Imaging adults on extracorporeal membrane oxygenation (ECMO)

Veno-venous extracorporeal membrane oxygenation (VV ECMO) cannula malposition identified with point-of-care ultrasound

BACKGROUND

Point-of-care ultrasound (POCUS) has become a mainstay in the evaluation of critically ill patients in the intensive care unit (ICU). ECMO patients are susceptible to complications during prolonged ICU stay, including cannula malposition, which has deleterious consequences. Although the literature surrounding utility of ultrasound on ECMO patients is expansive, direct comparison between radiographic imaging versus ultrasound for identification of cannula malposition is lacking.

CASE PRESENTATION

The authors identified four patients with cannula malposition discovered through POCUS that was missed on routine radiographic imaging. Identification and correction of malposition changed their ECMO course.

CONCLUSION

This case series is the first in literature demonstrating that ultrasound may be superior to radiographic images for ECMO cannula malposition. Further investigation into this subject is warranted.

Neuromonitoring of Pediatric and Adult Extracorporeal Membrane Oxygenation Patients: The Importance of Continuous Bedside Tools in Driving Neuroprotective Clinical Care

Extracorporeal membrane oxygenation (ECMO) is a form of temporary cardiopulmonary bypass for patients with acute respiratory or cardiac failure refractory to conventional therapy. Its usage has become increasingly widespread and while reported survival after ECMO has increased in the past 25 years, the incidence of neurological injury has not declined, leading to the pressing question of how to improve time-to-detection and diagnosis of neurological injury. The neurological status of patients on ECMO is clinically difficult to evaluate due to multiple factors including illness, sedation, and pharmacological paralysis. Thus, increasing attention has been focused on developing tools and techniques to measure and monitor the brain of ECMO patients to identify dynamic risk factors and monitor patients' neurophysiological state as a function in time. Such tools may guide neuroprotective interventions and thus prevent or mitigate brain injury. Current means to continuously monitor and prevent neurological injury in ECMO patients are rather limited; most techniques provide indirect or postinsult recognition of irreversible brain injury. This review will explore the indications, advantages, and disadvantages of standard-of-care, emerging, and investigational technologies for neurological monitoring on ECMO, focusing on bedside techniques that provide continuous assessment of neurological health.

Characterizing the Relationship Between Arterial Carbon Dioxide Trajectory and Serial Brain Biomarkers with Central Nervous System Injury During Veno-Venous Extracorporeal Membrane Oxygenation: A Prospective Cohort Study

BACKGROUND

Central nervous system (CNS) injury following initiation of veno-venous extracorporeal membrane oxygenation (VV-ECMO) is common. An acute decrease in partial pressure of arterial carbon dioxide (PaCO2) following VV-ECMO initiation has been suggested as an etiological factor, but the challenges of diagnosing CNS injuries has made discerning a relationship between PaCO2 and CNS injury difficult.

METHODS

We conducted a prospective cohort study of adult patients undergoing VV-ECMO for acute respiratory failure. Arterial blood gas measurements were obtained prior to initiation of VV-ECMO, and at every 2-4 h for the first 24 h. Neuroimaging was conducted within the first 7-14 days in patients who were suspected of having neurological injury or unable to be examined because of sedation. We collected blood biospecimens to measure brain biomarkers [neurofilament light (NF-L); glial fibrillary acidic protein (GFAP); and phosphorylated-tau 181] in the first 7 days following initiation of VV-ECMO. We assessed the relationship between both PaCO2 over the first 24 h and brain biomarkers with CNS injury using mixed methods linear regression. Finally, we explored the effects of absolute change of PaCO2 on serum levels of neurological biomarkers by separate mixed methods linear regression for each biomarker using three PaCO2 exposures hypothesized to result in CNS injury.

RESULTS

In our cohort, 12 of 59 (20%) patients had overt CNS injury identified on head computed tomography. The PaCO2 decrease with VV-ECMO initiation was steeper in patients who developed a CNS injury (- 0.32%, 95% confidence interval - 0.25 to - 0.39) compared with those without (- 0.18%, 95% confidence interval - 0.14 to - 0.21, P interaction < 0.001). The mean concentration of NF-L increased over time and was higher in those with a CNS injury (464 [739]) compared with those without (127 [257]; P = 0.001). GFAP was higher in those with a CNS injury (4278 [11,653] pg/ml) compared with those without (116 [108] pg/ml; P < 0.001). The mean NF-L, GFAP, and tau over time in patients stratified by the three thresholds of absolute change of PaCO2 showed no differences and had no significant interaction for time.

