Skeletal morbidity among survivors of critical illness

Survivorship outcomes for critically ill patients in Australia and New Zealand: A scoping review

INTRODUCTION

Impairments after critical illness, termed the post-intensive care syndrome, are an increasing focus of research in Australasia. However, this research is yet to be cohesively synthesised and/or summarised.

OBJECTIVE

The aim of this scoping review was to explore patient outcomes of survivorship research, identify measures, methodologies, and designs, and explore the reported findings in Australasia.

INCLUSION CRITERIA

Studies reporting outcomes for adult survivors of critical illness from Australia and New Zealand in the following domains: physical, functional, psychosocial, cognitive, health-related quality of life (HRQoL), discharge destination, health care use, return to work, and ongoing symptoms/complications of critical illness.

METHODS

The Joanna Briggs Institute scoping review methodology framework was used. A protocol was published on the open science framework, and the search used Ovid MEDLINE, Scopus, ProQuest, and Google databases. Eligible studies were based on reports from Australia and New Zealand published in English between January 2000 and March 2022.

RESULTS

There were 68 studies identified with a wide array of study aims, methodology, and designs. The most common study type was nonexperimental cohort studies (n = 17), followed by studies using secondary analyses of other study types (n = 13). HRQoL was the most common domain of recovery reported. Overall, the identified studies reported that impairments and activity restrictions were associated with reduced HRQoL and reduced functional status was prevalent in survivors of critical illness. About 25% of 6-month survivors reported some form of disability. Usually, by 6 to12 months after critical illness, impairments had improved.

CONCLUSIONS

Reports of long-term outcomes for survivors of critical illness in Australia highlight that impairments and activity limitations are common and are associated with poor HRQoL. There was little New Zealand-specific research related to prevalence, impact, unmet needs, ongoing symptoms, complications from critical illness, and barriers to recovery.

A pilot feasibility randomised controlled trial of bone antiresorptive agents on bone turnover markers in critically ill women

Critical illness is associated with increased bone turnover, loss of bone density, and increased risk of fragility fractures. The impact of bone antiresorptive agents in this population is not established. This trial examined the efficacy, feasibility, and safety of antiresorptive agents administered to critically ill women aged fifty years or greater. Women aged 50 years or greater admitted to an intensive care unit for at least 24 h were randomised to receive an antiresorptive agent (zoledronic acid or denosumab) or placebo, during critical illness and six months later (denosumab only). Bone turnover markers and bone mineral density (BMD) were monitored for 1 year. We studied 18 patients over 35 months before stopping the study due to the COVID-19 pandemic. Antiresorptive medications decreased the bone turnover marker type 1 cross-linked c-telopeptide (CTX) from day 0 to 28 by 43% (± 40%), compared to an increase of 26% (± 55%) observed with placebo (absolute difference - 69%, 95% CI - 127% to - 11%), p = 0.03). Mixed linear modelling revealed differences in the month after trial drug administration between the groups in serum CTX, alkaline phosphatase, parathyroid hormone, and phosphate. Change in BMD between antiresorptive and placebo groups was not statistically analysed due to small numbers. No serious adverse events were recorded. In critically ill women aged 50-years and over, antiresorptive agents suppressed bone resorption markers without serious adverse events. However, recruitment was slow. Further phase 2 trials examining the efficacy of these agents are warranted and should address barriers to enrolment.Trial registration: ACTRN12617000545369, registered 18th April 2017.

Pathophysiology and Therapeutic Management of Bone Loss in Patients with Critical Illness

Patients with critical illnesses are at higher risk of comorbidities, which can include bone mineral density loss, bone turnover marker increase, and fragility fractures. Patients admitted to intensive care units (ICUs) have a higher risk of bone fractures. Since hypermetabolism is a characteristic of ICU patients, such patients are often rapidly affected by systemic deterioration, which often results in systemic wasting disease. Major risk factors for ICU-related bone loss include physical restraint, inflammation, neuroendocrine stress, malnutrition, and medications. A medical history of critical illness should be acknowledged as a risk factor for impaired bone metabolism. Bone loss associated with ICU admission should be recognized as a key component of post-intensive care syndrome, and further research that focuses on treatment protocols and prevention strategies is required. Studies aimed at maintaining gut integrity have emphasized protein administration and nutrition, while research is ongoing to evaluate the therapeutic benefits of anti-resorptive agents and physical therapy. This review examines both current and innovative clinical strategies that are used for identifying risk factors of bone loss. It provides an overview of perioperative outcomes and discusses the emerging novel treatment modalities. Furthermore, the review presents future directions in the treatment of ICU-related bone loss.

