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[ Home ](https://mdster.com) 2. [ Blog ](https://mdster.com/blog) 3. [ Case Discussion ](https://mdster.com/blog?category=case-discussion) 4. ECPR for Refractory VF on VA-ECMO: Harlequin Case [ Case Discussion ](https://mdster.com/blog?category=case-discussion) ECPR for Refractory VF on VA-ECMO: Harlequin Case =================================================== A board-focused case discussion on ECPR selection, intra-arrest anesthesia, ETCO2 interpretation, and differential hypoxemia after femoral VA-ECMO. [ MDster Editorial Team ](https://mdster.com/about) · Jun 22, 2026 · 6 min read · 233 [ Reviewed by Dr. Ali Ragab, MBBCH, MSc, MCAI ](https://mdster.com/medical-reviewers/dr-ali-ragab) [Editorial Policy](https://mdster.com/editorial-policy) \| [Corrections Policy](https://mdster.com/corrections) [ Board Review ](https://mdster.com/blog?tag=board-review) [ Anesthesiology ](https://mdster.com/blog?tag=anesthesiology) [ ECPR ](https://mdster.com/blog?tag=ecpr) [ VA-ECMO ](https://mdster.com/blog?tag=va-ecmo) [ Cardiac Arrest ](https://mdster.com/blog?tag=cardiac-arrest) ![ECPR for Refractory VF on VA-ECMO: Harlequin Case](https://mdster.com/storage/blog/images/ecpr-for-refractory-vf-on-va-ecmo-harlequin-case.jpg) Share this article Share this post On this page 1. [ Why This Patient Earns ECPR ](#why-this-patient-earns-ecpr) 2. [ Reading the Physiology During CPR ](#reading-the-physiology-during-cpr) 3. [ Anesthesia During Cannulation: Less Drug, More Physiology ](#anesthesia-during-cannulation-less-drug-more-physiology) 4. [ Lung Rest Is Not Lung Neglect ](#lung-rest-is-not-lung-neglect) 5. [ Harlequin Syndrome After Femoral VA-ECMO ](#harlequin-syndrome-after-femoral-va-ecmo) 6. [ Neuroprognostication: Wait, Then Use Multiple Signals ](#neuroprognostication-wait-then-use-multiple-signals) 7. [ Key Points for Board Exams ](#key-points-for-board-exams) 8. [ Conclusion ](#conclusion) 9. [ Frequently Asked Questions ](#blog-faqs) 10. [ References ](#references-heading) On this page 1. [ Why This Patient Earns ECPR ](#why-this-patient-earns-ecpr) 2. [ Reading the Physiology During CPR ](#reading-the-physiology-during-cpr) 3. [ Anesthesia During Cannulation: Less Drug, More Physiology ](#anesthesia-during-cannulation-less-drug-more-physiology) 4. [ Lung Rest Is Not Lung Neglect ](#lung-rest-is-not-lung-neglect) 5. [ Harlequin Syndrome After Femoral VA-ECMO ](#harlequin-syndrome-after-femoral-va-ecmo) 6. [ Neuroprognostication: Wait, Then Use Multiple Signals ](#neuroprognostication-wait-then-use-multiple-signals) 7. [ Key Points for Board Exams ](#key-points-for-board-exams) 8. [ Conclusion ](#conclusion) 9. [ Frequently Asked Questions ](#blog-faqs) 10. [ References ](#references-heading) An anterior STEMI has deteriorated into refractory VF under mechanical CPR. The airway is secured, ETCO2 is 18 mmHg, and the arterial waveform shows compression-generated systolic pressure around 80 mmHg. The question is not whether this patient is critically ill; it is whether the low-flow state is still salvageable before irreversible brain injury and multiorgan ischemia dominate. Why This Patient Earns ECPR --------------------------- ECPR is not a longer ACLS algorithm. It is a systems intervention for selected arrests where circulation can be restored mechanically while the cause is treated. In this case, the strongest favorable factor is a witnessed arrest with immediate CPR and a reversible ischemic trigger in an ECMO-capable cardiac catheterization setting. High-yield selection features include: - Age 55 with no known terminal comorbidity - Witnessed arrest and minimal no-flow time - Shockable rhythm with refractory VF - Suspected treatable coronary occlusion - ETCO2 above the futility range during CPR - Mechanical CPR enabling cannulation and PCI workflow FindingInterpretationETCO2 18 mmHgAdequate pulmonary blood flow from compressionsCompression SBP 80 mmHgSome generated perfusion pressureAnterior MI with VFReversible coronary pathology until proven otherwise Clinical judgment still matters. Prolonged low-flow time, severe acidosis, unwitnessed arrest, fixed pupils from the outset, or major bleeding would shift the balance away from cannulation. Reading the Physiology During CPR --------------------------------- ETCO2 during CPR is a practical surrogate for pulmonary blood flow. A persistent value above 10 mmHg, and preferably approaching 20 mmHg, supports mechanically effective compressions. It