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Nutrición Hospitalaria

versión On-line ISSN 1699-5198versión impresa ISSN 0212-1611

Nutr. Hosp. vol.26 no.4 Madrid jul./ago. 2011




Hip fracture prognosis: could bioimpedance be an alternative to conventional nutritional assessment?

Pronóstico de la fractura de cadera: ¿podría la bioimpedancia ser una alternativa para la evaluación nutricional convencional?



L. Schiper1, D. Sadigursky1, D. A. V. Rosario1, S. P. Schiper1, L. C. Passos2 and J. Faintuch3

1Orthopedic and Traumatologic Clinic. Salvador. BA. Brazil.
2Department of Cardiology. School of Medicine. Federal University of Bahia. Salvador. BA. Brazil.
3Department of Gastroenterology. Hospital das Clinicas and Sao Paulo University Medical School. Sao Paulo. SP. Brazil.





Background: Risk-factors for mortality in hip fractures encompass nutritional status, nominally body mass index, but not body composition. Given the difficulty of anthropometric assessment in bedridden patients a prospective study with bioimpedance analysis was designed.
Methods: Elderly patients with hip fracture were consecutively recruited. Biochemical tests, primitive bioimpedance measurements (resistance, reactance and phase angle) and follow-up till one year were targeted.
Results: Patients (N = 69, 81.2 ± 8.1 years old, 72.5% females) stayed in the hospital for 15.5 ± 17.1 days, and 18.8% (13/69) required further hospitalization during the ensuing months. Mortality was 11.6% within 30 days, coinciding with hospital mortality, and an additional 11.6% till one year, thus reaching 23.2%. Anemia, hypoalbuminemia and low transferrin, along with elevated glucose and urea were frequent, suggesting undernutrition with metabolic derangements. Reactance, urea and creatinine were different in patients suffering both early and late demise. Resistance, white blood cell count and osteoporosis were risk factors for early mortality only , and anemia exclusively for late mortality.
Conclusions: Primitive bioimpedance measurements, which had not been hitherto investigated , were prognostically related to early and late mortality. These markers of disease-related malnutrition and especially reactance should be further studied in patients unfit for anthropometric evaluation due to fracture and immobility.

Key words: Hip fracture. Malnutrition. Bioimpedance analysis. Reactance. Body mass index. Morbidity. Mortality.


Antecedentes: Los factores de riesgo para mortalidad en las fracturas de cadera involucran estado nutricional, nominalmente índice de masa corporal, pero no composición corporal. Considerándose la dificultad de evaluación antropométrica de pacientes acamados, un estudio prospectivo con bioimpedancia fue programado.
Métodos: Pacientes de mayor edad con fractura de cadera fueron consecutivamente recrutados. Testes bioquímicos, medidas primitivas de bioimpedáncia (resisténcia, reactáncia, ángulo de fase) e seguimiento hasta un año fueron valorizados.
Resultados: Los pacientes (N = 69, 81,2 ± 8,1 años, 72,5% mujeres) quedáronse en el hospital por 15,5 ± 17,1 días, y el 18,8% (13/69) necesitaron de hospitalización adicional en los meses siguientes. La mortalidad de 30 días fue 11,6%, coincidiendo con la mortalidad hospitalaria, con 11,6% adicionales hasta un año, alcanzando un total de 23,2%. Anemia, hipoalbuminemia e baja de transferrina, asimismo glucosa y urea elevadas, se observaron con frecuencia, compatibles con desnutrición e trastornos metabólicos. La reactáncia, urea y creatinina eran diferentes en pacientes con mortalidad precoz y tardía. La resistencia, recuento de leucocitos y presencia de osteoporosis indicaron mortalidad precoz solamente, y anemia solo la mortalidad de un año.
Conclusiones: Las medidas primitivas de bioimpedáncia, que no habían sido hasta el momento investigadas en ese contexto, mostraronse pronosticamente relacionadas con mortalidad precoz y tardía. Estos marcadores y en especial la reactáncia merecen ser mas estudiados en pacientes donde la antropometria es difícil o imposible por razones de fractura y inmobilidad.

Palabras clave: Fractura de cadera. Desnutrición. Análisis de bioimpedancia. Reactancia. Índice de masa corporal. Morbilidad. Mortalidad.



Several demographic, clinical, and nutritional findings are prognostically important for mortality after hip fracture in the elderly.1-3 Besides osteoporosis which is believed to be the hegemonic predisposing factor, emphasis is often given to low body mass index,3 however this is not an easy measurement in recumbent persons with major bone trauma. Not more than half of the hospitals adopt any modality of nutritional screening,4 therefore BMI values from previous admissions are hardly an option. Reported or estimated heights are not reliable either5 and traumatic edema may be a pitfall for weight interpretation, thus rendering BMI utilization questionable.

