Intravenous Anesthetics

Question 1

What does repetitive administration of barbiturates result in?

Answer 1

It saturates the peripheral compartments, minimizing redistribution and making the duration of action more dependent on elimination. This is known as context sensitivity.

Question 2

How do barbiturates affect cerebral blood flow?

Answer 2

Barbiturates constrict the cerebral vasculature, leading to a decrease in cerebral blood flow, cerebral blood volume, and intracranial pressure.

Question 3

What is a respiratory risk associated with benzodiazepine induction?

Answer 3

Even small intravenous doses of diazepam and midazolam can result in respiratory arrest.

Question 4

How does ketamine differ from other anesthetic agents in terms of cardiovascular effects?

Answer 4

Ketamine increases arterial blood pressure, heart rate, and cardiac output, particularly after rapid bolus injections.

Question 5

What effect does etomidate have on hormone synthesis?

Answer 5

Induction doses of etomidate transiently inhibit enzymes involved in cortisol and aldosterone synthesis.

Question 6

What precaution must be taken when handling propofol?

Answer 6

Propofol formulations can support bacterial growth, so sterile technique must be followed, and it should be administered within 6 hours of opening the ampule.

Question 7

What are the primary mechanisms of action of barbiturates?

Answer 7

Barbiturates depress the reticular activating system in the brainstem and potentiate the action of GABA by increasing the duration of chloride ion channel openings.

Question 8

What determines the hypnotic potency and anticonvulsant activity of barbiturates?

Answer 8

Substitution at carbon C5 determines potency, with long-branched chains conveying more potency and phenyl groups contributing to anticonvulsant activity.

Question 9

What is the effect of replacing oxygen at C2 with a sulfur atom in barbiturates?

Answer 9

It increases lipid solubility, leading to greater potency, more rapid onset, and shorter duration of action, as seen in thiopental and thiamylal.

Question 10

How does the distribution of thiopental affect its duration of action?

Answer 10

The duration of action is determined by redistribution to peripheral compartments, which lowers plasma and brain concentration within 20-30 minutes.

Question 11

How does the pharmacokinetic profile of methohexital differ from thiopental?

Answer 11

Methohexital is cleared more rapidly by the liver than thiopental, leading to faster recovery of psychomotor function after a sleep dose.

Question 12

How does barbiturate biotransformation occur?

Answer 12

Barbiturates are principally biotransformed via hepatic oxidation to inactive water-soluble metabolites.

Question 13

What are the cardiovascular effects of barbiturates?

Answer 13

Barbiturates cause a decrease in blood pressure and an increase in heart rate, with hemodynamic responses varying based on the rate of administration and other factors.

Question 14

What respiratory effects do barbiturates have?

Answer 14

Barbiturates depress the medullary ventilatory center, leading to decreased ventilatory response to hypercapnia and hypoxia, and often cause apnea after induction.

Question 15

How do barbiturates affect cerebral oxygen consumption?

Answer 15

Barbiturates decrease cerebral oxygen consumption by up to 50%, without negatively impacting cerebral blood flow.

Question 16

What is the effect of barbiturates on renal function?

Answer 16

Barbiturates reduce renal blood flow and glomerular filtration rate in proportion to the fall in blood pressure.

Question 17

What is the immunological effect of sulfur-containing thiobarbiturates?

Answer 17

Sulfur-containing thiobarbiturates can evoke mast cell histamine release in vitro, which may affect asthmatic or atopic patients.

Question 18

How do benzodiazepines increase chloride ion channel openings?

Answer 18

Benzodiazepines bind to a different site on the GABA-A receptor, increasing the frequency of chloride ion channel openings.

Question 19

What effect does midazolam’s imidazole ring have on its solubility?

Answer 19

The imidazole ring of midazolam increases its water solubility at low pH, facilitating its absorption.

Question 20

What is the effect of diazepam and lorazepam on cardiovascular function?

Answer 20

They display minimal cardiovascular depressant effects, but can decrease arterial blood pressure, cardiac output, and peripheral vascular resistance slightly.

Question 21

How do benzodiazepines affect the ventilatory response to CO2?

Answer 21

Benzodiazepines depress the ventilatory response to CO2, with a risk of respiratory arrest if administered intravenously or in combination with other depressants.

Question 22

How do benzodiazepines affect cerebral blood flow and intracranial pressure?

Answer 22

Benzodiazepines reduce cerebral oxygen consumption, cerebral blood flow, and intracranial pressure, but not to the extent of barbiturates.

Question 23

What is the clinical effect of benzodiazepines on muscle relaxation?

Answer 23

Benzodiazepines have mild muscle-relaxing properties, mediated at the spinal cord level, not at the neuromuscular junction.

Question 24

What drug interactions should be considered with benzodiazepines?

Answer 24

Cimetidine, erythromycin, and heparin can alter the metabolism of benzodiazepines, leading to prolonged effects. They also potentiate the effects of other CNS depressants.

Question 25

How do benzodiazepines interact with opioids?

Answer 25

The combination of opioids and benzodiazepines significantly reduces arterial blood pressure and peripheral vascular resistance.

