![]() ![]() Hematologic – methemoglobinemia, cyanosisĪllergic – urticaria, rash, and rarely anaphylaxis Depressed contractility of the heart then leads to progressive hypotension and ultimately cardiac arrest. May include hypertension, tachycardia or bradycardia, arrhythmias, and asystole. If not treated promptly, these symptoms often progress to seizures, syncope, coma, respiratory depression, or cardiovascular collapse.Ĭardiovascular – often preceded by CNS symptoms but not always. One or all of these manifestations may be present.ĬNS (excitement) – an early manifestation of LAST that often begins with confusion or slurred speech but may include subjective symptoms like metallic taste in the mouth, tinnitus, oral numbness, dizziness, lightheadedness, or visual or auditory disturbances. Symptoms of LAST can vary, however there are 5 general ways in which LAST presents. Once studied more directly, it was found that intralipid acts as a “sink” by creating a lipid compartment within the plasma that attracts lipophilic compounds, such as local anesthetics, into the lipid sink, which is separate from the aqueous phase of the plasma. These findings were subsequently confirmed in other laboratories and clinical systemic analyses. The rats were also more easily resuscitated if given lipid emulsion therapy. The ability of lipid emulsion therapy to counteract the toxic effects of local anesthetics was discovered in 1998 by Weinberg et al when it was incidentally found that lab rats pre-treated with an infusion of lipids could withstand larger doses of bupivacaine before arresting. There are several brand name lipid emulsion therapies, however Intralipid, a soy-based lipid emulsion that contains long-chain triglycerides, is the most commonly used (Figure 1). Lipid emulsion therapy is an intravenous therapy that binds lipophilic toxins and therefore reverses their toxicity. Thankfully, lipid emulsion such as Intralipid is a safe and effective therapy used to treat LAST. For this reason and the fact that local anesthetic toxicity is rare, by the time this syndrome is identified, patients are often in cardiac arrest or peri-arrest. Unfortunately, many physicians are unaware of the toxic dose of local anesthetics and are unable to recognize the signs and symptoms of this toxicity. Although rare, this complication can be fatal. Current estimates of LAST toxicity in adults range from 7.5 to 20 per 10,000 peripheral nerve blocks and 4 per 10,000 epidurals. Local anesthetic systemic toxicity (LAST) is a feared complication of local anesthetic use.
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