WHEN IT'S NOT THE MEMBRANE LUNG'S FAULT

ABSTRACT

TOPIC Critical Care TYPE Fellow Case Reports INTRODUCTION: Veno-venous extracorporeal membrane oxygenation (VV-ECMO) is increasingly used in the management of respiratory failure failing to respond to conventional methods. This case highlights the importance of identifying and rectifying complications of ECMO. CASE PRESENTATION We present a 56-year-old male who presented after being diagnosed with COVID-19. His past medical history included diabetes mellitus and hypertension. He was admitted to the intensive care unit for rapidly worsening hypoxic respiratory failure requiring mechanical ventilation. Despite trials of paralysis and prone positioning for severe acute respiratory distress syndrome (ARDS), the patient did not improve and was cannulated with a 21 French right internal jugular (IJ) and 25 French right femoral cannulas under fluoroscopic guidance for VV-ECMO.On initiation, flow was suboptimal despite revolutions per minute (RPM) as high as 5000 generating flows of 2.1 liters per minute (LPM). Post oxygenator pressures were 500-520 mmHg. Rectifying this problem was delayed by 12 hours. A new left IJ vein return cannula was placed and the prior return cannula removed which had a kink on its distal end that was not seen on imaging. Flows improved significantly after this change.The return cannula blood was noted to be dark red, which prompted evaluation of membrane lung function which was normal. A co-oximetry demonstrated significantly elevated methemoglobinemia of 15%. Medications were reviewed and none were noted to cause methemoglobinemia. Patient was treated with repeated doses of methylene blue.The patient developed multi-organ failure as well as refractory vasoplegic shock on multiple vasopressors. The family made the decision to transition patient's care to comfort care on day 5 of VV-ECMO. DISCUSSION: This case demonstrates the grave consequences of late identification and correction of flow limitation in VV-ECMO and how a kinked cannula led to severe hemolysis causing methemoglobinemia. In literature, cooxyhemoglobin correlated with increasing hemolysis, however there is indirect evidence that with increased hemolysis, increase oxygen radicals can lead to the formation of methemoglobin. Methemoglobinemia is a known cause of renal failure, as well as multi-organ failure. Monitoring levels of methemoglobin have both diagnostic and therapeutic advantages.This case also highlights a rather atypical cause of dark blood in return cannula, other than membrane lung dysfunction. Methemoglobin in classic teaching causes "chocolate-red" blood, with a low spO2 and a relatively high PaO2, as noted in our patient. CONCLUSIONS: It is important to be well versed with the possible complications of ECMO. Common differential diagnoses for flow limitation include hypovolemia, shock, increased abdominal/thoracic pressures, kinked cannula, thrombus formation or obstructed drainage from the return cannula. REFERENCE #1 Hemolysis in pediatric patients receiving centrifugal-pump extracorporeal membrane oxygenation prevalence, risk factors, and outcomes. Lou S., MacLaren G., Best D., Delzoppo C., Butt W. Crit Care Med. 2014 May;42(5)1213-20. REFERENCE #2 Methemoglobinemia A Diagnosis Not to Be Missed. Lata K., Janardhanan., R. AJM ONLINE CLINICAL COMMUNICATION TO THE EDITOR. 2015 Oct;128(10) E45-6. REFERENCE #3 The Complex Relationship of Extracorporeal Membrane Oxygenation and Acute Kidney Injury Causation or Association? Kilburn D. J., Shekar K., Fraser J. F., Biomed Res Int. 2016 Feb. 2016;20161094296. DISCLOSURES No relevant relationships by Anna Abbasi, source=Web Response No relevant relationships by Cliff Chen, source=Web Response No relevant relationships by Ethan Karle, source=Web Response No relevant relationships by Shyam Shankar, source=Web Response No relevant relationships by Blaine Winterton, source=Web Response