMO Nurse

An Introduction to ECMO Troubleshooting

Like other ECMO nurses, I will never forget the first time I had to troubleshoot an extracorporeal membrane oxygenation (ECMO) circuit. My patient had returned to the intensive care unit from the operating room (OR) after a long surgery and was coagulopathic, resulting in a massive transfusion. While the patient was settling into the unit, the ECMO flows started to fluctuate, the low-flow alarm started to sound, and all staff were immediately catapulted into fight or flight mode.

Then I heard it: the sound of air in the circuit. It sounds like water quickly moving through a pipe or foam erupting from an agitated soda can. On a good day, ECMO is a relatively silent therapy. Upon doing a quick ECMO circuit check, I noticed the pump had filled with foam, creating a temporary air lock. During the commute from the OR, a bag of packed red blood cells infusing into a central venous catheter ran dry, and air was quickly drawn into the circuit.

I called for help and stood by with the clamps, ready to snap them on the return cannula at any minute. If possible, we want to avoid stopping the ECMO circuit, as it can result in imminent patient decompensation. Luckily, the air became entrapped in the oxygenator and was able to be aspirated by venting the venous (inlet) side of the oxygenator with a little extra coaxing from an agile perfusionist who quickly arrived on the scene. This story illustrates the importance of the ECMO nurse’s quick recognition of a circuit problem, followed by rapid intervention to prevent patient harm.

Critical care nurses are uniquely positioned to troubleshoot ECMO circuits and escalate concerns to the appropriate members of the healthcare team. ECMO programs may use one of several staffing frameworks to provide care for patients receiving ECMO therapy. The options include the following:

• A critical care nurse and a perfusionist
• A critical care nurse and an ECMO specialist (respiratory therapist or other designated team member)
• Two critical care nurses
• One critical care nurse with an ECMO specialist or perfusionist on call.

Regardless of the staffing platform, the critical care nurse is a consistent presence at the bedside. As such, this nurse is likely to notice mild to moderate changes in a patient assessment that may indicate a clinical problem related to the ECMO circuit.

Most facilities have a streamlined approach for teaching new ECMO nurses that includes attending an initial ECMO course facilitated by the enterprise ECMO coordinator/clinical nurse specialists (CNSs). Cardiovascular perfusionists collaborate with the ECMO coordinator/CNS team during the hands-on skills stations to enhance collaboration (or something similar). This procedure is helpful because nurses are able to practice troubleshooting various emergency scenarios and demonstrate high-risk skills with a fully primed ECMO circuit in a risk-free environment. After class, it is important to pair a new ECMO nurse with a senior ECMO nurse, as they continue to gain experience with independently caring for this complex population. Critical care nurses can earn AACN’s ECMO Micro-Credential to confirm the knowledge they gained from working with ECMO patients.

Clinical Problems in ECMO Therapy

The ECMO nurse is always at the bedside with patients, and is the first line of defense for preventing and addressing critical clinical problems. We excel at recognizing an emergency, especially related to ECMO, and can perform a timely intervention to potentially save a life. Acceptable interventions may vary depending on the institutional policy and education, but bedside nurses are empowered to discover, escalate and intervene when participating in the care of critically ill, complex patients. As ECMO programs continue to expand in our post-pandemic world, critical care nurses will continue to be leaders on ECMO care teams.

Three unique clinical situations can occur when a patient receives ECMO therapy, and the bedside nurse may be the first individual to detect a patient's change.

North-South Syndrome

North-South Syndrome is unique to patients receiving veno-arterial (V-A) ECMO therapy with a femoral return cannula in the artery. This syndrome represents recovering heart function in the setting of poor pulmonary function. The improving heart muscle pushes poorly oxygenated blood into the aorta, where there is a mixing of blood ejected from the heart and oxygenated blood from the ECMO circuit. If the mixing cloud is low in the aorta, the patient will have a pink, richly perfused head and right upper extremity, and poorly perfused left arm and bilateral lower extremities. North-South Syndrome manifests as differential hypoxia; there is a stark contrast between upper and lower body perfusion, which can be illustrated with regional oximetry. (Regional oximetry is a noninvasive form of monitoring that selectively samples tissue oxygenation at deeper levels than a standard pulse oximeter, which only monitors pulsatile arterial blood oxygen content.) If the mixing cloud continues to migrate farther down the aorta, the left arm may exhibit signs of tissue hypoxia as well.

The role of the ECMO nurse is to recognize the clinical issue upon patient assessment and escalate concerns to the appropriate provider. The ECMO nurse may cite decreased regional oximetry values in the right arm and cerebrum (compared with the left arm and lower limbs) as adjunctive values that complement visual assessment as a cause for concern. The primary intervention involves strategic reconfiguration of the ECMO circuit by the surgeon or cannulating physician. Usually, a right subclavian venous return cannula or a right jugular venous return cannula is added to ensure the right atrium and subsequently the lungs are filled with oxygenated blood.

