Anesthesia and Analgesia Terminology

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Questions and Answers

What is the primary function of general anesthetics?

To prevent pain sensation

To produce loss of consciousness and amnesia

To block conduction of nerve impulses in peripheral nerves or spinal cord

To block cortical neuronal activity underlying consciousness and all sensation (correct)

What is the main difference between ester-type and amide-type local anesthetics?

Ester-type is more potent than amide-type

Ester-type is used for general anesthesia, while amide-type is used for local anesthesia

Ester-type has a longer duration of action than amide-type

Ester-type gets metabolized to PABA derivatives, while amide-type gets metabolized by CYP450 enzymes (correct)

What is the purpose of adding epinephrine to an anesthetic?

To produce vasoconstriction, slowing the anesthetic's rate of absorption (correct)

To increase the anesthetic's potency

To decrease the anesthetic's duration of action

To increase the anesthetic's duration of action

Which type of local anesthetics is more likely to cause hypersensitivity reactions?

Ester-type Signup and view all the answers

What is the primary factor that determines the rate at which the anesthetic's partial pressure in blood increases?

Blood:gas partition coefficient Signup and view all the answers

Which stage of anesthesia is characterized by suppression of reticular-activating system, loss of consciousness, and inhibition of spinal reflexes?

Stage 3 Signup and view all the answers

Which of the following anesthetics does not produce amnesia or complete loss of consciousness?

Fentanyl Signup and view all the answers

What is the primary advantage of using Fentanyl in cardiac surgery?

It does not cause cardiovascular toxicity Signup and view all the answers

What is the characteristic of Ketamine that makes it useful in pediatric anesthesia?

Children are less likely to experience adverse effects during recovery Signup and view all the answers

What is the primary mechanism by which Thiopental and Propofol cause unconsciousness?

Prevention of neurons in spinal cord from firing Signup and view all the answers

What is the primary disadvantage of using Ketamine?

It tends to cause unpleasant effects during recovery Signup and view all the answers

What is the characteristic of Propofol that makes it preferred over Thiopental?

It is rapidly metabolized and eliminated Signup and view all the answers

What is the primary mechanism by which Fentanyl produces analgesia?

It acts as a strong opioid agonist Signup and view all the answers

What is the primary effect of Thiopental and Propofol on cardiac and respiratory function?

They depress cardiac and respiratory function Signup and view all the answers

Study Notes

Anesthetics

Anesthesia: loss of all sensation
Analgesia: loss of pain sensation
Local anesthetics: block conduction of nerve impulses in peripheral nerves or spinal cord
General anesthetics: block cortical neuronal activity underlying consciousness and all sensation

General Anesthesia

Used to prevent consciousness during major surgical procedures
Produces loss of consciousness and amnesia (patient doesn't recall the surgical procedure)

Drug Properties

Local anesthetics divided into two main groups: ester-type (e.g., cocaine, benzocaine) and amide-type (e.g., lidocaine, bupivacaine)
Duration of action: short, medium, or long, determined by rate of diffusion and absorption away from site of administration
Factors influencing duration: chemical properties, pH, and blood flow
Epinephrine can be added to prolong an anesthetic's duration of action by producing vasoconstriction

Metabolism

Ester-type local anesthetics metabolized to PABA derivatives
Amide-type local anesthetics metabolized by CYP450 enzymes
Metabolites excreted in urine in both cases

Allergic Reactions

Reactions are fairly common, especially in those who receive repeated administration of topical anesthetics
Ester-type anesthetics cause hypersensitivity reactions more frequently than amide-type anesthetics

Nerve Block Anesthesia

Local anesthetic injected into or adjacent to a peripheral nerve or nerve plexus
Examples: radial nerve block, infraorbital block, brachial plexus and cervical plexus blockade

Spinal Intrathecal Anesthesia

Used to block somatosensory and motor fibers during procedures like surgery on lower limb or pelvic structures
Anesthetic injected into subarachnoid intrathecal space below level at which spinal cord terminates
Spread of anesthetic controlled by horizontal tilt of patient and specific gravity of local anesthetic solution
Risks: HA associated with CSF leakage from LP, respiratory depression if anesthetic ascends too high, and small risk of meningitis and infection

Lidocaine

Produces local anesthesia after topical or parenteral administration
Most widely-used local anesthetic
Available in many forms (e.g., topical solutions/ointment, oral sprays, viscous gels, and parenteral formulations)
Part of EMLA (along with prilocaine), can anesthetize intact skin to a depth of 5 mm
Used in kids for local anesthesia before venipuncture, IV placement, or circumcision

Induction Rate

Three major factors determine induction rate of anesthesia: alveolar partial pressure of the anesthetic in inspired air, ventilation rate, and rate of increase in anesthetic partial pressure in blood
Blood:gas partition coefficient influences induction rate

Pharmacologic Effects

Four stages of anesthesia induction:
- Stage 1: analgesia and conscious sedation
- Stage 2: paradoxical excitation (not usually observed with modern anesthesia)
- Stage 3: goal of surgical anesthesia, LOC, and inhibition of spinal reflexes
- Stage 4: can cause cardiovascular collapse, depression of respiratory and vasomotor nuclei in brainstem

Thiopental and Propofol

Both drugs have rapid onset of action, causing unconsciousness in about 20 seconds
Duration of action is short (5-10 minutes) due to redistribution from brain to peripheral tissues
Propofol is rapidly metabolized and eliminated, causing little hangover
Thiopental accumulates in fats and muscles, causing slow elimination and some hangover
Both drugs can depress cardiac and respiratory function

Fentanyl

Strong opioid agonist used to treat moderate-to-severe pain
Given IV or epidurally in combo with other drugs for surgical or obstetric analgesia and anesthesia
Used to provide anesthesia during cardiac surgery (e.g., CABG) because it doesn't cause CV toxicity
Doesn't produce amnesia or complete LOC, so usually combined with a benzo (e.g., midazolam) to produce amnesia and increased sedation

Ketamine

Produces dissociative anesthesia when given IV
Characterized by analgesia, reduced sensory perception, immobility, and amnesia
Increases blood pressure but has little effect on respiration
Major drawback: tendency to cause unpleasant effects during recovery like delirium, hallucinations, irrational behavior
Often used in kids because they are less likely to experience these adverse effects (usually combined with a benzo)

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Description

Learn the key terms related to anesthesia, including general and local anesthetics, analgesia, and their effects on the body.