Local Anesthetic Systemic Toxicity

Abstract

Local anesthetics are used very often in medicine and dentistry. They have few adverse effects, but the increased use of these drugs has resulted in a higher incidence of local and systemic anesthetic toxicity (LAST). From the initial symptoms to the deleterious effects on cardiac and the central nervous system, LAST is an important consequence of which we should be aware. LAST is known since the introduction and use of local anesthetics; it was originally associated with seizures and respiratory failure. However, in the 1970s, side effects on the heart were also identified, as the fatal cardiac toxicity associated with bupivacaine was discovered in healthy patients. Prevention and safe administration of regional anesthesia remains primary factors in the avoidance of the toxicity of these drugs. When a patient has LAST, treatment should be started immediately to reduce seizures. If there is cardiac arrest, follow ACLS guidelines. Intravenous lipids improve cardiac conduction, contractility and coronary perfusion by removing liposoluble local anesthetic from cardiac tissue.

Local Anesthetic Use in Musculoskeletal Injections

“…15,16 Both lidocaine and bupivacaine bind to and block cardiac sodium channels; however, bupivacaine does so with a higher affinity and slower dissociation, thus resulting in higher risk of adverse cardiac effects. 1,17 Ropivacaine, a levo enantiomer of bupivacaine, was created in part because of this cardiac toxicity, as it has lower potency at myocardial sodium and potassium channels. 1 Ropivacaine also has more vasoconstrictive properties compared to lidocaine and bupivacaine, Potential for toxicity 7,11,12 Potential for toxicity when combined with dexamethasone 9 Typical dose, mL which can prolong duration of action and delay systemic absorption.…”

“…1 Ropivacaine also has more vasoconstrictive properties compared to lidocaine and bupivacaine, Potential for toxicity 7,11,12 Potential for toxicity when combined with dexamethasone 9 Typical dose, mL which can prolong duration of action and delay systemic absorption. 5 Additionally, compared to lidocaine and bupivacaine, ropivacaine has a higher cardiovascular collapse to CNS ratio, which is "the ratio of drug dose required to cause catastrophic cardiovascular collapse to the drug dose required to produce seizures," 17 meaning that CNS features will be detected earlier and allow for treatment of systemic toxicity prior to cardiovascular compromise. 18 The effect on chondrocytes should also be considered when choosing local anesthetics.…”

“…Bupivacaine has the highest potency and provides the longest duration of action, although it has been shown to have an increased risk of adverse effects, including cardiac, CNS, and chondrocyte toxicity. 1,17 Lidocaine has been shown to have a high potential for tenocyte toxicity even at low concentrations. 6,9,10 Ropivacaine has generally been found to be least toxic to chondrocytes and tenocytes among the 3 local anesthetics and therefore may be a more desirable choice.…”

“…The Table presents a comparison of lidocaine, bupivacaine, and ropivacaine with regard to their use in musculoskeletal joint and tendon injections. [1][2][3][5][6][7][8][9][10][12][13][14][15][16][17][18][23][24][25][26][27]…”

Is local anesthetic systemic toxicity a concern?

“…Highly vascularized sites, such as with intercostal blocks, can increase the risk of direct intravascular injection and systemic absorption. 5,6 LA doses should be decreased in newborns under age 4 months as protein binding is reduced, which results in increased LA plasma levels. 2 Older adults are at an increased risk of LAST because of age-related peripheral nervous system changes, which lead to increased sensitivity to LAs.…”