The effects of low-dose epinephrine infusion on spleen size, central and hepatic circulation and circulating platelets

• Published in: Clinical physiology and functional imaging Vol. 33; no. 1; pp. 30 - 37
• Main Authors: Bakovic, Darija, Pivac, Nediljko, Eterovic, Davor, Breskovic, Toni, Zubin, Petra, Obad, Ante, Dujic, Zeljko
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.01.2013; Blackwell; Wiley Subscription Services, Inc
• Subjects: Adult; Biological and medical sciences; Blood Flow Velocity - drug effects; Blood Platelets - drug effects; Blood Pressure - drug effects; Cardiac Output - drug effects; Circulating; Circulation; Counting; Epinephrine; Epinephrine - administration & dosage; Erythrocyte Indices; Fundamental and applied biological sciences. Psychology; Heart Rate - drug effects; Hepatic Veins - diagnostic imaging; Hepatic Veins - drug effects; Humans; Infusion; Infusions, Intravenous; large platelets; Leukocyte Count; Liver Circulation - drug effects; Male; mean platelet volume; Multipurpose vehicles; Organ Size - drug effects; Platelet Count; Platelets; risk of thrombosis; Spleen; Spleen - diagnostic imaging; Spleen - drug effects; spleen volume; sympathetic stimulation; Sympathomimetics - administration & dosage; Time Factors; Ultrasonography; Vascular Resistance - drug effects; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Young Adult; Epinephrine; Spleen; sympathetic stimulation; risk of thrombosis; Low dose; spleen volume; Cardiovascular disease; Stimulation; Catecholamine; Sympathetic nervous system; Thrombosis; Vascular disease; Vertebrata; Platelet; Mammalia; Autonomic nervous system; Neurotransmitter; large platelets; mean platelet volume
• ISSN: 1475-0961; 1475-097X
• DOI: 10.1111/j.1475-097X.2012.01156.x

Summary In several conditions associated with adrenergic stimulation, an increase in peripheral count of larger platelets has been observed, but the mechanism remained elusive. Larger platelets have greater prothrombotic potential and increase the risk of acute thrombotic events. The human spleen retains one‐third of total body platelets, with mean volume (MPV) about 20% greater than that of circulating platelets. We aimed to answer whether low‐dose epinephrine infusion results in spleen contraction and MPV increase. We undertook the continuous ultrasonic measurements of spleen volume, hepatic and central circulation with concurrent blood sampling in response to intravenous infusion of epinephrine (6 min of 0·06 µg kg−1 per min, followed by 3 min of 0·12 µg kg−1 per min) in nine healthy young subjects. The spleen volume started to decrease immediately after the onset of infusion, in the presence of substantial decreases in peripheral resistance and mean blood pressure and increases in heart rate and cardiac output. The majority of spleen emptying, approximately 25%, (95% CI 71·3–299·7) was observed 1 min after infusion onset, the hepatic vein flow peaked at the end of infusion for 28·4% (95% CI 1074·6–407·9), while increases in platelet count for approximately 31% (95% CI 187·8–314·8) and MPV for 4·4% (95% CI 7·3–10·9) lagged until 1 min after infusion cessation. We suggest that spleen is a dynamic reservoir of large platelets, which are mobilized even by low‐dose epinephrine infusion in conditions of decreased blood pressure.