Increased risk of cardio toxicity associated with local anesthetics requires a dose reduction in all of the following except
Life threatening cardiovascular toxicity, including left ventricular depression, atrioventricular hea block,ventricular arrhythmia is seen more in patients with deceased liver function, acidosis and in shock. The risk factors for developing LAST (Local Anesthetic systemic toxicity)can be categorized into those that are related to the injected drug, the patient, or the technique. Drug The cardiovascular collapse/CNS (CC/CNS) ratio is "the ratio of drug dose required to cause catastrophic cardiovascular collapse to the drug dose required to produce seizures." A low CC/CNS ratio is associated with more cardiotoxic agents, while LAs with a higher CC/CNS ratio have a greater safety margin. This is because the earlier presentation of CNS features may expedite earlier diagnosis (and thus, treatment) of LAST before cardiovascular collapse ensues. Ropivacaine and levobupivacaine, for example, have higher CC/CNS ratios than racemic bupivacaine; therefore, it seems logical to preferentially use these drugs when long-acting LAs are desired. Vigilance is always required, however, as all LA drugs may cause LAST. Patient Age Patients at the extremes of age have consistently been shown to be at the greatest risk of LAST. Pregnancy Renal disease Patients with severe renal disease not only have a hyperdynamic circulation and reduced clearance of LAs, but also have an increased a1-acid glycoprotein concentration. As a result, free plasma concentrations are largely unchanged and dose reduction is often unnecessary, unless the patient is uremic with metabolic acidosis. Cardiac disease Dose reduction is unnecessary in mild-moderate hea failure where tissue perfusion is preserved, but is recommended in severe hea failure. Hepatic dysfunction
Pregnancy
Acidosis
Pediatric
Increased cardiac output
Regional Anesthesia