CONCLUSIONS

Although rapid decreases in PaCO2 following initiation of VV-ECMO were slightly greater in patients who had CNS injuries versus those without, data overlap and absence of relationships between PaCO2 and brain biomarkers suggests other pathophysiologic variables are likely at play.

Multimodality Imaging in Advanced Heart Failure for Diagnosis, Management and Follow-Up: A Comprehensive Review

Advanced heart failure (AHF) presents a complex landscape with challenges spanning diagnosis, management, and patient outcomes. In response, the integration of multimodality imaging techniques has emerged as a pivotal approach. This comprehensive review delves into the profound significance of these imaging strategies within AHF scenarios. Multimodality imaging, encompassing echocardiography, cardiac magnetic resonance imaging (CMR), nuclear imaging and cardiac computed tomography (CCT), stands as a cornerstone in the care of patients with both short- and long-term mechanical support devices. These techniques facilitate precise device selection, placement, and vigilant monitoring, ensuring patient safety and optimal device functionality. In the context of orthotopic cardiac transplant (OTC), the role of multimodality imaging remains indispensable. Echocardiography offers invaluable insights into allograft function and potential complications. Advanced methods, like speckle tracking echocardiography (STE), empower the detection of acute cell rejection. Nuclear imaging, CMR and CCT further enhance diagnostic precision, especially concerning allograft rejection and cardiac allograft vasculopathy. This comprehensive imaging approach goes beyond diagnosis, shaping treatment strategies and risk assessment. By harmonizing diverse imaging modalities, clinicians gain a panoramic understanding of each patient's unique condition, facilitating well-informed decisions. The aim is to highlight the novelty and unique aspects of recently published papers in the field. Thus, this review underscores the irreplaceable role of multimodality imaging in elevating patient outcomes, refining treatment precision, and propelling advancements in the evolving landscape of advanced heart failure management.

Radiation Exposure in Extracorporeal Life Support

Extracorporeal membrane oxygenation (ECMO) exposes patients to multiple radiologic studies. We hypothesized ECMO patients endure radiation exposure in excess of the International Commission of Radiological Protection (ICRP) recommendations of cumulative effective dose (CED, >20 mSv and 5-year cumulative limit of CED >100 mSv). We conducted a retrospective observational study in an academic medical center between January 2016 and December 2018 involving adult admissions (N = 306) on ECMO. Ionizing radiation was calculated from reference values to determine CED. Approximately 9.4% (N = 29) patients accrued CED >50 mSv and 4.5% (N = 14) accrued CED >100 mSv during ECMO. Over the entire hospitalization, 28% (N = 85) accrued >50 mSv and 14.7% (N = 45) accrued CED >100 mSv. Median CED during ECMO was 2.3 mSv (IQR, -0.82 to 8.1 mSv), and the entire hospitalization was 17.4 mSv (IQR, -4.5 to 56.6 mSv). Thirteen percent of the median CED accrued during hospitalization could be attributed to ECMO. Longer hospitalization was associated with a higher CED (50 days [IQR, -25 to 76 days] in CED >50 vs. 19 days [IQR, -10 to 32 days] in CED <50). Computer tomography (CT) scans and interventional radiology (IR) procedures contributed to 43.8% and 44.86%, respectively, of CED accrued on ECMO and 52.2% and 37.1% of CED accumulated during the whole hospitalization. Guidelines aimed at mitigating radiation exposure are urgently needed.

