Regional metabolism of articaine in 10 patients undergoing intravenous regional anaesthesia during day case surgery

Abstract

Aims To study the pharmacokinetics of articaine and its metabolite articainic acid, in patients undergoing intravenous regional anaesthesia.

Methods Ten patients (three male, seven female, ASA class 1–2), scheduled for surgery of the hand or forearm were included in the study. Articaine (40 ml, 0.5% solution (200 mg) was injected over 30 s. In total fifteen arterial blood samples were taken; one before injection and then at 10 min intervals, starting 10 min after completion of injection, until the tourniquet was released; thereafter blood samples were drawn at intervals of 1, 5, 10, 15, 20, 25, 30, 45, 60, 75 and 90 min. The tourniquet was released 30 min after completing the injection.

Results During tourniquet application and regional analgesia of 30 min duration, 55% of articaine was hydrolysed by plasma (20%) and tissue (35%) esterase activity to the metabolite articainic acid. After releasing the tourniquet, articaine and its metabolite appeared in the blood; articaine was rapidly eliminated with a t_1/2z of approximately 60 min. The plasma concentration of the metabolite articainic acid was the sum of the amount formed during IVRA (55%) and the amount formed after tourniquet release (45%).

Conclusions Articaine is a safe agent for intravenous regional anaesthesia (IVRA) with rapid onset of good surgical anaesthesia. During tourniquet application and regional analgesia, 55% of the administered dose is already hydrolysed, thus reducing the chance of side effects after tourniquet release.

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