Practical use of local anesthetics in regional anesthesia

The choice of local anesthetics in regional anesthesia depends on desired onset, intensity, and duration of block, as well as possible adverse effects. This review highlights recent advances in day-case spinal anesthesia; considerations in selecting local anesthetic volume, concentration, and mass in peripheral nerve blockade; and the pharmacokinetics of ropivacaine.

Spinal anesthesia using 2-chloroprocaine offers fast onset and rapid recovery, whereas mepivacaine and lidocaine are suitable for longer procedures. Intrathecal lidocaine in the lithotomy position carries a significant risk of transient neurologic symptoms and should be avoided. Dosing studies of local anesthetics in peripheral nerve blockade suggest that mass of drug, not volume or concentration, primarily determines block onset, success, and duration. Commonly used doses of ropivacaine for Transversus Abdominis Plane blocks can result in high plasma concentrations and local anesthetic systemic toxicity.

There are effective alternatives to bupivacaine in day-case spinal anesthesia but more safety and outcome data are required, particularly for 2-chloroprocaine. The trend toward smaller doses of local anesthetics in ultrasound-guided regional anesthesia improves safety but should be weighed against possible reductions in speed of onset and analgesic duration. Strategies to reduce the risk of local anesthetic systemic toxicity should be employed when performing large-volume fascial plane blocks with ropivacaine.