Question 26

What is the effect of benzodiazepines on the minimum alveolar concentration (MAC) of volatile anesthetics?

Answer 26

Benzodiazepines reduce the MAC of volatile anesthetics by as much as 30%.

Question 27

What is the primary mechanism of action of ketamine?

Answer 27

Ketamine is an NMDA receptor antagonist, which inhibits excitatory neurotransmitter effects in selected areas of the brain and causes dissociation between the thalamus and limbic cortex.

Question 28

What kind of anesthesia does ketamine produce?

Answer 28

Ketamine produces dissociative anesthesia, where the patient may appear conscious but is unable to process or respond to sensory input.

Question 29

What structural similarity does ketamine share with phencyclidine?

Answer 29

Ketamine is a structural analogue of phencyclidine, retaining many of its psychotomimetic effects.

Question 30

How does ketamine affect the cardiovascular system?

Answer 30

Ketamine increases arterial blood pressure, heart rate, and cardiac output due to central sympathetic stimulation and inhibition of norepinephrine reuptake.

Question 31

What is the effect of ketamine on the respiratory system?

Answer 31

Ketamine minimally affects ventilatory drive but can cause apnea with rapid intravenous bolus or when combined with opioids. It is also a potent bronchodilator.

Question 32

What is ketamine’s effect on cerebral circulation?

Answer 32

Ketamine increases cerebral blood flow, oxygen consumption, and intracranial pressure, though when combined with a benzodiazepine, it may not increase intracranial pressure.

Question 33

How is ketamine metabolized?

Answer 33

Ketamine is biotransformed in the liver to several metabolites, including norketamine, which retains anesthetic activity.

Question 34

How does ketamine affect patients with coronary artery disease or uncontrolled hypertension?

Answer 34

Large bolus injections of ketamine should be administered cautiously in these patients due to the risk of increased myocardial work and blood pressure.

Question 35

What are the psychotomimetic effects of ketamine?

Answer 35

Ketamine can cause hallucinogenic effects, though they are often minimized in clinical practice with the use of sedatives like midazolam.

Question 36

What are the major side effects of ketamine at subanesthetic doses?

Answer 36

At subanesthetic doses, ketamine can cause hallucinogenic effects, though these are usually avoided with premedication.

Question 37

What interactions does ketamine have with other anesthetic agents?

Answer 37

Ketamine has a synergistic interaction with volatile anesthetics and an additive effect with propofol, benzodiazepines, and other GABA-receptor agents.

Question 38

What effect does ketamine have on sympathetic stimulation?

Answer 38

Ketamine’s central sympathetic stimulation increases heart rate, blood pressure, and cardiac output.

Question 39

How does ketamine affect airway reflexes?

Answer 39

Ketamine tends to preserve upper airway reflexes but may cause partial airway obstruction, especially in patients at risk for aspiration pneumonia.

Question 40

What is the effect of ketamine on cerebral oxygen consumption and blood flow?

Answer 40

Ketamine increases both cerebral oxygen consumption and cerebral blood flow, although this may not be detrimental when combined with controlled ventilation.

Question 41

What is the cardiovascular effect of large doses of ketamine?

Answer 41

Large doses of ketamine can unmask direct myocardial depressant effects, especially in cases of sympathetic blockade or exhaustion of catecholamine stores.

Question 42

What is the role of the S(+) stereoisomer of ketamine?

Answer 42

The S(+) stereoisomer has greater potency and a stronger affinity for NMDA receptors, offering increased anesthetic potency and decreased psychotomimetic side effects.

Question 43

What is the pharmacokinetics of ketamine in terms of absorption?

Answer 43

Ketamine can be administered orally, nasally, rectally, subcutaneously, and epidurally, but is commonly given intravenously or intramuscularly for rapid onset.

Question 44

How does ketamine distribute in the body?

Answer 44

Ketamine is highly lipid-soluble and undergoes rapid brain uptake and redistribution, with a distribution half-life of 10–15 minutes.

Question 45

What is the excretion route of ketamine’s metabolites?

Answer 45

End products of ketamine biotransformation are primarily excreted in the urine.

Question 46

What are the effects of ketamine on ventilation?

Answer 46

Ketamine typically does not significantly affect ventilatory drive, but rapid bolus administration or combination with opioids may result in apnea.

Question 47

How does ketamine interact with α-adrenergic and β-adrenergic antagonists?

Answer 47

These antagonists unmask ketamine’s direct myocardial depressant effects, which are usually outweighed by its sympathetic stimulation.

Question 48

What is the use of ketamine for deep sedation in clinical practice?

Answer 48

Ketamine is often combined with other agents like propofol or midazolam for deep conscious sedation during procedures like nerve blocks and endoscopy.

Question 49

What is the role of ketamine in trauma or hypovolemia?

Answer 49

Ketamine is useful in trauma or hypovolemic patients due to its ability to maintain sympathetic stimulation and increase blood pressure, heart rate, and cardiac output.

Question 50

What are the major side effects associated with ketamine use?

Answer 50

The major side effects of ketamine include increased intracranial pressure, psychotomimetic effects, and possible airway obstruction in some patients.