Lignocaine Toxicity - A Synopsis

What Is Lignocaine?

Lignocaine, also referred to as lidocaine, is an amino amide-type local anesthetic that is marketed under the trade name Xylocaine. When Lignocaine is injected into or applied topically to the area around neural tissue, it causes temporary loss of sensory, motor, and autonomic function. Lignocaine normally starts functioning within a few minutes and lasts for 30 minutes to three hours when used as local anesthesia or as a nerve-blocking agent. It is frequently combined with a small quantity of Epinephrine to increase the duration of its effects and lessen bleeding. It is the most widely used local anesthetic and is used in all medical practices. Lignocaine is used in the form of injection, inhalation, or as a topical agent.

What Is Lignocaine Toxicity?

Lignocaine is a commonly used local anesthesia. Therefore, the drug can cause toxicity when used incorrectly or in high dosage. However, Lignocaine has a good safety margin before reaching dangerous blood levels. Lignocaine toxicity is influenced by the absorption rate and the drug's overall dose. In addition, Lignocaine can be applied through various routes. Doctors should be careful of the dose of any additional local anesthetics that may have been given to the same patient because toxic doses of drugs seem to build up. Localized Lignocaine toxicity at the injection site might affect muscles and peripheral or neuraxial nerves. After administering high-concentration of Lignocaine spinal anesthesia, temporary neurological signs and symptoms have also been reported multiple times.

What Causes Lignocaine Toxicity?

• Long-term use of high concentrations of Lignocaine is thought to cause toxicity to the local nerves and muscles.

• Preservatives present in combination with Lignocaine can also cause toxicity in some cases.

• Due to the absorption of large dosages of Lignocaine, which primarily depends on the blood flow at the site of injection.

• Systemic Lignocaine toxicity can result after the injection of large volumes of Lignocaine into a muscular region, such as for lumbar plexus or sciatic nerve blocks.

• It is crucial to note that even low amounts accidentally injected into an artery going to the brain can result in CNS (central nervous system) symptoms.

How Common Is Lignocaine Toxicity?

• Lignocaine toxicity is prevalent among older adults.

• Both sexes are affected by this toxicity equally.

• Pregnant women are also susceptible to Lignocaine toxicity.

• Depending on the type of block, rates of severe systemic toxicity range from one in 10,000 for epidurals to one in 2000 for peripheral nerve blocks.

What Are the Symptoms of Lignocaine Toxicity?

Signs and symptoms of Lignocaine toxicity include:

• The central nervous system is the site of warning signs of toxicity in conscious patients.

• Numbness in the circumoral region.

• Numbness or paresthesia of the tongue.

• Nervousness.

• Agitation.

• Feeling paranoid.

• Muscle twitching.

• Seizures (abnormal and uncontrolled electrical disturbance in the brain).

• Depression of the central nervous system.

• Loss of consciousness.

• Coma (refers to a prolonged period of unconsciousness).

• Hypotension or decreased blood pressure.

• Atrioventricular heart block (partial or complete blockage of the electrical signal that regulates heartbeat).

• Irregular heartbeat.

• Ventricular tachycardia (increased heartbeat).

What Is the Differential Diagnosis of Lignocaine Toxicity?

Other conditions that may present with symptoms similar to Lignocaine toxicity include

• Coincidental seizures or seizures in general.

• Panic attacks along with hyperventilation.

• Hematoma (symptoms may be similar to local Lignocaine toxicity).

How Is Lignocaine Toxicity Diagnosed?

Lignocaine toxicity can be diagnosed with the help of the following tests:

• Clinical Evaluation: The diagnosis of Lignocaine toxicity is primarily based on clinical evaluation. The major variables to consider while thinking about systemic symptoms are the timing, dosage, and location of the Lignocaine injection.

• Imaging Tests: The diagnosis of transient neurological symptoms cannot be made with a computed tomography (CT) or magnetic resonance imaging (MRI) scan of the spine. However, it will be useful to rule out additional factors that could compress the spinal structures.

• Blood Examination: It is possible to measure the plasma level of Lignocaine, but it will take too long for the results to be useful for making treatment choices.

How Is Lignocaine Toxicity Treated?

• Increasing the seizure threshold with pharmaceutical therapies, such as Benzodiazepines, Barbiturates, or Propofol, can treat the symptoms of local anesthetic systemic toxicity.

• High doses of oxygen are administered to treat hyperventilation.

• Reducing the concentration of free Lignocaine in the plasma by administering lipid emulsions is the other basis of treatment. Due to the high lipid solubility, Lignocaine that is free and circulating in the blood binds with these lipid emulsions, and eventually, the plasma levels of Lignocaine are lowered.

• The American Society of Regional Anesthesia and Pain Medicine recommends the following treatment plan:

1. Call for help.

2. Initial focus (this involves airway management and suppression of seizure).

3. Alert the nearest facility having cardiopulmonary bypass capability.

4. Management of cardiac arrhythmia (this is done with the help of basic and advanced cardiac life support, avoiding antihypertensive drugs, and reducing the dosage of Epinephrine).

5. Lipid emulsion therapy.

What Are the Complications of Lignocaine Toxicity?

Some of the rare yet possible complications of Lignocaine toxicity:

• Seizures (abnormal electrical activity in the brain).

• Coma (prolonged period of unconsciousness).

• Hypotension (reduced blood pressure).

• Atrioventricular heart block (atrioventricular block is a condition when the AV or atrioventricular node or the His-Purkinje system's conduction system abnormalities causes prevention or delay in electrical transmission from the atria to the ventricles).

• Idioventricular rhythm (idioventricular rhythm is a slow, regular ventricular beat that has a heartbeat rate of under 50 beats per minute, no P waves, and a prolonged QRS interval).

• Ventricular tachycardia (ventricular tachycardia is a condition affecting the normal heart rhythm caused by irregular electrical signals in the heart's lower chambers).

• Cardiovascular collapse (failure of the cardiovascular system).

• Death.

Conclusion

Lignocaine is a commonly used anesthetic drug that is usually safe. However, the drug's toxicity can also frequently occur due to its vast usage in the medical field. The location of the manifestation of the symptoms determines the treatment and the prognosis of Lignocaine toxicity in an individual. Central nervous system (CNS) toxicity has a fair prognosis without complications. It is either self-limited or very responsive to treatment with Benzodiazepines and does not require additional neurologic testing. However, extended resuscitation may be necessary in cases of cardiac toxicity, and the prognosis is frequently excellent if spontaneous circulation is restored.