Bio-impedance spectroscopy for total body water assessment in pediatric surgical patients: A single center pilot cohort study


      • Fluid shifts following major surgery are difficult to accurately assess.
      • Excess fluid administration may increase morbidity and mortality.
      • Reliable bedside instruments for assessment of fluid status are desirable.
      • BIS is a feasible tool for serial post-operative monitoring of fluid status.



      Excess peri‑operative fluid administration is associated with higher morbidity and mortality. We aimed to examine the feasibility of bio-impedance spectroscopy (BIS) to record serial peri‑operative fluid volumes in the pediatric surgical population.


      Children who underwent major elective general surgery from March 2019 to March 2020 were included. Total body water (TBW) assessment by BIS was recorded prior to surgery and on subsequent post-operative days (POD). We recorded the duration, tolerance and completion of each BIS assessment. We used Spearman coefficient and Bland Altman analysis to examine correlation and agreement between fluid balance (FB) in ml/kg calculated from intake/output (IO) recording and measured by BIS.


      20 (87%) of 23 consented patients, median age 2.5 (1–17) years and 13 (65%) male, completed pre-operative and post-operative measurements, and were included in the analysis. Median time required for BIS assessments was 10 (5–15) minutes, and there were no recorded side effects or intolerance. The correlation coefficient for fluid balance measurements on POD 1 between BIS and IO methods was 0.59 (p = 0.01); mean bias (limits) of agreement was 26 (111 to 163) mL/kg. The trend in TBW measured by BIS declined from POD 1–3, while the recorded FB increased.


      Bedside BIS is feasible and well-tolerated. Despite moderate correlation between fluid balance assessment by BIS and IO on POD 1, the wide limits of agreement between values from these methods preclude their use interchangeably. The role of BIS in assessment of fluid status in the pediatric surgical population should be further examined.

      Level of evidence

      Level III



      BIS (bio-impedance spectroscopy), TBW (total body water), POD (post-operative day), FB (fluid balance), IO (intake/output), ICU (intensive care unit), ICC (intra-class correlation), EMR (electronic medical record), IQR (interquartile range)
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