Magnetic resonance in patients with cardiovascular devices. SEC-GT CRMTC/SEC-Heart Rhythm Association/SERAM/SEICAT consensus document

Magnetic resonance has become a first-line imaging modality in various clinical scenarios. The number of patients with different cardiovascular devices, including cardiac implantable electronic devices, has increased exponentially. Although there have been reports of risks associated with exposure to magnetic resonance in these patients, the clinical evidence now supports the safety of performing these studies under specific conditions and following recommendations to minimize possible risks. This document was written by the Working Group on Cardiac Magnetic Resonance Imaging and Cardiac Computed Tomography of the Spanish Society of Cardiology (SEC-GT CRMTC), the Heart Rhythm Association of the Spanish Society of Cardiology (SEC-Heart Rhythm Association), the Spanish Society of Medical Radiology (SERAM), and the Spanish Society of Cardiothoracic Imaging (SEICAT). The document reviews the clinical evidence available in this field and establishes a series of recommendations so that patients with cardiovascular devices can safely access this diagnostic tool.

Magnetic resonance in patients with cardiovascular devices. SEC-GT CRMTC/SEC-Heart Rhythm Association/SERAM/SEICAT consensus document

Magnetic resonance has become a first-line imaging modality in various clinical scenarios. The number of patients with different cardiovascular devices, including cardiac implantable electronic devices, has increased exponentially. Although there have been reports of risks associated with exposure to magnetic resonance in these patients, the clinical evidence now supports the safety of performing these studies under specific conditions and following recommendations to minimize possible risks. This document was written by the Working Group on Cardiac Magnetic Resonance Imaging and Cardiac Computed Tomography of the Spanish Society of Cardiology (SEC-GT CRMTC), the Heart Rhythm Association of the Spanish Society of Cardiology (SEC-Heart Rhythm Association), the Spanish Society of Medical Radiology (SERAM), and the Spanish Society of Cardiothoracic Imaging (SEICAT). The document reviews the clinical evidence available in this field and establishes a series of recommendations so that patients with cardiovascular devices can safely access this diagnostic tool.

Imaging in the Intensive Care Unit

Radiology plays an important role in the management of the most seriously ill patients in the hospital. Over the years, continued advances in imaging technology have contributed to an improvement in patient care. However, even with such advances, the portable chest radiograph (CXR) remains one of the most commonly requested radiographic examinations. While they provide valuable information, CXRs remain relatively insensitive at revealing abnormalities and are often nonspecific. Chest computed tomography (CT) can display findings that are occult on CXR and is particularly useful at identifying and characterizing pleural effusions, detecting barotrauma including small pneumothoraces, distinguishing pneumonia from atelectasis, and revealing unsuspected or additional abnormalities which could result in increased morbidity and mortality if left untreated. CT pulmonary angiography is the modality of choice in the evaluation of pulmonary emboli which can complicate the hospital course of the ICU patient. This article will provide guidance for interpretation of CXR and thoracic CT images, discuss some of the invasive devices routinely used, and review the radiologic manifestations of common pathologic disease states encountered in ICU patients. In addition, imaging findings and complications of more specific clinical scenarios in which the incidence has increased in the ICU setting, such as patients who are immunocompromised, have interstitial lung disease, or COVID-19, will also be discussed. Communication between the radiologist and intensivist, particularly on complicated cases, is important to help increase diagnostic accuracy and leads to an improvement in the management of the most critically ill patients.

Transesophageal Echocardiography-Guided Extracorporeal Membrane Oxygenation Cannulation in COVID-19 Patients

OBJECTIVES

A paucity of data supports the use of transesophageal echocardiography (TEE) for bedside extracorporeal membrane oxygenation (ECMO) cannulation. Concerns have been raised about performing TEEs in patients with COVID-19. The authors describe the use and safety of TEE guidance for ECMO cannulation for COVID-19.

DESIGN

Single-center retrospective cohort study.

SETTING

The study took place in the intensive care unit of an academic tertiary center.

PARTICIPANTS

The authors included 107 patients with confirmed SARS-CoV-2 infection who underwent bedside venovenous ECMO (VV ECMO) cannulation under TEE guidance between May 2020 and June 2021.

INTERVENTIONS

TEE-guided bedside VV ECMO cannulation.

MEASUREMENTS

Patient characteristics, physiologic and ventilatory parameters, and echocardiographic findings were analyzed. The primary outcome was the number of successful TEE-guided bedside cannulations without complications. The secondary outcomes were cannulation complications, frequency of cannula repositioning, and TEE-related complications.

