Effects of ketamine on left ventricular performance

Area of Science:

• Cardiovascular Physiology
• Anesthesiology
• Pharmacology

Background:

• Ketamine hydrochloride is a widely used anesthetic agent.
• Understanding its cardiovascular effects is crucial for safe clinical application.
• The influence of autonomic blockade on ketamine's cardiac response requires further elucidation.

Purpose of the Study:

• To investigate the cardiac response to ketamine hydrochloride in dogs.
• To determine the effects of beta-adrenergic blockade (propranolol) and combined beta-adrenergic and cholinergic blockade (propranolol and atropine) on ketamine's cardiovascular actions.

Main Methods:

• Anesthetic doses of ketamine hydrochloride (4 mg/kg) were administered intravenously or into the left atrium of dogs.
• Cardiovascular parameters including heart rate, cardiac output, left ventricular systolic pressure, left ventricular end-diastolic pressure, and dP/dt max were measured.
• Experiments were conducted in the absence of other drugs, during beta-adrenergic blockade with propranolol, and during combined blockade with propranolol and atropine.

Main Results:

• Ketamine alone increased heart rate, cardiac output, and left ventricular systolic pressure.
• Beta-adrenergic blockade attenuated the heart rate increase and caused a transient fall in dP/dt max.
• Combined blockade resulted in no change in heart rate but a fall in dP/dt max and a rise in left ventricular end-diastolic pressure.
• Systemic vascular resistance remained unaltered by ketamine.

Conclusions:

• Ketamine administration stimulates sympathetic discharge and reduces vagal tone to the heart.
• In the absence of autonomic regulation, ketamine exhibits myocardial depressant effects.
• The study highlights the significant role of the autonomic nervous system in modulating ketamine's cardiovascular impact.