Management of Local Anesthetic Systemic Toxicity (LAST) Cardiac Arrest

Introduction to LAST Management

The American Heart Association recommends that standard-dose epinephrine (1 mg) should be reduced or avoided in cardiac arrest from local anesthetic toxicity because high-dose epinephrine may impair the effectiveness of lipid emulsion therapy and worsen outcomes 1

The American Heart Association guidelines note that intravenous lipid emulsion is the primary treatment for LAST-induced cardiac arrest and should be administered immediately, using a 20% emulsion with an initial bolus of 1.5 mL/kg lean body mass over 1 minute, followed by an infusion of 0.25 mL/kg per minute for 30-60 minutes 1
Lipid emulsion therapy combined with high-dose epinephrine showed no additional benefit compared to lipid emulsion alone, suggesting that standard or high-dose epinephrine may be counterproductive 2

The International Consensus specifically notes that two animal studies showed lipid emulsion was superior to standard vasopressor therapy (including epinephrine) for return of spontaneous circulation (ROSC) in local anesthetic toxicity 2
If epinephrine is used, consider reduced doses (less than the standard 1 mg) or avoid it initially while prioritizing lipid emulsion therapy 1, 2

Lipid emulsion creates a lipid compartment in serum that reduces the concentration of lipophilic local anesthetics in tissues while also increasing cardiac inotropy through other mechanisms 1
The lipid sequestration mechanism by which lipid emulsion works to reduce local anesthetic concentration in tissues may be impaired by standard-dose epinephrine 1

When cardiac arrest occurs from local anesthetic toxicity, immediately give lipid emulsion as the primary antidote, continue high-quality CPR, and use reduced-dose or no epinephrine initially, as standard-dose epinephrine may interfere with lipid emulsion efficacy and has not been shown to improve outcomes in this specific toxicologic emergency 1, 2

The American Heart Association guidelines identify bupivacaine as the local anesthetic most frequently implicated in local anesthetic systemic toxicity (LAST) leading to cardiovascular collapse, with IV lipid emulsion therapy being particularly indicated for patients with cardiac arrest due to bupivacaine toxicity 3, 4, 5
The American Heart Association guidelines note that while bupivacaine, lidocaine, and ropivacaine are the most commonly reported agents associated with LAST, bupivacaine is specifically singled out in treatment recommendations 3, 4, 5

Bupivacaine causes profound cardiovascular collapse through profound inhibition of voltage-gated sodium channels in cardiac cell membranes, which is more severe than with other local anesthetics 3, 4

IV lipid emulsion should be administered early in suspected bupivacaine toxicity, particularly when cardiac arrest occurs 3, 4, 5

Bupivacaine can be used cautiously in patients with stable cardiac disease, but it requires heightened vigilance due to its potent cardiotoxicity compared to other local anesthetics, particularly in the event of accidental intravascular injection 6

Patients with stable, controlled cardiovascular conditions have tolerated local anesthetics with epinephrine in dental surgery settings, with the American Academy of Dermatology guidelines recommending that epinephrine in small amounts is safe for dermatologic surgery in patients with stable cardiovascular disease, but consultation with the patient's cardiologist is recommended when the patient's ability to safely undergo a procedure is in question 7

The maximum dosing limit for bupivacaine with epinephrine is 3.0 mg/kg, and without epinephrine is 2.5 mg/kg, which must be calculated before administration to prevent toxicity in all patients, but especially those with cardiac disease 8, 9
Patients with cardiac disease receiving bupivacaine require continuous observation with documented vital signs, including oxygen saturation and heart rate at least every 5 minutes, and ECG monitoring should be readily available 8, 9

When using bupivacaine in patients with cardiac history, immediate availability of lipid emulsion therapy is critical, with administration of 20% intravenous lipid emulsion as the primary antidote in case of cardiac arrest from bupivacaine toxicity 6