Does local anesthetic stereoselectivity or structure predict myocardial depression in anesthetized canines?

Area of Science:

• Anesthesiology
• Cardiovascular Pharmacology
• Toxicology

Background:

• Accidental intravascular local anesthetic (LA) administration can cause myocardial depression.
• The factors influencing susceptibility to this cardiac depression are not fully understood.
• Investigating the roles of stereoselectivity and molecular structure in LA-induced cardiotoxicity is crucial.

Purpose of the Study:

• To compare the cardiac depressant effects of four local anesthetics: bupivacaine, ropivacaine, levobupivacaine, and lidocaine.
• To determine whether LA stereoselectivity or molecular structure is more associated with myocardial depression risk.

Main Methods:

• Open-chest dogs underwent direct left ventricular pressure monitoring and echocardiography.
• Animals received escalating infusions of bupivacaine, ropivacaine, levobupivacaine, or lidocaine until cardiovascular collapse.
• Echocardiographic indices and hemodynamic parameters were analyzed to assess cardiac function.

Main Results:

• All tested local anesthetics (LAs) caused dose-dependent cardiac depression, including decreased dP/dtmax, ejection fraction, fractional shortening, and cardiac output.
• Ropivacaine exhibited the least cardiac depressant effect among the long-acting agents.
• Lidocaine required significantly higher concentrations to induce similar levels of myocardial depression compared to bupivacaine, levobupivacaine, and ropivacaine.

Conclusions:

• Smaller molecular size and piperidine-free structure appear to be more significant factors in mitigating the risk of LA-induced myocardial depression than stereoselectivity.
• These findings have implications for selecting local anesthetics to minimize cardiotoxic risks during procedures.