Injections into joints of anesthetics (numbing agents) and pain relieving medications have been used for a long time. They were considered “safe” based on clinical research in the mid-1980s. The use of single injection anesthetics such as lidocaine and bupivacaine gradually expanded to include modern day use of pain pumps.
A pain pump delivers a continuous, steady low-dose of anesthetic to the joint. With maximum pain control (for example after joint replacement surgery), patients are able to reduce the amount of narcotics used with each surgical episode. With less pain, they are able to get up, move, and enter into a rehab program sooner. And that is a huge benefit of pain pumps.
Locally injected medications do have some systemic effects (e.g., heart attack, depression, seizures) but these are rare. There is new evidence that delivery of anesthetics into joints may have some local toxic effects previously unrecognized. Whereas the joint can quickly clear the effects of a single (local) injection of anesthetics, there isn’t a similar ability with continuous exposure.
Scientists are taking a new and fresh look at this potential problem. The use of postoperative pain pumps is getting a second look. The use of anesthetics delivered by pain pump may be something to be reconsidered if not discouraged or even discontinued. In a recent report, surgeons from the University of California – San Francisco provided an update on current findings related to toxic effects of local anesthetics on joint cartilage. Here’s a quick summary.
Basic science studies have shown that numbing agents (bupivacaine, lidocaine, ropivacaine) do indeed kill cartilage cells called chondrocytes. Even brief exposure can decrease cell metabolism and cause cellular disruption. The end result is chondrocyte breakdown and self-destruction. This effect of anesthetics on cartilage cells is called chondrotoxicity.
Once the thin protective layer is destroyed, the number of dead cells increases. More time and further exposure to anesthetic agents are the two main risk factors for chondrotoxicity. The damage to chondrocytes after contact with anesthetics is permanent. Damage done by pain pumps after surgery is similar to changes seen with early osteoarthritis.
The authors who reviewed this new information suggest further study is needed in this area. There is a need to verify these findings and to uncover any long-term effects of pain pumps on joints. Surgeons won’t be quick to stop the use of pain pumps because of the positive benefits. But given these new findings, it may be something to discuss with the surgeon before proceeding ahead.