The epigenetic legacy of ICU feeding and its consequences

PURPOSE OF REVIEW

Many critically ill patients face physical, mental or neurocognitive impairments up to years later, the etiology remaining largely unexplained. Aberrant epigenetic changes have been linked to abnormal development and diseases resulting from adverse environmental exposures like major stress or inadequate nutrition. Theoretically, severe stress and artificial nutritional management of critical illness thus could induce epigenetic changes explaining long-term problems. We review supporting evidence.

RECENT FINDINGS

Epigenetic abnormalities are found in various critical illness types, affecting DNA-methylation, histone-modification and noncoding RNAs. They at least partly arise de novo after ICU-admission. Many affect genes with functions relevant for and several associate with long-term impairments. As such, de novo DNA-methylation changes in critically ill children statistically explained part of their disturbed long-term physical/neurocognitive development. These methylation changes were in part evoked by early-parenteral-nutrition (early-PN) and statistically explained harm by early-PN on long-term neurocognitive development. Finally, long-term epigenetic abnormalities beyond hospital-discharge have been identified, affecting pathways highly relevant for long-term outcomes.

SUMMARY

Epigenetic abnormalities induced by critical illness or its nutritional management provide a plausible molecular basis for their adverse effects on long-term outcomes. Identifying treatments to further attenuate these abnormalities opens perspectives to reduce the debilitating legacy of critical illness.

A machine learning-based prediction model for in-hospital mortality among critically ill patients with hip fracture: An internal and external validated study

INTRODUCTION

Few studies have investigated the in-hospital mortality among critically ill patients with hip fracture. This study aimed to develop and validate a model to estimate the risk of in-hospital mortality among critically ill patients with hip fracture.

METHODS

For this study, data from the Medical Information Mart for Intensive Care III (MIMIC-III) Database and electronic Intensive Care Unit (eICU) Collaborative Research Database were evaluated. Enrolled patients (n=391) in the MIMIC-III database were divided into a training (2/3, n=260) and a validation (1/3, n=131) group at random. Using machine learning algorithms such as random forest, gradient boosting machine, decision tree, and eXGBoosting machine approach, the training group was utilized to train and optimize models. The validation group was used to internally validate models and the optimal model could be obtained in terms of discrimination (area under the receiver operating characteristic curve, AUROC) and calibration (calibration curve). External validation was done in the eICU Collaborative Research Database (n=165). To encourage practical use of the model, a web-based calculator was developed according to the eXGBoosting machine approach.

RESULTS

The in-hospital death rate was 13.81% (54/391) in the MIMIC-III database and 10.91% (18/165) in the eICU Collaborative Research Database. Age, gender, anemia, mechanical ventilation, cardiac arrest, and chronic airway obstruction were the six model parameters which were identified using the Least Absolute Shrinkage and Selection Operator (LASSO) method combined with 10-fold cross-validation. The model established using the eXGBoosting machine approach showed the highest area under curve (AUC) value (0.797, 95% CI: 0.696-0.898) and the best calibrating ability, with a calibration slope of 0.999 and intercept of -0.019. External validation also revealed favorable discrimination (AUC: 0.715, 95% CI: 0.566-0.864; accuracy: 0.788) and calibration (calibration slope: 0.805) in the eICU Collaborative Research Database. The web-based calculator could be available at https://doctorwangsj-webcalculator-main-yw69yd.streamlitapp.com/.

CONCLUSION

The model has the potential to be a pragmatic risk prediction tool that is able to identify hip fracture patients who are at a high risk of in-hospital mortality in ICU settings, guide patient risk counseling, and simplify prognosis bench-marking by controlling for baseline risk.

Toward nutrition improving outcome of critically ill patients: How to interpret recent feeding RCTs?

Although numerous observational studies associated underfeeding with poor outcome, recent randomized controlled trials (RCTs) have shown that early full nutritional support does not benefit critically ill patients and may induce dose-dependent harm. Some researchers have suggested that the absence of benefit in RCTs may be attributed to overrepresentation of patients deemed at low nutritional risk, or to a too low amino acid versus non-protein energy dose in the nutritional formula. However, these hypotheses have not been confirmed by strong evidence. RCTs have not revealed any subgroup benefiting from early full nutritional support, nor benefit from increased amino acid doses or from indirect calorimetry-based energy dosing targeted at 100% of energy expenditure. Mechanistic studies attributed the absence of benefit of early feeding to anabolic resistance and futile catabolism of extra provided amino acids, and to feeding-induced suppression of recovery-enhancing pathways such as autophagy and ketogenesis, which opened perspectives for fasting-mimicking diets and ketone supplementation. Yet, the presence or absence of an anabolic response to feeding cannot be predicted or monitored and likely differs over time and among patients. In the absence of such monitor, the value of indirect calorimetry seems obscure, especially in the acute phase of illness. Until now, large feeding RCTs have focused on interventions that were initiated in the first week of critical illness. There are no large RCTs that investigated the impact of different feeding strategies initiated after the acute phase and continued after discharge from the intensive care unit in patients recovering from critical illness.

