A Systematic Review of the Prothrombotic Effects of an Acute Change in Posture: A Possible Mechanism Underlying the Morning Excess in Cardiovascular Events?

摘要

Background: Epidemiologic studies have demonstrated a morning excess of acute cardiovascularnevents, which has subsequently been refined to the 2 to 3 h after awakening. It is thereforenreasonable to assume that some activity associated with awakening may trigger such cardiovas-ncular events, with the assumption of an upright posture being of potential significance.nObjective: To identify and systematically review the literature to determine the effects of acutenchanges in posture on hemorheology and hemostasis.nData sources: Electronic databases MEDLINE, EMBASE, PSYCHINFO, and CINAHL (earliestndate available to February 5, 2006) and conference abstracts were searched.nStudy selection: Studies examining the hemorheologic and hemostatic response to a change innposture from a supine position to an upright position were eligible for inclusion. Two reviewersnindependently selected the studies for inclusion.nResults: The experimental evidence reviewed demonstrates that the assumption of an uprightnposture is associated with a significant degree of hemoconcentration, which is characterized by annincrease in hematocrit and a decrease in plasma volume. Research examining the effect of posturalnchange on hemostasis has been limited, although a small number of studies have demonstrated somensignificant changes in markers of coagulation, fibrinolysis, and platelet reactivity.nConclusions: A sudden change in posture may act as a potential trigger for the onset of cardiovascularnevents occurring in the 3 h after awakening via effects on hemostasis and hemorheology. However,nother possible triggering factors such as dehydration, mental stress, and physical exertion must alsonbe considered