INTRODUCTION: Despite its minimally invasive nature, percutaneous nephrolithotomy (PCNL ) may be associated with significant pain. Challenges in pain control may prevent timely discharge (and expose patients to adverse effects of opioid use). We sought to evaluate whether our patients who underwent erector spinae plane (ESP) regional blocks experienced improved postoperative pain control and decreased opioid use after PCNL (compared with those who did not receive blocks). METHODS: We retrospectively reviewed consecutive PCNL cases on patients admitted for greater than 24 hours without pre-existing opioid regimens for chronic pain. Cases were completed by a single high-volume surgeon. Patients who accepted an ESP block were compared to those who did not receive a block. Patients received either a single injection or a disposable pump delivering intermittent boluses of ropivacaine 0.2%. Demographic and perioperative data were analyzed. The primary outcomes were opioid use measured in morphine milligram equivalent (MME ) and patient-reported pain scores during the first 24 hours of hospitalization. RESULTS: From March 2019 to August 2021, 44 patients were identified who met criteria - 28 of whom received an ESP block (including 14 continuous blocks). The patients who received blocks had significantly decreased opioid use (18.3 vs. 81.3 MME, p=0.004) and a longer mean time to first non-zero pain score (p=0.004). Continuous blocks had similar opioid use to single shot blocks (21.0 vs. 15.6 MME, p=0.952). CONCLUSIONS: ESP regional blocks appear to offer an effective adjunct method for pain control after PCNL and may reduce post-PCNL opioid use while maintaining adequate patient analgesia.

Current methods for studying central nervous system myelination necessitate permissive axonal substrates conducive to myelin wrapping by oligodendrocytes. We have developed a neuron-free culture system in which electron-spun nanofibers of varying sizes substitute for axons as a substrate for oligodendrocyte myelination, thereby allowing manipulation of the biophysical elements of axonal-oligodendroglial interactions. To investigate axonal regulation of myelination, this system effectively uncouples the role of molecular (inductive) cues from that of biophysical properties of the axon. We use this method to uncover the causation and sufficiency of fiber diameter in the initiation of concentric wrapping by rat oligodendrocytes. We also show that oligodendrocyte precursor cells display sensitivity to the biophysical properties of fiber diameter and initiate membrane ensheathment before differentiation. The use of nanofiber scaffolds will enable screening for potential therapeutic agents that promote oligodendrocyte differentiation and myelination and will also provide valuable insight into the processes involved in remyelination.