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Basic Elements of General Anesthesia

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General anesthesia is used in surgeries to inhibit pain. This topic presents the basic elements of general anesthesia and its indications.

Medically reviewed by

Dr. Shivpal Saini

Published At April 24, 2023
Reviewed AtMay 12, 2023


General anesthesia is the medicine used in many surgeries to control the pain reflex of the patient. General anesthesia is of different types. There are six basic elements of general anesthesia—unconsciousness, amnesia (memory loss of specific events for a certain period), analgesia, muscle relaxation, lower motor response to stimulus, and reversibility, and all these are described below. This topic elaborates on general anesthesia, its elements, different types, indications, and side effects.

What Is General Anesthesia?

General anesthesia is a type of medicine used in surgery to make a patient unconscious and go to sleep while the surgery is performed. These medicines are given mainly by a particular doctor called an anesthesiologist. These are delivered either by injection or by inhaling some gas. While the patient is in sleep mode, the doctor inserts a tube into the neck of the patient to continue breathing as the patient is completely unconscious and disabled to continue the breathing process independently.

What Are the Basic Elements of General Anesthesia?

General anesthesia provides unconsciousness, making the patient forget about certain events, providing painless procedure, muscle relaxation, lower motor response to stimuli, and reversibility. These basic elements of general anesthesia are described below:

  • Unconsciousness - It is a type of state of coma in which a patient cannot act and react. The patient is unable to respond to any activity going around. The patient's central nervous system has been depressed and not working.

  • Amnesia - It is memory loss. The patient has forgotten their memory. It causes the patient not to form a memory of traumatic surgery. General anesthesia disrupts the memory parts of the brain. Sometimes, amnesia persists for about three months in the elderly and children undergoing general anesthesia.

  • Analgesia - It is the inability to feel pain. Analgesia occurs as the nervous system has been depressed. All the neurotransmission signals are not sent as it gets blocked. And thus, the patient cannot feel pain.

  • Muscle relaxation - The muscle gets relaxed. The muscle is free from any stress and anxiety with no pain. It induces better sleep.

  • Lower Motor Response to Stimuli - A reflex that comes automatically on stimulus action is a motor response. General anesthesia lowers its activity to react to stimulus so the surgery can be performed without patient interruption.

  • Reversibility - The activity like unconsciousness, amnesia, analgesia, lower motor reflex, and muscle relaxation generated by general anesthesia are all temporary. General anesthesia can reverse back in a few hours and make the patient's central nervous system work as before.

What Are the Different Types of General Anesthesia?

Two systems deliver general anesthesia. They are:

Inhalation Anesthetics - Inhalation anesthetics are delivered by inhaling the gasses. Inhalation anesthetics are the gasses or liquids the mask gives the respiratory system. Some of them are volatile (evaporate quickly) agents, and some are gasses.

  1. Volatile Anesthetics - These are the agents that are volatile liquids at room temperature, and on inhalation, they start vaporizing into gases. Some commonly used volatile anesthetics are Sevoflurane, Desflurane, and Isoflurane.

  2. Gas Anesthetics - These are gas forms of anesthetics stored in cylinders. A commonly used gas anesthetic is Nitrous oxide.

Injectable Anesthetics - Injectable anesthetics are delivered by injecting the medicine into the veins (intravenously). There are different types of injectable drugs. Some of them are:

  1. Inducing Agents (Sedatives) - They commonly use anesthetics with rapid onset and short duration of action. Some examples of it are Propofol, Etomidate, and Sodium thiopental.

  2. Benzodiazepines - They are slow-acting agents. Some examples of it are Diazepam, Lorazepam, and Midazolam.

  3. Dissociative Agents - They have a short duration of action with a wide safety margin. They are used in combination with sedatives. An example is Ketamine.

  4. Alpha-2 Receptor Agonist - These have sedative properties. An example is Dexmedetomidine.

  5. Muscle Relaxants - They are combined with other drugs to be devoid of analgesic and sedative effects. An example is Succinylcholine.

What Are the Indications of General Anesthesia?

Indications of general anesthesia are:

  • Surgeries that are not possible with the help of regional or local anesthesia.

  • Surgeries with more significant blood loss.

  • Uncooperative patients are sometimes made to go for general anesthesia.

  • If the patient ideally requests to go for general anesthesia.

What Are Contraindications to General Anesthesia?

Contraindications to general anesthesia are:

  • Patients with medical conditions can have difficulty in the airway. These cases require regional anesthesia to handle the problems related to airway maintenance during general anesthesia.

  • A patient with family conditions of malignant hyperthermia (high body temperature) and pseudocholinesterase (an enzyme used in the metabolism of anesthetic drugs) deficiency.

What Are the Side Effects of General Anesthesia?

Side effects of general anesthesia are:

  • Temporary confusion and memory loss are most common in elderly patients.

  • Dizziness.

  • Difficulty in passing urine.

  • Bruising and soreness on injection for injectable anesthetics.

  • Nausea and vomiting.

  • Shivering and feeling cold.

  • Sore throat due to a breathing tube inserted into the airway.

What Are the Risk Factors That Can Increase the Risk for the Patient Undergoing General Anesthesia?

Risk factors for general anesthesia are:

  • Obstructive sleep apnea.

  • Seizures.

  • Any kidney, heart, or lung diseases.

  • High blood pressure.

  • Alcohol abuse.

  • Smoking.

  • Any history of anesthesia reactions.

  • Drug allergy.

  • Diabetes (a metabolic condition causing elevated blood sugar levels).

  • Obesity.

What Is the Difference Between General Anesthesia and Sedation?

Sedation and general anesthesia are the same in both conditions; the patient goes to a state of unconsciousness, but differences do occur. Sedation makes the patient feel tired and develops a relaxed state of consciousness, and the patient's breathing process is completely maintained independently. Sedation recovery is faster. It is delivered by injection in veins (intravenously).

Whereas general anesthesia is the complete loss of consciousness, which impairs the breathing process of the patient, and requires a doctor to maintain it. General anesthesia takes more time than sedation to recover. It can be delivered either by injectable or inhalation method.


General anesthesia is a temporary and complete loss of consciousness to perform any surgery. General anesthesia's basic elements are unconsciousness, amnesia, analgesia, and reversibility, which is delivered by injection in the vein or by inhaling the gasses or volatile liquids. It has a few risk factors that can severely affect the patient's condition if general anesthesia is given. In addition, it aids the surgeon perform the surgery uninterrupted for a better outcome.

Dr. Shivpal Saini
Dr. Shivpal Saini

General Surgery


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