Effects of Local Anesthetics on Peripheral Nerve Injury and Repair
Susanna C. Byram, MD, PhD1,2, Samantha E. Bialek, BA2, Vicki Husak, MS2, Daniel Balcarcel, BS3, James Park, MD3, and Eileen M. Foecking, PhD1,2,4
1Department of Anesthesiology, Loyola University Medical Center, Maywood, IL , 2Research Service Department of Veterans Affairs, Edward Hines Jr. VA Hospital, Hines, IL, 3Stritch School of Medicine, Loyola University Medical Center, Maywood, IL,4Department of Otolaryngology—Head and Neck Surgery, Loyola University Medical Center, Maywood, IL
- Perioperative nerve injury can occur as a complication from peripheral nerve blocks.
- It has been well documented that all Local Anesthetics (LAs) are toxic to neurons.
- Previous work suggests that LAs play a role in cell death, particularly in the setting of a preexisting or concomitant injury in the area where the local anesthetic is applied.
- An improved understanding of the effects of LAs on neuron survival will: 1) help identify LAs with safer neurotoxicity profiles; 2) lead to strategies to identify patients at higher risk for permanent neural deficits.
- To determine which LAs can exacerbate neuron cell death when applied to an injured peripheral nerve.
- We hypothesized that previously injured neurons will be more susceptible to the toxicity of certain commonly used LAs and this will result in increased motoneuron cell death.
Methods and Design:
- 128 C57B/6 mice were anesthetized with 2% isoflurane and the right facial nerve of each animal was exposed at its exit from the stylomastoid foramen.
- The facial nerve was either left intact (sham) or transected (axotomy) with iridectomy scissors.
- The left facial nerve was left intact and serves as an internal control.
Results: (All figures)
- The average FMN survival in mice treated with ropivacaine, bupivacaine, and tetracaine was significantly less than the average FMN survival in mice treated with saline, chloroprocaine, lidocaine, mepivacaine and liposomal bupivacaine.
- Three commonly used, long-acting local anesthetics (ropivacaine, bupivacaine, tetracaine) have a significant detrimental effect on overall motoneuron survival when applied to an injured nerve.
- The shorter acting local anesthetics including lidocaine, 2,3-chloroprocaine, mepivacaine, did not have a significant effect on motoneuron survival when applied to an injured nerve.
- The longest acting local anesthetic, liposomal bupivicaine, did not have a significant effect on motoneuron survival when applied to an injured nerve thus providing a potential alternative for peripheral nerve block of at-risk patients.
- There is no significant effect on FMN survival following treatment with any local anesthetics on an uninjured (sham) nerve.
The knowledge gained from these studies may impact how clinicians choose the appropriate local anesthetic to use on at-risk patients during peripheral nerve blocks.
Future studies will explore the effect of the these local anesthetics on other peripheral nerve injury models as well as study the underlying mechanisms involved in the motoneuron cell loss. These models could include facial nerve crush injury, delayed application of LA on a facial nerve injury, peripheral neuropathy models or other peripheral nerve injury models.
Funding support from The Department of Anesthesiology at Loyola University Medical Center, Maywood, IL.