Shock/Sepsis/Trauma/Critical careSustained bone mineral density changes after burn injury1
Introduction
Burn injury instigates a severe hypermetabolic response. Resting energy expenditure increases rapidly after injury and, without early excision and grafting, can be as much as 200–300% greater than basal values [1]. This hypermetabolic response produces rapid and severe depletion of body energy stores, particularly skeletal muscle mass, and contributes to several important systemic derangements, including immunosuppression, delayed wound healing, insulin resistance, and bone resorption. Much of modern burn treatment has been developed in an attempt to ameliorate, shorten, or satisfy this hypermetabolism. Early and aggressive burn wound excision does not itself reduce metabolic demands, but prompt wound closure can shorten the period of hypermetabolism 2, 3, 4. Similarly, early provision of nutritional support by the enteral route does not reduce hypermetabolism 5, 6, but the provision of sufficient calories and nitrogen is essential to wound healing and survival in patients with large injuries. More recently, a number of studies have documented that post-burn catabolism can be reduced, and wound healing and protein synthesis promoted, by manipulating the hormonal environment existing in burn patients. These measures include blocking catecholamines with propranolol, administering counter-regulatory agents like insulin and insulin-like growth factor-1, or the use of anabolic agents such as growth hormone, testosterone, oxandrolone, and other interventions 7, 8, 9, 10, 11, 12.
There is good evidence that hypermetabolism does not abate when the acute burn injury is healed, regardless of the therapies used during acute burn treatment [13]. Catabolism of lean body mass has been documented for at least 9 months in severely burned children 13, 14. This loss can occur even with increased nutritional delivery relative to energy expenditure. In fact, increased feeding has been shown to correlate strongly with increased body mass index (BMI), indicating that aggressively fed burn patients gain body fat while losing lean body mass [3]. Loss of lean body mass contributes to morbidity during the acute phase of burn care and slows rehabilitation and return to function in society.
Burn-induced skeletal changes have been documented in both adults and children. These changes appear to be sustained and could represent an important impediment to functional recovery after burn injury. There is clinical evidence suggesting that severe burn injury can result in growth delays in children for up to 3 years after injury [15]. Decreased bone mineral density (BMD) has been documented to occur within 8 weeks of burn injury and to be sustained for up to 5 years [16]. BMD changes are thought to occur because of markedly reduced bone formation 16, 17. Indeed, several animal models have demonstrated histomorphometrically that bone formation rates are decreased after thermal injury 18, 19, 20. Increased production of the inflammatory cytokines IL-1 and IL-6 21, 22, sustained plasma levels of glucocorticoids 23, 24, and immobilization 25, 26 have all been proposed to contribute to burn-induced skeletal changes.
The most widely used bone-mass measurement technique is dual-energy X-ray absorptiometry (DEXA) 27, 28. Portable peripheral DEXA models have gained popularity due to their portability and ease of use 28, 29. We used pDEXA®, a portable DEXA that analyzes forearm composition, to study body-composition changes after severe burn injury. pDEXA has advantages over whole-body DEXA because it can be used to scan patients who are critically ill and intubated while they remain in bed in the intensive care unit. The region of interest for this study was the proximal radius and ulna and their surrounding tissue.
Although several retrospective studies have shown that body-composition changes in bone mineral, fat, and lean mass occur after severe burn injury, there are few prospective studies showing the timing and magnitude of these changes. Therefore, we performed a 24-month prospective descriptive study to measure the magnitude of bone density, fat, and lean mass changes after burn injury.
Section snippets
Materials and methods
The Institutional Review Board and Radiation Safety Committees of the University of Utah approved this study. Written informed consent was obtained from each patient or next-of-kin if the patient was unable to provide informed consent. Parental consent was obtained for patients under the age of 18. Patients eligible for enrollment in the study were as follows: patients younger than 10 years or older than 60 years with a ≥10% TBSA burn, and patients aged 10–59 years with a ≥20% TBSA burn. Only
Results
Thirty-five patients, for whom informed consent could be obtained within 10 days of burn injury, were enrolled into the study between September 1997 and December 1999. Data from the 29 patients who had multiple pDEXA scans were analyzed for this study. Twenty-three patients (79%) were male. The mean age was 40 ± 24 years (range 5–87), with 7 patients under the age of 18 years and 7 patients over 60 years of age. All patients were healthy before injury and reported no significant co-morbidities.