MAIN RESULTS

TEE-guided cannulation was successful in 99% of the patients. Initial cannula position was adequate in all but 1 patient. Fourteen patients (13%) required cannula repositioning during ECMO support. Forty-five patients (42%) had right ventricular systolic dysfunction, and 9 (8%) had left ventricular systolic dysfunction. Twelve patients (11%) had intracardiac thrombi. One superficial arterial injury and 1 pneumothorax occurred. No pericardial tamponade, hemothorax or intraabdominal bleeding occurred in the authors' cohort. No TEE-related complications or COVID-19 infection of healthcare providers were reported during this study.

CONCLUSIONS

Bedside TEE guidance for VV ECMO cannulation is safe in patients with severe respiratory failure due to COVID-19. No tamponade or hemothorax, nor TEE-related complications were observed in the authors' cohort.

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.

Bicaval dual lumen cannula placement using transthoracic echocardiography in COVID-19 scenario: pearls and pitfalls

A woman in her 50s who had been diagnosed with COVID-19 developed deep vein thrombosis in the left femoral vein extending into inferior vena cava (IVC). An IVC filter was placed to prevent fatal pulmonary embolism. Her respiratory failure subsequently deteriorated despite optimal mechanical ventilation and required venovenous extracorporeal membrane oxygenation (VV-ECMO) as a rescue therapy. Femoro-jugular VV-ECMO configuration was not suitable due to the IVC filter, hence a single-site venous cannulation using bicaval dual lumen (AvalonElite) cannula was selected. Placement of the Avalon cannula conventionally requires guidance by fluoroscopy or transoesophageal echocardiography, which were not feasible in COVID-19 patients. Hence, transthoracic echocardiography guidance was chosen. Guidewire looping into the right ventricle might lead to cannula malposition and imminent right ventricular rupture, but these could be detected by 'bending' sign. Transthoracic echocardiography could be a feasible guidance method for Avalon cannulation, nonetheless a thorough protocol should be followed to avoid cannula malposition during the procedure.

Extracorporeal membrane oxygenation (ECMO) in COVID-19 patients: a pocket guide for radiologists

During the coronavirus disease 19 (COVID-19) pandemic, extracorporeal membrane oxygenation (ECMO) has been proposed as a possible therapy for COVID-19 patients with acute respiratory distress syndrome. This pictorial review is intended to provide radiologists with up-to-date information regarding different types of ECMO devices, correct placement of ECMO cannulae, and imaging features of potential complications and disease evolution in COVID-19 patients treated with ECMO, which is essential for a correct interpretation of diagnostic imaging, so as to guide proper patient management.

Treatment of acute respiratory failure: extracorporeal membrane oxygenation

Background: Extracorporeal membrane oxygenation (ECMO) support for tissue oxygenation can improve the survival of patients with life-threatening respiratory distress syndrome or cardiac failure.Current Concepts: Recently, the use of ECMO in acute respiratory distress syndrome has first been reported by a multicenter randomized controlled trial, known as the conventional ventilation or ECMO for severe adult respiratory failure trial. The ECMO application is dramatically increasing with the increasing number of patients experiencing acute respiratory failure due to coronavirus disease 2019 pneumonia. In this review, we explain the indications of the ECMO application and ECMO-associated complications.Discussion and Conclusion: The ECMO application in lung diseases, such as coronavirus disease 2019 and acute respiratory distress syndrome, has significant outcomes in securing the treatment periods and reducing mortality. Therefore, accumulating knowledge and experience in the ECMO application can produce positive outcomes.

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.

Protocolized Whole-Body Computed Tomography Imaging After Extracorporeal Membrane Oxygenation (ECMO) Cannulation for Cardiac Arrest

Evaluate the utility of whole-body computed tomography (WBCT) imaging in detecting clinically significant findings in patients who have undergone extracorporeal membrane oxygenation (ECMO) cannulation for cardiac arrest (extracorporeal cardiopulmonary resuscitation or "eCPR"). Single-center retrospective review of 52 consecutive patients from 2017 to 2019 who underwent eCPR and received concomitant WBCT imaging. WBCT images were reviewed for clinically significant findings (compression-related injuries, cannulation-related complications, etiology of cardiac arrest, incidental findings, and evidence of hypoxic brain injury) as well as the frequency of interventions performed as a direct result of such findings. Thirty-eight patients met inclusion criteria for analysis. Clinically significant WBCT findings were present in 37/38 (97%) of patients with 3.3 ± 1.7 findings per patient. An intervention as a direct result of WBCT findings was performed in 54% (20/37) of patients with such findings. Evidence of hypoxic brain injury on WBCT was associated with clinical brain death as compared with those without such findings (10/15 [67%] vs 1/22 [4%], P < 0.001), respectively. WBCT scan after eCPR frequently detects clinically significant findings which commonly prompt an intervention directly affecting the patient's clinical course. We advocate for protocolized use of WBCT imaging in all eCPR patients.

