title: Active core rewarming avoids bioelectrical impedance changes in postanesthetic patients.
abstract: BACKGROUND
  Postoperative hypothermia is a common cause of complications in patients who underwent laparoscopic cholecystectomy. Hypothermia is known to elicit electrophysiological, biochemical, and cellular alterations thus leading to changes in the active and passive membrane properties. These changes might influence the bioelectrical impedance (BI). Our aim was to determine whether the BI depends on the core temperature.
  
  
  METHODS
  We studied 60 patients (52 female and 8 male) age 40 to 80 years with an ASA I-II classification that had undergone laparoscopic cholecystectomy under balanced inhalation anesthesia. The experimental group (n = 30) received active core rewarming during the transanesthetic and postanesthesic periods. The control group (n = 30) received passive external rewarming. The BI was recorded by using a 4-contact electrode system to collect dual sets of measurements in the deltoid muscle. The body temperature, hemodynamic variables, respiratory rate, blood-gas levels, biochemical parameters, and shivering were also measured. The Mann-Whitney unpaired t-test was used to determine the differences in shivering between each group at each measurement period. Measurements of body temperature, hemodynamics variables, respiratory rate, and BI were analyzed using the two-way repeated-measures ANOVA.
  
  
  RESULTS
  The gradual decrease in the body temperature was followed by the BI increase over time. The highest BI values (95 ± 11 Ω) appeared when the lowest values of the temperature (35.5 ± 0.5°C) were reached. The active core rewarming kept the body temperature within the physiological range (over 36.5°C). This effect was accompanied by low stable values (68 ± 3 Ω) of BI. A significant decrease over time in the hemodynamic values, respiratory rate, and shivering was seen in the active core-rewarming group when compared with the controls. The temporal course of shivering was different from those of body temperatue and BI. The control patients showed a significant increase in the serum-potassium levels, which were not seen in the active-core rewarming group.
  
  
  CONCLUSIONS
  The BI analysis changed as a function of the changes of core temperature and independently of the shivering. In addition, our results support the beneficial use of active core rewarming to prevent accidental hypothermia.
authors.affiliation: Laboratorio de Medicina Genómica, Hospital Regional "Primero de Octubre", Av, IPN, No, 1669, Mexico, D, F,, C,P, 07760, Mexico. jantgonzalez@issste.gob.mx.
authors.forename: Alma Rebeca
authors.initials: AR
authors.lastname: Gutiérrez-Cruz
authors.forename: Bernardo
authors.initials: B
authors.lastname: Soto-Rivera
authors.forename: Bertha Alicia
authors.initials: BA
authors.lastname: León-Chávez
authors.forename: Ernesto
authors.initials: E
authors.lastname: Suaste-Gómez
authors.forename: Daniel
authors.initials: D
authors.lastname: Martinez-Fong
authors.forename: Juan Antonio
authors.initials: JA
authors.lastname: González-Barrios