Plain bupivacaine: an unpredictable spinal anaesthetic agent

Area of Science:

• Anesthesiology
• Neurosurgery
• Pharmacology

Background:

• Intrathecal anesthesia involves injecting medication into the cerebrospinal fluid.
• Bupivacaine is a commonly used local anesthetic for spinal anesthesia.
• Optimizing block characteristics is crucial for surgical outcomes and patient safety.

Purpose of the Study:

• To investigate the influence of bupivacaine concentration, volume, and injection site on the height of spinal anesthesia.
• To evaluate the impact of these variables on the incidence of arterial hypotension.

Main Methods:

• Four groups of 10 patients received intrathecal bupivacaine (0.5% or 0.75%) at varying doses (15-20 mg) and volumes (2-4 ml).
• Injections were administered at either the L2/3 or L3/4 intervertebral spaces.
• The height of the anesthetic blockade and incidence of hypotension were recorded.

Main Results:

• A wide range of block heights was observed within each group, limiting statistically significant differences.
• A significantly higher mean block height was achieved with 20 mg of bupivacaine compared to 15 mg.
• Injection at L2/3 resulted in a mean maximum anesthetic level of T7, four segments higher than L3/4 injection (T11), with increased hypotension.

Conclusions:

• The injection site (L2/3 vs. L3/4) significantly influences the cephalad spread of intrathecal bupivacaine.
• Higher doses of bupivacaine lead to a greater block height.
• Increased block height, particularly with L2/3 injections, is associated with a higher incidence of arterial hypotension, necessitating careful consideration of injection parameters.