Chest computed tomography in children undergoing extra-corporeal membrane oxygenation: a 9-year single-centre experience

Advances in pulmonary management and weaning from ECLS

ECMO for neonatal and pediatric respiratory failure provides gas exchange to allow lung recovery from reversible pulmonary ailments. This is a comprehensive discussion on the various strategies and advances utilized by pediatric ECLS specialists today. ECMO patients require continual monitoring, serial gasses and radiographs, near-infrared spectroscopy (NIRS - to monitor oxygen delivery to regional tissue beds), and more quality ECLS directed care. As the foundation to lung recovery, good EMCO closely monitors ECLS flow rates, sweep gasses, and membrane lung function. Mixed venous oxygen saturation (Sv02) greater than 65% indicates good oxygen delivery and sweep gas adjustments maintain PaCO2 of 40-45 mm Hg. Lung recovery ventilatory settings do not fully rest the lungs but maintain normal or nontoxic pressure and oxygen levels. Neonatal recovery settings are PIP (cm H20) of 15-20, PEEP of 5-10, ventilator rate of 12-20 and an inspiratory time of 0.5-1 s, and FiO2 of 0.3-0.5. Pediatric recovery settings are PIP (cm H20) < 25, PEEP of 5-15, ventilator rate of 10-20 and an inspiratory time of 0.8-1 s, and FiO2 of <0.5. Some studies demonstrate a higher recovery PEEP level decreases duration of ECMO, but do not demonstrate a mortality difference. Multiple adjunctive therapies such as surfactant, routine pulmonary clearance and respiratory physiotherapy, iNO, prone positioning, bronchoscopy, POCUS, CT imaging, and extubation or "awake ECLS" can significantly affect pulmonary recovery. Patience is necessary as lung recovery may take weeks or even months on the nontoxic settings. On these settings, dynamic recovery will be revealed by improvement in tidal volume, minute ventilation and radiographic pulmonary aeration, prompting discussion about weaning. When this pulmonary compliance recovery becomes evident, decreasing ECLS flow while also decreasing circuit FiO2 and/or sweep gas are common components to ECMO weaning strategies.

Performing chest computed tomography on pediatric patients on extracorporeal membrane oxygenation (ECMO): a stepwise approach

Chest CT in pediatric patients on extracorporeal membrane oxygenation (ECMO) can be done safely and provide valuable high-quality diagnostic images to help guide patient management. An understanding of the basics of the ECMO circuit, cannula locations, where and how to inject contrast media, and how to time image acquisition is vital for the radiologist. Additionally, understanding the precautions associated with performing these exams is essential to ensure the safety of the child. This article provides a brief review of pediatric ECMO and its challenges and considerations, as well as a stepwise approach to perform and optimize these exams safely.

Optimizing neonatal cardiac imaging (magnetic resonance/computed tomography)

Magnetic resonance imaging (MRI) and CT perform an important role in the evaluation of neonates with congenital heart disease (CHD) when echocardiography is not sufficient for surgical planning or postoperative follow-up. Cardiac MRI and cardiac CT have complementary applications in the evaluation of cardiovascular disease in neonates. This review focuses on the indications and technical aspects of these modalities and special considerations for imaging neonates with CHD.

CT Angiography of Venoarterial Extracorporeal Membrane Oxygenation

Imaging plays a central role in the workup of thromboembolic events and bleeding complications in patients treated with venoarterial extracorporeal membrane oxygenation (ECMO) (VA-ECMO), and radiologists should be familiar with the expected hemodynamic changes and flow-related artifacts associated with the VA-ECMO system. VA-ECMO is a form of temporary mechanical circulatory support for critically ill patients with acute, refractory cardiac or cardiopulmonary failure. As the use of VA-ECMO continues to increase, it is important to be aware of associated hemodynamic changes and challenges at imaging. Patients treated with VA-ECMO are at high risk for thromboembolic events and bleeding complications and, thus, often require evaluation with CT angiography (CTA). VA-ECMO can be implemented by using central or peripheral cannulation. The peripheral femorofemoral VA-ECMO circuit in particular alters the sequence and direction of contrast medium enhancement substantially, resulting in flow-related artifacts that can mimic or obscure disease at CTA. Nonopacification can be mistaken for spurious thrombus or simulate complete vascular occlusion, while mixing artifacts can mimic dissections. Misinterpretation of flow-related CTA artifacts can lead to inappropriate surgical or medical intervention. A methodical and multiphasic approach should be taken to CTA imaging strategies and interpretation for patients treated with VA-ECMO. There is no universal CTA protocol for patients on VA-ECMO. Each protocol must be designed for the study indication, with consideration of the configuration of the ECMO cannulas, contrast material injection site, region of interest, native cardiac output, and ECMO flow rate. The authors provide examples of common and unusual VA-ECMO-related artifacts, with a focus on strategies for optimizing CTA image acquisition. Online supplemental material is available for this article. ^©RSNA, 2021.

