From the Guidelines
Lidocaine toxicity can lead to hypoxemia through several pathophysiological mechanisms, including respiratory depression, bronchospasm, laryngospasm, myocardial depression, and seizures, which can be managed with supportive care and lipid emulsion therapy as recommended by the 2023 American Heart Association guidelines 1.
Pathophysiology of Lidocaine Toxicity
Lidocaine, a local anesthetic and antiarrhythmic agent, primarily affects the central nervous system and cardiovascular system when toxic levels are reached. At high concentrations, lidocaine causes respiratory depression by directly suppressing the respiratory center in the brainstem, leading to decreased respiratory drive and hypoventilation. This results in carbon dioxide retention and decreased oxygen uptake, causing hypoxemia.
- Respiratory effects:
- Respiratory depression
- Bronchospasm
- Laryngospasm
- Cardiovascular effects:
- Myocardial depression
- Vasodilation
- Decreased cardiac output
Management of Lidocaine Toxicity
Treatment focuses on supportive care, including oxygen supplementation, ventilatory support if needed, and in severe cases, lipid emulsion therapy is recommended with a Class I, LOE C-LD recommendation for local anesthetic poisoning 1. The administration of intravenous lipid emulsion can help bind the lipophilic lidocaine molecules and reduce free drug concentration in the bloodstream.
- Supportive care:
- Oxygen supplementation
- Ventilatory support
- Lipid emulsion therapy:
- 20% intralipid at 1.5 mL/kg bolus
- Followed by 0.25 mL/kg/min infusion for 30-60 minutes Additionally, benzodiazepines are recommended to treat seizures associated with local anesthetic systemic toxicity with a Class I, LOE C-LD recommendation 1. Sodium bicarbonate and atropine may also be considered for life-threatening wide-complex tachycardia and bradycardia associated with local anesthetic toxicity, respectively 1.
From the FDA Drug Label
The net effect is normally a modest hypotension when the recommended dosages are not exceeded Excessive blood levels may cause changes in cardiac output, total peripheral resistance, and mean arterial pressure These changes may be attributable to a direct depressant effect of the local anesthetic agent on various components of the cardiovascular system. Objective adverse manifestations become increasingly apparent with increasing venous plasma levels above 6. 0 mcg free base per mL.
Lidocaine toxicity can lead to hypoxemia due to its effects on the cardiovascular system. The drug can cause:
- Hypotension: a decrease in blood pressure, which can lead to reduced oxygen delivery to tissues
- Changes in cardiac output: a decrease in the amount of blood pumped by the heart, which can also reduce oxygen delivery
- Changes in total peripheral resistance: an increase in resistance to blood flow, which can further reduce oxygen delivery These effects can ultimately lead to hypoxemia, a condition where there is not enough oxygen in the blood 2.
From the Research
Lidocaine Toxicity and Hypoxemia Pathophysiology
- Lidocaine toxicity can lead to disastrous complications, including cardiac toxicity and arrest, as well as hypoxemia 3, 4, 5, 6
- The pathophysiology of lidocaine toxicity involves the drug's effects on the central nervous and cardiovascular systems, which can lead to seizures, altered mental status, and cardiac arrest 3, 5, 6
- Hypoxemia can occur as a result of respiratory depression or cardiac arrest, which can further exacerbate the toxicity 3, 6
Risk Factors for Lidocaine Toxicity
- High doses of lidocaine, especially in patients with advanced heart failure or other susceptible factors, can increase the risk of toxicity 4
- Iatrogenic overdose of lidocaine can occur due to improper dosage or administration 3, 5
- Patients with idiopathic cardiomyopathy or other cardiovascular conditions may be more susceptible to lidocaine toxicity 4
Treatment of Lidocaine Toxicity
- Intravenous lipid emulsion therapy has been shown to be effective in treating lidocaine toxicity, although the mechanism is not well understood 3, 6
- Supportive treatment, including airway protection and cardiac resuscitation, is also crucial in managing lidocaine toxicity 3, 5, 6
- Recognition of the symptoms of lidocaine toxicity and prompt treatment are essential to prevent morbidity and mortality 3, 4, 5, 6