Ventilation-Perfusion Scan: A Primer for Practicing Radiologists

Lung scintigraphy, or ventilation-perfusion (V/Q) scan, is one of the commonly performed studies in nuclear medicine. Owing to variability in clinical applications and different departmental workflows, many trainees are not comfortable interpreting the results of this study. This article provides a simplified overview of V/Q imaging, including a review of its technique, interpretation methods, and established and emerging clinical applications. The authors review the role of V/Q imaging in evaluation of acute and chronic pulmonary embolism, including the role of SPECT/CT and comparing V/Q scan with CT angiography. In addition, a variety of other applications of pulmonary scintigraphy are discussed, including congenital heart disease, pretreatment planning for lung cancer and emphysema, posttransplant imaging for bronchiolitis obliterans, and less common vascular and nonvascular pathologic conditions that may be detected with V/Q scan. This article will help radiologists and residents interpret the results of V/Q scans and understand the various potential clinical applications of this study. Online supplemental material is available for this article. ^©RSNA, 2021.

Challenges of acute phase neuroimaging in VA-ECMO, pitfalls and alternative imaging options

Large vessel occlusion in patients on ECMO is challenging to appreciate clinically secondary to sedation or induced paralysis, thus placing more emphasis on neurovascular imaging. However, emergent CTA and CTP are both inaccurate and unreliable in ECMO patients due to altered circuitry and interference with normal physiologic hemodynamics. In this review, the utility of DSA is discussed in evaluating the altered hemodynamics of VA-ECMO circuits and patency of major vasculature. In addition, the potential use of TCD in ECMO patients is discussed.

Imaging Adult ECMO

Adult extracorporal membrane oxygenation utilization in the ICU has rapidly increased. Newer technology and cannulation strategies and the complex hemodynamics make imaging interpretation challenging. There is also a high rate of complications. This review details the common indications, cannulation strategies, relevant hemodynamics and complications which impact imaging interpretation. Recommendations for modifying computed tomography protocols and techniques to obtain diagnostic images and some of the imaging pitfalls are also discussed.

Femoral neuropathy following venoarterial-extracorporeal membrane oxygenation therapy: a case report

Background

Although life-threatening complications of extracorporeal membrane oxygenation (ECMO) are well described, non-life threatening complications are less known. Herein, we report a case of femoral neuropathy (FN) due to nerve compression caused by cannula compression and deep vein thrombosis (DVT) after successful ECMO therapy, which seriously undermined one’s quality of life.

Case presentation

A 70-year old male presented to the emergency department for chest pain. The patient had cardiac arrest before percutaneous coronary intervention (PCI) and was inserted with ECMO. Although he was successfully weaned from ECMO 4 days after PCI, he consistently complained swelling, abnormal sensation, and weakness in his right lower extremity, where the cannulas were inserted. Imaging studies showed deep vein thrombosis (DVT) in his right leg, which was further treated with anticoagulants. Symptoms, however, remained after the regression of DVT. Nerve conduction study revealed femoral neuropathy, which may have been caused by ECMO cannula compression and tissue swelling.

Conclusion

The current case proposes that non-life threatening complications of ECMO therapy can seriously affect quality of life. Venous drainage distant from the arterial cannula may prevent such complications.

Clinical experience of whole-body computed tomography as the initial evaluation tool after extracorporeal cardiopulmonary resuscitation in patients of out-of-hospital cardiac arrest

Background

The routine application of whole-body CT after extracorporeal cardiopulmonary resuscitation (ECPR) in out-of-hospital cardiac arrest (OHCA) has not been extensively investigated. We aimed to evaluate the benefit of CT in this context.

