Transcranial bioimpedance measurement in horses: a pilot study.

The study assessed the practicability of using transcranial bioimpedance (TCBI) measurements in conscious and anaesthetized horses, discovering that the body position of horses during anesthesia influences the TCBI values.

Research Method

• The study used four research and sixteen client-owned horses presented for surgery.
• To determine the optimal electrode position for TCBI measurement, computed tomography scans of cadaver heads were used.
• The study initially measured TCBI in four conscious, resting horses over an 80-minute period. This was to investigate the feasibility of the method and any changes in TCBI over time.
• After establishing the method’s feasibility, the TCBI was then measured throughout anaesthesia on 16 different horses, who were in different positions – dorsal and lateral recumbency.
• Data analysis was conducted using a general linear model and gamma regression, which was used as a model of characteristic impedance [Zc; (Ω)] against time.
• Data were presented and compared as mean ± standard deviation using a paired t test.

Research Findings

• There was no notable change in R0 of the TCBI value observed over 80 minutes in conscious horses. The horses, aged 15.3 ± 7.3 years and weighing 512 ± 38 kg, tolerated the technique well with no apparent adverse effects.
• In the 16 horses that were anaesthetized for a duration of 92 ± 28 minutes, Zc fell during anaesthesia. This drop was more significant in horses in lateral recumbency than in those in dorsal recumbency, with a p-value of 0.008.
• There was no significant relationship observed between the horses’ Zc values and their body mass or age among the anaesthetized horses, aged 7.4 ± 4.7 years and weighing 479 ± 134 kg.

Conclusions from Research

• The study found that TCBI could be easily measured in horses.
• There was no significant change observed in TCBI values over time in conscious horses. However, in anesthetized horses, there was a decrease noticed over time.
• The decrease was more pronounced in horses in lateral recumbency, suggesting that TCBI changes in anaesthetized horses can be related to various factors, such as the horse’s recumbency position, general anesthesia, surgery, or a combination of these factors.