right radial arterial line demonstrates a PaO2 of 150 mm Hg and his post‐oxygenator blood gas PaO2 remains at 400 mm Hg. His lactate levels remain normal. The total ECMO flows have decreased by 0.5 L/min with the same device RPMs. What is the most likely explanation for this finding?The oxygenator efficiency has decreased.There is inadequate oxygen delivery to the tissue resulting in tissue hypoxia.The patient now has severe ARDS.The patient’s heart and left ventricular ejection fraction are beginning to recover.The right radial blood gas is likely venous.As the cardiac function improves in patients on peripheral VA ECMO, the native cardiac output will compete with retrograde aortic ECMO flow, thereby “pushing” left ventricular blood further across the aortic arch. This phenomenon of moving the mixing point more distally into the aortic arch demonstrates the “Harlequin syndrome” that is often seen with femoral‐femoral veno‐arterial ECMO. A sample of arterial blood from a right radial arterial line may demonstrate a more “normal” PaO2 rather than the supranormal PaO2 that is indicative of ECMO circuit blood, and this is often a sign that the cardiac function is beginning to recover. Because most modern ECMO circuits utilize an afterload‐sensitive centrifugal pump, total VA ECMO flows will often decrease as cardiac function improves and the circuit afterload increases.A high post‐oxygenator PaO2 suggests adequate and unchanged oxygenator function, and so long as end‐organ perfusion remains normal, it is unlikely that tissue hypoxia is occurring.A PaO2:FiO2 ratio > 300 does not meet clinical criteria for severe ARDS, and a PaO2 > 100 mm Hg is unlikely to be from a venous blood sample.Answer: DEckman PM, Katz JN, El Banayosy A, et al. Veno‐Arterial extracorporeal membrane oxygenation for cardiogenic shock: an introduction for the busy clinician. Circulation. 2019; 140(24):2019–2037. doi: https://doi.org/10.1161/CIRCULATIONAHA.119.034512. Epub 2019 Dec 9. PMID: 31815538.12 Which of the following sites of hemorrhage is most common during ECMO support?IntracranialCannula siteSolid organGastrointestinalPulmonaryBleeding complications occur in approximately 24% of ECMO patients. The ELSO registry records these complications. Participation in this registry is voluntary; however, in some instances, the exposure may not be 100% of patients resulting in an under‐representation of certain types of bleeding complications (e.g. the percentage of surgical site bleeding may be artificially lowered by including nonsurgical patients in the denominator). However, it appears that cannula site hemorrhage is the most common bleeding complication (8%) followed by surgical site bleeding (7%), gastrointestinal bleeding (6%), pulmonary hemorrhage (4%), and central nervous system bleeding (3%).Figure 3.2 Harlequin syndrome.Source: From Eckman PM, Katz JN, El Banayosy A, et al. Veno‐arterial extracorporeal membrane oxygenation for cardiogenic shock: an introduction for the busy clinician. Circulation. 2019;140(24):2019–2037, with permission.Strategies for managing cannula site bleeding include prevention by under‐sizing the insertion site incision for cannula insertion, application of topical hemostatics around the cannula site, placement of purse string sutures around the insertion site, or lowering the anticoagulation target.Answer: BBrodie D, Slutsky AS, Combes A . Extracorporeal life support for adults with respiratory failure and related indications: a review. JAMA. 2019; 322(6):557–568. doi: https://doi.org/10.1001/jama.2019.9302. PMID: 31408142.
