Abstract
Immobility plus preexisting chronic disease or acute trauma can activate the coagulation system, thus increasing the risk for thromboembolic events. The effects of long-term bed-rest immobility and microgravity on the coagulation system of healthy persons (e.g., during crewed Mars missions) have not yet been studied. The main objective of the second Berlin BedRest Study (BBR2-2) “Coagulation Part” was to investigate adaptations of the hemostatic system during long-term bed rest (60 days) under simulated microgravity (6° head-down-tilt [6°HDT]) and after mobilization in three different volunteer groups (randomly assigned to CTR= inactive control group; RE= resistive exercise only group; and RVE= resistive exercise with whole-body vibration group). In 24 males (aged 21–45 years), before, during, and after long-term bed rest, key parameters of coagulation were measured from venous blood samples: D-dimer (DD), thrombin–antithrombin III complex (TAT), and prothrombin fragment F1 + 2 (PT-F1 + 2). Additionally, modified rotational thrombelastometry (ROTEM®) analysis was performed. Times of exploratory analyses were as follows: baseline data collection 2 days before bed rest (BDC-2); eight different days of 6°HDT bed rest (HDT1–HDT60), and two different days after reambulation (R + 3 and R + 6). We found significant changes in DD, TAT, and PT-F1 + 2 over the total time course, but no consistent effect of physical interventions (RE, RVE) on these parameters. Notably, no parameter reached levels indicative of intravascular thrombin formation. All ROTEM® parameters remained within the normal range and no pathological traces were found. Sixty days of 6°HDT bed rest are not associated with pronounced activation of the coagulation system indicative of intravascular thrombus formation in healthy volunteers independent of the training type during the bed rest.
Highlights
Immobility is a central issue in daily life and has a variety of different physiological and clinical aspects (Kahn et al 2012)
Twenty-four medically and psychologically healthy males were recruited to undergo 60 days of strict 6°head-down-tilt bed rest (HDTBR) for the BBR2-2 “Coagulation Part,” which was conducted in four campaigns of six subjects each in 2007 and 2008
One subject (RE group) left bed rest on day 30 of bed rest (HDT30) for medical reasons unrelated to this study. Another subject of the RVE group had already at baseline an abnormal high DD value, whereas the rest of the subject’s hemostatic parameters were within the normal reference range and ultrasonography of leg and pelvic veins did not show any evidence of a deep venous thrombosis
Summary
Immobility is a central issue in daily life and has a variety of different physiological and clinical aspects (Kahn et al 2012). Fluid shifts with leg edema and the focus on travel-related coagulation changes are key scientific topics Another aspect of immobility is in-hospital immobility of patients on bed rest. Since the introduction of heparins and other anticoagulants, the incidence of inhospital thromboembolism has decreased significantly (Kahn et al 2012) These clinical findings cannot be transferred to HDTBR because these studies were performed in healthy volunteers. Several studies have investigated vascular adaptations but not coagulation changes after prolonged immobility and have reported an inward remodeling of conduit arteries, altered carotid wall thickness, venous enlargement, and increased distensibility and venous compliance in dependent veins (van Duijnhoven et al 2008, 2010b; Kolegard et al 2009).There is a paucity of data regarding bed-rest studies on subjects without preexisting disease. We hypothesized that long-term bed rest does not seriously modulate the hemostatic system (e.g., inducing a hyper-/hypocoagulable state) of healthy men
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