When the unexpected happens: intracardiac extracorporeal membrane oxygenation venous cannula kinking

The letter reports the case of a patient with a rightsided congenital diaphragmatic hernia (CDH) placed on veno-arterial extracorporeal membrane oxygenation (VA-ECMO) shortly after birth. The patient presented with severe persistent pulmonary hypertension, which was unresponsive to maximal medical therapy. The peculiar anatomical and physiological features of the right CDH played a critical role in causing an unintended azygos vein cannulation. A few cases have been previously reported in the literature dealing with incidental azygos vein cannulation in right-sided CDH patients.1–3 Since ECMO runs are impaired by insufficient drainage, cannula repositioning is generally required.1–3 A term newborn with right-sided CDH and severe pulmonary hypertension with systemic hypotension required VA-ECMO. After surgical cannulation, a high drainage pressure exceeding −60 mmHg was required to maintain a 120 mL/kg/min of cardiac index (CI) during ECMO, despite the appropriate size and position of cannulas on chest x-ray (CXR). To achieve adequate cardiac index with Biomedicus 10 Fr cannula, the pressure range is usually <−20 mmHg. Due to very negative drainage pressure, transthoracic echocardiography (TTE) was performed, and an anterior pericardial thrombus (2 × 2 cm) with cardiac tamponade was detected. In addition, the venous cannula was found to be in the azygos vein. The presence of a thrombus and a posteriorly located pericardial effusion made the percutaneous approach unfeasible. Therefore, open thorax surgery was performed, and the cannula was repositioned. Surgeons chose to retract the cannula a few centimeters and reinsert it with a manual guide without the white introducer, thus maintaining the extracorporeal support. Postoperative venous drainage pressure continued to be excessively negative. CXR and TTE showed an anomalous tip position of the cannula, suggesting its kinking inside the right atrium. The cannula was kinked on the floor of the atrium, and the tip was oriented cranially toward the superior vena cava (Figure 1). Re-intervention was needed to restore proper cannula position and adequate ECMO flows. Therefore, the repositioning of the cannula under TTE and CXR guidance was successfully completed through the previous neck incision (Figure 2). After surgical re-cannulation, the venous cannula was correctly positioned inside the right atrium. The drainage pressure did not exceed −15 mmHg to maintain a 120 mL/kg/min of the CI during ECMO. The patient died after 15 days of VA-ECMO due to a slow but progressive multi-organ failure. Cannula problems complicate about 12.8% of all neonatal respiratory ECMO.4 Both cannula malposition and kinking can affect the proper functioning of the ECMO support, and they should be carefully ruled out with suboptimal venous drainage and insufficient ECMO flow.1 Nevertheless, their diagnosis can be challenging, and both CXR, TTE, and transesophageal echocardiography (TEE) are essential tools.2,5,6 Indeed, in adults undergoing noncardiac thoracic surgery, TTE or TEE are used to detect intracardiac lesions, provide guidance for ECMO cannulas placement, and manage the hemodynamic state of patients.7–9 Moreover, When the unexpected happens: intracardiac extracorporeal membrane oxygenation venous cannula kinking