Question 1

Because the minimum flow rate required to remove condensation in the gas compartment usually results in excessive elimination of carbon dioxide, what should the therapist do?

Accepted Answer

Because the minimum flow rate required to remove condensation usually results in excessive elimination of carbon dioxide, sweep gas is often blended with a carbogen mixture, which reduces the driving pressure across the membrane and maintains normocarbia.

Question 2

What is the advantage of having the centrifugal pump automatically respond to resistances against which it is pumping?

Accepted Answer

Centrifugal pumps are nonocclusive devices because energy is transferred to the blood by a rapidly rotating cone-shaped pump head that creates a constrained vortex. Blood is actively pulled inward and propelled outward by the energy created by the vortex, thus drainage is considered active. Because this type of pump is nonocclusive is it dependent on the patient's preload and afterload. As preload decreases, such as decreased venous drainage, or if afterload increases due to increased systemic vascular resistance, flow will decrease.

Question 3

What are the major advantages of venovenous ECMO?

Accepted Answer

One advantage of VV support is that carotid artery ligation is not required, full pulsatile native blood flow is maintained, and the potential for air or particulate emboli from the circuit is less. A disadvantage is the lack of cardiovascular support. However, the presence of mild to moderate myocardial dysfunction should not discourage the use of the VV approach because the improved oxygenation and lower airway pressures achieved with implementation of VV ECMO often improve cardiac function.

Question 4

Which of the following conditions are cardiac applications of ECMO?
I. High cardiac output syndrome
II. Cardiac arrest
III. Preoperative stabilization
IV. Cardiomyopathy

Accepted Answer

Table 19-1 Indications for Cardiac ECMO
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Question 5

The therapist in charge of a patient on ECMO is monitoring ACT every 30 minutes. The last ACT was 100 seconds. What should the therapist suggest at this time?

Accepted Answer

The classic method for monitoring anticoagulation is to measure the activated clotting time (ACT) with a point-of-care device. The heparin dose is titrated to achieve an ACT range of typically 160 to 180 seconds.

Question 6

Which of the following strategies is greatly responsible for decreasing the need for ECMO in neonates?

Accepted Answer

The introduction of high-frequency oscillatory ventilation (HFOV) decreased the need for ECMO and is a standard of care in the management of hypoxemic respiratory failure. Since HFOV utilizes higher mean airway pressure than CMV, an OI of 60 has been considered a more realistic threshold for identifying mortality risk and the need for ECMO when this form of ventilation is used.

Question 7

A neonate on mechanical ventilation with respiratory distress has a PaO₂ of 50 mm Hg, a of 20 cm H₂O and FiO₂ of 0.8. Why should the therapist suggest therapies other than ECMO?

Accepted Answer

Ortega and colleagues found that when the OI exceeded 40 during conventional mechanical ventilation, the risk of mortality exceeded 80%. Their results have been reproduced by other institutions, and the OI remains a widely accepted predictor of mortality in neonates with respiratory failure, and is used as part of the selection criteria for using ECMO.

Question 8

Which of the following conditions is considered contraindications for neonatal ECMO?

Accepted Answer

Typically the need for ECMO is identified within the first couple of days. The need for ECMO following a prolonged period of mechanical ventilation, such as 7 to 10 days, suggests atypical lung pathology that may not be reversible. Another consideration for deciding not to use ECMO is the patient's size and gestational age. There are ECMO catheter size limitations for newborns less than 2 kg, and newborns less than 32 weeks gestation may be at greater risk for developing intracranial hemorrhage when exposed to anticoagulants.

Question 9

What are the most common causes of a decrease in venous return in ECMO?
I. Hypervolemic state
II. Malpositioning of the venous cannula
III. Kinking of the cannula
IV. Shifting of the mediastinum

Accepted Answer

The most common causes of a decrease in venous return include malpositioning of the venous cannula, kinking of the cannula, shifting of the mediastinum, or a hypovolemic state.

Question 10

It is not uncommon for patients undergoing ECMO to experience renal failure. What can be done to enhance renal function?

Accepted Answer

It is not uncommon for patients requiring ECMO to develop renal insufficiency from pre-ECMO fluid resuscitation, acute renal dysfunction, and blood product replacement. To augment renal function and remove larger quantities of fluid, a semipermeable membrane or hemofilter can be added to the ECMO circuit.

Question 11

Which of the following mechanisms affect the output of VV ECMO?
I. Size of the tubing
II. The rotations per minute
III. Tension of the rollers
IV. Patient's blood pressure

Accepted Answer

The output depends on the size of the tubing, the rotations per minute (RPMs), and the tension or occlusion of the rollers on the raceway.

Question 12

What is the key reason for making ECMO so successful in newborns?

Accepted Answer

Nearly 30,000 newborns with respiratory failure have been reported in the ELSO Registry, which represents the bulk of the neonatal ECMO experience. This includes patients with the diagnosis of persistent pulmonary hypertension of the newborn, meconium aspiration syndrome, respiratory distress syndrome, sepsis, and air leak syndromes, all reversible conditions, which is a key element for positive outcomes when providing ECMO.

