Transcranial Doppler in Acute COVID-19 Infection: Unexpected Associations

Background and Purpose: Stroke may complicate coronavirus disease 2019 (COVID-19) infection based on clinical hypercoagulability. We investigated whether transcranial Doppler ultrasound has utility for identifying microemboli and clinically relevant cerebral blood flow velocities (CBFVs) in COVID-19. Methods: We performed transcranial Doppler for a consecutive series of patients with confirmed or suspected COVID-19 infection admitted to 2 intensive care units at a large academic center including evaluation for microembolic signals. Variables specific to hypercoagulability and blood flow including transthoracic echocardiography were analyzed as a part of routine care. Results: Twenty-six patients were included in this analysis, 16 with confirmed COVID-19 infection. Of those, 2 had acute ischemic stroke secondary to large vessel occlusion. Ten non-COVID stroke patients were included for comparison. Two COVID-negative patients had severe acute respiratory distress syndrome and stroke due to large vessel occlusion. In patients with COVID-19, relatively low CBFVs were observed diffusely at median hospital day 4 (interquartile range, 3-9) despite low hematocrit (29.5% [25.7%-31.6%]); CBFVs in comparable COVID-negative stroke patients were significantly higher compared with COVID-positive stroke patients. Microembolic signals were not detected in any patient. Median left ventricular ejection fraction was 60% (interquartile range, 60%-65%). CBFVs were correlated with arterial oxygen content, and C-reactive protein (Spearman ρ=0.28 [P=0.04]; 0.58 [P<0.001], respectively) but not with left ventricular ejection fraction (ρ=-0.18; P=0.42). Conclusions: In this cohort of critically ill patients with COVID-19 infection, we observed lower than expected CBFVs in setting of low arterial oxygen content and low hematocrit but not associated with suppression of cardiac output.