Effect of influenza-induced fever on human bioimpedance values.
OBJECTIVE
Bioelectrical impedance analysis (BIA) is a widely used technique to assess body composition and nutritional status. While bioelectrical values are affected by diverse variables, there has been little research on validation of BIA in acute illness, especially to understand prognostic significance. Here we report the use of BIA in acute febrile states induced by influenza.


METHODS
Bioimpedance studies were conducted during an H1N1 influenza A outbreak in Venezuelan Amerindian villages from the Amazonas. Measurements were performed on 52 subjects between 1 and 40 years of age, and 7 children were re-examined after starting Oseltamivir treatment. Bioelectrical Impedance Vector Analysis (BIVA) and permutation tests were applied.


RESULTS
For the entire sample, febrile individuals showed a tendency toward greater reactance (p=0.058) and phase angle (p=0.037) than afebrile individuals, while resistance and impedance were similar in the two groups. Individuals with repeated measurements showed significant differences in bioimpedance values associated with fever, including increased reactance (p<0.001) and phase angle (p=0.007), and decreased resistance (p=0.007) and impedance (p<0.001).


CONCLUSIONS
There are bioelectrical variations induced by influenza that can be related to dehydration, with lower extracellular to intracellular water ratio in febrile individuals, or a direct thermal effect. Caution is recommended when interpreting bioimpedance results in febrile states.
University of Cagliari, Cagliari, Italy.
Elisabetta
E
Marini
University of Cagliari, Cagliari, Italy.
Roberto
R
Buffa
Venezuelan Institute of Scientific Research (IVIC), Caracas, Venezuela.
Monica
M
Contreras
Amazonic Center for Research and Control of Tropical Diseases (CAICET), Puerto Ayacucho, Amazonas, Venezuela.
Magda
M
Magris
Amazonic Center for Research and Control of Tropical Diseases (CAICET), Puerto Ayacucho, Amazonas, Venezuela; Foundation Center for Studies on Growth and Development of the Venezuelan Population, (Fundacredesa), Caracas, Venezuela.
Glida
G
Hidalgo
Foundation Center for Studies on Growth and Development of the Venezuelan Population, (Fundacredesa), Caracas, Venezuela.
Wilmer
W
Sanchez
Popular Ministry of Health, Caracas, Venezuela.
Vanessa
V
Ortiz
Venezuelan Institute of Scientific Research (IVIC), Caracas, Venezuela.
Maryluz
M
Urbaez
University of Cagliari, Cagliari, Italy; University Carlos III of Madrid, Madrid, Spain.
Stefano
S
Cabras
New York University School of Medicine, New York, New York, United States of America.
Martin J
MJ
Blaser
New York University School of Medicine, New York, New York, United States of America; University of Puerto Rico, San Juan, Puerto Rico, United States of America.
Maria G
MG
Dominguez-Bello
D000293:Adolescent; D000328:Adult; D000998:Antiviral Agents / Q000627:therapeutic use; D001823:Body Composition / Q000187:drug effects / Q000502:physiology*; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D017097:Electric Impedance; D005260:Female; D005334:Fever / Q000503:physiopathology*; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype; D007251:Influenza, Human / Q000188:drug therapy / Q000503:physiopathology*; D008297:Male; D053139:Oseltamivir / Q000627:therapeutic use; D014687:Venezuela / Q000453:epidemiology; D055815:Young Adult
D000998:Antiviral Agents; D053139:Oseltamivir