Clinical evaluation of an infusion of xylazine, guaifenesin and ketamine for maintenance of anaesthesia in horses.

This research study aimed to evaluate the potential of a mixture of xylazine, guaifenesin, and ketamine for maintaining anaesthesia in horses. Results showed that the concoction induced largely desirable effects, and was suitable for most surgical procedures, excluding laryngeal surgery. There were alterations to blood pressure, heart rate, blood gases and recovery times, as well as temporary significant changes to certain blood components.

Study Methodology

• The researchers conducted the study on 40 horses, where they maintained general anaesthesia through a continuous intravenous infusion of a mix of 500 ml 10% guaifenesin solution, 1 g ketamine and 500 mg xylazine.
• The median duration of the infusion was 65 minutes, with a range between 51 to 95 minutes.

Observations and Findings

• The anaesthesia was characterised by active palpebral reflexes, varied degrees of nystagmus (rapid involuntary eye movement), and occasional swallowing.
• While the swallow reflex was considered undesirable for laryngeal surgery, the infusion was satisfactory for all other surgical procedures performed.
• All the horses’ arterial blood pressure maintained well throughout the process, with the median mean arterial blood pressure equalling 85 mmHg after 30 minutes of anaesthesia.
• In the infusion group, the heart rate and PaCO2 (carbon dioxide partial pressure) levels were significantly lower, while paO2 (oxygen partial pressure) levels were significantly higher, compared to control horses anaesthetised with halothane, a different anaesthetic agent.
• The recovery from anaesthesia was good (Grades 1-2) in 33 out of 40 horses. Median times to sternal recumbency (lying down with the chest touching the ground) and standing were 24 and 38 minutes, respectively.

Changes in Blood Components

• The infusion caused a significant fall in packed cell volume, haemoglobin concentration, and red blood cell count (Significant at P < 0.01).
• There was also a noticeable rise in plasma glucose concentration (P < 0.01).
• All these alterations in blood components returned to pre-infusion levels within 24 hours.