Recirculation

Recirculation is unique to patients receiving veno-venous (V-V) ECMO therapy and is a complication related to cannulation strategy. Ideally, a patient on V-V ECMO with separate drainage and return cannulas will have at least an 8- to 10-centimeter gap between them. In the setting of recirculation, oxygenated blood from the return cannula is immediately pulled back into the drainage cannula, and therefore little or no blood from the ECMO circuit is returned to the patient, or perfused through the native heart. There is a constant loop of blood through the ECMO circuit. This situation results in hypoxemia, and minimal color change in the ECMO cannulas (both are bright red as a result, since blood from the ECMO circuit is not reaching the patient; normally, blood from the drainage cannula has a blue hue, and blood in the return cannula is bright red).

The ECMO nurse will notice a decline in the patient’s oxygen content on an arterial blood gas, but a simultaneous blood gas drawn from the ECMO circuit immediately after the oxygenator will show stellar PO2 value. The pre-oxygenator oxygen saturation may increase. While it may be tempting to increase the blood flow rate for a patient with worsening hypoxia, higher pump speeds will likely increase the rate of recirculation and will not result in improved oxygenation. When recirculation is significant, anticipate that the appropriate provider will manipulate the cannulas or reconfigure the circuit entirely to increase the distance between drainage and return cannulas.

Refractory Hypoxemia

Refractory hypoxemia describes the inability to achieve adequate arterial oxygenation despite delivery of optimal levels of inspired oxygen. Most patients on ECMO receive supplemental oxygen from a mechanical ventilator and the ECMO circuit. Refractory hypoxemia may indicate a patient problem, equipment problem or both. For the patient receiving ECMO, troubleshooting refractory hypoxemia may include evaluation of the following considerations:

• Oxygenator function: Failure of the oxygenator to provide adequate amounts of oxygen may occur quickly (such as in the case of rapid clot accumulation in patients with disseminated intravascular coagulation) or slowly as components of the blood are activated in the setting of a foreign material (causing a biofilm of clot or fibrin to form on the membrane of the oxygenator). This situation may impair gas exchange and oxygen transfer at the level of the membrane. If the patient exhibits hypoxemia refractory to conventional treatment in the setting of a failing oxygenator, it may be time to replace the oxygenator.
• Oxygen uptake: Increasing the blood flow rate may augment oxygenation by increasing the amount of red blood cells that come in contact with the oxygenator for gas exchange. Physiologic factors that may increase myocardial oxygen demand and oxygen consumption include pain, agitation, infection, tachycardia and an increase in cardiac output.
• Oxygen carrying capacity: Suboptimal oxygen carrying capacity has a direct impact on oxygen delivery to the tissues, which is one of the primary goals of ECMO therapy. Without optimal oxygen carrying capacity, ECMO therapy may not be as effective. In the setting of anemia, the team may consider a blood transfusion to increase the oxygen carrying capacity of the blood.
• Flow status: A formula is used to calculate the initial ECMO flow rate for patients receiving ECMO therapy; however, there may be limitations in the ability to achieve the goal flows depending on the patients’ body habitus, drainage and return cannula sizes. Some patients will need much higher blood flow rates on ECMO support, and reconfiguring the ECMO circuit may be necessary to increase flow capacity by adding a drainage cannula and/or increasing the size of the return cannula. However, the team will always be limited by the rated flow of the oxygenator and/or pump, which is typically about 7 liters/minute.

Factors That Impact ECMO Blood Flow Rate

Urgent and Emergent Considerations in ECMO Therapy

Patients on ECMO therapy are receiving the highest level of life support available. Interruptions in therapy may be catastrophic for the patient, so it is imperative to be vigilant and provide continuous surveillance for early detection of any clinically significant problems.

Low Flows: Low flows must be corrected promptly to prevent the patient’s deterioration. Troubleshooting may include assessing for the presence of clots, kinks, cannula malposition or true hypovolemia.

• If the patient is experiencing pain, agitation or interruptions in continuous sedation, they may have a vasovagal episode that will compete with the reperfusate blood in the return cannula and cause low flows.
• If the patient is profoundly hypotensive, venous pooling and a reduction in venous return may limit preload and cause a reduction in flows.
• Other considerations in the setting of a low flow alarm include oxygenator thrombosis, decoupling of the pump, or vasoconstriction, which increases afterload to the pump.

Low flows are an urgent priority, but there are several other ECMO emergencies that require prompt intervention.