An update of the effects of vitamins D and C in critical illness

Many critically ill patients are vitamin D and vitamin C deficient and the current international guidelines state that hypovitaminoses should be compensated. However, uncertainty about optimal dosage, timing and indication exists in clinical routine, mainly due to the conflicting evidence. This narrative review discusses both micronutrients with regards to pathophysiology, clinical evidence of benefits, potential risks, and guideline recommendations. Evidence generated from the most recent clinical trials are summarized and discussed. In addition, pragmatic tips for the application of these vitamins in the clinical routine are given. The supplementations of vitamin D and C represent cost-effective and simple interventions with excellent safety profiles. Regarding vitamin D, critically ill individuals require a loading dose to improve 25(OH)D levels within a few days, followed by a daily or weekly maintenance dose, usually higher doses than healthy individuals are needed. For vitamin C, dosages of 100-200 mg/d are recommended for patients receiving parenteral nutrition, but needs may be as high as 2-3 g/d in acutely ill patients.

Acute and severe trabecular bone loss in a rat model of critical illness myopathy

Prolonged mechanical ventilation for critically ill patients with respiratory distress can result in severe muscle wasting with preferential loss of myosin. Systemic inflammation triggered by lung mechanical injury likely contributes to this myopathy, although the exact mechanisms are unknown. In this study, we hypothesized that muscle wasting following mechanical ventilation is accompanied by bone loss. The objective was to determine the rate, nature, and extent of bone loss in the femora of rats ventilated up to 10 days and to relate the bone changes to muscle deterioration. We have developed a rat model of ventilator-induced muscle wasting and established its feasibility and clinical validity. This model involves pharmacologic paralysis, parenteral nutrition, and continuous mechanical ventilation. We assessed the hindlimb muscle and bone of rats ventilated for 0, 2, 5, 8, and 10 days. Routine histology, microCT, and biomechanical evaluations were performed. Hindlimb muscles developed changes consistent with myopathy, whereas the femurs demonstrated a progressive decline in trabecular bone volume, mineral density, and microarchitecture beginning Day 8 of mechanical ventilation. Biomechanical testing showed a reduction in flexural strength and stiffness on Day 10. The bone changes correlated with the loss of muscle mass and myosin. These results demonstrate that mechanical ventilation leads to progressive trabecular bone loss parallel to muscle deterioration. The results of our study suggest that mechanically ventilated patients may be at risk of compromised bone integrity and muscle weakness, predisposing to post-ventilator falls and fractures, thereby warranting interventions to prevent progressive bone and muscle decline.

Musculoskeletal complications following critical illness: A scoping review

PURPOSE

To explore the extent to which musculoskeletal (MSK) complications have been reported following critical illness, identifying evidence gaps and providing recommendations for future research.

MATERIALS AND METHODS

We searched five databases from January 1st 2000 to March 31st 2021. We included published original research reporting MSK complications in patients discharged from hospital following an admission to an intensive care unit (ICU). Two reviewers independently screened English language articles for eligibility. Data extracted included the MSK area of investigation and MSK outcome measures. The overall quality of study was evaluated against standardised reporting guidelines.

RESULTS

4512 titles were screened, and 32 met the inclusion criteria. Only one study included was interventional, with the majority being prospective cohort studies (n = 22). MSK complications identified included: muscle weakness or atrophy, chronic pain, neuromuscular dysfunction, peripheral joint impairment and fracture risk. The quality of the overall reporting in the studies was deemed adequate.

CONCLUSIONS

We identified a heterogenous body of literature reporting a high prevalence of a variety of MSK complications extending beyond muscle weakness, therefore future investigation should include evaluations of more than one MSK area. Further investigation of MSK complications could inform the development of future post critical illness rehabilitation programs.

Challenges and Opportunities for Osteoporosis Care During the COVID-19 Pandemic

PURPOSE

The coronavirus disease 2019 (COVID-19) has both directly and indirectly affected osteoporosis diagnosis and treatment throughout the world.

METHODS

This mini-review summarizes the available evidence regarding the effects of COVID-19, its treatment, and the consequences of the pandemic itself on bone health. Additionally, we review evidence and expert recommendations regarding putative effects of osteoporosis medications on COVID-19 outcomes and vaccine efficacy and summarize recommendations for continuation of osteoporosis treatment during the pandemic.

