Exparel

Exparel is bupivacaine (a numbing novocaine-like substance) that is contained in tiny fat-coated droplets (lysosomes). Normally, this numbing agent is gone within 4-6 hours but when you place the active liquid in these lysosomes, it takes the body some time to break down the lysosome coating. This means that this numbing medication will become effective over a longer period of time. I don’t yet use this medication for a number of reasons.

First, I like to wait to see if there are any serious side effects that were not noted when the substance was approved initially. A good example is the continuous infusion lidocaine pump device that was marketed for knee and should surgeries not too long ago. The continuous infusion of numbing medication did control pain but a certain number of patients developed chondrolysis. The cartilage lining their joints dissolved away and most developed severe arthritis. Tis side effect was not initially noted in the approval studies. Exparel has not been out long enough to know the longer term effects.

The second problem is that I always worry that numbing medications applied to an open spinal canal can obviously numb the cauda equina (the nerve roots in the center of the canal). This could create saddle anesthesia and bowel/bladder loss (temporarily until the numbing medication wore off). These are the exact same symptoms as cauda equina syndrome-a surgical emergency, which could theoretically be seen in the case of a post-operative seroma or hematoma forming and compressing the canal. The presence of these symptoms would prompt many more post-operative MRIs.

I do inject straight Marcaine (bupivacaine) in the muscles immediately after surgery and I inject duramorph (morphine) into the spinal canal. This technique for the most part eliminates pain for 24 hours and there is no anesthesia effect (cauda equina type symptoms) that occur with this regime.

Dr. Corenman