Norepinephrine increases the concentration of adenosine 3',5'-monophosphate (cyclic AMP) in an incubated suspension of brain microvessels. This response can be matched by other drugs that stimulate the beta receptors, but the alpha-adrenergic agonist phenylephrine is without effect; beta-adrenergic blockade abolishes the response while alpha-adrenergic blockade produces no change. The data support the contention that cerebral capillary function is subject to adrenergic neural control.

Despite varying CT appearances of PIV LRTI, it most often shows airway-centric disease and is similar to the appearance of RSV infection, both of which are members of the Paramyxoviridae family of viruses.

Objective To investigate the incidence of thromboembolic events, specifically pulmonary embolism (PE), deep vein thrombosis (DVT), and cerebrovascular accidents (CVA), in patients who tested positive for COVID-19 through RT-PCR in a regional healthcare system in Connecticut. Materials and methods All CT angiogram (CTA) and venous duplex extremity ultrasound (US) examinations performed on 192 consecutively documented cases of COVID-19 were retrospectively reviewed at a multi-centered healthcare system. Clinical characteristics and patient outcomes were evaluated and compared between two groups based on the presence or absence of acute thromboembolic events. Results Of the 16,264 patients tested for COVID-19, 3727 (23%) were positive. Out of those, 192 patients underwent 245 vascular imaging studies including chest CTA (86), venous duplex ultrasound (134), and CTA head and neck (25). Among those who underwent imaging, 49 (26%) demonstrated acute thromboembolic events which included 13/86 (15%) with PE, 34/134 (25%) with DVT, and 6/25 (24%) with CVA. One patient had positive results on all 3 examinations, and 2 patients had positive results on both chest CTA and venous duplex US. Males were more likely to have a thromboembolic event than females (33/103 (34%) vs. 14/89 (16%), p = 0.009). No significant difference was observed with respect to age, cardiopulmonary comorbidities, malignancy history, diabetes, or dialysis. Conclusion Approximately 26% of COVID-19 patients with positive testing who underwent vascular imaging with CTA or venous duplex ultrasound had thromboembolic events including PE, DVT, and CVA. This indicates that COVID-19 patients are at increased risk for thromboembolic complications.

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