RESULTS

The use of standard screening procedures to assess for osteoporosis and fracture risk declined dramatically early in the pandemic, while rates of fragility fractures were largely unchanged. COVID-19, its treatments, and public health measures to prevent viral spread are each likely to negatively affect bone health. Osteoporosis treatments are not known to increase risk of adverse events from COVID-19, and preclinical data suggest possible beneficial effects of some therapies. Vitamin D deficiency is clearly associated with adverse outcomes from COVID-19, but it remains unclear whether vitamin D supplementation may improve outcomes. Osteoporosis treatment should be continued whenever possible, and recommendations for substituting therapies, if required, are available.

CONCLUSION

The COVID-19 pandemic has decreased screening and disrupted treatment for osteoporosis. Osteoporosis medications are safe and effective during the pandemic and should be continued whenever possible. Further studies are needed to fully understand the impact of the COVID-19 pandemic on long-term bone health.

Osteoporosis and the Critically Ill Patient

Improved survival after critical illness has led to recognition of impaired recovery following critical illness as a major public health problem. A consistent association between critical illness and accelerated bone loss has been described, including changes in bone turnover markers, bone mineral density, and fragility fracture rate. An association between accelerated bone turnover and increased mortality after critical illness is probable. Assessment of the effect of antifracture agents on fracture rate and mortality in the high-risk population of postmenopausal women with prolonged ventilation is warranted.

Changes in bone mineral density in women before critical illness: a matched control nested cohort study

The contribution of premorbid bone health to accelerated bone loss following critical illness is unknown. This study compared bone density in women before critical illness to women who did not become critically ill. Overall bone density was similar, although femoral neck bone mass increased immediately prior to critical illness.

PURPOSE

The relative contribution of acute and chronic factors to accelerated loss of bone mineral density (BMD) following critical illness is unknown. This study compared the BMD trajectory of women before critical illness to the BMD trajectory of women who did not become critically ill.

METHODS

This prospective, nested, age- and medication-matched, case-control study compared trajectory of BMD in women in the Geelong Osteoporosis study (GOS) requiring admission to an Australian Intensive Care Unit (ICU) between June 1998 and March 2016, to women not admitted to ICU. The main outcome was age and medication use adjusted change in BMD.

RESULTS

A total of 52 women, with a mean age of 77 ± 9 years were admitted to ICU, predominantly post-surgery (75%), during the study period. A greater age-adjusted annual rate of decline was observed for pre-ICU women compared to no-ICU women for AP spine BMD (-0.010 ± 0.002 g/cm² vs -0.005 ± 0.002 g/cm², p = 0.01) over the 15-year study period. In participants with multiple BMDs 2 years before critical illness, a significantly greater increase in femoral neck BMD compared to age- and medication-matched controls was observed (difference in BMD, ICU vs no-ICU = 0.037 ± 0.013 g/cm², p = 0.006).

CONCLUSION

In a cohort of women with predominantly surgical ICU admission, bone health prior to critical illness was comparable to age- and medication-matched controls, with a relative increase in femoral neck bone mass immediately prior to critical illness. These findings suggest critical illness-related bone loss cannot be entirely explained as a continuation of pre-morbid bone trajectory.

Sepsis Reduces Bone Strength Before Morphologic Changes Are Identifiable

OBJECTIVES

Survivors of critical illness have an increased prevalence of bone fractures. However, early changes in bone strength, and their relationship to structural changes, have not been described. We aimed to characterize early changes in bone functional properties in critical illness and their relationship to changes in bone structure, using a sepsis rodent model.

DESIGN

Experimental study.

SETTING

Animal research laboratory.

SUBJECTS

Adult Sprague-Dawley rats.

INTERVENTIONS

Forty Sprague-Dawley rats were randomized to cecal ligation and puncture or sham surgery. Twenty rodents (10 cecal ligation and puncture, 10 sham) were killed at 24 hours, and 20 more at 96 hours.

MEASUREMENTS AND MAIN RESULTS

Femoral bones were harvested for strength testing, microCT imaging, histologic analysis, and multifrequency scanning probe microscopy. Fracture loads at the femoral neck were significantly reduced for cecal ligation and puncture-exposed rodents at 24 hours (83.39 ± 10.1 vs 103.1 ± 17.6 N; p = 0.014) and 96 hours (81.60 ± 14.2 vs 95.66 ± 14.3 N; p = 0.047). Using multifrequency scanning probe microscopy, collagen elastic modulus was lower in cecal ligation and puncture-exposed rats at 24 hours (1.37 ± 0.2 vs 6.13 ± 0.3 GPa; p = 0.001) and 96 hours (5.57 ± 0.5 vs 6.13 ± 0.3 GPa; p = 0.006). Bone mineral elastic modulus was similar at 24 hours but reduced in cecal ligation and puncture-exposed rodents at 96 hours (75.34 ± 13.2 vs 134.4 ± 8.2 GPa; p < 0.001). There were no bone architectural or bone mineral density differences by microCT. Similarly, histologic analysis demonstrated no difference in collagen and elastin staining, and C-X-C chemokine receptor type 4, nuclear factor kappa beta, and tartrate-resistant acid phosphatase immunostaining.

