Shime et al used bioelectrical impedance to monitor pediatric patients undergoing cardiac surgery. Changes in bioelectrical impedance reflect changes in the body composition and total body water, which correlate with the severity of illness. The authors are from Kyoto Prefectural University of Medicine and Meiji University of Oriental Medicine in Kyoto, Japan.



(1) A body impedance monitor was used with the electrodes placed on both feet with the patient in a supine, immobilized position.

(2) The current applied was 500µA at 50 kHz.


BI ratio =

= (bioelectrical impedance post-operative) / (bioelectrical impedance on pre-operative)


Timing of assessment:

(1) preoperative

(2) D0 = immediately after surgery

(3) D1 = 16 hours after surgery

(4) D2 = 40 hours after surgery


Patients usually showed a BI < 1 at D0. Those who did not survive showed a low BI at D1 which persisted for several days, while those who did well had a return to preoperative levels at D1 with further rise on D2.


BI at D1 (16 hours post operative)

Stay in ICU

Mortality Rate

< 0.8

16.3 days +/- 3.12


0.8 – 0.99

12.2 days +/- 2.2


>= 1.0

4.1 +/- 0.3


from Table 1, page 519



• The original table had ranges for 0.8 – 1.0 and >= 1.0, resulting at an overlap at precisely 1.0. I adjusted these ranges to prevent confusion.



• Bioimpedance analyzers from different manufacturers may give different readings. The same instrument should be used to take all of the readings.


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