Ask Dr. Zhao: What’s the difference between general and local anesthesia?

By Pei-Shan Zhao

 

Anesthesia is necessary to block pain. As patients cannot experience pain during their operations and surgeons do not want patients moving about, anesthesia keeps the patients from feeling pain and rooted in one place.

General anesthesia allows the patient to “sleep” with the use of anesthesia, completely unaware of the surgery. Local anesthesia allows the patient to remain awake without feeling pain, which is the key difference between general and local anesthesia.

Technically, one is not asleep during anesthesia but in a state of unconsciousness. Unlike sleep, when one can be awakened, patients cannot be aroused when under general anesthesia. Patients can only be conscious once the doctor stops giving them anesthesia.

Image courtesy of Flickr. 圖片來自Flickr。

Image courtesy of Flickr. 

Some patients who undergo surgery with local anesthesia wonder why they fall asleep during the operation. That is because sedatives are administered to calm the patient’s nerves during surgery. However, there is no way for the surgeon to operate with sedatives alone. Local anesthesia is required so the patient does not feel pain. Therefore, the anesthesia these patients have is local anesthesia with sedation.

Local anesthesia is frequently chosen for small operations, such as excision of small lumps of the breast or for kidney failure patients who need hemodialysis to create an arteriovenous fistula, a passage connecting an artery to a vein, in their arms. If you can manage your nerves during an operation, you can tell your doctor you do not need sedatives.

 

What is the difference between local and neuraxial “waist-down” anesthesia?

Regional anesthesia includes neuraxial anesthesia, anesthesia administered inside the spinal column, and peripheral nerve blocks. Local anesthesia is injection of local anesthetic into the operation site, making that area numb. It is one of the peripheral nerve blocks. Therefore, local anesthesia and neuraxial “waist-down” anesthesia are part of regional anesthesia. Neuraxial anesthesia also includes spinal and epidural anesthesia for operations from the waist down. This stabilizes the patient during surgery and does not affect the patient’s breathing.

Operations above the belly button use different types of regional anesthesia. Peripheral nerve blocks are suited for hand or arm surgeries, allowing patients to breathe independently while they get a shot of anesthetic to the neck or armpit.

Some neck surgeries, such as a carotid endarterectomy to strip plaque from artery walls in the neck, can also use the same method of an anesthetic shot to the neck. However, a popular practice uses peripheral nerve blocks to block pain after an operation. For example, many shoulder surgeries use general anesthesia so the patient is unconscious. However, doctors recommend giving a local anesthetic shot in the patient’s neck before or after the operation to help ease the patient’s pain. Most operations in the chest and stomach area require general anesthesia.

During regional anesthesia, it is normal to feel touch and pressure. That is because pain and pressure are transmitted through different nerves — anesthesia primarily eases pain. Therefore, local anesthetics used in regional anesthesia will result in different levels of sensitivity for the patient because they affect nerves differently.

 

Pei-Shan Zhao is an attending anesthesiologist and director of the Asian Community Outreach Program in the department of anesthesiology, Tufts Medical Center. He is a graduate of Peking University’s School of Medicine, and trained at Peking University and Caritas St. Elizabeth’s Medical Center in Boston.

This post is also available in: Chinese

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