CONCLUSIONS

In a rodent sepsis model, trabecular bone strength is functionally reduced within 24 hours and is associated with a reduction in collagen and mineral elastic modulus. This is likely to be the result of altered biomechanical properties, rather than increased bone mineral turnover. These data offer both mechanistic insights and may potentially guide development of therapeutic interventions.

Effect of vitamin D3 on bone turnover markers in critical illness: post hoc analysis from the VITdAL-ICU study

In this post hoc analysis of the VITdAL-ICU study, an RCT in critically ill adults with 25-hydroxyvitamin D levels ≤20 ng/ml, vitamin D3 did not have a significant effect on β-Crosslaps and osteocalcin.

INTRODUCTION

Observational studies have shown accelerated bone loss in ICU survivors. A reversible contributor is vitamin D deficiency. In a post hoc analysis of the VITdAL-ICU study, we evaluated the effect of high-dose vitamin D3 on the bone turnover markers (BTM) β-Crosslaps (CTX) and osteocalcin (OC).

METHODS

The VITdAL-ICU study was a randomized, double-blind, placebo-controlled trial in critically ill adults with 25-hydroxyvitamin D levels ≤20 ng/ml who received placebo or high-dose vitamin D3 (a loading dose of 540,000 IU and starting 1 month after the loading dose five monthly maintenance doses of 90,000 IU). In this analysis on 289 survivors (209 telephone, 80 personal follow-up visits), BTM were analyzed on days 0, 3, 7, 28, and 180; self-reported falls and fractures were assessed. Bone mineral density (BMD) was measured after 6 months.

RESULTS

At baseline, CTX was elevated; OC was low in both groups-after 6 months, both had returned to normal. There were no differences between groups concerning BTM, BMD, falls, or fractures. In linear mixed effects models, CTX and OC showed a significant change over time (p < 0.001, respectively), but there was no difference between the vitamin D and placebo group (p = 0.688 and p = 0.972, respectively).

CONCLUSIONS

Vitamin D supplementation did not have a significant effect on BTM. Further studies should assess the effectiveness of vitamin D on musculoskeletal outcomes in ICU survivors.

Occurrence of Clinical Bone Fracture Following a Prolonged Stay in Intensive Care Unit: A Retrospective Controlled Study

Clinical consequences of critical illness and critical care (CC) on bone health remain largely unexplored. This retrospective study aimed to assess the number of new bone fractures (BF) following a prolonged length of stay (LOS) in intensive care unit (ICU). Adults admitted in our tertiary ICU during 2013 with a stay >7 days were included (CC group). Patients who died in ICU or lost to follow-up were excluded. For each CC patient still alive after 2 years of follow-up, 2 control patients, scheduled for surgery during 2013, were recruited and matched for gender and age. Basal fracture risk before admission was calculated using FRAX tool. General practitioners were phoned to check out new bone fracture (BF) during 2 years after admission. Of the 457 enrolled CC patients, 207 did not meet inclusion criteria and 72 died during FU (median age 72 [65-77] years). New BF occurred in 9 of the 178 patients still alive at the end of FU (5%). Median age of these patients was 64 [53-73] years. Fractured patients did not differ from non-fractured ones based on demographic and clinical characteristics, excepting for FRAX risks that were higher in fractured patients. In the control group, 327 patients were analyzed. Their rate of BF was 3.4% without statistical significance compared to the CC group. FRAX risks were similar in both groups. The risk of new BF in CC group, expressed as an odds ratio, was 50% higher than in the control group without achieving statistical significance (odds ratio 1.53; 95% confidence interval 0.62-3.77; p = 0.35). When comparing ICU survivors to patients who underwent uncomplicated surgery in the present preliminary study included limited cohorts, the fracture risk in the 2 years following prolonged ICU stay was not statistically higher. However, CC fractured patients had higher FRAX risks than non-fractured patients. Such screening could help to target prevention and appropriate treatment strategies.

The association of time and medications with changes in bone mineral density in the 2 years after critical illness

Background

Critical illness is associated with increased risk of fragility fracture and loss of bone mineral density (BMD), although the impact of medication exposures (bone anti-fracture therapy or glucocorticoids) and time remain unexplored. The objective of this study was to describe the association of time after ICU admission, and post-ICU administration of bone anti-fracture therapy or glucocorticoids after critical illness, with change in BMD.

