Platelet cytosolic calcium concentration in patients with fiver cirrhosis. Relationship with hepatic and systemic hemodynamics

Background/Aims: Due to structural and functional similarities between platelets and vascular smooth muscle cells, platelet cytosolic calcium concentration ([Ca ²⁺](i)) has been suggested to be a useful tool to study regulatory mechanisms of peripheral vascular tone. The aim of the present study was to investigate platelet [Ca ²⁺](i) in patients with cirrhosis and whether this parameter is related with the systemic and splanchnic vasodilatation found in these patients. Methods: Seventeen patients with cirrhosis and eight age- and sex-matched controls were studied. Mean arterial pressure, cardiac output, femoral blood flow and basal and thrombin- stimulated platelet [Ca ²⁺](i) were measured. Cardiac output (thermal dilution), azygos blood flow, hepatic venous pressure gradient and hepatic blood flow were also measured in patients with cirrhosis. Results: Patients with cirrhosis had severe portal hypertension and a significantly higher cardiac output and femoral blood flow and a significantly lower systemic and femoral vascular resistance than controls. Patients with cirrhosis had a lower basal platelet [Ca ²⁺](i) than normal subjects. However, there was no relationship between platelet [Ca ²⁺](i) and any of the hemodynamic parameters that evaluate systemic or splanchnic vasodilatation. Conclusions: This study shows that cirrhotic patients with portal hypertension have a significant reduction in platelet basal [Ca ²⁺](i). The lack of correlation between platelet [Ca ²⁺](i) and hepatic and systemic hemodynamics does not support the use of platelet [Ca ²⁺](i) as a model to study mechanisms involved in the pathophysiology of the hyperdynamic circulation associated to portal hypertension.