key: cord-351134-khgneone
authors: Bleakley, Caroline; Smith, Miss Rosie; Garfield, Benjamin; Jackson, Timothy; Remmington, Chris; Patel, Brijesh V.; Price, Susanna
title: Contrast echocardiography in VV-ECMO dependent COVID-19 patients
date: 2020-07-17
journal: J Am Soc Echocardiogr
DOI: 10.1016/j.echo.2020.07.012
sha: 
doc_id: 351134
cord_uid: khgneone

nan

The use of contrast echocardiography in patients receiving veno-venous ECMO (VV-ECMO) for severe acute respiratory failure (SARF) is not widely published, and there is understandable caution surrounding its use in this population. The novel coronavirus 2019 (COVID-19) pandemic resulted in an unprecedented burden on critical care facilities (1) due to SARF. Our centre is one of 5 nationally commissioned VV-ECMO services in the United Kingdom and has seen VV-ECMO activity quadruple during the first pandemic surge. Consequently, there has been growing emphasis on transthoracic echocardiography (TTE) to diagnose cardiac complications of COVID-19 supported with VV-ECMO (2,

Mechanically ventilated patients receiving VV-ECMO are amongst the most challenging in which to obtain diagnostic TTE images. Predictably, we found that as the volume of VV-ECMO patients increased, so too did the requirement for TTE using ultrasound enhancing agents (UEA). Contrast echocardiography is routinely used in our institution and this work was approved through the local governance board as a service evaluation. We carried out bedside TTE in 37 consecutive VV-ECMO patients, of which SonoVue (Bracco International) TTE was performed in 10 (27%). SonoVue boluses (0.5-0.7ml), reconstituted in the standard format, were administered via the post-oxygenator limb of the ECMO circuit. Repeated boluses of the UEA were required in all cases, with a maximum total dose in any one patient of 2.5mls. All patients met criteria for the use of UEA's as outlined in the recently published guidance (4). Very-low mechanical index imaging (VLMI) was performed with standard commercially available tissue cancellation sequences (Philips Healthcare, Andover, MA).

VLMI allows excellent tissue delineation and results in less microbubble destruction than the higher mechanical index left ventricular opacification (LVO) settings. Diagnostic images were obtained in all cases.

In line with our institutional protocols for critical care echo in extracorporeal support (developed in collaboration with our specialist perfusion team), during each contrast study the VV-ECMO circuit was managed by experienced perfusionists. This included disabling the appropriate interventions on the ECMO console prior to UEA administration to ensure safe administration. UEA's are known to activate the protective integrated air bubble alarms which trigger interventions to disable flow -a safety feature of the Cardiohelp ECLS system (MAQUET Medical Systems USA, Wayne, NJ) (5) and in all cases, the integrated detector for air bubbles was indeed triggered by the UEA. This would usually lead to a pump shut down due to activation of additional safety interventions and, unless this alarm is cleared, a further "zero-flow mode" is engaged. This mode provides sufficient revolutions per minute to prevent back flow from the return cannula without providing forward flow, hence equilibrium is maintained in the circuit. However, the resultant cessation of flow, and consequently oxygenation, can result in rapid desaturation and potentially hypoxic arrest. It is therefore of pressing importance that centers offering VV-ECMO adopt protocols and staff training to allow the safe administration of UEA's, facilitating diagnostic echocardiography in the most critical patients.

To our knowledge, this is the largest published series affirming the applicability of a UEA in VV-ECMO. Appropriate protocols should be instituted at centers offering VV-ECMO, ensuring safe management of the circuit by the perfusion team. Enhanced echocardiography may therefore be an appropriate bedside technique during the current viral surge in critical VV-ECMO supported SARF, helping to address diagnostic uncertainty in cases with challenging echocardiography visualisation.

ESC Guidance for the Diagnosis and Management of CV Disease during the COVID-19 Pandemic

ASE Statement on Protection of Patients and Echocardiography Service Providers During the 2019 Novel Coronavirus Outbreak

American Society of Echocardiography Guidelines Update

Beware of life-threatening activation of air bubble detector during contrast echocardiography in patients on venoarterial extracorporeal membrane oxygenator support