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Bioimpedance as a measure of fluid overload in patients recently admitted to intensive care

Introduction

Fluid overload is associated with adverse outcomes in critical illness; however, better methodology is required for its quantification. Bioelectrical impedance analysis (BIA) represents a noninvasive method for quantification of fluid overload [1], but has not been widely taken up in the ICU.

Methods

We assessed changes in fluid balance and performed daily BIA (using a Maltron BioScan 920-II; Maltron International Ltd, UK) over 3 days in consecutive ICU admissions with LOS >72 hours.

Results

Of 24 patients 71% were male, median age was 65 years and APACHE II score was 15. Eleven patients had a medical diagnosis and 13 a surgical or trauma reason for admission. Seventy-one percent were mechanically ventilated and 67% were on vasopressors or inotropes. Median BIA-estimated extracellular water was 25.2 l (IQR 22 to 28) on day 1, equating to excess fluid of 7.2 l (IQR 5 to 13.9). Median right body resistance normalized to height at 50 kHz (R50/h) on day 1 was 214 Ω/m (IQR 187 to 256). Daily change in ECW and R50/h correlated with daily fluid balance between BIA measurements (R2 = 0.48 and 0.37 respectively) (Figure 1).

Figure 1
figure1

Change in BIA-measured ECW (a) or R/h at 50 kHz (b) versus daily fluid balance.

Conclusion

BIA suggests many patients already have significant fluid overload on the first day of ICU admission. Overall, changes in device-specific algorithms for ECW estimation and measured resistances correlated with recorded fluid balance; however, there were inconsistencies in the number of individual patients. Prospective assessment is required to establish whether BIA measurements can be used to assist fluid management in the ICU.

References

  1. 1.

    Earthman C, et al: Bioimpedance spectroscopy for clinical assessment of fluid distribution and body cell mass. Nutr Clin Pract. 2007, 22: 389-10.1177/0115426507022004389.

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O'Connor, M., Galtrey, E., Kirwan, C. et al. Bioimpedance as a measure of fluid overload in patients recently admitted to intensive care. Crit Care 19, P188 (2015). https://doi.org/10.1186/cc14268

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Keywords

  • Fluid Balance
  • Critical Illness
  • Fluid Overload
  • Fluid Management
  • Bioelectrical Impedance Analysis