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ABA Anesthesiology study materials
ABA Anesthesiology study resources

ABA Anesthesiology practice questions

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Question 1Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

The minimum alveolar concentration (MAC) of an inhaled anesthetic is best defined as the alveolar concentration at one atmosphere that:

  1. blocks the adrenergic response to laryngoscopy in 50% of patients
  2. prevents explicit recall of intraoperative events in 99% of patients
  3. produces loss of consciousness in 95% of an unselected surgical population
  4. abolishes movement in response to a noxious stimulus in 50% of subjects Correct answer.

Explanation

MAC is defined by a quantal endpoint: immobility in response to a standardized noxious stimulus in 50% of subjects at one atmosphere. Other endpoints, such as suppression of autonomic responses or prevention of awareness, occur at different multiples of MAC and have their own labels. MAC therefore describes potency for immobility, not hypnosis or amnesia.

Question 2Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Which change shifts the oxyhemoglobin dissociation curve to the right?

  1. A fall in core body temperature during cardiopulmonary bypass
  2. An increase in blood pH from hyperventilation
  3. An increase in arterial carbon dioxide tension Correct answer.
  4. A decrease in erythrocyte 2,3-diphosphoglycerate content

Explanation

A rightward shift means hemoglobin releases oxygen more readily at any given partial pressure, so P50 rises. Carbon dioxide lowers hemoglobin affinity through the Bohr effect, and acidosis, hyperthermia, and increased 2,3-diphosphoglycerate do the same. Hyperventilation produces the opposite shift by raising pH.

Question 3Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Local anesthetics block nerve conduction primarily by:

  1. binding the inner pore of voltage-gated sodium channels Correct answer.
  2. activating potassium channels in the axon membrane
  3. enhancing GABA-A receptor chloride currents
  4. inhibiting acetylcholinesterase at the neuromuscular junction

Explanation

Local anesthetics reach the cytoplasmic side of the axon and bind the inner vestibule of voltage-gated sodium channels, stabilizing the inactivated state. This reduces the inward sodium current needed to depolarize the membrane to threshold and prevents propagation of the action potential. Small unmyelinated fibers are blocked before large myelinated fibers because they require fewer nodes to be blocked.

Question 4Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Functional residual capacity is the sum of:

  1. expiratory reserve volume and residual volume Correct answer.
  2. inspiratory reserve volume together with tidal volume
  3. tidal volume and inspiratory capacity
  4. vital capacity and residual volume

Explanation

Functional residual capacity is the volume of gas remaining in the lungs at the end of a normal passive expiration. It therefore consists of the expiratory reserve volume plus the residual volume, which cannot be exhaled. It is the main oxygen reservoir during apnea and is reduced by obesity, supine position, and general anesthesia.

Question 5Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Propofol produces hypnosis predominantly through:

  1. blockade of H1 histamine receptors
  2. activation of alpha-2 adrenergic receptors
  3. positive modulation of GABA-A receptors Correct answer.
  4. antagonism at NMDA receptors

Explanation

Propofol binds a site on the GABA-A receptor and enhances chloride conductance, hyperpolarizing neurons and depressing cortical activity. This is the same broad mechanism shared with barbiturates and volatile anesthetics, although the binding sites differ. Its rapid offset reflects rapid redistribution and high hepatic clearance rather than a unique receptor action.

Question 6Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Diffusion hypoxia after discontinuation of nitrous oxide occurs because:

  1. nitrous oxide is slowly metabolized to nitrate by hepatic enzymes
  2. nitrous oxide diffuses into alveoli and dilutes alveolar oxygen Correct answer.
  3. nitrous oxide increases whole-body oxygen consumption during recovery
  4. nitrous oxide provokes bronchoconstriction during emergence from anesthesia

Explanation

Nitrous oxide has a low blood:gas solubility, so large volumes move rapidly down concentration gradients. When the inspired gas is withdrawn, nitrous oxide floods from blood into alveoli faster than oxygen can replace it, lowering alveolar oxygen tension. Administering high inspired oxygen for several minutes after discontinuation prevents this.

