A combination of methotrimeprazine, midazolam and guaiphenesin, with and without ketamine, in an anaesthetic procedure for horses.

The research article investigates an anesthetic procedure for horses using a combination of methotrimeprazine, midazolam and guaiphenesin, with and without ketamine, and its effects on the horses’ recumbency and recovery.

Research Overview

• The research focuses on testing an anaesthesia induction procedure on horses using a combination of 0.5 mg/kg of methotrimeprazine, 0.1 mg/kg of midazolam and 100 mg/kg of a 10 per cent guaiphenesin solution.
• A secondary part of the research was testing the addition of 1.6 mg/kg of ketamine to the anaesthesia mixture.
• These tests were conducted on a group of 15 horses and anaesthesia was maintained with halothane in oxygen.

Effects and Side-effects

• The study found that the horses became recumbent (lying down) quickly and smoothly after the induction.
• Positive post-operative behaviour was observed as the horses recovered quietly and with minor ataxia (lack of muscle coordination).
• The study noted tachycardia (an abnormally fast heart rate) after the anaesthesia was induced but no other changes from pre-operative values were found prior to the administration of halothane in oxygen.
• However, after the maintenance of anaesthesia with halothane in oxygen, side effects such as hypothermia, hypotension, bradypnoea (abnormally slow breathing), hyperoxaemia (excess oxygen in the blood), respiratory acidosis (excess acid in the body due to a malfunction in the process of removing carbon dioxide through the lungs) and a decrease in the respiratory minute volume (the total amount of air capacity in the lungs) were observed.

Ketamine Addition

• The research also explored the effect of adding ketamine to the anesthesia mixture.
• This was evaluated in another group of 15 horses, finding that horses given ketamine in addition to the original combination were easier to intubate (insert a tube into the windpipe to maintain an open airway) and they recovered more quickly compared to those that were only given the methotrimeprazine, midazolam, and guaiphenesin combination.