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This pilot study aimed to evaluate the 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 anaesthetized horses. Prospective, observational study. A total of four research horses and 16 client-owned horses presented for surgery. After establishing optimal electrode position using computed tomography scans of cadaver heads, TCBI [described using impedance at zero frequency, R 0, (Ω)] was measured in four conscious, resting horses to investigate the 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 recumbency. Data were analysed using a general linear model; gamma regression was chosen as a model of characteristic impedance [Z c ; (Ω)] against time. Data are presented as mean ± standard deviation. No change in R 0 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) anaesthetized for 92 ± 28 minutes, Z c fell during anaesthesia, decreasing more in horses in lateral recumbency than in horses in dorsal recumbency (p = 0.008). There was no relationship between Z c and body mass or age. TCBI is readily measured in horses. TCBI did not change with time in conscious horses, but decreased with time in anaesthetized horses; this change was greater in horses in lateral recumbency, indicating that TCBI changes in anaesthetized horses may be related to the effects of recumbency, general anaesthesia, surgery or a combination of these factors. [ABSTRACT FROM AUTHOR]

Highlights from the article: B Purpose: b Previous studies from our group demonstrated that chest compression (CCs) applied according to depth feedback produced potentially fatal intrathoracic damage in paediatric porcine models. The objective of this study is to assess if CPR feedback from an automated external defibrillator (AED) using the impedance cardiogram (ICG) can guide CC application to achieve high levels of end-tidal carbon dioxide (EtCO SB 2 sb ), shock success (SS) and return of spontaneous circulation (ROSC) without significant intrathoracic damage.