Brain-wave monitoring shows promise in monitoring horses under anesthesia

Placing of EEG electrodes on a horse (a) during general anesthesia and (b) standing anesthesia. Images: Drewnowska et al.

Monitoring the brain waves of horses could be a useful tool for determining stable levels of general anesthesia during surgery, a recently published review concludes.

The authors say that monitoring brain-wave activity is not suitable as a single parameter for determining the desired depth of general anesthesia in horses, but it does show the effect of drugs on the activity of the cerebral cortex.

Evidence considered in their review showed it to be a promising additional monitoring tool to complement current methods of monitoring vital signs while under anesthesia.

Olga Drewnowska, Barbara Lisowska and Bernard Turek, writing in the journal Applied Sciences, set out to explore the current evidence around the potential use of real-time electroencephalography (EEG) as an add-on to current approaches, which include monitoring hemodynamic and respiratory parameters.

The trio note that EEGs are a relatively simple and noninvasive way to measure the bioelectric activity of the central nervous system.

It is widely used in diagnostics for brain disorders, but has also been introduced into other branches of medicine, including anesthesiology.

“Even though it has been used to assess depth of anesthesia in many animal species, the validity of its usage is still not clear.”

They say that due to the fact that EEG analyzers are designed for humans, there are still limitations around their use in horses. However, the incorporation of telemetry to transmit the readings, instead of using wires, opens up more possibilities for the technology.

Their review traversed the methods for electrode mounting and their position on the frontal part of the skull, above the line of the eyes and below the ears.

There is no need for shaving when placing the superficial electrodes provided there is a proper medium that will conduct the signal (gel or glue).

The researchers say the evidence to date points to its promise as a monitoring adjunct under general anesthesia.

However, its possible usefulness in horses requires a broader understanding of EEG wave changes under balanced anesthesia using different methods and determining the ranges of waves synonymous with deep sleep, profound anesthesia and analgesia.

“Future studies hopefully will improve our ability to adapt the currently used technologies in human hospitals for use in equine anesthesia and pain management.”

Drewnowska and Turek are with the Faculty of Veterinary Medicine at the Warsaw University of Life Sciences in Poland; Lisowska is with the National Geriatrics, Rheumatology and Rehabilitation Institute, also in Poland.

What do we know about the use of EEG Monitoring during equine anesthesia: a review
Olga Drewnowska, Barbara Lisowska and Bernard Turek
Appl. Sci. 2019, 9(18), 3678;

The review, published under a Creative Commons License, can be read here

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