Question 13

The therapist should evaluate raceway occlusion because too much roller tension could be associated with which of the following events?

Accepted Answer

Evaluating raceway occlusion is essential: too much roller tension (overoccluded) may cause tubing damage and hemolysis, and too little roller tension (underoccluded) may result in inadequate flow.

Question 14

The ECMO specialist has noticed excessive clotting in the circuit despite increase doses of heparin. What is the most feasible explanation for this event?

Accepted Answer

If excessive clotting in the circuit is noted, a deficiency in ATIII is a possible cause. Heparin has no direct anticoagulant effect on the blood by itself but combines with a cofactor, antithrombin III (ATIII), to prevent thrombi from forming. This stops the conversion of fibrinogen to fibrin and ultimately prevents blood from clotting. A deficiency in ATIII can cause heparin to be ineffective, resulting in the use of excessive amounts of heparin.

Question 15

Which of the following parameters have been suggested as factors that may help predict outcome for pediatric ECMO? I. PaO₂ <50 mm Hg II. PaO₂/FiO₂ <75 III. OI >35 IV. Pre-ECMO pH <7.20

Accepted Answer

There is no definitive consensus on when ECMO should be initiated in pediatric respiratory failure. Single-center reviews have attempted to identify pre-ECMO factors that may help predict outcome. Mehta and colleagues suggested that an OI >35 or a pre-ECMO pH of <7.20 may result in higher mortality. In a case series by Turner and colleagues, it was suggested that there are no true contraindications to using ECMO in pediatric patients with refractory respiratory failure. They further commented that ECMO is appropriate if patients are transferred to an ECMO center early, if lung-protective ventilation is used, and when severe neurologic injury is not present. In addition, the PaO₂/FiO₂ (P/F) ratio has also been validated as a metric of oxygenation deficit severity in pediatric acute respiratory distress syndrome (PARDS).

Question 16

Which of the following statements describes venoarterial ECMO?

Accepted Answer

ECMO support begins by accessing the vasculature in order to establish drainage and reinfusion sites. In newborns and infants, perfusion cannulas are surgically placed in a vein, commonly the right internal jugular, and an artery, usually the right common carotid. This is the classic venoarterial (VA) configuration in which deoxygenated venous blood is drained from the patient and blood that is fully saturated with oxygen is artificially pumped and returned to the arterial system.

Question 17

Which of the following are the principle components of the ECMO system?
I. A pump
II. A standardized ECMO circuit
III. A gas exchange device
IV. A ventilator

Accepted Answer

The ECMO system has two principle components, a pump and gas exchange device. Additional circuit components include cannulas, pressure monitoring modules, gas metering devices, heater/cooler exchanger, and circuit tubing. Some of the newer devices have pressure, temperature, and blood analyzer fully integrated into their system. Although the mechanical principles are fairly universal, there is a lack of standardization of the ECMO circuit and therefore the general design is institution-specific.

Question 18

In the gas membrane exchanger, what is one of the limiting factors to the transfer rate of oxygen across the membrane?

Accepted Answer

The transfer rate of O₂ is limited by the thickness of the blood film between the membrane layers. As the blood film becomes thicker, the oxygenating efficiency decreases.

Question 19

Which of the following groups of patients has the highest mortality rate when treated with ECMO?

Accepted Answer

The use of ECMO as a bridge to heart transplantation is associated with higher waitlist mortality and poor survival to discharge, thus providing an impetus for developing alternative methods of prolonged mechanical circulatory support.

Question 20

During administration of venovenous ECMO, the therapist notices that the SvO₂ is greater than SaO₂. What is the best explanation to this phenomenon?

Accepted Answer

If SvO₂ is greater than SaO₂, the recirculation is excessive, which would require either an adjustment in cannula position or change in blood flow rate.

Quiz 19: Extracorporeal Membrane Oxygenation

Because the minimum flow rate required to remove condensation in the gas compartment usually results in excessive elimination of carbon dioxide, what should the therapist do?

What is the advantage of having the centrifugal pump automatically respond to resistances against which it is pumping?

What are the major advantages of venovenous ECMO?

Which of the following conditions are cardiac applications of ECMO? I. High cardiac output syndrome II. Cardiac arrest III. Preoperative stabilization IV. Cardiomyopathy

The therapist in charge of a patient on ECMO is monitoring ACT every 30 minutes. The last ACT was 100 seconds. What should the therapist suggest at this time?

Which of the following strategies is greatly responsible for decreasing the need for ECMO in neonates?

A neonate on mechanical ventilation with respiratory distress has a PaO2 of 50 mm Hg, a of 20 cm H2O and FiO2 of 0.8. Why should the therapist suggest therapies other than ECMO?

Which of the following conditions is considered contraindications for neonatal ECMO?

What are the most common causes of a decrease in venous return in ECMO? I. Hypervolemic state II. Malpositioning of the venous cannula III. Kinking of the cannula IV. Shifting of the mediastinum