Bioimpedance analysis (BIA), though an accepted measurement of nutritional status and body compartments, has not been investigated in this context. In a prospective protocol, the hypothesis was that both early and late mortality could be associated with changes in BIA indices, especially with reactance which is sensitive to body fluid shifts.6-9



Sixty-nine consecutive patients were investigated, 34 with fracture of neck of femur and 35 with intertrochanteric lesion. Groups were demographically and metabolically well matched therefore they are analyzed together.

Inclusion criteria were age > 65 years (males and females) and informed consent. Exclusion criteria were sepsis, shock, coma, pathologic fracture, use of corticosteroids, previous operation of the hip, use of pacemaker or refusal to participate in the protocol. Informed consent was given by all patients or caregivers, and the protocol was approved by the Institutional Ethical Committee.

Questionnaires targeting demographics and comorbidities were used, and diagnosis was based on current treatment. Derived BIA compartments (lean body mass, body fat and total body water) were not part of the protocol, only primitive findings (resistance, reactance and phase angle),as weight and height would be required in the equation. Fracture risk assessment according to the WHO/FRAX algorithm was not computed either, due to lacking BMI.1 The standard tetrapolar technique was applied at the healthy side of the body, after overnight fasting and voiding (BIA Quantum II, RJL Systems, Clinton Township, MI, USA). Serum albumin, transferrin, BUN, creatinine, along with hematologic counts were measured by automated methods. Principal end-points were 30-day and one year mortality. Results (mean ± SD or percentage) were compared by Chi-Square test, analysis of variance (ANOVA) or Student's "t" test as appropriate. Classification by tertiles for comparison of risk factors was also conducted.



Patients were mostly females, and arterial hypertension, osteoporosis along with diabetes were fairly prevalent. Nearly one fifth required additional admission during the ensuing 12 months, mostly because of falls and clinical problems.

Participants suffered from some degree of anemia, hypoalbuminemia and low transferrin. In contrast white blood cell count (WBC) tended to be elevated, consistent with acute trauma and inflammation. Nevertheless creatinine was normal, with no case above 2 mg/dL (table I).


Gender and age played no role in death rate, however diminished resistance (P = 0.024) and reactance (P = 0.048) adversely affected 30-day results. As expected, participants suffering from osteoporosis had a worse outlook too (P = 0.006).

One year mortality was linked to reactance (P < 0.001) and anemia (P = 0.039). Noteworthy findings concerned also BUN and creatinine, both of which interfered with early and total mortality (P < 0.001).

Figure 1 illustrates impact on one-year mortality according to reactance values, and for comparison those of creatinine as well.



Proximal femoral fracture is the most severe lowenergy trauma and the paramount complication of osteoporosis, as it tends to followed by morbidity, disability and particularly mortality.1,2,10

Recent studies unveil excess mortality not only during 12 months, but up to 10 years.2,10 One is not dealing with an ordinary traumatic disorder, but with a cluster of abnormalities encompassing osteoporosis, frailty, impaired nutrition and organ dysfunctions.

In the WHO/Canadian series based on more than 46,000 subjects, osteoporosis was deemed relevant but not overarching, as mechanical fragility is only part of the context. Clinical risk factors were indispensable to develop a fracture risk assessment tool including prior fractures and family history, age, gender, body mass index, ethnicity, smoking, alcoholism, glucocorticoid use and rheumatoid arthritis.1

The importance of protein-energy compartments in these studies is underscored in a meta-analysis targeting BMI, with a total follow-up of over 250,000 person years.3 Indeed, deranged nutritional status could underlie several of the alluded to comorbidities including alcoholism, rheumatoid arthritis and perhaps osteoporosis itself, notably in subjects with substantial weight loss.11

Frailty indexes, which robustly correlate with falls, fractures and mortality in this population ,also partly rely on weight loss history.12

Primitive bioimpedance measurements, nominally resistance and reactance, are weight-independent and thus ideal for bedridden patients. To the best of our knowledge, this is the first study to demonstrate that resistance and reactance could be employed for early as well as late mortality investigation.

Decreased resistance points toward underweight whereas low reactance signals body fluid shifts (overhydration),6-9 conditions consistent with anemia, systemic inflammation and possible renal compromise as here demonstrated. Bioimpedance analysis could thus represent an advantage in comparison to classic anthropometrics (BMI, body weight changes), which do not distinguish between water retention or elimination and changes in fat and lean body mass.

In synthesis these variables, particularly reactance, are more specific for disease-related malnutrition,9 and severely impaired mobility is not a deterrent to their adoption.



This study received no financial grant and the authors have no conflict of interest to declare.



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Joel Faintuch.
Hospital das Clinicas.
Av. Eneias C. Aguiar, 255.
CP: 05043 São Paulo. Brazil.

Recibido: 7-III-2011.
Aceptado: 5-IV-2011.

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