Methods

In this prospective observational study, conducted in a tertiary hospital ICU, we studied adult patients requiring mechanical ventilation for at least 24 hours and measured BMD annually for 2 years after ICU discharge. We performed mixed linear modelling to describe the association of time, and post-ICU administration of anti-fracture therapy or glucocorticoids, with annualised change in BMD.

Results

Ninety-two participants with a mean age of 63 (±15) years had at least one BMD assessment after ICU discharge. In women, a greater loss of spine BMD occurred in the first year after critical illness (year 1: -1.1 ± 2.0% vs year 2: 3.0 ± 1.7%, p = 0.02), and anti-fracture therapy use was associated with reduced loss of BMD (femur 3.1 ± 2.4% vs -2.8 ± 1.7%, p = 0.04, spine 5.1 ± 2.5% vs -3.2 ± 1.8%, p = 0.01). In men anti-fracture and glucocorticoid use were not associated with change in BMD, and a greater decrease in BMD occurred in the second year after critical illness (year 1: -0.9 ± 2.1% vs year 2: -2.5 ± 2.1%, p = 0.03).

Conclusions

In women a greater loss of spine BMD was observed in the first year after critical illness, and anti-fracture therapy use was associated with an increase in BMD. In men BMD loss increased in the second year after critical illness. Anti-fracture therapy may be an effective intervention to prevent bone loss in women after critical illness.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1657-6) contains supplementary material, which is available to authorized users.

Evaluation of Bone Metabolism in Critically Ill Patients Using CTx and PINP

Background. Prolonged immobilization, nutritional and vitamin D deficiency, and specific drug administration may lead to significant bone resorption. Methods and Patients. We prospectively evaluated critically ill patients admitted to the ICU for at least 10 days. Demographics, APACHE II, SOFA scores, length of stay (LOS), and drug administration were recorded. Blood collections were performed at baseline and on a weekly basis for five consecutive weeks. Serum levels of PINP, β-CTx, iPTH, and 25(OH)vitamin D were measured at each time-point. Results. We enrolled 28 patients of mean age 67.4 ± 2.3 years, mean APACHE II 22.2 ± 0.9, SOFA 10.1 ± 0.6, and LOS 31.6 ± 5.7 days. Nineteen patients were receiving low molecular weight heparin, 17 nor-epinephrine and low dose hydrocortisone, 18 transfusions, and 3 phenytoin. 25(OH)vitamin D serum levels were very low in all patients at all time-points; iPTH serum levels were increased at baseline tending to normalize on 5th week; β-CTx serum levels were significantly increased compared to baseline on 2nd week (peak values), whereas PINP levels were increased significantly after the 4th week. Conclusions. Our data show that critically ill patients had a pattern of hypovitaminosis D, increased iPTH, hypocalcaemia, and BTMs compatible with altered bone metabolism.

Changes in Bone Mineral Density in the Year after Critical Illness

RATIONALE

Critical illness may be associated with increased bone turnover and loss of bone mineral density (BMD). Prospective evidence describing long-term changes in BMD after critical illness is needed to further define this relationship.

OBJECTIVES

To measure the change in BMD and bone turnover markers (BTMs) in subjects 1 year after critical illness compared with population-based control subjects.

METHODS

We studied adult patients admitted to a tertiary intensive care unit (ICU) who required mechanical ventilation for at least 24 hours. We measured clinical characteristics, BTMs, and BMD during admission and 1 year after ICU discharge. We compared change in BMD to age- and sex-matched control subjects from the Geelong Osteoporosis Study.

MEASUREMENTS AND MAIN RESULTS

Sixty-six patients completed BMD testing. BMD decreased significantly in the year after critical illness at both femoral neck and anterior-posterior spine sites. The annual decrease was significantly greater in the ICU cohort compared with matched control subjects (anterior-posterior spine, -1.59%; 95% confidence interval, -2.18 to -1.01; P < 0.001; femoral neck, -1.20%; 95% confidence interval, -1.69 to -0.70; P < 0.001). There was a significant increase in 10-year fracture risk for major fractures (4.85 ± 5.25 vs. 5.50 ± 5.52; P < 0.001) and hip fractures (1.57 ± 2.40 vs. 1.79 ± 2.69; P = 0.001). The pattern of bone resorption markers was consistent with accelerated bone turnover.

CONCLUSIONS

Critically ill individuals experience a significantly greater decrease in BMD in the year after admission compared with population-based control subjects. Their bone turnover biomarker pattern is consistent with an increased rate of bone loss.