does not guarantee neurologically intact survival, but it argues against abandoning a potentially reversible arrest. A sudden rise from 18 to 40 mmHg usually signals ROSC because accumulated venous CO2 is abruptly delivered to the lungs. Confirm it with an arterial waveform, pulse check during rhythm analysis, and hemodynamic response. Do not use ETCO2 alone to terminate resuscitation, especially when ECPR is being actively pursued. The differential diagnosis of persistent VF in this setting remains narrow but lethal: - Ongoing LAD occlusion or left main disease - Severe hypoxemia, acidosis, or hyperkalemia - Coronary dissection or catheter complication - Tamponade if instrumentation has occurred - Mechanical MI complication, less common acutely but catastrophic Anesthesia During Cannulation: Less Drug, More Physiology --------------------------------------------------------- The anesthesia task is to prevent awareness and movement without stealing the last coronary perfusion pressure. Standard induction thinking fails here. The patient is already in a low-flow state, and every vasodilatory milligram may reduce cerebral and coronary delivery. AgentHemodynamic issuePropofolSympatholysis, venodilation, myocardial depression, blunted baroreflexEtomidateMinimal effect on SVR and contractility; preserves reflex tone better Etomidate is generally preferred for cannulation sedation in refractory arrest or profound cardiogenic shock. Propofol may become reasonable later, after ECMO flow and vasopressor support are established, but standard boluses before flow can be disastrous. Use neuromuscular blockade when movement threatens cannulation or circuit safety. The insider point is to document why paralysis was necessary and to ensure amnesia once circulation improves. Paralysis without adequate sedation after return of circulation is an avoidable harm. Initial anticoagulation usually uses unfractionated heparin during cannulation if there is no major bleeding or coagulopathy. Many ECMO programs use a bolus-based strategy followed by ACT, anti-Xa, or institutional monitoring. In active CPR after MI, bleeding and thrombosis risks both exist, so the regimen should be protocolized rather than improvised. > **Clinical Pearl:** After VA-ECMO starts, the right radial arterial line becomes the truth-teller for brain and coronary oxygen delivery. A beautiful femoral saturation can be dangerously reassuring. Lung Rest Is Not Lung Neglect ----------------------------- Once VA-ECMO flow reaches about 4 L/min, ventilator goals shift toward limiting ventilator-induced lung injury. Reduce injurious pressures, avoid unnecessary hyperoxia, and maintain enough PEEP to prevent derecruitment. A reasonable target is low driving pressure with plateau pressure below conventional lung-protective thresholds when feasible. However, peripheral femoral VA-ECMO has a trap: if the LV begins ejecting while lungs remain edematous, the upper body may receive hypoxemic native output. Consequently, do not aggressively down-titrate FiO2 or PEEP until right radial oxygenation is known. Harlequin Syndrome After Femoral VA-ECMO ---------------------------------------- The post-cannulation ABG is the board-exam pivot: right radial PaO2 is 45 mmHg while the left foot pulse oximeter reads 99%. This is differential hypoxemia, also called Harlequin syndrome or North-South syndrome. The mechanism is dual circulation. Retrograde oxygenated ECMO flow enters from the femoral artery, while the recovering LV ejects blood that has crossed poorly functioning lungs. If native output pushes the mixing cloud distal to the aortic arch, the brain, coronaries, and right arm receive hypoxemic blood, while the lower body remains well oxygenated. Management options escalate by invasiveness: 1. Improve native lung oxygenation with recruitment, PEEP, bronchoscopy if indicated, and higher ventilator FiO2. 2. Increase ECMO flow cautiously to move the mixing point proximally, watching LV distension and afterload. 3. Convert to V-AV ECMO by adding a right IJ return limb to oxygenate blood entering the pulmonary circulation. 4. Consider axillary or central arterial return when upper-body oxygen delivery remains unacceptable. 