Write a short note on Bupivacaine.

Pharmacology

Bupivacaine is a potent, long-acting amide local anaesthetic, widely used for prolonged nerve blocks, epidural and spinal anaesthesia, and postoperative analgesia. Its long duration reflects high protein binding, and its potency its high lipid solubility. It has a slow onset and a maximum dose of about 2 mg/kg.

Cardiotoxicity

Bupivacaine’s important drawback is that it is the most cardiotoxic local anaesthetic: it binds avidly to cardiac sodium channels and dissociates slowly, so an inadvertent intravascular dose can cause refractory ventricular arrhythmias and cardiac arrest that are very difficult to resuscitate. This is why it is never used for intravenous regional (Bier’s) anaesthesia, and why ropivacaine and levobupivacaine (less cardiotoxic) were developed.

Levobupivacaine & Ropivacaine

The recognition of bupivacaine’s cardiotoxicity drove the development of two safer long-acting agents that retain much of its useful profile: levobupivacaine, the single (S) enantiomer of bupivacaine, and ropivacaine, a closely related compound, both of which are less cardiotoxic because they bind cardiac sodium channels less avidly. Ropivacaine has the additional feature of producing relatively more sensory than motor block at low concentrations, which is useful for labour and postoperative epidural analgesia where preserving some motor power and mobility is desirable.

Cardiotoxicity may precede CNS signs — uniquely dangerous.

• Bupivacaine: potent, long-acting amide; slow onset; max ~2 mg/kg; for prolonged blocks/epidural/spinal.
• Most cardiotoxic LA — refractory arrhythmias/arrest if intravascular.
• Never used for Bier’s block; levobupivacaine/ropivacaine are safer alternatives.
• Treat toxicity with lipid emulsion + prolonged CPR; prevention is key.