Acute 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.
Patients were prospectively recruited ≤ 24 hours following intensive care unit (ICU) admission to a University Teaching and 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 an age of 54.4 years (95% Confidence Interval (CI) 49.1-59.6)years and APACHE II score 23.9 (95%CI 22.4-25.5).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.
BMD did not change between day 1 and 10 in the cohort overall (0.434 (95%CI 0.405-0.463) vs. 0.425 g/cm(2) (95%CI 0.399-0.450), p = 0.58).Multivariable logistical regression revealed admission corrected calcium (OR 1.980 (95%CI 1.089-3.609), p = 0.026) and admission PaO2 to FiO2 ratio (OR 0.916 (95%CI 0.833-0.998), 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 -5.73-0.118)%, n = 34 vs. 2.40 (95%CI 0.204-4.586)%,n = 12, p = 0.029). In the 34 patients with Acute Respiratory Distress Syndrome, fracture risk increased by 19.4% (95%CI 13.9-25.0%).
Patients with acute respiratory distress syndrome demonstrated early and rapid bone demineralisation with associated increase in fracture risk.