Methods

We retrospectively analyzed all OHCA patients who had received ECPR between January 2006 to May 2019. Electronic records were reviewed to filter out patients who had a whole-body CT as their first clinical evaluation after ECPR. CT findings and major hospital outcomes were evaluated.

Results

From January 2006 to May 2019, 700 patients had received ECPR in our institution. We identified 93 OHCA patients who received whole-body CT as the first clinical evaluation after ECPR. 22.6% of those had no acute findings detected on CT requiring immediate treatment. In the remaining 77.4%, CT had findings that might lead to alterations in clinical course. Most important findings were myocardial infarction (57.0%), hypoxic brain injury (29.0%), sternal/rib fractures (16.1%), aortic dissection (7.5%), pulmonary embolism (5.4%), and cardiac tamponade (5.4%). There were no significant differences in ICU/hospitalization days, time on ECMO support, survival and neurological outcomes between those with and without immediate CT. In our OHCA cohort, there were 27 patients with CT evidence of hypoxic brain injury, of whom 22.2% (n = 2) managed to wean from ECMO support, 14.8% (n = 4) survived to discharge, but only 3.7% (n = 1) survived with good neurological outcome. Hypoxic brain injury on CT has a 95% specificity in predicting poor neurological outcome, with a false positive rate of only 3.7%. Logistic regression suggested a potential correlation between CT findings of hypoxic brain injury and poor neurological outcome [Odds ratio (OR) = 12.53 (1.55 to 10.1), p = 0.02)].

Conclusions

Routine whole-body CT after ECPR in OHCA patients appears to have a limited role, as the majority is caused by ACS. However, it may be a useful tool when CPR-related injury or non-ACS causes of OHCA are suspected, as well as in cases where the cause of OHCA is unknown. On the contrary, routine brain CT may be a valuable tool in guiding anticoagulant therapy during ECMO and in aiding outcome prediction.

Screening pulmonary angiogram and the effect on anticoagulation strategies in severe respiratory failure patients on venovenous extracorporeal membrane oxygenation

BACKGROUND

Venovenous extracorporeal membrane oxygenation in the treatment of severe respiratory failure in adults continues to increase with survival improving; however, it remains associated with serious complications.

OBJECTIVE

The aim of this study was to evaluate the prevalence of pulmonary embolism (PE) in patients with severe respiratory failure requiring venovenous extracorporeal membrane oxygenation (VV ECMO) and in those managed with conventional mechanical ventilation.

METHODS

A single-center, observational cohort, retrospective study was undertaken of patients with severe respiratory failure managed with conventional ventilation or requiring ECMO in a tertiary referral university teaching hospital.

RESULTS

We identified 343 patients with severe respiratory failure between January 2014 and December 2017. VV ECMO was used to support 290 patients and 53 were managed by conventional mechanical ventilation. The prevalence of PE was 9.6% (33/343), of which those supported with VV ECMO was 10% (29/290) and conventional ventilation 7.5% (4/53). There was no difference in survival rates between cohorts with PE versus no PE (ECMO survival to discharge P = .56; conventional ventilation survival to discharge P = .21).

CONCLUSIONS

The prevalence of pulmonary embolism in severe respiratory failure has important clinical implications for both short and long-term anticoagulation strategies. Routine screening pulmonary angiogram is warranted in this cohort.

Imaging of Cardiac Support Devices

Patients hospitalized in the intensive care unit (ICU) often have multiple support lines and devices that need routine imaging evaluation by radiologists. In patients with cardiogenic shock or depressed cardiac function, mechanical circulation support devices are used in combination with medical therapies to improve patient outcomes and sometimes can stabilize patients for surgical intervention. This article discusses some of the more commonly encountered mechanical circulation devices seen in ICU patients, including intra-aortic balloon pumps, Impella devices, extracorporeal membrane oxygenation cannulas, and ventricular assist devices. Normal appearance and commonly encountered device-related complications that can be diagnosed on imaging are reviewed.

Chest radiographs of cardiac devices (Part 2): Ventricular assist devices

Heart failure is considered a worldwide pandemic affecting 26 million people globally. Patients who are unfit or waiting for cardiac transplantation may benefit from alternate mechanical support therapies using ventricular assist devices. It is not uncommon for radiologists, especially those working in institutions with a high volume of cardiac transplantations, to be presented with radiographs containing these devices. The role of the radiologist is not only to accurately identify these devices, but also to evaluate for any complications.

