Types of Anesthesia - General, Local, Spinal and Epidural

Anesthesia is a medical procedure that aims to temporarily block the brain's ability to recognize a painful stimulus. Thanks to anesthesia, doctors are able to perform surgeries and other invasive procedures without the patient feeling pain.

In this text we will briefly explain the most common types of anesthesia in medical practice, including general, epidural, spinal and local anesthesia.

Local and general anesthesia
Local and general anesthesia

Feeling of pain

To understand how anesthesia works, a quick explanation of what pain is is worth.

Pain is one of the most important defense mechanisms of our body, being activated every time a tissue of ours is suffering some type of stress or injury.

Initially, it may seem strange to think that a mechanism that serves to protect us causes a sensation as bad as pain. But, think about it, if you touch a very hot surface, your brain needs to warn you to remove your hand as soon as possible before you get serious burns. The best way for you to respond immediately, without thinking or questioning, is to make him feel that the action of touching the heat is extremely uncomfortable. With pain, you will not only remove your hand as fast as you can, you will not want to put it back in any way.

To be able to feel pain, there must be receptors to identify lesions of the tissues and sensory nerves specialized in carrying the sensation of pain. Our skin, for example, is widely innervated by sensory nerves capable of recognizing minimal traumatic events. When we undergo a cut, a burn, a sting or any other injury to the skin tissue, these nerves are activated, rapidly sending electrical signals towards the spinal cord, which in turn transports them to the brain, where the sensation of pain is recognized.

Therefore, if we want to block the sensation of pain, we can act in three points:
  • 1. At the exact location where the injury is occurring, by blocking the pain receptors present on the skin.
  • 2. In the spinal cord, blocking a painful signal coming from a peripheral nerve, preventing it from continuing its path and reaching the brain.
  • 3. In the brain, preventing it from recognizing the painful signs that come to you.

These three ways of acting on pain are the basic mechanisms of local, regional, and general anesthesia, respectively.

Objectives of anesthesia

The main goal of any of the 3 modes of anesthesia is to block the pain sensation.

In simple procedures, in which only local anesthesia is required, the sole purpose of the procedure is to cut the pain. However, in cases of surgery, especially large ones, it is not enough to just remove the pain. In these, the anesthetic procedure also has other functions, such as blocking the patient's muscles, preventing the patient from moving during surgery, and causing amnesia, causing the patient to forget most of the events during the surgery, even if he remain awake during the surgical procedure.

As already mentioned, there are basically 3 types of anesthesia: general, regional and local. Let's talk briefly about each one.

General anesthesia

General anesthesia is the anesthetic modality indicated for the most complex and large surgeries. We indicate general anesthesia when the surgical procedure is very complex, and it is not feasible to anesthetize only one region of the body. It is important to note that the type of anesthesia indicated for skin cuts is completely different from the anesthesia that needs to be done when cutting a part of the intestine or removing an organ from the abdomen. In extensive surgeries it is not possible to block different layers and tissues of the organisms only with local anesthetics.

In general anesthesia, the patient becomes unconscious, unable to move, and usually intubated and coupled to an artificial respirator. One reason the patient does not feel is because he or she is deeply sedated, as if the brain has been partially "turned off".

There is a myth that general anesthesia is a dangerous anesthetic procedure. Is not true. Currently, general anesthesia is a fairly safe procedure. In most cases, when the patient undergoing extensive surgery has complications, the reason is not general anesthesia. Complications are usually derived from serious illnesses that the patient already had, such as advanced cardiac, renal, hepatic or pulmonary problems, or complications of surgery, such as bleeding or injury / failure of vital organs.

In healthy patients, the complication rate of general anesthesia is only 1.4 per 1 million surgeries. Therefore, problems with general anesthesia are similar to plane crashes: they are rare but frightening because when they occur, there is intense exposure in the media, leading to the false impression that they are frequent.

Regional anesthesia

Regional anesthesia is an anesthetic procedure used in simpler surgeries where the patient can remain awake. This type of anesthesia blocks pain in only a certain region of the body, such as an arm, a leg, or the entire lower body, below the abdomen.

The 2 types of regional anesthesia most used are:
  • Spinal anesthesia
  • Epidural anesthesia

A. Spinal anesthesia

To perform spinal anesthesia, a small gauge needle is inserted into the back, so as to reach the subarachnoid space, inside the spinal column. Then, an anesthetic is injected into the spinal fluid, producing temporary numbness and muscle relaxation.

The presence of the anesthetic within the spinal column blocks the nerves that pass through the lumbar spine, causing painful stimuli from the lower limbs and abdomen to fail to reach the brain.

Spinal anesthesia is widely used for orthopedic lower limb procedures and for cesarean sections.

B. Epidural anesthesia

Epidural anesthesia is very similar to spinal anesthesia, but there are some differences:
  • 1. In epidural anesthesia, the anesthetic is injected into the epidural region, which is located around the spinal canal, and not properly inside, as in the case of spinal anesthesia.
  • 2. In epidural anesthesia, the anesthetic is injected by a catheter, which is implanted in the epidural space. While in the spinal anesthesia the anesthetic is administered by a needle only once, in the epidural the anesthetic is being administered constantly through the catheter.
  • 3. Epidural anesthesia may continue to be administered postoperatively to control pain in the first hours after surgery. Just keep the infusion of analgesics through the catheter.
  • 4. The amount of anesthetics administered is much lower in the spinal cord.

Epidural anesthesia is commonly used during normal delivery.

The most common complication of spinal and epidural anesthesia is headache, which occurs when there is extravasation of liquor through the hole made by the needle in the spinal canal. This loss of fluid causes a reduction in the pressure of the cerebrospinal fluid around the central nervous system, which is the cause of the headache.

In the coming weeks we will write an article about anesthesia during delivery, where we will discuss spinal and epidural anesthesia in more detail.

Local anesthesia

Local anesthesia is the most common anesthetic procedure and is used to block pain in small areas of the body, usually on the skin. Unlike general and regional anesthesia, which must be administered by an anesthesiologist, local anesthesia is used by almost all specialties.

Local anesthesia is usually done by injecting lidocaine into the skin and subcutaneous tissues. It serves to block pain in a variety of medical procedures, such as biopsies, deep vein punctures, skin sutures, lumbar puncture, puncture of ascitic fluid or pleural effusion, etc.

Local anesthesia can also be done by gel or spray, as in the case of digestive endoscopies, where the doctor applies a spray with local anesthetic to the pharynx in order to reduce the discomfort caused by the passage of the endoscope.

Local anesthesia works by blocking the receptors for skin pain and the more superficial nerves, preventing them from sending painful signals to the brain.
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