13 General and trauma surgeons are often called upon to consult on ECMO patients. Which statement about surgical procedures for ECMO patients is most accurate?Intra‐abdominal operations should not be performed on ECMO patients, as intraoperative mortality typically exceeds 50%.Tracheostomy can be performed safely and effectively on ECMO patients.The use of antifibrinolytic agents (such as aminocaproic acid or tranexamic acid) for mitigating bleeding in ECMO patients has not been described.Interruption of anticoagulation for any period of time will result in immediate catastrophic circuit failure.Caesarean section is absolutely contraindicated during ECMO support.Noncardiac surgical procedures on ECMO patients are common and are required in as many as 50% of patients. Most studies have not demonstrated increased mortality among patients who underwent surgical procedures. Use of ECMO in pregnancy is also well described with Caesarean sections successfully performed in patients on ECMO.One of the most common procedures performed on ECMO patients is tracheostomy, and many reviews have demonstrated safety and efficacy of tracheostomy on ECMO patients. In fact, tracheostomy may decrease sedation requirements and decrease time on ECMO. Bleeding is still a risk; however, it is our approach to use electrocautery on the skin and soft tissue down to the trachea, turning the ventilator FiO2 < 60% and then proceeding with a percutaneous tracheostomy technique.Additionally, in many centers, antifibrinolytic medications are used prophylactically during surgical procedures or to treat bleeding complications in ECMO patients, and it is unlikely that short‐term interruption of anticoagulation infusions will cause circuit failure.Answer: BJuthani BK, Macfarlan J, Wu J, et al. Incidence of general surgical procedures in adult patients on extracorporeal membrane oxygenation. J Intensive Care Soc. 2019 May; 20(2):155–160. doi: https://doi.org/10.1177/1751143718801705. Epub 2018 Oct 2. PMID: 31037108; PMCID: PMC6475990.Salna M, Tipograf Y, Liou P, et al. Tracheostomy is safe during extracorporeal membrane oxygenation support. ASAIO J. 2020; 66(6):652–656. doi: https://doi.org/10.1097/MAT.0000000000001059. PMID: 31425269.Buckley LF, Reardon DP, Camp PC, et al. Aminocaproic acid for the management of bleeding in patients on extracorporeal membrane oxygenation: four adult case reports and a review of the literature. Heart Lung. 2016; 45(3):232–6. doi: https://doi.org/10.1016/j.hrtlng.2016.01.011. Epub 2016 Feb 20. PMID: 26907195.Agerstrand C, Abrams D, Biscotti M, et al. Extracorporeal membrane oxygenation for cardiopulmonary failure during pregnancy and postpartum. Ann Thorac Surg. 2016; 102(3):774–779. doi: https://doi.org/10.1016/j.athoracsur.2016.03.005. Epub 2016 May 4. PMID: 27154158.
14 A 45‐year‐old woman is placed on femoral‐femoral veno‐arterial ECMO via a 25 Fr venous cannula in the left femoral vein and a 17 Fr arterial cannula in the right femoral artery. Six hours after cannulation, the patient remains on moderate‐dose inopressors and is well supported with an ECMO flow of 3.5 L/min. The bedside nurse notices mottling of the right foot. What is the most likely etiology and reasonable next step?The patient has a right femoral DVT and is developing phlegmasia cerulea dolens. She requires a venous thrombolysis procedure.The patient has decreased cardiac output and requires an increase in inopressors.The arterial reinfusion cannula has thrombosed and must be replaced immediately.The arterial cannula is causing distal limb ischemia. A distal perfusion catheter should be placed emergently.The patient has an ischemic foot and a below‐the‐knee amputation should be performed.The incidence of distal limb ischemia is 10–70% in peripheral VA ECMO patients. It is associated with an increased risk of morbidity and mortality. It must be recognized and treated urgently by placement of a distal perfusion catheter/cannula. If not recognized promptly, amputation may be required; however, reperfusion to the ischemic limb should be attempted prior to any consideration for amputation.It is possible to have a DVT leading to phlegmasia in ECMO patients; however, it is more likely to occur in the leg with the venous cannula and unlikely immediately after cannulation.It is unlikely that decreases in cardiac output or insufficient/absent ECMO flows would result in localized ischemia.Answer: DBonicolini E, Martucci G, Simons J, et al. Limb ischemia in peripheral veno‐arterial extracorporeal membrane oxygenation: a narrative review of incidence, prevention, monitoring, and treatment. Crit Care. 2019; 23(1):266. doi: https://doi.org/10.1186/s13054‐019‐2541‐3. PMID: 31362770; PMCID: PMC6668078.
15 A 40‐year‐old man with severe influenza‐induced ARDS is placed on venovenous ECMO via left and right common femoral veins. He requires ECMO for 12 days, and throughout his course is maintained on a continuous heparin infusion with an average activated partial thromboplastin time (aPTT) of 60 seconds. He is successfully decannulated after improvement in lung function, and then maintained on a continuous heparin infusion for 48 hours after decannulation. Two days after decannulation the patient has sudden‐onset tachycardia, hypoxemia, and hypotension. There is no change in the physical
