The accident happened after only 1 ml of local anesthetic was injected. Pay attention to this detail!

In clinical practice, we know that a few milliliters of local anesthetics will not cause any problems. For example, when treating premature ventricular beats, several milliliters of lidocaine may be injected into the blood vessels.

However, the case we are going to introduce to you today is very special: in this case, the accident occurred after only more than 1 ml of local anesthetic was injected.

Obviously, few people would believe such a thing. However, this incident really happened.

Events

The patient was undergoing thyroid surgery. According to the anesthesia plan, cervical plexus block plus general anesthesia was decided.

Before anesthesia, the patient is given certain analgesics and sedatives to reduce the pain of cervical plexus block. After that, the cervical plexus nerve block is started.

Since the operation was mainly performed on the right lobe of the thyroid gland, the anesthesiologist planned to perform a cervical plexus nerve block for the patient, including the right deep plexus and superficial plexus, and the left superficial plexus.

After routine disinfection and draping, a 6G needle was used to puncture the right C4 transverse process. The needle was inserted vertically. After the needle tip touched the bone, blood was seen during aspiration. The needle was withdrawn a little, and after no blood or cerebrospinal fluid was found, 0.375% ropivacaine was slowly injected. The patient immediately became agitated, had rapid breathing, and soon developed tremors in the limbs and facial muscles, followed by shallow and weak breathing.

After discovering the abnormal situation, the anesthesiologist immediately stopped injecting the drug. At this time, only 2 ml of the drug was injected. He immediately gave the patient oxygen and called his colleagues to prepare for rescue.

After mask pressurized oxygen, artificial respiration, and intravenous injection of 5 mg of diazepam, the convulsion stopped, blood pressure, pulse, and pulse oxygen saturation returned to normal, spontaneous breathing stabilized after 10 minutes, and the patient was fully awake after 30 minutes.

After highly suspecting local anesthetic poisoning, it was decided to abandon the cervical plexus block and directly perform the operation under general anesthesia. There were no abnormalities during the general anesthesia process, and the patient successfully completed the operation.

Some people may ask: 1 ml is poisonous? Is that impossible?

In fact, when the anesthesiologist pushes 2 ml, only a little more than 1 ml of local anesthetic enters the blood vessels, or it may be only 1 ml.

So, can local anesthetic poisoning occur with 1 ml?

Yes.

If the local anesthetic is injected into other parts of the body, it is difficult to cause local anesthetic poisoning with only 1 ml of local anesthetic. However, the injection site in this case is very special - near the vertebral artery.

The vertebral artery directly supplies blood to the nerve center. A small amount of local anesthetic enters the cerebral circulation through the vertebral artery, and can reach a toxic dose in the central nervous system. Based on the relationship between cerebral circulation, vertebral-base circulation and cardiac output, as well as the pharmacology and toxicology of local anesthetics, some people have calculated the toxic dose of local anesthetics that accidentally enter the vertebral artery. The toxic dose is 1.5% of the toxic dose that accidentally enters the vein.

Only 1.5% of the dose is injected into the vein, which is a very small dose! In addition, since the vertebral artery or internal carotid artery is very close to the brain tissue, clinical effects and clinical manifestations can occur within a few seconds, which can also explain why local anesthetic poisoning occurs when only a small amount of local anesthetic is injected.

Therefore, we must be careful to avoid intravascular injection, especially injection into the arteries that supply blood to the brain.

Someone raised the question: Is it possible to add some intravascular injectable markers to the local anesthetic?

The answer is no.

Adding 10-15 μg of epinephrine to local anesthetics, if injected into blood vessels, can increase the heart rate by ≥10 beats/min or increase systolic blood pressure by ≥15 mmHg. However, there is a key problem: local anesthetics injected into the vertebral artery or internal carotid artery go directly to the brain, and the first symptoms are not cardiac symptoms.

Another point of knowledge: the changes may not be obvious when using beta-blockers, during the active phase of labor, at advanced age, or under general anesthesia.

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