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

A Guide to Contrast-Enhanced Computed Tomography in Adult Patients Supported With Extracorporeal Membrane Oxygenation

Veno-arterial extracorporeal membrane oxygenation (VA ECMO) fundamentally alters patient physiology and blood flow relevant to contrast delivery for computed tomography (CT) imaging. Here, we present a comprehensive guide to contrast-enhanced CT scanning in adult ECMO patients, addressing common questions related to contrast delivery via the ECMO circuit, and modifications to ECMO settings and scanning techniques, to avoid non-diagnostic CT scans. The approach is described in detail for patients supported on VA ECMO, with the return cannula sited in the femoral artery. Lesser modifications required for veno-venous ECMO (VV ECMO) are included in the supplemental material. Establishing a common understanding between the intensive care clinician, the CT radiographer, and the radiologist, concerning the patient's blood-flow-physiology, is the overarching goal. Our stepwise approach facilitates clear communication around modifications to the ECMO pump settings, contrast route and rate, as well as the scanning technique, for each individual scenario.

Safety Considerations in MRI and CT

OBJECTIVE

MRI and CT are indispensable imaging modalities for the evaluation of patients with neurologic disease, and each is particularly well suited to address specific clinical questions. Although both of these imaging modalities have excellent safety profiles in clinical use as a result of concerted and dedicated efforts, each has potential physical and procedural risks that the practitioner should be aware of, which are described in this article.

LATEST DEVELOPMENTS

Recent advancements have been made in understanding and reducing safety risks with MR and CT. The magnetic fields in MRI create risks for dangerous projectile accidents, radiofrequency burns, and deleterious interactions with implanted devices, and serious patient injuries and deaths have occurred. Ionizing radiation in CT may be associated with shorter-term deterministic effects on biological tissues at extremely high doses and longer-term stochastic effects related to mutagenesis and carcinogenesis at low doses. The cancer risk of radiation exposure in diagnostic CT is considered extremely low, and the benefit of an appropriately indicated CT examination far outweighs the potential risk. Continuing major efforts are centered on improving image quality and the diagnostic power of CT while concurrently keeping radiation doses as low as reasonably achievable.

ESSENTIAL POINTS

An understanding of these MRI and CT safety issues that are central to contemporary radiology practice is essential for the safe and effective treatment of patients with neurologic disease.

Perioperative extracorporeal membrane oxygenation in pediatric congenital heart disease: Chinese expert consensus

BACKGROUND

Congenital heart disease (CHD) is one of the main supportive diseases of extracorporeal membrane oxygenation in children. The management of extracorporeal membrane oxygenation (ECMO) for pediatric CHD faces more severe challenges due to the complex anatomical structure of the heart, special pathophysiology, perioperative complications and various concomitant malformations. The survival rate of ECMO for CHD was significantly lower than other classifications of diseases according to the Extracorporeal Life Support Organization database. This expert consensus aims to improve the survival rate and reduce the morbidity of this patient population by standardizing the clinical strategy.

METHODS

The editing group of this consensus gathered 11 well-known experts in pediatric cardiac surgery and ECMO field in China to develop clinical recommendations formulated on the basis of existing evidences and expert opinions.

RESULTS

The primary concern of ECMO management in the perioperative period of CHD are patient selection, cannulation strategy, pump flow/ventilator parameters/vasoactive drug dosage setting, anticoagulation management, residual lesion screening, fluid and wound management and weaning or transition strategy. Prevention and treatment of complications of bleeding, thromboembolism and brain injury are emphatically discussed here. Special conditions of ECMO management related to the cardiovascular anatomy, haemodynamics and the surgical procedures of common complex CHD should be considered.

CONCLUSIONS

The consensus could provide a reference for patient selection, management and risk identification of perioperative ECMO in children with CHD. Video abstract (MP4 104726 kb).

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.

Optimizing Contrast-Enhanced Thoracoabdominal CT in Patients During Extracorporeal Membrane Oxygenation

RATIONALE AND OBJECTIVES

To evaluate the quality and value of contrast-enhanced (CE) chest- and abdominal computed tomography (CT) and CT angiography in neonates, children, and adults undergoing extracorporeal membrane oxygenation (ECMO) using a customized protocol for contrast delivery.

MATERIALS AND METHODS

All patients admitted for CE thoracic- and/or abdominal CT while on ECMO were prospectively included in the study. A protocol for contrast delivery adapted for the type of ECMO circulation, cannulation sites, anatomy of interest, and desired contrast phase was applied. Clinical information, ECMO and CT technique, including contrast administration strategy, was noted for each patient. Two radiologists separately evaluated the quality of the scan. The value of the examination was decided in consensus with the referring ECMO physician.

RESULTS

One hundred thirty CE thoracoabdominal scans were performed at 103 different occasions during the study time. Eighty-nine scans were performed during veno-arterial ECMO and 41 during veno-venous ECMO. In the majority, contrast was delivered to the oxygenator with preserved ECMO flow. A peripheral or central venous line with reduced flow was utilized in the remaining cases. Mean scan quality was graded 4.2 on a five-grade scale. In 56% of the examinations, the findings affected the immediate treatment of the patient.

CONCLUSION

High-quality CT and CT angiography can be achieved in ECMO patients of different ages and clinical issues considering the type of ECMO circulation, ECMO cannulation sites, preferred contrast phase and anatomy of interest. CT diagnoses affect the treatment of the patient.