Imaging Device Therapy: Essentials for the Imager

Treatment of patients with heart failure with reduced ejection fraction has evolved. Recently, a fully implantable remote hemodynamic monitoring sensor in the pulmonary artery was approved in the treatment of patients at risk of heart failure readmissions. Several novel devices designed to offload the left atrium by creating a small interatrial shunt are being investigated. Cardiac imaging plays a vital role in the selection process, implantation, and monitoring of individuals with such devices. This article discusses in detail various imaging techniques and key clinical points relating to several cardiac devices used in the treatment of patients with heart failure.

Malposition of the Extracorporeal Membrane Oxygenation Venous Cannula in an Accessory Hepatic Vein

We report a case of a refractory cardiogenic shock secondary to myocardial infarction in a 70-year-old patient requiring femoral venoarterial extracorporeal membrane oxygenation (VA-ECMO). At initial transesophageal echocardiography, the venous cannula tip was seen in the inferior vena cava (IVC), but not in right atrium. On day 8, ultrasonic examination identified that the end of the venous cannula was in the hepatic vein (HV). Despite such malposition, no disturbance in extracorporeal membrane oxygenation (ECMO) venous return was observed. Moving or replacing the cannula was considered a high-risk maneuver potentially resulting in hepatic laceration with hemoperitoneum. Because of adequate venous drainage, allowing sufficient blood flow, venous cannula repositioning was delayed until day 10, when a ventricular defect was repaired and ECMO was weaned off. At the time of VA-ECMO implantation, the venous cannula has to be positioned in the right atrium using real time echo monitoring. Visualization of the guide wire in the IVC but not in the right atrium is insufficient to ensure appropriate venous cannula positioning. Indeed, either accidental catheterization or cannula migration into the HV is possible during ECMO. Health care professionals dealing with ECMO have to be aware of this possible malposition, to correct it and prevent insufficient venous drainage or traumatic complications.

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.

Acute Bowel Ischemia Associated with Left Ventricular Thrombus and Arteriovenous Extracorporeal Membrane Oxygenation

Indications for extra corporeal membrane oxygenation (ECMO) have expanded in recent years, and it has become an invaluable tool in the care of adult patients in severe cardiogenic shock or respiratory failure. Understanding the physiologic effect of ECMO has also further developed, allowing for improvements in the management of the potential morbidities associated with this technology. Here, we present a case of acute bowel ischemia that developed while the patient was on central venoarterial ECMO.

Perioperative Management of the Adult Patient on Venovenous Extracorporeal Membrane Oxygenation Requiring Noncardiac Surgery

The use of venovenous extracorporeal membrane oxygenation is increasing worldwide. These patients often require noncardiac surgery. In the perioperative period, preoperative assessment, patient transport, choice of anesthetic type, drug dosing, patient monitoring, and intraoperative and postoperative management of common patient problems will be impacted. Furthermore, common monitoring techniques will have unique limitations. Importantly, patients on venovenous extracorporeal membrane oxygenation remain subject to hypoxemia, hypercarbia, and acidemia in the perioperative setting despite extracorporeal support. Treatments of these conditions often require both manipulation of extracorporeal membrane oxygenation settings and physiologic interventions. Perioperative management of anticoagulation, as well as thresholds to transfuse blood products, remain highly controversial and must take into account the specific procedure, extracorporeal membrane oxygenation circuit function, and patient comorbidities. We will review the physiologic management of the patient requiring surgery while on venovenous extracorporeal membrane oxygenation.

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.

Swedish-Norwegian co-operation in the treatment of three hypothermia victims: a case report

BACKGROUND

Accidental hypothermia with cardiac arrest represents a challenge for pre-hospital rescuers as well as in-hospital staff. For pre-hospital personnel, the main focus is to get the patient to the correct destination without unnecessary delay. For in-hospital personnel early information is vital to assess the possibility for resuscitation with extracorporeal re-warming. The challenge is augmented when rescuers must cross national borders to reach and/or deliver the patients. We present a case where three adolescent boys suffered severe hypothermia after a canoeing accident in Sweden.

