Free MAC Pharmacology & Physiology in Anesthesia Questions and Answers — Questions and Answers
Question 1: Which receptor type is primarily targeted by general anesthetics?
- NMDA receptors
- Alpha-adrenergic receptors
- GABA-A receptors (Correct answer)
- Dopamine receptors
Correct answer: GABA-A receptors
General anesthetics primarily exert their effects by enhancing the activity of GABA-A receptors in the central nervous system. These receptors are inhibitory, and their potentiation by anesthetics leads to increased chloride ion influx, hyperpolarizing neurons and reducing neuronal excitability. This mechanism contributes to the sedation, hypnosis, and anxiolysis characteristic of general anesthesia.
Question 2: What is the primary effect of opioids in anesthesia?
- Muscle relaxation
- Amnesia
- Analgesia (Correct answer)
- Immobility
Correct answer: Analgesia
Opioids are a class of drugs whose primary effect in anesthesia is analgesia, meaning pain relief. They achieve this by binding to specific opioid receptors in the central nervous system, modulating pain perception and response. This potent analgesic property is crucial for managing pain during surgical procedures and ensuring patient comfort.
Question 3: Which inhaled anesthetic has the fastest onset?
- Halothane
- Isoflurane
- Desflurane (Correct answer)
- Enflurane
Correct answer: Desflurane
Desflurane has the fastest onset among common inhaled anesthetics due to its very low blood-gas partition coefficient. This low solubility means that it is minimally absorbed into the blood and tissues, allowing it to rapidly reach the brain and exert its anesthetic effects. Consequently, patients achieve anesthesia quickly and also recover rapidly once administration is stopped.
Question 4: Which physiological parameter is most affected by propofol?
- Heart rate
- Blood pressure (Correct answer)
- Respiratory rate
- Body temperature
Correct answer: Blood pressure
Propofol is well-known for its significant dose-dependent cardiovascular depressant effects, with the most prominent being a reduction in blood pressure. This hypotensive effect results from decreased systemic vascular resistance and myocardial contractility. Therefore, blood pressure is a critical physiological parameter that must be closely monitored during propofol administration.
Question 5: Which local anesthetic is most cardiotoxic?
- Lidocaine
- Bupivacaine (Correct answer)
- Procaine
- Mepivacaine
Correct answer: Bupivacaine
Bupivacaine is recognized as the most cardiotoxic local anesthetic due to its strong binding to cardiac sodium channels and slow dissociation rate. This can lead to severe cardiac arrhythmias and myocardial depression, especially in cases of accidental intravascular injection. Its cardiotoxicity is a significant concern compared to other local anesthetics like lidocaine.
Question 6: What is the mechanism of action of succinylcholine?
- Non-depolarizing blockade
- Receptor antagonism
- Depolarizing blockade (Correct answer)
- Voltage-gated channel inhibition
Correct answer: Depolarizing blockade
Succinylcholine is a depolarizing neuromuscular blocker that acts as an acetylcholine receptor agonist at the neuromuscular junction. It binds to and activates nicotinic acetylcholine receptors, causing persistent depolarization of the motor endplate. This initial depolarization leads to transient muscle fasciculations, followed by sustained muscle relaxation and paralysis as the muscle becomes refractory to further stimulation.
Question 7: Which organ is primarily responsible for metabolizing most anesthetics?
- Kidneys
- Lungs
- Liver (Correct answer)
- Spleen
Correct answer: Liver
The liver is the primary organ responsible for metabolizing the vast majority of anesthetic drugs, both inhaled and intravenous. Hepatic enzymes, particularly the cytochrome P450 system, break down these compounds into inactive metabolites. These metabolites are then typically excreted from the body, often via the kidneys.
Question 8: How does ketamine differ from other induction agents?
- Depresses respiration
- Causes vasodilation
- Maintains airway reflexes (Correct answer)
- Induces paralysis
Correct answer: Maintains airway reflexes
Ketamine is unique among induction agents because it induces a state of 'dissociative anesthesia,' which often preserves pharyngeal and laryngeal reflexes. Unlike other anesthetics that depress these protective airway reflexes, ketamine's ability to maintain airway patency and spontaneous respiration can be a significant advantage, particularly in patients with difficult airways or those at risk of aspiration.
Question 9: Which electrolyte disturbance enhances the effect of non-depolarizing neuromuscular blockers?
- Hypernatremia
- Hyperkalemia
- Hypokalemia (Correct answer)
- Hypocalcemia
Correct answer: Hypokalemia
Hypokalemia, or low potassium levels, enhances the effect of non-depolarizing neuromuscular blockers. Potassium plays a crucial role in maintaining the resting membrane potential and excitability of muscle cells. Reduced extracellular potassium can hyperpolarize the muscle cell membrane, making it more resistant to depolarization and thus increasing the effectiveness and duration of action of these blocking agents.
Free MAC Pharmacology & Physiology in Anesthesia Questions and Answers
Which receptor type is primarily targeted by general anesthetics?