Bed rest.

We address a gap in the knowledge of lead turnover under conditions of prolonged bed rest and microgravity by developing a quantitative model of the amount of lead returned to blood circulation from bone. We offer the hypothesis that skeletal unloading, such as typically occurs during extended bed rest or microgravity, will result in bone lead being released to the blood, as has already been demonstrated in the case of calcium. We use initial bone lead concentrations to develop predictive models of blood lead elevation. Our theoretical calculations with typical bone lead loads measured in today's 40-60-year-old generation, suggest that the estimated blood lead concentrations in long duration (e.g., 100 days) space flight could average between 20 and 40 microg dl(-1), a range with well-established toxic effects. For a similar duration of bed rest, estimated blood lead concentration could be as high as 10-20 microg dl(-1), which is a level of concern, particularly if we consider females of childbearing age. The preliminary experimental results were obtained under multi-institutional collaborations, with the main outcome received from an on-going bed rest study, Prevention of Microgravity-Induced Stone Risk by KMgCitrate, conducted at the General Clinical Research Center (GCRC) of the University of Texas Southwestern Medical Center, Dallas. Based on theoretical modeling and some preliminary experimental results, this concept may have important clinical implications by allowing prediction of the magnitude of blood lead elevation, thereby establishing the means to prevent lead toxicity during long duration space flight of astronauts and in conditions of prolonged bed rest such as complicated pregnancy, spinal cord injury induced paralysis and comatose patients.

Bed Rest↗

PubMed2005

Bed rest or ambulation in the initial treatment of patients with acute deep vein thrombosis or pulmonary embolism: findings from the RIETE registry.

BACKGROUND: Traditionally, many patients with acute deep vein thrombosis (DVT) are treated not only by anticoagulation therapy but additionally by strict bed rest, which is aimed at reducing the risk of pulmonary embolism (PE) events. However, this risk has not been subjected to empirical verification. PATIENTS AND METHODS: The Registro Informatizado de la Enfermedad TromboEmbólica is a Spanish registry of consecutively enrolled patients with objectively confirmed, symptomatic acute DVT or PE. In this analysis, the clinical characteristics, details of anticoagulant therapy, and clinical outcomes of enrolled patients with and without strict bed rest prescribed during the first 15 days were compared. Patients in whom ambulation was not possible were not included in this analysis. RESULTS: A total of 2,650 patients entered the study (DVT, 2,038 patients; PE, 612 patients). Of these patients, 1,050 DVT patients (52%) and 385 PE patients (63%) were prescribed strict bed rest. New events of symptomatic, objectively confirmed PE developed during the 15-day study period in 11 patients with DVT (0.5%) and 4 patients with PE (0.7%). Five of these 15 patients (33%) died as a result of their PE. Age < 65 years (odds ratio [OR], 3.1; 95% confidence interval [CI], 0.98 to 11) and cancer (OR, 3.0; 95% CI, 0.98 to 9.1) were associated with an increased rate of new PEs. There were not significant differences between bedridden and ambulant patients in terms of new PE events, fatal PE, or bleeding complications. CONCLUSIONS: Our findings confirm those from previous reports suggesting that bed rest has no influence on the risk of developing PE among patients with acute DVT of the lower limbs. In addition, our findings show for the first time the lack of influence of bed rest even in patients presenting with acute submassive PE.

Bed Rest↗