Pharmacology Lecture 9: Inhalation Anesthesia

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Questions and Answers

What is the primary use of inhalation anesthetics?

To cause skeletal muscle relaxation

To reverse anesthesia

To induce anesthesia

To maintain anesthesia (correct)

What determines the potency of an inhalation anesthetic?

Inspired anesthetic concentration

Lipid solubility (correct)

MAC value

Blood solubility

Which of the following is an inorganic agent used in inhalation anesthesia?

Halothane

Isoflurane

Desflurane

Nitrous oxide (correct)

What is the MAC of nitrous oxide?

100 Signup and view all the answers

Which of the following factors affects the transfer of general anesthetics from the lung to the blood and then to the brain?

All of the above Signup and view all the answers

How does the rate of induction of anesthesia change with an increase in anesthetic concentration in the inspired air?

It increases Signup and view all the answers

Which anesthetic is 2 times more potent than enflurane?

Halothane Signup and view all the answers

What determines the speed of induction of anesthesia?

Blood solubility Signup and view all the answers

What is the key factor that determines the rate of absorption of inhalation anesthetics from the lungs?

Blood/gas partition coefficient Signup and view all the answers

What is a common adverse effect of volatile anesthetics?

Respiratory depression Signup and view all the answers

What is a unique characteristic of isoflurane?

It is minimally metabolized and eliminated unchanged in the expired air Signup and view all the answers

What is the Minimum Alveolar Concentration (MAC) of isoflurane?

1.4% Signup and view all the answers

What is a potential complication of using isoflurane?

Malignant hyperthermia Signup and view all the answers

What is the MAC of sevoflurane?

2% Signup and view all the answers

What happens to most of the sevoflurane administered to a patient?

It is eliminated unchanged in the expired air Signup and view all the answers

What is a common approach to mitigating the adverse effects of volatile anesthetics?

Using them in combination with intravenous agents Signup and view all the answers

What is a characteristic of etomidate's pharmacological action?

It has a similar action to barbiturates. Signup and view all the answers

What is a benefit of propofol anesthesia?

It has rapid recovery and antiemetic properties. Signup and view all the answers

What is a unique feature of ketamine anesthesia?

It is used in trauma cases where cardiovascular depression is necessary. Signup and view all the answers

What is the term used to describe ketamine anesthesia?

Dissociative anesthesia. Signup and view all the answers

What is the elimination half-life of etomidate?

2.9 hrs Signup and view all the answers

What is a characteristic of propofol?

It is very lipid soluble. Signup and view all the answers

What is the onset of action of propofol?

50 seconds Signup and view all the answers

What type of anesthesia are drugs that are inhaled as gases or vapors?

Inhalation anesthesia Signup and view all the answers

What is the typical effect of propofol injection in inducing general anesthesia in adults?

Unconsciousness within 30-40 seconds Signup and view all the answers

What is the stage of anesthesia characterized by excitement, shouting, and violent behavior?

Stage II Signup and view all the answers

What is the purpose of co-administering an IV skeletal muscle relaxant during general anesthesia?

To facilitate intubation and muscle relaxation Signup and view all the answers

What is the typical method of inducing general anesthesia in children without IV access?

Inhalation induction with non-pungent agents Signup and view all the answers

During which stage of anesthesia can surgery proceed?

Stage III Signup and view all the answers

What is monitored continuously during the maintenance phase of general anesthesia?

Both vital signs and response to stimuli Signup and view all the answers

What is a characteristic of Stage IV anesthesia?

Cessation of breathing and circulatory failure Signup and view all the answers

What is the purpose of administering volatile anesthetics during the maintenance phase?

To control the depth of anesthesia Signup and view all the answers

What is the primary benefit of general anesthesia in patients undergoing surgical procedures?

Sedation and reduction of anxiety Signup and view all the answers

Why are opioids often used in combination with inhalation agents during general anesthesia?

Because inhalation agents are not good analgesics Signup and view all the answers

What happens to reflexes during Stage II anesthesia?

They are enhanced Signup and view all the answers

What can be used to avoid Stage II anesthesia?

I.V anesthetics Signup and view all the answers

During the maintenance phase, what is the goal of monitoring the patient's vital signs and response to stimuli?

To carefully balance the amount of drug inhaled and/or infused with the depth of anesthesia Signup and view all the answers

What is the primary purpose of using IV infusions of various drugs during the maintenance phase?

To supplement inhalation agents Signup and view all the answers

What is the characteristic of breathing during Stage III anesthesia?

Regular Signup and view all the answers

What is the final benefit of general anesthesia mentioned in the content?

Suppression of undesirable reflexes Signup and view all the answers

Study Notes

Inhalation Anesthesia

Inhalation anesthetics are used to maintain anesthesia after administration of I.V anesthetics
Induction and recovery depend on potency and efficacy, which depend on lipid solubility

Types of Inhalation Anesthetics

Inorganic agent: nitrous oxide (N2O)
Non-flammable halogenated hydrocarbons: halothane (Fluothane®), isoflurane (Forane®), desflurane (Suprane®), sevoflurane (Ultane®)
Ethers: isoflurane (Forane®), desflurane (Suprane®), sevoflurane (Ultane®)

Minimum Alveolar Concentration (MAC)

MAC is the concentration of an anesthetic required to eliminate movement in 50% of patients when exposed to skin incision
Anesthetic agents with higher MAC have lower potency (e.g., N2O has a MAC of 100)
Examples of MAC values: halothane (0.75), ether (2), enflurane (1.5)

Factors Affecting Transfer of GA from Lung to Blood then Brain

Solubility in blood (inverse relationship with speed of induction)
Anesthetic concentration in inspired air (increased concentration increases rate of induction)
Pulmonary ventilation (rate of induction directly depends on rate and depth of ventilation)

Intravenous Anesthetics

Etomidate (Amidate®): short elimination half-life (2.9 hrs), has a greater margin of safety due to limited effects on CVS and respiratory system
Propofol (Diprivan®): short recovery time, associated with less nausea and vomiting, rapid onset of action (50 sec), and recovery time (4-8 min)
Ketamine: can be given I.V or I.M, used in trauma cases and painful procedures in children, produces dissociative anesthesia

Stages of Anesthesia (Depth)

Stage II (delirium): from loss of consciousness to beginning of surgical anesthesia, characterized by excitement, shouting, crying, and violent behavior
Stage III (surgical anesthesia): patient is unconscious, surgery may proceed during this stage, characterized by regular breathing and muscle relaxation
Stage IV (medullary paralysis): seen only with overdose, characterized by cessation of breathing, circulatory failure, and death

General Anesthesia

Provides five important benefits: sedation and reduction of anxiety, lack of awareness and amnesia, skeletal muscle relaxation, suppression of undesirable reflexes, and pulmonary blood flow
Can be induced with IV anesthetic like propofol, followed by additional inhalation and/or IV drugs to produce the desired depth of surgical anesthesia
In children, inhalation induction is used with non-pungent agents like halothane or sevoflurane to induce general anesthesia

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Description

This quiz covers the concepts of inhalation anesthesia, its administration, and effects on consciousness and skeletal muscle relaxation.