Some physiological effects of ketamine in sheep

Area of Science:

• Anesthesiology
• Veterinary Pharmacology
• Cardiopulmonary Physiology

Background:

• Ketamine is a widely used anesthetic agent.
• Understanding its effects on cardiovascular and respiratory systems is crucial for safe administration.
• Comparative studies with other anesthetics are valuable.

Purpose of the Study:

• To compare the effects of intravenous (IV) and intracerebroventricular (ICV) ketamine on sheep's cardiovascular and respiratory systems.
• To compare ketamine's effects with those of IV barbiturate and steroid anesthetics.

Main Methods:

• Sheep were administered ketamine via IV and ICV routes.
• Cardiovascular parameters (arterial blood pressure) and respiratory parameters (PaO2, PaCO2) were monitored.
• Effects were compared to those of intravenous barbiturate and steroid anesthetics.

Main Results:

• IV ketamine caused a dose-dependent, transient fall in arterial blood pressure, occasionally followed by a pressor phase.
• IV ketamine induced brief respiratory depression, followed by stimulation and elevated PaO2.
• ICV ketamine resulted in a mild, transient rise in mean arterial blood pressure.
• Ketamine's respiratory depression was shorter than barbiturate-induced depression but similar to steroid-induced depression.
• Steroid anesthetic normalized blood gas tensions quickly; ketamine showed elevated PaO2 post-depression.
• ICV ketamine's respiratory effects were difficult to assess due to variable apnea.

Conclusions:

• Intravenous ketamine significantly impacts cardiovascular and respiratory function in sheep, with distinct effects compared to ICV administration.
• Ketamine's respiratory profile differs from barbiturates and steroids, showing transient depression followed by stimulation.
• Further research may clarify the specific mechanisms and clinical implications of these observed effects.