Do you also feel a little scared when you are given a local anesthetic? Let's talk about LAST (Local Anesthetic Systemic Toxicity)!

Have you ever taken a local anesthetic to get a tooth extracted, stitch up a wound, or have a minor surgery? And then you just feel numb and nothing happens? It may sound strange, but this anesthetic is a very important thing in medicine. However, very rarely, that is, very rarely, this anesthetic can cause a small problem for our body. That's what we call Local Anesthetic Systemic Toxicity , or LAST . Don't worry, this is very rare. But it's good to know a little about this.

So what is LAST (Local Anesthetic Systemic Toxicity)?

Simply put, LAST is the effect that when a drug is ingested, it has on our body's systems, especially the Central Nervous System (CNS), which is the brain and spinal cord, and the Cardiovascular System, which is the heart and blood vessels.

Think about how painkillers work. They temporarily block the nerves (peripheral nerves) in a certain part of our body. Then those nerves stop sending sensations like pain and touch to the brain. That's why we feel like we're tingly in that area. These painkillers come in the form of injections, gels, and sprays.

So, LAST occurs within minutes of taking the painkiller. But the best part is, there is treatment for this. If your doctor sees these symptoms, they will act quickly.

What are the symptoms of LAST? How do we recognize it?

LAST mainly affects our central nervous system (CNS). The first symptoms may be:

Symptoms related to the central nervous system (CNS):

• Seizures: This is the most common symptom. There is sudden convulsions and loss of consciousness.
• Agitation or confusion: A feeling of being unable to sit still, unable to concentrate, and not understanding what is happening.
• Ear changes: A constant ringing in the ears (Tinnitus) .
• Numbness around your mouth: Numbness around your mouth, like when a dentist injects medicine.
• Metallic taste in your mouth: It tastes like having a piece of iron in your mouth.
• Slurred speech (Dysarthria): Words become slurred and it becomes difficult to speak clearly.
• Hallucinations: Seeing or hearing things that are not really there.
• Eye movement abnormalities: The eyes move uncontrollably, appearing to move from one side to the other.

Symptoms related to the Cardiovascular System:

The LAST condition can also affect our heart. Then symptoms such as these may occur:

• Low blood pressure: The pressure decreases.
• Changes in heart rate: Heart rate may be too slow (Bradycardia) , too fast (Tachycardia) , or irregular heart rhythms (Arrhythmias) .
• Shortness of breath (Dyspnea): Difficulty breathing, wheezing.
• Cardiac arrest: The sudden cessation of the heart's electrical activity. This can be caused by a complete loss of electrical activity in the heart (asystole) , or by the heart's cells beating very rapidly and irregularly (ventricular fibrillation) .

Important: If not treated quickly, LAST can lead to respiratory arrest or coma .

These symptoms usually appear within five minutes of taking a painkiller. Sometimes these symptoms can start very mild and gradually increase, or they can suddenly become severe. That's why doctors will monitor you closely after giving you a painkiller, especially if you're at high risk for developing LAST.

Why does this LAST occur? What are the reasons?

The main cause of LAST is accidental injection of a painkiller into a blood vessel. Think about it, the painkiller is supposed to be injected near a nerve. But sometimes if it gets into a blood vessel, the medicine can quickly spread throughout the body and cause this condition.

It is reported that the risk of LAST occurring when performing nerve blocks that numb the limbs is about 20%. However, this is not all:

• LAST has also been developed as a topical medication that is applied to the skin in the form of a gel .
• LAST has also been caused by medications that irritate the mucous membranes of the mouth, throat, and airways .

This means that LAST can occur no matter how you use the painkiller. However, some factors increase this risk.

Who is at higher risk of developing LAST? (Risk Factors)

Certain things related to your health condition may increase your risk of developing LAST.

Risk factors related to your health:

• Metabolic acidosis: When the chemical balance in the body changes and the acidity increases.
• Low oxygen levels in the body (Hypoxia): When the amount of oxygen in the blood decreases.
• Pre-existing heart disease: Especially those with conditions such as ischemia , arrhythmias , conduction abnormalities , and low ejection fraction .
• People over the age of 65: Also, babies under 4 months old are at higher risk of developing LAST.
• Liver or kidney disease: People with these conditions may develop delayed LAST because it takes longer for the drug to leave the body.
• Pregnancy.
• Mitochondrial diseases: These are diseases that affect the energy-producing parts of our cells called mitochondria.

Risk factors associated with Hiri medicine:

Some anesthetics, such as bupivacaine , are more likely to cause LAST than others. Also, the risk increases when anesthetics are given in higher doses .

Risk factors associated with the oral medication method:

Some methods of administering painkillers may also increase the risk of LAST. A study of 125 cases of LAST found:

• Infiltration techniques are methods in which medication is injected under the skin. This accounts for about 20% of LAST cases.
• Central neuraxial blocks, like epidural and caudal blocks, are given to the spine. They account for about 15% of all reported cases.
• About 13% have been reported due to continuous infusion of pain medication, such as saline .

Finally, LAST is more likely to occur when anesthetics are injected into areas with high vascularity . For example, LAST cases are more commonly reported when penile nerve blocks are performed.

How do doctors diagnose LAST? (Diagnosis)

Doctors diagnose LAST primarily based on your symptoms . Because LAST is an emergency that requires immediate treatment, diagnosis cannot be delayed. Very rarely, your doctor may order an EKG (electrocardiogram) to help confirm this.

What are the treatments for LAST?

Local Anesthetic Systemic Toxicity is a medical emergency. Therefore, doctors will begin treatment very quickly. The usual treatments are as follows:

• Airway management: Oxygen therapy is given immediately to maintain your breathing, and ventilation is given if necessary.
• Seizure prevention or treatment: This involves giving medications such as benzodiazepines .
• IV infusion of lipid emulsion: This is a special medication that is given into a vein . It works by absorbing the painkillers from the blood and tissues. This reduces the concentration of painkillers that reach the brain and heart.
• CPR (Cardiopulmonary Resuscitation): If LAST affects the functioning of the heart, doctors perform CPR and use other methods to stabilize the heart.

After the treatment, you will be kept under medical observation for at least six hours to check whether the treatment is successful and if there are any other complications.

What will happen to someone who has LAST? (Prognosis)

Those who are diagnosed and treated early usually have a better outcome. Treatment can largely reverse the condition of LAST.

However, if severe LAST is not treated promptly, it can lead to coma or even death. However, this is very rare. For example, according to data from poison control centers in the United States, there were only four deaths from painkillers in 2016.

Can LAST be prevented?

LAST cannot always be prevented, but doctors use some methods and guidelines to reduce this risk.

For example, your doctor will use the lowest effective dose of pain medication necessary . Also, sometimes they will use ultrasound imaging to give the injection, to make sure it doesn't accidentally go into a blood vessel.

If you have risk factors for developing LAST, your doctor will carefully consider the safest pain medication, dosage, and route of administration for you.

When you go to get a painkiller, you probably don't think much about LAST. You're probably more worried about whether the injection will hurt or if you'll feel too numb. That's normal, because LAST is very rare. But remember, your doctor will take good care of you after giving you a painkiller. If you develop symptoms of LAST, they will act quickly.

Finally, take-home message:

If you have any questions, concerns, or doubts about your anesthetic, don't hesitate to ask your doctor. They are there to help you. Local Anesthetic Systemic Toxicity (LAST) is nothing to be afraid of, as it is very rare and has good treatments. The most important thing is to be aware of this and talk openly with your doctor. Then you can face any medical treatment with peace of mind.

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