Bupivacaine Pharmacokinetics in Ultrasound-guided Axillary Brachial Plexus Block.

A Clinical and Pharmacokinetic Study to Evaluate the Influence of Two Bupivacaine Concentrations on Peak Plasma After Ultrasound-guided Axillary Brachial Plexus Block

Introduction: The risk of systemic toxicity when using bupivacaine is a persistent problem, making its pharmacokinetic study crucial to the safety of regional anesthesia (RA). Little evidence exists regarding the effect of different concentrations of this drug on peak plasma levels. The present study compares two bupivacaine concentrations to establish how the concentration and exchange area affect the peak plasma level of this drug during axillary brachial plexus block. Latency and postoperative analgesia periods were also compared.

Methods: 32 patients were randomly assigned to two groups. In the 0.25% group, 10 ml of 0.25% bupivacaine was injected per nerve; in the 0.5% group, 5 ml of 0.5% bupivacaine was injected per nerve. Peripheral blood samples were collected every 15 min during the first hour and every 30 min during the second hour to establish serum level dosage. High-performance liquid chromatography coupled with mass spectrometry was used for the analysis.

Inclusion Criteria:

• candidates for elective surgery of the distal forearm and hand for whom brachial plexus anesthesia and analgesia were indicated.
• physical status of I or II according to American Society of Anesthesiologists (ASA) criteria
• body mass index (BMI) of less than 35 kg/m2
• Signed the free and informed consent document.

Exclusion Criteria:

• cognitive impairment
• infection at the block puncture site
• coagulopathy
• history of bupivacaine allergy