Point-of-care contrast enhanced lung ultrasound and COVID-19

Abstract

Objectives: Bedside lung ultrasound has been indispensable during the coronavirus disease 2019 (COVID-19) pandemic, allowing us to rapidly assess critically unwell patients. We demonstrate the unique application of contrast-enhanced ultrasound with the aim of further understanding this disease.

Methods: Patient demographics were recorded alongside recent cross-sectional imaging and inflammatory markers. Ultrasound was conducted by experienced operators in a portable setting. Conventional six-point lung ultrasound method was used to evaluate B-lines, small (subpleural) consolidation and the pleura. Areas of small consolidation were targeted after intravenous administration of ultrasound contrast.

Results: The areas of small consolidations, a potential sign of pneumonia on B-mode lung ultrasound, usually enhance on contrast-enhanced ultrasound. Our study revealed these areas to be avascular, indicating an underlying thrombotic/infarction process. Findings were present in 100% of the patients we examined. We have also shown that the degree of infarction correlates with CT severity (r = 0.4) and inflammatory markers, and that these areas improve as patients recover.

Conclusions: We confirmed the theory of immune thrombus by identifying the presence of microthrombi in the lungs of 100% of our patients, despite 79% having had a recent negative CT pulmonary angiogram study. contrast-enhanced ultrasound can be utilised to add confidence to an uncertain COVID-19 diagnosis and for prognosticating and monitoring progress in confirmed COVID-19 patients. Contrast-enhanced ultrasound is clearly very different to CT, the gold standard, and while there are specific pathologies that can only be detected on CT, contrast-enhanced ultrasound has many advantages, most notability the ability to pick up microthrombi at the periphery of the lungs.

Keywords: Coronavirus, consolidation, microthrombi, computed tomography, bedside ultrasound, critical care, microbubble.

Figure 1.

(a) Chest radiograph show no dense consolidation or pleural effusion, (b, c) Simultaneous B-mode and CEUS show multiple hypoechoic areas (arrows) with no enhancement, (d) contemporaneous CTPA show typical features of severe COVID-19 with peripheral ground glass opacity (arrows). There was no pulmonary embolism. (e) Follow-up chest radiograph demonstrates bilateral, peripheral airspace opacification (arrows). (f, g) Simultaneous ultrasound performed show an increased number of hypoechoic areas throughout all six zones (arrows), all of which showed no enhancement. (h) Contemporaneous CTPA show progression of disease, with areas of dense consolidation (arrows) in addition to ground glass opacification. There was no pulmonary embolism.

Figure 2.

(a) Chest radiograph shows typical features of COVID-19 with bilateral peripheral airspace opacification (arrows). (b, c) Simultaneous B-mode and CEUS demonstrates a hypoechoic area (arrow) with no enhancement, and simultaneous CT (d) demonstrated findings of severe disease. (e, f) B-mode and CEUS follow-up after clinical improvement showed resolution of previous hypoechoic areas. One area had retracted with delayed hypoenhancement, signal was seen from individual microbubbles in the capillary bed implying reperfusion (arrow). (g) Follow-up chest radiograph several weeks later shows total resolution of COVID-19 infection.