Computed tomographic imaging in peripheral VA-ECMO: where has all the contrast gone?

Trends on Near-Infrared Spectroscopy Associated With Acute Brain Injury in Venoarterial Extracorporeal Membrane Oxygenation

We aimed to determine the association between cerebral regional oxygen saturation (rSO 2 ) trends from cerebral near-infrared spectroscopy (cNIRS) and acute brain injury (ABI) in adult venoarterial extracorporeal membrane oxygenation (VA-ECMO) patients. ABI was defined as intracranial hemorrhage, ischemic stroke, hypoxic ischemic brain injury, or brain death during ECMO. rSO 2 values were collected from left and right cerebral oximetry sensors every hour from ECMO cannulation. Cerebral desaturation was defined as consecutive hours of rSO 2 < 40%. rSO 2 asymmetry was determined by (a) averaging left/right rSO 2 difference over the entire ECMO run; (b) consecutive hours of rSO 2 asymmetry. Sixty-nine VA-ECMO patients (mean age 56 years, 65% male) underwent cNIRS. Eighteen (26%) experienced ABI. When the mean rSO 2 asymmetry was >8% there was significantly increased odds of ABI (aOR = 39.4; 95% CI = 4.1-381.4). Concurrent rSO 2 < 40% and rSO 2 asymmetry >10% for >10 consecutive hours (asymmetric desaturation) was also significantly associated with ABI (aOR = 5.2; 95% CI = 1.2-22.2), but neither criterion alone were. Mean rSO 2 asymmetry>8% exhibited 39% sensitivity and 98% specificity for detecting ABI, with an area under the curve (AUC) of 0.86, and asymmetric desaturation had 33% sensitivity and 88% specificity, with an AUC of 0.72. These trends on NIRS monitoring may help detect ABI in VA-ECMO patients.

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 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.

Mechanical Circulatory Support for Acute Heart Failure Complicated by Cardiogenic Shock

Acute heart failure is a potentially life-threatening condition that can lead to cardiogenic shock, which is associated with hypotension and organ failure. Although there have been many studies on the treatment for cardiogenic shock, early mortality remains high at 40-50%. No new medicines for cardiogenic shock have been developed. Recently, there has been a gradual decline in the use of the intra-aortic balloon pump mainly due to a lack of adequate hemodynamic support. Extracorporeal membrane oxygenation and the percutaneous ventricular assist device have become more widely used in recent years. A thorough understanding of the mechanisms of such mechanical support devices and their hemodynamic effects, components of the devices, implantation technique, management, criteria for indications or contraindications of use, and clinical outcomes as well as multidisciplinary decision making may improve the outcomes in patients experiencing cardiogenic shock.

Clinical Pearls of Venoarterial Extracorporeal Membrane Oxygenation for Cardiogenic Shock

Extracorporeal membrane oxygenation (ECMO) is a technique that uses a pump to drain blood from a body, circulate blood through a membrane lung, and return the oxygenated blood back into the body. Venoarterial (VA) ECMO is a simplified version of the heart-lung machine that assists native pulmonary and/or cardiac function. VA ECMO is composed of a drainage cannula in the venous system and a return cannula in the arterial system. Because VA ECMO can increase tissue perfusion by increasing the arterial blood flow, it is used to treat medically refractory cardiogenic shock or cardiac arrest. VA ECMO has a distinct physiology that is referred to as differential flows. It can cause several complications such as left ventricular distension with pulmonary edema, distal limb ischemia, bleeding, and thromboembolism. Physicians who are using this technology should be knowledgeable on the prevention and management of these complications. We review the basic physiology of VA ECMO, the mechanism of complications, and the simple management of VA ECMO.

Hemodynamic effects of perfusion level of peripheral ECMO on cardiovascular system

Background

Peripheral ECMO is an effective cardiopulmonary support in clinical. The perfusion level could directly influence the performances and complications. However, there are few studies on the effects of the perfusion level on hemodynamics of peripheral ECMO.

Methods

The geometric model of cardiovascular system with peripheral ECMO was established. The blood assist index was used to classify the perfusion level of the ECMO. The flow pattern from the aorta to the femoral artery and their branches, blood flow rate from aorta to brain and limbs, flow interface, harmonic index of blood flow, wall shear stress and oscillatory shear index were chosen to evaluate the hemodynamic effects of peripheral ECMO.

Results

The results demonstrated that the flow rate of aorta outlets increased and perfusion condition had been improved. And the average flow to the upper limbs and brain has a positive correlation with BAI (r = 0.037, p < 0.05), while there is a negative correlation with lower limbs (r = − 0.054, p < 0.05). The HI has negative correlation with BAI (p < 0.05, r < 0). The blood interface is further from the heart with the BAI decrease. And the average WSS has negative correlation with BAI (p < 0.05, r = − 0.983) at the bifurcation of femoral aorta and has positive correlation with BAI (p < 0.05, r = 0.99) at the inner aorta. The OSI under different BAI is higher (reaching 0.4) at the inner wall of the aortic arch, the descending aorta and the femoral access.

Conclusions

The pathogenesis of peripheral ECMO with different perfusion levels varies; its further research will be thorough and extensive.

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.

Hemodynamic changes in patients with extracorporeal membrane oxygenation (ECMO) demonstrated by contrast-enhanced CT examinations - implications for image acquisition technique

Extracorporeal membrane oxygenation (ECMO) is an established tool for respiratory and circulatory support. In computed tomography, altered hemodynamics in ECMO patients requires special considerations and handling in contrast injection and its timing. In this article, we demonstrate changes in hemodynamics in ECMO patients captured on contrast-enhanced CT examinations and pitfalls in strategies for contrast injection in relation to the ECMO flow, cardiac function and the placement of ECMO cannulas. Contrast-enhanced CT of patients with ECMO requires prior knowledge of the ECMO cannulas, central venous lines, changes of hemodynamics induced by low cardiac output and the influence of adjustment of ECMO on blood flow in order to optimize injection of the contrast material and timing of the scan. Special considerations include temporary reduction of the ECMO flow, selection of the injection site and increasing volume or flow rate of the contrast material.

Building a bridge to save a failing ventricle: radiologic evaluation of short- and long-term cardiac assist devices

Heart failure is recognized with increasing frequency worldwide and often progresses to an advanced refractory state. Although the reference standard for treatment of advanced heart failure remains cardiac transplantation, the increasing shortage of donor organs and the unsuitability of many patients for transplantation surgery has led to a search for alternative therapies. One such therapy is mechanical circulatory support, which helps relieve the load on the ventricle and thereby allows it to recover function. In addition, there is increasing evidence supporting the use of mechanical devices as a bridge to recovery in patients with acute refractory heart failure. In this article, the imaging evaluation of various commonly used short- and long-term cardiac assist devices is discussed, and their relevant mechanisms of action and physiology are described. Imaging, particularly computed tomography (CT), plays a crucial role in preoperative evaluation for assessment of candidacy for implantation of a left ventricular assist device (LVAD) or total artificial heart (TAH). Also, echocardiography and CT are indispensable in assessment of complications associated with cardiac devices. Complications commonly associated with short-term assist devices include bleeding and malpositioning, whereas long-term devices such as LVADs may be associated with infection, pump thrombosis, and cannula malfunction, as well as bleeding. CT is also commonly performed for preoperative planning before LVAD or TAH explantation, replacement of a device or one of its components, and cardiac transplantation. Online supplemental material is available for this article.

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.