Examples of ECMO Emergencies

• Air entrapment: Air may become entrained in the circuit when it is cavitated from solution (i.e., blood) in the setting of excessive negative pressure, or from erroneous entry into the circuit (i.e., while connecting continuous veno-venous filtration to the ECMO circuit). Once this happens, it is critical to prevent the air from migrating to the patient, which may in turn cause a catastrophic air embolus. The appropriate nursing intervention is to clamp the circuit proximal to the air to prevent it from traveling to the patient, stop the circuit and anticipate a circuit exchange. If the air is trapped and manifesting as foam in the upper quadrant of the oxygenator, the operator may be able to aspirate it. If this is not possible, or if the air migrates outside the oxygenator toward the patient, an exchange is needed. To prevent air entrapment, the nurse can be proactive in capping all central lines and ensuring intravenous bags or blood products do not run dry when finished.
• Circuit rupture: This rupture may occur as a result of loose man-made connections or degradation of the disposable ECMO circuit components over time. The appropriate nursing intervention is to isolate the compromised area with two sets of clamps, stop the circuit, and resuscitate the patient while the ECMO circuit is repaired.
• Catastrophic decannulation: Catastrophic decannulation refers to unplanned removal of an ECMO cannula from the patient, potentially leading to exsanguination. Prevention of this emergency is key and best accomplished by having an individual dedicated to watching the ECMO cannulas whenever the patient moves. If unplanned decannulation occurs, clamp the dislodged cannula, stop the circuit, hold pressure on the decannulated vessel, and resuscitate the patient until therapy is restored. Also anticipate that massive transfusion may be necessary.
• Clots: Formation of clots in the outlet of the oxygenator in a patient who is sufficiently anticoagulated is rare but may be catastrophic if the clots become unstable and migrate toward the patient. If a large clot is noted in the outflow tract of the pump, escalate the problem to the perfusionist or ECMO specialist immediately and anticipate the pump will need to be exchanged. If the clot is migrating toward the patient, immediately clamp the cannula proximal to the clot, stop the circuit and resuscitate the patient. Do not hand crank, as this will push the clot to the patient.
• Motor failure, battery failure and catastrophic power loss: These are always clinical emergencies that warrant immediately switching to the backup pump or emergency hand crank, depending on the type of console used.
• No color change: This situation is an emergency because it indicates there is no gas exchange occurring at the level of the oxygenator membrane. It will impact patient oxygenation. The nurse should immediately assess the status of the sweep gas flow rate and ECMO FiO2 to ensure both are on and set at the appropriate rate. Additionally, verify that the oxygen source is connected to the oxygenator, and the oxygen source is established and functioning. Of note, no color change is considered normal only when the sweep or FiO2 have been intentionally weaned off for a patient receiving V-V ECMO therapy. If the sweep gas is turned off in a patient receiving V-A ECMO therapy, deoxygenated blood is rapidly returned to the arterial system, resulting in a massive shunt that will provoke rapid decompensation.
• Spontaneous decoupling of the pump: This situation may be caused by the pump getting bumped, or being placed on a moving motor. The result may be a loud chattering noise from the pump and lead to fluctuations in the pump flows. Ultimately, the pump will need to be stopped and removed from the motor in order for it to reset. If the pump itself has been damaged, a circuit exchange may be required.

Additional Considerations

Oxygenator Function

Accumulation of condensation in the oxygenator is an inevitable phenomenon in extracorporeal circuits. It is a result of sudden cooling of the gas flow proximal to the outlet cover (after exiting the fiber bundle) where the warming effect of blood is no longer present. Condensation buildup impairs the function of the microporous hollow fibers in the oxygenator that allow for gas exchange. Sighing or sweeping out the oxygenator may help release condensation to permit more surface area for gas exchange. Sighing is thought to potentially increase the longevity of the oxygenator and improve the efficacy of gaseous exchange. Sighing the oxygenators should not be used as a therapeutic treatment for increasing CO2 expulsion, as aggressive CO2 removal may lead to cerebral vasoconstriction. Policies vary among facilities, but clinical experts may recommend increasing the sweep gas flow rate for 10 liters/minute for 10-15 seconds. The operator may not be able to see condensation, but awareness of the phenomenon is important. Fibrin and clots will also accumulate in the oxygenator over time, but they are accepted as a permanent (not removable) part of the oxygenator once visible.

Cardiopulmonary Resuscitation

If a patient experiences cardiac arrest while on ECMO, it can be difficult to quickly and correctly identify whether or not to perform cardiopulmonary resuscitation (CPR).

• If a patient on V-A ECMO arrests, first assess to see if the ECMO circuit is on and functioning.
  • Generally, if the pump is on and flowing, you don’t need to perform CPR since the ECMO circuit is still able to support tissue perfusion.
  • If the pump is not flowing for any reason, troubleshoot the ECMO circuit and perform CPR to support the patient.
• V-V ECMO therapy is different, since the circuit is only providing pulmonary support. Even if the circuit is on and flowing in the setting of cardiac arrest, blood is returned to systemic circulation through a vein and will not support organ perfusion. In order to prevent end-organ damage, the team needs to provide high-quality CPR to patients on V-V ECMO while determining the cause of the arrest. If necessary, the circuit can be reconfigured to V-A ECMO.

Summary

Nurses who feel empowered to participate in ECMO care and discussion collaborate effectively, engage with other stakeholders, and are motivated to speak up and intervene, ultimately leading to improved patient outcomes. Providing resources to ECMO nurses and including them in discussions about clinical problems with ECMO support may contribute to early recognition and intervention in the future.

It is easy to focus on the large piece of life-sustaining equipment in the room, but it is important to remember that behind all the equipment is someone’s loved one. Avoid referring to a patient as “the ECMO in bed 6,” for example. Address them by their name. The patient is receiving ECMO therapy.

An ECMO-educated nurse is a capable, knowledgeable and essential member of the healthcare team!

How will you use these troubleshooting tips in your practice?