Safety and Efficacy of Rescue Nerve Blocks
Authors: Lee Kevin , Herr Michael J. , Jones Jerry W. 
Published: March 2022

Background: The overall incidence of complications following peripheral nerve blocks is very low. Peripheral nerve blocks performed under ultrasound guidance are widely thought to present a lower risk to direct needle trauma than paresthesia and nerve stimulation techniques and have been shown to decrease opioid consumption by providing analgesia directly to the site of injury. Currently, when a nerve block fails altogether or provides inadequate analgesia, pain and opioid consumption increases which in turn decrease patient satisfaction and increases healthcare costs. Concerns remain whether the benefits of opioid reduction outweigh the risk of inadvertent needle trauma and other potential complications when performing a nerve block replacement, or ‘rescue block’. Objective: Examine whether performing a rescue peripheral nerve block provides adequate analgesia to elicit a decrease in opioid consumption. Analyze the incidence of nerve injury following ultrasound-guided ‘rescue’ continuous peripheral nerve blocks. Methods: Data was retrospectively collected from patient electronic medical records from a Level 1 academic Trauma Center at Regional One Hospital in Memphis, Tennessee from March 1, 2019 to May 31 2021. Inclusion criteria was patients over 18 years of age at time of admission who received consecutive continuous peripheral nerve blocks in the same relative location during a time when the peripheral nerves were likely partially or fully anesthetized (a rescue block). The primary outcomes assessed were 24-hour opioid consumption prior to the initial continuous nerve block, just prior to and after the ‘rescue’ block. Adverse outcomes potentially due to performing a ‘rescue’ block were also examined, including direct needle trauma, nerve injury related to extended exposure to local anesthetics, and local anesthetic systemic toxicity. Types of nerve blocks performed, range and median number of catheter days, and reason for rescue block was recorded for all patients. All available electronic healthcare records were reviewed to identify potential injury. Nerve blocks were categorized into low and high risk for direct needle trauma based on the incidence of needle trauma found in the literature and whether the needle was required to be adjacent to a discrete nerve or nerve bundle in order to perform the procedure. Results: 55 patients were examined. Of the 55 patients, 5 had multiple locations both blocked and rescued, bringing the total rescue procedures examined up to 60. Additionally, 10 patients had their rescue site re-blocked multiple times due to either multiple surgeries, displacements, or duration of analgesia required bringing the total number of rescue blocks performed to 74. Patients that received an initial continuous peripheral nerve block consumed significantly fewer opioids during the 24 hour period following the block than the 24-hour period before the block was performed (P=0.033). Continuous peripheral nerve blocks (CNPB) were replaced or ‘rescued’ for two general reasons: Failed or Inadequate Analgesia (21) and to Extend the Utilization of adequately functioning infusions (35). Once a rescue nerve block was performed, there was no significant change in opioid consumption than after the original block (P=0.64). Of the 60 rescue blocks that were recorded, there were 0 adverse outcomes that were attributed to the rescue block procedure. Conclusion: Following failed CPNB or when performed to extend the utilization of CPNB infusions, ultrasound-guided ’rescue’ nerve blocks result in reduced opioid consumption to a similar level as the initial peripheral nerve block, and do not result in an increase in the incidence direct needle trauma. Given the relatively low incidence of needle trauma and other nerve block-related complications, larger studies are needed to confirm these initial findings, however, ultrasound provides numerous clinical strategies that can be employed that may reduce the incidence of direct needle trauma compared with traditional nerve localization techniques.