The role of biochemical of bone turnover markers in osteoporosis and metabolic bone disease: a consensus paper of the Belgian Bone Club

The exact role of biochemical markers of bone turnover in the management of metabolic bone diseases remains a topic of controversy. In this consensus paper, the Belgian Bone Club aimed to provide a state of the art on the use of these biomarkers in different clinical or physiological situations like in postmenopausal women, osteoporosis in men, in elderly patients, in patients suffering from bone metastasis, in patients with chronic renal failure, in pregnant or lactating women, in intensive care patients, and in diabetics. We also gave our considerations on the analytical issues linked to the use of these biomarkers, on potential new emerging biomarkers, and on the use of bone turnover biomarkers in the follow-up of patients treated with new drugs for osteoporosis.

INTRAVENOUS PAMIDRONATE IS ASSOCIATED WITH REDUCED MORTALITY IN PATIENTS WITH CHRONIC CRITICAL ILLNESS

OBJECTIVE

Chronic critical illness (CCI), characterized by prolonged mechanical ventilation and tracheostomy, commonly manifests with elevated bone resorption, which has previously been shown to abate after treatment with intravenous (IV) bisphosphonates. Our study assessed the impact of pamidronate administration on clinical outcomes in a CCI cohort.

METHODS

A retrospective case series was performed on 148 patients admitted to The Mount Sinai Hospital Respiratory Care Unit (RCU) from 2009-2010. We identified patients with CCI who did (n = 30) or did not (n = 118) receive IV pamidronate (30 to 90 mg). Both groups included patients with normal and abnormal renal function. Pamidronate was administered for elevated urine or serum N-telopeptide, hypercalciuria, or hypercalcemia.

RESULTS

RCU and 1-year mortality were significantly lower in the pamidronate group (0 and 20%, respectively) compared to nonreceivers (19 and 56%, respectively) (P = .0077 and P = .0004, respectively). After adjusting for differences in baseline creatinine, estimated glomerular filtration rate, and serum calcium, the association with reduced mortality remained significant at 1 year (P = .0132) and with borderline significance for RCU mortality (P = .0911). Creatinine was significantly lower 7 days following pamidronate administration (P = .0025), with no significant difference at 14 days compared to baseline. Pamidronate receivers showed a greater increase in albumin during the RCU stay (2.49 to 3.23 g/dL), compared to nonreceivers (2.43 to 2.64 g/dL) (P = .0007). Pamidronate administration was associated with a significantly reduced rate of hypoglycemia compared to RCU patients not receiving pamidronate (0.09 versus 0.12; P = .0071).

CONCLUSION

Pamidronate use in a CCI population is associated with reduced mortality, lower hypoglycemia rates, improved albumin, and stable renal function.

ABBREVIATIONS

BMI = body mass index CCI = chronic critical illness CI = confidence interval CKD = chronic kidney disease CTx = C-telopeptide eGFR = estimated glomerular filtration rate ICU = intensive care unit IV = intravenous NTx = N-telopeptide PMV = prolonged mechanical ventilation RCU = respiratory care unit.

Critical illness-induced bone loss is related to deficient autophagy and histone hypomethylation

BACKGROUND

Survivors of critical illness are at increased risk of fractures. This may be due to increased osteoclast formation during critical illness, leading to trabecular bone loss. Such bone loss has also been observed in Paget's disease, and has been related to deficient autophagy. Deficient autophagy has also been documented in vital organs and skeletal muscle of critically ill patients. The objective of this study was to investigate whether deficient autophagy can be linked to critical illness-induced bone loss.

METHODS

Osteoclasts grown in vitro and their precursor cells isolated from peripheral blood of critically ill patients and from matched healthy volunteers were analysed for the expression of autophagy genes (SQSTM1, Atg3 and Atg7), and proteins (p62, Atg-5, and microtubule-associated protein light chain 3-II (LC3-II)) and for autophagy and epigenetic signalling factors via PCR arrays and were treated with the autophagy inducer rapamycin. The effect of rapamycin was also investigated at the tissue level in an in vivo rabbit model of critical illness.

RESULTS

Many more osteoclasts formed in vitro from the blood precursor cells isolated from critically ill patients, which accumulated p62, and displayed reduced expression of Atg5, Atg7, and LC3-II compared to healthy controls, suggesting deficient autophagy, whilst addition of rapamycin reduced osteoclast formation. PCR arrays revealed a down-regulation of histone methyltransferases coupled with an up-regulation of negative regulators of autophagy. Critically ill rabbits displayed a reduction in trabecular and cortical bone, which was rescued with rapamycin.

