Key safety point: Based on our 15-year experience performing UGNBs, we have observed cases of suspected early LAST with thoracic fascial plane blocks and hematoma blocks (including erector spinae plane, serratus anterior, and sternal hematoma blocks). After calculating the maximum accepted dose of anesthetic and drawing up less, we believe that clinicians should take more time to perform these blocks by waiting 30 seconds to 2 minutes between each 3-5 mL aliquot of anesthetic injection. During the pauses, clinicians should monitor the patient’s vital signs and inquire about symptoms to enable early detection of toxicity. We recognize that pausing between anesthetic injections should be standard for all UGNBs, but feel special attention should be paid when placing local anesthetic in highly vascular regions in close proximity to the heart.

Treatment Protocol

Early recognition and treatment of LAST is critical. The cornerstone of treatment is intravenous lipid emulsion, which is believed to draw lipophilic local anesthetic from sensitive tissues, like the brain and heart, into the bloodstream and act as a “lipid sink,” binding and inactivating local anesthetic.⁴ We highly recommend that a simplified protocol for intralipid administration be discussed and practiced by clinicians performing UGNBs, clinical administrators, and hospital pharmacists far in advance of the first block performed in the ED. As with all critical, time-sensitive, and uncommon procedures (like cricothyrotomy and thoracotomy), a simplified pathway reduces cognitive load during stressful events.

In cases of suspected LAST, there is no clearly defined point at which intralipid should be administered. In patients with late symptoms (seizure, altered mental status, dysthymias, cardiac collapse, etc.), the pathway is obvious and intralipid should be administered immediately. In patients with possible early symptoms, the decision can be challenging however, based on our experience, we recommend frequent and careful monitoring, with immediate administration of intralipid if symptoms progress.

In addition to early intralipid, seizures should be treated with benzodiazepines and standard Advanced Cardiac Life Support (ACLS) guidelines should be followed for arrhythmias and cardiac arrest, with some notable modifications. Smaller doses of epinephrine are recommended (start at <1 mcg/kg). Local anesthetics, beta blockers, calcium channel blockers, and vasopressin should not be used.

Highland ED Protocol for Intralipid Administration

Because LAST is a very rare (and stressful) event, we have developed a simplified process for our clinicians. As part of our departmental protocol, all patients receiving USGNBs must have functional intravenous access and be placed on a cardiac monitor prior to starting the procedure. Also, the patient must be kept on a continuous cardiac monitor for 60 minutes after the block has been completed. UGNBs distal to the elbow or knee (forearm and tibial nerve blocks specifically) that require volumes less than 10 ml of anesthetic can be performed without continuous monitoring.