5. Treat LV distension if present, because afterload from VA-ECMO can worsen pulmonary edema. Reducing native cardiac output with deeper sedation or beta-blockade is physiologically coherent but rarely satisfying; it may oppose the recovery you are trying to support. Use it only as a bridge while definitive circuit or lung strategies are organized. Neuroprognostication: Wait, Then Use Multiple Signals ----------------------------------------------------- After ECPR stabilization, early nihilism is dangerous. Sedatives, neuromuscular blockers, shock liver, renal dysfunction, hypothermia, and reperfusion injury all confound the neurologic exam. Current post-cardiac arrest guidance supports waiting at least 72 hours after return of circulation and normothermia before reliable poor-outcome prognostication, using a multimodal approach. Useful modalities include serial neurologic examination, EEG, SSEP, brain CT or MRI, and biomarkers where locally validated. The key exam answer is not a single test; it is timing plus concordance plus absence of confounders. Key Points for Board Exams -------------------------- - ECPR is favored by witnessed arrest, immediate CPR, shockable rhythm, reversible cause, and rapid cannulation capability. - ETCO2 of 18 mmHg during CPR suggests effective compressions; an abrupt rise suggests ROSC but requires confirmation. - Etomidate is usually preferred over propofol during low-flow cannulation because it better preserves hemodynamics. - Femoral VA-ECMO can create differential hypoxemia when native LV output competes with retrograde ECMO flow. - Right radial ABG or right-sided oximetry is essential for detecting upper-body hypoxemia. - Do not finalize neuroprognosis before at least 72 hours after return of circulation and normothermia, absent confounders. Conclusion ---------- This case rewards physiologic thinking over checklist anesthesia. The same VA-ECMO flow that rescues systemic perfusion can hide cerebral hypoxemia if monitoring is in the wrong limb. For the board candidate, the sequence is clear: select ECPR carefully, preserve perfusion during cannulation, interpret ETCO2 in context, ventilate intelligently, and recognize Harlequin syndrome before the brain pays the price. Frequently Asked Questions ---------------------------- ### Why is ETCO2 useful during ECPR cannulation? ETCO2 reflects pulmonary blood flow generated by compressions. A value of 18 mmHg supports effective CPR, while an abrupt rise often suggests ROSC, though confirmation is required. ### Why choose etomidate instead of propofol in this case? Etomidate has less vasodilatory and myocardial depressant effect, making it better suited to profound shock or low-flow arrest during cannulation. ### Which pulse oximeter site best detects Harlequin syndrome? Use right-sided monitoring, ideally right radial ABG plus right hand or right ear oximetry, because these reflect arch-vessel oxygen delivery. ### How is differential hypoxemia treated on femoral VA-ECMO? Options include lung recruitment, higher ventilator FiO2, cautious ECMO flow increase, V-AV ECMO conversion, axillary or central return, and management of LV distension. ### When should neuroprognostication occur after ECPR? Reliable poor-outcome prognostication should generally wait at least 72 hours after return of circulation and normothermia, using multiple concordant tests without confounders. References (5) ------------------ 1. 1. [ Richardson ASC, et al. Extracorporeal Cardiopulmonary Resuscitation in Adults: ELSO Interim Guideline Consensus Statement. ASAIO Journal. 2021. ](https://pubmed.ncbi.nlm.nih.gov/33627592/) 2. 2. [ Lorusso R, et al. ELSO Interim Guidelines for Venoarterial ECMO in Adult Cardiac Patients. ASAIO Journal. 2021. ](https://pubmed.ncbi.nlm.nih.gov/34339398/) 3. 3. [ American Heart Association. 2025 Guidelines for CPR and ECC: Adult Advanced Life Support. ](https://cpr.heart.org/en/resuscitation-science/cpr-and-ecc-guidelines/adult-advanced-life-support) 4. 4. [ American Heart Association. 2025 Guidelines for CPR and ECC: Adult and Pediatric Special Circumstances of Resuscitation. ](https://cpr.heart.org/en/resuscitation-science/cpr-and-ecc-guidelines/adult-and-pediatric-special-circumstances-of-resuscitation) 5. 5. [ European Resuscitation Council and ESICM. Guidelines 2025: Post-Resuscitation Care. ](https://www.erc.edu/media/atqopqm4/gl2025-07-post-resus-e.pdf) Study pathway Build momentum in Anesthesiology with focused, exam‑style practice -------------------------------------------------------------------- - Airway, ventilation, and crisis drills - High‑yield anesthesia pharmacology made practical - Track weak topics and improve faster Free 5-day trial No credit card required. 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