Discussion
The present study prospectively documents the progression of body-composition changes after burn injury. Burn catabolism resulting in decreased weight loss is well documented 3, 8, 9, 10, 11, 12, 13, 14, 32, but less is known about the mechanism and severity of skeletal changes.
Bone mineral density changes have been studied in several animal models. Schaffler et al., showed greatly reduced bone formation in the affected limb of a rat scald model [20]. Decreased bone surfaces and bone-formation
Conclusions
BMD measurements show significant decreases after burn injury in a majority of patients. BMD did not return to baseline for up to 2 years after injury, suggesting that burn-induced osteopenia continues long after healing of the burn wound. There was also a tendency for decreased forearm lean mass post-burn, whereas fat mass remained unchanged. Although this study cannot predict the clinical significance of these changes, it does support the need for continued long-term musculoskeletal
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Cited by (34)
Bone mineral density and low bone mass in severely burned patients: A retrospective cohort study
2021, BoneCitation Excerpt :For example, Edelman et al. performed serial DXAs on 29 burn patients at different times after the burn, from the acute phase and up to 2 years later. They found significant changes in BMD in the long term (most changes in density were reached 131 days after the burn), with similar losses between adults and children [28]. The applicability of the densitometric evaluation in this group of patients has already been reported [29].
Fracture admissions after burns: A retrospective longitudinal study
2017, BurnsCitation Excerpt :Minor burns also result in impacts on bone metabolism, with non-severe burns found to reduce trabecular bone density long after resolution of inflammation [16]. In both adults and children, these changes to bone metabolism and effects on bone mass and density potentially predispose burn patients to osteoporosis and increased risk of fractures [4,8,11,17–19]. Our previous population-based research found that paediatric and adult burn patients experienced twice the admissions for musculoskeletal morbidity after discharge from hospital for their initial injury when compared with children and adults with no history of injury serious enough to undergo admission [20,21].
Effect of vitamin D supplementation and isokinetic training on muscle strength, explosive strength, lean body mass and gait in severely burned children: A randomized controlled trial
2017, BurnsCitation Excerpt :Thus burned patients require VD supplementation to counteract these deficits. Furthermore, sufficient calcium and VD are important for burned patients to decrease the risk of fractures after discharge [33–35]. VD has a direct effect on muscle tissue via VD receptors in muscle.
Increased admissions for musculoskeletal diseases after burns sustained during childhood and adolescence
2015, BurnsCitation Excerpt :The rate of admissions for a principal diagnosis bone mineral disorder among members of the burn cohort with minor burns and burns of unspecified TBSA were almost five to six times than rates observed for the uninjured cohort, respectively. While these results are consistent with expectations based on previous research [20–22], the effects of burn on bone mineral density disease were longer-lasting, remaining elevated for the 33-year study period with results driven by outcomes of those with minor burns and burns of unspecified severity. No principal diagnosis admissions for bone mineral disorders after burn were identified for persons with severe burns and this finding may reflect in-hospital and after discharge treatment and management plans for younger survivors of severe burns, with reduced subsequent admissions [42–45].
Contributions of severe burn and disuse to bone structure and strength in rats
2013, BoneCitation Excerpt :Reductions in bone growth and changes in bone remodeling can have long-lasting adverse consequences for patients during rehabilitation. Decreased bone mineral content (BMC), which occurs within 8 weeks of injury, may last up to five years due to the reduction in bone formation [3,5,15] and thus may be associated with a higher incidence of fractures and osteoporosis [3,16,17]. Using two- and three-dimensional imaging techniques, such as micro-computed tomography (μCT), allows for complete information on the microarchitecture of the bone [13].
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Presented at the 34th Annual Meeting of the American Burn Association, Chicago, IL, April 21–24, 2002.