Question 7Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Hyperventilation-induced hypocapnia affects cerebral blood flow by:

  1. increasing it through cerebral vasodilation
  2. producing no measurable change in cerebral blood flow
  3. decreasing it through cerebral vasoconstriction Correct answer.
  4. increasing it only when PaO2 falls below 60 mmHg

Explanation

Cerebral arterioles respond to changes in perivascular pH, which follows arterial carbon dioxide tension. A fall in PaCO2 alkalinizes the milieu and causes vasoconstriction, reducing cerebral blood flow by roughly 2 to 4 percent per mmHg. This is why hyperventilation is used briefly to reduce intracranial pressure and why it can cause cerebral ischemia if prolonged.

Question 8Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

After four elimination half-lives of a drug following first-order kinetics, approximately what fraction of the original dose remains?

  1. 12.5%
  2. 6.25% Correct answer.
  3. 50%
  4. 25%

Explanation

Each half-life halves the remaining amount, so four half-lives leave 0.5 raised to the fourth power, or 6.25 percent. This corresponds to roughly 94 percent elimination, which is why steady state is approached within about four to five half-lives. The same arithmetic applies to accumulation during a constant infusion.

Question 9Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Context-sensitive half-time is best described as the time required for plasma concentration to decrease by 50% after:

  1. an oral dose after reaching peak plasma concentration
  2. administration of a single intravenous bolus
  3. stopping an infusion that had reached steady state Correct answer.
  4. a bolus followed by a five-minute infusion

Explanation

Context-sensitive half-time describes the decline after terminating an infusion that has been running long enough to build up peripheral stores. Prolongation with infusion duration reflects slow redistribution from tissue compartments back into plasma rather than a change in elimination. Drugs such as remifentanil are minimally affected because ester hydrolysis keeps their context-sensitive half-time short regardless of infusion length.

Question 10Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Neostigmine reverses a nondepolarizing neuromuscular blockade by:

  1. inhibiting acetylcholinesterase at the neuromuscular junction Correct answer.
  2. increasing plasma protein binding of the blocking drug
  3. blocking presynaptic acetylcholine release
  4. directly displacing the blocking drug from the nicotinic receptor

Explanation

Neostigmine inhibits acetylcholinesterase, so acetylcholine accumulates in the synaptic cleft and competes more effectively with the nondepolarizing blocker. Because the same acetylcholine surge acts at muscarinic sites, an antimuscarinic agent is given concurrently to prevent bradycardia and secretions. Reversal is unreliable when blockade is deep.

Question 11Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

A volatile anesthetic with a low blood:gas partition coefficient, compared with one with a high coefficient, will:

  1. require a higher inspired concentration to achieve the same MAC
  2. achieve a slower rise in alveolar concentration
  3. be more extensively metabolized by hepatic cytochrome enzymes
  4. produce a faster rise in alveolar and arterial partial pressure Correct answer.

Explanation

Blood:gas solubility determines how much agent is taken up by blood before alveolar partial pressure can rise. A poorly soluble agent is taken up less, so alveolar partial pressure approaches inspired partial pressure quickly and induction is faster. This is why desflurane, with a blood:gas coefficient near 0.45, induces more rapidly than isoflurane.

Question 12Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

The characteristic cardiovascular profile of ketamine includes:

  1. dose-dependent myocardial depression accompanied by bradycardia
  2. tachycardia and hypertension from sympathetic stimulation Correct answer.
  3. minimal change in heart rate and blood pressure
  4. bradycardia and peripheral vasodilation

Explanation

Ketamine increases heart rate, mean arterial pressure, and cardiac output, largely through sympathetic outflow and inhibition of catecholamine reuptake. This effect usually masks a direct depressant action on the myocardium, which becomes clinically apparent in catecholamine-depleted patients. It is why ketamine is often chosen for induction in hypovolemic or septic patients.

Question 13Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Inhalational anesthetics inhibit hypoxic pulmonary vasoconstriction, an effect that can produce:

  1. bronchodilation with increased functional residual capacity
  2. increased pulmonary artery pressure with improved oxygenation
  3. increased shunt fraction and reduced arterial oxygenation Correct answer.
  4. systemic vasodilation with reflex tachycardia

Explanation

Hypoxic pulmonary vasoconstriction diverts blood away from poorly ventilated alveoli, limiting shunt and preserving oxygenation. Volatile anesthetics blunt this reflex, so blood continues to perfuse underventilated lung regions and venous admixture increases. The effect is most relevant in patients with large regional ventilation-perfusion mismatch.