CONCLUSIONS

Deficient autophagy in osteoclasts and their blood precursor cells at least partially explained aberrant osteoclast formation during critical illness and was linked to global histone hypomethylation. Treatment with the autophagy activator Rapamycin reduced patient osteoclast formation in vitro and reduced the amount of bone loss in critically ill rabbits in vivo. These findings may help to develop novel therapeutic targets to prevent critical illness-induced bone loss.

A pilot study of change in fracture risk in patients with acute respiratory distress syndrome

Introduction

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.

Methods

Patients 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.

Results

BMD 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%).

Conclusions

Patients with acute respiratory distress syndrome demonstrated early and rapid bone demineralisation with associated increase in fracture risk.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0892-y) contains supplementary material, which is available to authorized users.

The association between critical illness and changes in bone turnover in adults: a systematic review

SUMMARY

Critical illness may lead to altered bone turnover and associated adverse health outcomes. This systematic review found moderate evidence for a positive association between critical illness and increased bone turnover. Prospective cohort studies that identify the extent and risk factors for critical illness related bone loss are required.

INTRODUCTION

Intensive care patients face health issues that extend beyond their critical illness and result in significant morbidity and mortality. Critical illness may result in altered bone turnover due to associated immobilisation, inflammation, exposure to medications that effect bone and calcium metabolism, and endocrine dysfunction. The aim of this study was to synthesise the existing evidence for altered bone turnover in adults admitted to intensive care.

METHODS

A literature search using MEDLINE and EMBASE was performed from 1965 to March 2013. Reviewed studies investigated the relationship between critical illness and evidence of altered bone turnover (bone turnover markers, bone mineral density, or fracture). Studies were rated upon their methodological quality, and a best-evidence synthesis was used to summarise the results.

RESULTS

Four cohort and seven case-control studies were identified for inclusion, of which five studies were rated as being of higher methodological quality. Ten of the studies measured bone turnover markers, and one study fracture rate. Findings were consistent across studies, and best-evidence analysis resulted in a conclusion that moderate evidence exists for an association between critical illness requiring admission to intensive care and altered bone turnover.

CONCLUSION

A positive association between critical illness requiring intensive care admission and bone turnover exists, although data are limited, and the risk factors and the nature of the relationship are not yet understood. Prospective cohort studies that identify risk factors and extent of critical illness related bone turnover changes are required.

Critical illness myopathy

PURPOSE OF REVIEW

To describe the incidence, major risk factors, and the clinical, electrophysiological, and histological features of critical illness myopathy (CIM). Major pathogenetic mechanisms and long-term consequences of CIM are also reviewed.

RECENT FINDINGS

CIM is frequently associated with critical illness polyneuropathy (CIP), and may have a relevant impact on patients' outcome. CIM has an earlier onset than CIP, and recovery is faster. Loss of myosin filaments on muscle biopsy is important to diagnose CIM, and has a good prognosis. Critical illness, use of steroids, and immobility concur in causing CIM.

SUMMARY

A rationale diagnostic approach to CIM using clinical, electrophysiological, and muscle biopsy investigations is important to plan adequate therapy and to predict recovery.

Critical illness-related bone loss is associated with osteoclastic and angiogenic abnormalities

Critically ill patients are at increased risk of fractures during rehabilitation, and can experience impaired healing of traumatic and surgical bone fractures. In addition, markers of bone resorption are markedly increased in critically ill patients, while markers of bone formation are decreased. In the current study, we have directly investigated the effect of critical illness on bone metabolism and repair. In a human in vitro model of critical illness, Fluorescence-activated cell sorting (FACS) analysis revealed an increase in circulating CD14+/CD11b+ osteoclast precursors in critically ill patient peripheral blood compared to healthy controls. In addition, the formation of osteoclasts was increased in patient peripheral blood mononuclear cell (PBMC) cultures compared to healthy controls, both in the presence and absence of osteoclastogenic factors receptor activator of NF-κB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF). Culturing PBMCs with 10% critically ill patient serum further increased osteoclast formation and activity in patient PBMCs only, and neutralization studies revealed that immunoglobulin G (IgG) antibody signaling through the immunoreceptor Fc receptor common γ chain III (FcRγIII) played an important role. When analyzing bone formation, no differences in osteogenic differentiation were observed using human periosteal-derived cells (hPDCs) treated with patient serum in vitro, but a decrease in the expression of vascular endothelial growth factor receptor 1 (VEGF-R1) suggested impaired vascularization. This was confirmed using serum-treated hPDCs implanted onto calcium phosphate scaffolds in a murine in vivo model of bone formation, where decreased vascularization and increased osteoclast activity led to a decrease in bone formation in scaffolds with patient serum-treated hPDCs. Together, these findings may help to define novel therapeutic targets to prevent bone loss and optimize fracture healing in critically ill patients.