Abstract
IntroductionAcute skeletal muscle wasting is a major contributor to post critical illness physical impairment. However, the bone response remains uncharacterized. We prospectively investigated the early changes in bone mineral density (BMD) and fracture risk in critical illness.MethodsPatients were prospectively recruited ≤24 hours following intensive care unit (ICU) admission to a university teaching or a community hospital (August 2009 to April 2011). All were aged >18 years and expected to be intubated for >48 hours, spend >7 days in critical care and survive ICU admission. Forty-six patients were studied (55.3% male), with a mean age of 54.4 years (95% confidence interval (CI): 49.1 to 59.6) and an APACHE II score of 23.9 (95% CI: 22.4 to 25.5). Calcaneal dual X-ray absorptiometry (DXA) assessment of BMD was performed on day 1 and 10. Increase in fracture risk was calculated from the change in T-score.ResultsBMD did not change between day 1 and 10 in the cohort overall (0.434 (95% CI: 0.405 to 0.463) versus 0.425 g/cm2 (95% CI: 0.399 to 0.450), P = 0.58). Multivariable logistical regression revealed admission corrected calcium (odds ratio (OR): 1.980 (95% CI: 1.089 to 3.609), P = 0.026) and admission PaO2-to-FiO2 ratio (OR: 0.916 (95% CI: 0.833 to 0.998), P = 0.044) to be associated with >2% loss of BMD. Patients with acute respiratory distress syndrome had a greater loss in BMD than those without (−2.81% (95% CI: −5.73 to 0.118%), n = 34 versus 2.40% (95% CI: 0.204 to 4.586%), n = 12, P = 0.029). In the 34 patients with acute respiratory distress syndrome, fracture risk increased by 19.4% (95% CI: 13.9 to 25.0%).ConclusionsPatients with acute respiratory distress syndrome demonstrated early and rapid bone demineralisation with associated increase in fracture risk.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-015-0892-y) contains supplementary material, which is available to authorized users.
Highlights
Acute skeletal muscle wasting is a major contributor to post critical illness physical impairment
We performed a pilot study to investigate the early effects of critical illness on bone mineral density (BMD) and fracture risk, and sought clinical factors that might be associated with early bone demineralization
Four patients had pre-morbid conditions associated with possible disrupted calcium homeostasis. Their baseline dual X-ray absorptiometry (DXA) measurement was no different from the remaining cohort
Summary
Acute skeletal muscle wasting is a major contributor to post critical illness physical impairment. We prospectively investigated the early changes in bone mineral density (BMD) and fracture risk in critical illness. Rapid and early muscle wasting contributes to the significant long-term functional impairment observed in survivors of critical illness [1,2,3,4]. Mechanical unloading as a consequence of bed rest [8], inflammation [9], acidaemia [10], vitamin D deficiency [11], corticosteroid use [12] and hypoxia [13] may all worsen bone health and reduce bone mineral density (BMD). We performed a pilot study to investigate the early effects of critical illness on BMD and fracture risk, and sought clinical factors that might be associated with early bone demineralization
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