CASE PRESENTATION

Three 14-year-old boys were canoeing a mountain lake close to the Norwegian border when their boat capsized and they all fell into the cold water. The rescue operation was hampered by rough weather conditions, and immersion times spanned from 63 to 125 min. Flight times from the scene of accident to the nearest ECMO center in Norway (Trondheim) and Sweden (Umeå) were about 30 and 90 min respectively. Two of the victims showed no vital signs after retrieval from the water and had extremely low body temperatures. They were brought to Trondheim University Hospital where they were resuscitated successfully with extracorporeal re-warming. Unable to be weaned from ECMO in the initial phase, both patients were retrieved by mobile ECMO teams to Karolinska University Hospital, from where they were discharged to their homes with good outcomes, although with some sequelae. A third victim with moderate to severe hypothermia without cardiac arrest was treated at a local hospital, from where he after a short stay was discharged without physical sequelae.

CONCLUSION

These cases are a reminder of the traditional mantra that «no one is dead until warm and dead». Good communication between pre- and in-hospital staff can be vital for optimizing patient treatment when handling victims of severe hypothermia, and especially when there is multiple victims. Communication between neighboring countries, but even neighboring regions within the same country, can be challenging. We encourage regions similar to ours to review protocols regarding hypothermia management, making them more robust before incidents like this take place.

Doppler Ultrasound Evaluation of Circulatory Support Devices

In the setting of mechanical circulatory support devices, including ventricular assist devices, extracorporeal membrane oxygenation, intraaortic balloon pumps, and the total artificial heart, the spectral Doppler waveform is significantly altered, reflecting systemic hemodynamic changes. As the prevalence of these devices increases, a better understanding of both the devices themselves and their associated Doppler ultrasound findings is necessary for accurate image interpretation. This article reviews the clinical indications, pathophysiology, and sonographic findings of these devices, with emphasis on the variation in arterial Doppler waveforms that can be seen with normal function, as well as the major complications.

CT Angiography of the Head in Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation is an artificial cardiopulmonary bypass technique used to support patients with severe pulmonary failure or both pulmonary and cardiac failure. The hemodynamic changes produced by extracorporeal membrane oxygenation affect the appearance of CTA of the head images, often confounding interpretation if the correct history and understanding of extracorporeal membrane oxygenation are not known. This technical report describes the principles of extracorporeal membrane oxygenation, techniques to optimize intracranial CTA imaging, and pitfalls.

Contrast opacification on thoracic CT angiography: challenges and solutions

Contrast flow and enhancement patterns seen on thoracic CT angiography (CTA) can often be challenging and may often reveal more than is immediately apparent. A non-diagnostic CTA following the initial contrast injection can be secondary to many causes; these include both extrinsic factors, such as injection technique/equipment failure (iv cannula, power injector), and intrinsic, patient-related factors. Contrast pressure and flow graphs often contain useful information regarding the etiology of a non-diagnostic scan. Understanding these graphs will help the radiologist plan a repeat contrast injection to overcome the deficiencies of the first injection and thus obtain a diagnostic scan. The current review article outlines normal and abnormal intravenous contrast dynamics, discusses how to recognize etiologies of non-diagnostic scans, and ultimately addresses techniques to overcome obstacles towards obtaining normal contrast opacification of the target vessel. In addition, there are some life-threatening findings, which unless sought for, may remain hidden in plain sight.

Key Points

• Using contrast enhancement and flow patterns to identify the cause of a non-diagnostic CTA.

• Recognize life threatening causes of altered contrast dynamics such as cardiac asystole.

• Non-target vessel opacification may hold key to underlying pathophysiology.

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.

Echocardiography for adult patients supported with extracorporeal membrane oxygenation

Venoarterial (VA) and venovenous (VV) extracorporeal membrane oxygenation (ECMO) support is increasingly being used in recent years in the adult population. Owing to the underlying disease precipitating severe respiratory or cardiac failure, echocardiography plays an important role in the management of these patients. Nevertheless, there are currently no guidelines on the use of echocardiography in the setting of ECMO support. This review describes the current state of application of echocardiography for patients supported with both VA and VV ECMO.