Intravenous anaesthesia in horses after xylazine premedication.

This research article investigates the effects of combining xylazine with various anaesthesia drugs (ketamine, methohexitone and thiopentone) in horses, including the onset of anaesthesia, smoothness of process, and the maintenance of vital functions. The study also looks into the prevention of atrioventricular block post xylazine injection.

Experiment Set-up and Anesthetic Drugs

• The experiment was conducted on four ponies where each was given large doses of a drug called xylazine (1.1 mg per kg), in conjunction with other anesthesia drugs: ketamine, methohexitone, and thiopentone.
• The onset of anesthesia was observed to be more delayed when using ketamine in comparison to the other two barbiturate-based drugs. Despite this, all three drug combinations were effective and acceptable in smoothness of induction and recovery post anesthetic state.

Effects on Heart and Blood Pressure

• The administration of xylazine led to a heart condition known as atrioventricular (A-V) block in the ponies. However, this could be prevented by administering atropine before xylazine.
• Regardless of the combinations of the drugs used, the blood pressure of the ponies was well maintained throughout the experiment.

Effects on Arterial Oxygen, Blood pH and Carbon Dioxide Tension

• The arterial oxygen tension began to decrease once the ponies went into a state of recumbency, a state where they lie down.
• However, there were no significant changes in the arterial blood pH or carbon dioxide tension, despite the recumbent state.

Cardiac Output and Recumbency

• In one pony, the researchers measured the cardiac output and found it to be least affected when ketamine was used as the anaesthetic drug.
• The experiment also observed that ketamine and methohexitone had similar effects in terms of the duration of recumbency, while thiopentone led to a significantly longer period of recumbency.

Recovery

• In every case, the ponies were able to stand up post anaesthesia at the first attempt without any struggle or agitation.
• It is important to note that the ability of the three drug combinations to produce an anesthesia conducive to surgical procedures was not tested in this study.