Abstract
Introduction
The treatment and diagnostics of discogenic low back pain often employ local anesthetic agents. Lidocaine and bupivacaine are most commonly used for controlling and relieving the pain in interventional spine procedures. It is known that these local anesthetics may be cytotoxic to the intervertebral disc cells following the intradiscal injections and that they may provoke or accelerate the intervertebral disc degeneration. However, the potential effects of these agents still remain unclear, as many studies so far have been accomplished on animal cells. The purpose of the study was to evaluate the effect of various local anesthetics on human intervertebral disc cells in vitro and to compare the cytotoxicity of lidocaine, bupivacaine, and its mixture to saline control solution.
Materials and Methods
Annulus fibrosus and nucleus pulposus cells were isolated from human lumbar intervertebral disc fragments following discectomies. They were cultured in the microtiter plates and exposed to various concentrations of lidocaine, bupivacaine, as well as their mixture. The saline solution was used for control. Three different dilutions (undiluted, 1:2, and 1:4) of anesthetic agents were tested. The cells were treated for 6, 24, and 48 hours. They were then examined with the crystal violet cell staining. The percentage of live cells after treatment was determined.
Results
Human intervertebral disc cells demonstrated a time- and dose-dependent response to lidocaine and bupivacaine. Nucleus pulposus cells were more susceptible than annulus fibrosus cells to the toxic effects of both anesthetic agents. Lidocaine was the most toxic in all three tested concentrations (undiluted, 1:2, and 1:4) with the cell survival of 0, 10, and 20%, respectively. Bupivacaine presented less cytotoxicity than lidocaine with the survival rates of 10, 60, and 80%, respectively. Lidocaine–bupivacaine mixture showed an intermediate toxicological effect. The cell death was mainly caused by necrosis rather than apoptosis.
Conclusions
When incubating the human intervertebral disc cells in vitro with a combination of anesthetic agents commonly used for discography, the cytotoxic effects were observed in a dose- and time-dependent manner. According to our study, lidocaine and its mixtures should be avoided due to their high toxicity to the intervertebral disc cells. Bupivacaine was the least toxic, especially when used in 1:4 dilutions and may be thus recommended for the intradiscal diagnostics. It is assumed that the genesis of disc degeneration might be contributed also by the toxic effects of the anesthetics used, culminating to progressive tissue damage after the diagnostic measures.