Electroencephalogram of Healthy Horses During Inhaled Anesthesia

Area of Science:

• Veterinary Neurology
• Equine Anesthesiology

Background:

• Electroencephalography (EEG) is crucial for assessing equine cerebral cortical function.
• Previous diagnostic validity studies used various anesthetic drugs, potentially confounding results.
• Standardized interpretation criteria were applied despite differing anesthetic protocols.

Purpose of the Study:

• To investigate the impact of two common inhalation anesthetics, isoflurane and halothane, on the EEG of healthy horses.
• To evaluate EEG changes under varying concentrations of these anesthetics.

Main Methods:

• A prospective study involving six healthy horses.
• Administration of isoflurane or halothane at 1.2, 1.4, and 1.6 times the minimum alveolar concentration.
• EEG recording during controlled ventilation, spontaneous ventilation, and nerve stimulation.

Main Results:

• Isoflurane induced burst suppression and epileptiform-like discharges.
• Halothane produced variable EEG patterns, including epileptiform-like discharges and intermittent bursts of theta, alpha, and beta activity.
• Anesthesia-related complications led to the death of one horse and euthanasia of two others.

Conclusions:

• Halothane and isoflurane cause unpredictable EEG effects in horses, even when used alone.
• It is recommended to avoid these inhalation anesthetics during equine EEG procedures.
• Alternative methods for general anesthesia induction and maintenance are advised for equine EEG.