Computed tomography in paediatric heart disease

Cardiovascular CT (CCT) is an important imaging modality in congenital and acquired paediatric heart disease. Technological advances have resulted in marked improvements in spatial and temporal resolution of CCT with a concomitant increase in speed of data acquisition and a decrease in radiation dose. This has elevated CCT from being sparingly used to an essential diagnostic tool in the daily multimodality imaging practice alongside echocardiography, cardiovascular MR and invasive angiography. The application of CCT in paediatric congenital and acquired heart disease can be both technically and diagnostically challenging. This review highlights important considerations for current state of the art CCT across the spectrum of heart disease encountered in children.

Chest computed tomography angiography in children on extracorporeal membrane oxygenation (ECMO)

Performing chest CT angiography on pediatric patients on extracorporeal membrane oxygenation (ECMO) can be challenging. Successfully performing CT angiography in these children requires substantial communication and coordination between the radiologists and clinical care providers. Additionally, the radiologist must understand the child's anatomy and disease pathophysiology, flow dynamics of the ECMO circuit, image acquisition timing, contrast injection site, and volume, rate and duration of contrast administration. In this article we highlight the vital factors the radiologist needs to consider to optimize the chest CT angiography in pediatric patients on ECMO.

Portable CT Pulmonary Angiogram in an Infant on Veno-Arterial Extracorporeal Membrane Oxygenation in the Pediatric Intensive Care Unit

PURPOSE

Computed tomography (CT) has been shown to change management in children on extracorporeal membrane oxygenation (ECMO). Although techniques have been described to transport these critically ill patients to the CT suite in the radiology department, transport out of the intensive care setting is not without risk, and using portable CT is a practical alternative. However, obtaining a CT pulmonary angiogram (CTPA) in a patient on veno-arterial (VA) ECMO presents unique challenges due to bypass of the cardiopulmonary system, which may lead to suboptimal opacification of the pulmonary arteries.

METHODS

We describe a method to obtain a diagnostic CTPA study in an infant on VA ECMO in the intensive care unit using portable CT. Our solution involved temporary withholding ECMO and using the venous cannula to deliver a compact contrast bolus to the right atrium to adequately opacify the pulmonary arteries. Special attention was given to the delivery of the contrast bolus, which was given by hand injection, to ensure it coincided with image acquisition and minimized the time ECMO was withheld.

RESULTS

We were able to successfully obtain a diagnostic CTPA study in an infant on VA ECMO in the intensive care unit using portable CT.

CONCLUSION

This case demonstrates that in select instances CTPA in infants on VA ECMO can be achieved using a portable CT system.

Imaging adults on extracorporeal membrane oxygenation (ECMO)

Extracorporeal membrane oxygenation (ECMO) is increasingly being used in adults following failure to wean from cardiopulmonary bypass, after cardiac surgery or in cases of severe respiratory failure. Knowledge of the different types of ECMO circuits, expected locations of cannulas and imaging appearance of complications is essential for accurate imaging interpretation and diagnosis. Commonly encountered complications are malposition of cannulas, adjacent or distal haemorrhage, stroke, stasis thrombus in access vessels, and distal emboli. This article will describe the imaging appearance of different ECMO circuits in adults as well as commonly encountered complications. If a CT (computed tomography) angiogram is being performed on these patients to evaluate for pulmonary embolism, the scan may be suboptimal from siphoning off of the contrast by the ECMO. In such cases, an optimal image can be obtained by lowering the flow rate of the ECMO circuit or by disabling the circuit for the duration of image acquisition.

Key Points

• Femoroatrial VV ECMO: femoral vein drainage cannula and right atrial return cannula.

• Femorofemoral VV ECMO: return and drainage cannulas placed in femoral veins.

• Dual-lumen single cannula VV ECMO: via the right IJ/Femoral vein with the tip in the IVC/SVC.

• Peripheral VA ECMO: peripheral venous drainage cannula and peripheral arterial return cannula.

• Central VA ECMO: direct right atrial drainage cannula and aortic return cannula.