Transcranial Bioimpedance Measurement in Horses: a pilot study

Rachael Gregson, Martin Shaw, Ian Piper, Richard Clutton

Research output: Contribution to journalArticlepeer-review


This pilot study aimed to evaluate feasibility of transcranial bioimpedance (TCBI) measurement and variability of TCBI values in healthy conscious horses and to study effects of body position and time on TCBI in anaesthetised horses.
Study Design
Prospective observational study.
Four research horses and sixteen client-owned horses presented for surgery.
After establishing optimal electrode position using computed tomography (CT) scans of cadaver heads, TCBI [described using impedance at zero frequency, R0, (Ω)] was measured in four conscious, resting horses to investigate feasibility and changes in TCBI over time (80 minutes). Data were compared using a paired t-test. TCBI was then measured throughout anaesthesia (duration 92 ± 28 minutes) in 16 horses in dorsal and lateral recumbancy. Data were analysed using a general linear model (GLM); gamma regression was chosen as a model of characteristic impedance [Zc; (Ω)] against time. Data are presented as mean ± standard deviation.
No change in R0 was seen in conscious horses (age = 15.3 ± 7.3 years, body mass = 512 ± 38 kg) over 80 minutes. The technique was well-tolerated and caused no apparent adverse effects. In 16 horses (age = 7.4 ± 4.7 years; body mass = 479 ± 134 kg) anaesthetised for 92 ± 28 minutes, Zc fell during anaesthesia, decreasing more in horses in lateral recumbancy when compared to horses in dorsal recumbancy (p = 0.008). There was no relationship between Zc and body-mass or age.
and clinical relevance TCBI is readily measured in horses. TCBI did not change with time in conscious horses, but decreased with time in anaesthetised horses; this change was greater in horses in lateral recumbancy. This indicates that changes in TCBI in anaesthetized horses may be related to the effects of recumbancy, general anaesthesia, surgery or a combination of these factors.
Original languageEnglish
JournalVeterinary Anaesthesia and Analgesia
Early online date27 Apr 2019
Publication statusE-pub ahead of print - 27 Apr 2019


  • General Anaesthesia
  • Horse
  • bioimpedance
  • Transcranial bioimpedance


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