Question 14Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

A 70-kg patient receives 100 mg of a drug by intravenous bolus, and the resulting initial plasma concentration is 2 mg/L. What is the apparent volume of distribution?

  1. 200 L
  2. 140 L
  3. 20 L
  4. 50 L Correct answer.

Explanation

Volume of distribution is calculated by dividing dose by plasma concentration, giving 100 mg divided by 2 mg/L, or 50 L. The result is an apparent value rather than a real anatomic space, because it lumps together plasma, interstitial, and tissue distribution. A large apparent volume of distribution indicates extensive tissue uptake and predicts slower elimination for a given clearance.

Question 15Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Compared with a local anesthetic whose pKa is far above physiologic pH, an agent with a pKa closer to 7.4 is expected to have:

  1. greater systemic toxicity
  2. more extensive plasma protein binding
  3. a more rapid onset of conduction block Correct answer.
  4. a longer duration of action at the nerve

Explanation

The uncharged base form of a local anesthetic is what crosses the lipid nerve membrane; the proportion present as base depends on the drug's pKa relative to tissue pH. An agent with a pKa near 7.4 has a larger uncharged fraction at tissue pH and therefore penetrates to the channel more quickly. Onset is thus faster, while duration and toxicity depend mainly on protein binding, lipid solubility, and vasoactivity.

Question 16Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Local anesthetics work poorly when injected into infected, acidic tissue because:

  1. more drug stays ionized and cannot cross the nerve membrane Correct answer.
  2. sodium channels become refractory to blockade
  3. protein binding increases at low pH
  4. the drug is rapidly metabolized by local tissue enzymes

Explanation

Acidosis increases the protonated, charged fraction of the local anesthetic at the expense of the membrane-permeant base. Less drug reaches the axoplasmic binding site, so block is weaker or fails. Increased local blood flow and inflammatory hyperalgesia further reduce the clinical effect.

Question 17Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Which statement about potency and efficacy is correct?

  1. Full and partial agonists at a receptor always produce equal maximal effects
  2. Potency is the dose needed for an effect; efficacy is the maximal effect Correct answer.
  3. Efficacy is measured by the ED50 value of a drug
  4. Potency describes the maximal effect; efficacy describes receptor affinity

Explanation

Potency refers to the amount of drug required to produce a specified effect and is expressed by values such as ED50 or a lower potency meaning a larger dose is needed. Efficacy is the greatest effect the drug can produce, reflecting intrinsic activity at the receptor. A highly potent drug may still have low efficacy, as with fentanyl-like opioids versus partial agonists.

Question 18Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Ondansetron reduces postoperative nausea and vomiting by:

  1. agonizing alpha-2 adrenergic receptors centrally
  2. blocking dopamine D2 receptors in the chemoreceptor trigger zone
  3. blocking muscarinic receptors in the vestibular apparatus
  4. antagonizing serotonin 5-HT3 receptors Correct answer.

Explanation

Ondansetron is a selective 5-HT3 receptor antagonist that blocks serotonin-mediated emetogenic signals from the gut and the chemoreceptor trigger zone. Because it acts on a specific receptor, it lacks the sedation and extrapyramidal effects seen with D2 blockade. Other antiemetics used in anesthesia act at different receptors, such as D2, muscarinic, histamine H1, or neurokinin-1 sites.

Question 19Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Dexmedetomidine produces sedation with relatively little respiratory depression because it:

  1. antagonizes NMDA receptors in the limbic system
  2. blocks histamine H1 receptors in the hypothalamic tuberomammillary nucleus
  3. acts as a GABA-A agonist in the cerebral cortex
  4. is a selective alpha-2 agonist acting in the locus coeruleus Correct answer.

Explanation

Dexmedetomidine is a highly selective alpha-2 adrenergic agonist whose main sedative action is on presynaptic alpha-2A receptors in the locus coeruleus. This produces a state resembling natural sleep with preserved respiratory drive and some responsiveness to stimulation. Bradycardia and hypotension from sympathetic inhibition are its most characteristic adverse effects.

Question 20Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Which change favors net movement of fluid from the capillary into the interstitium?

  1. An increase in plasma albumin concentration
  2. A decrease in plasma oncotic pressure Correct answer.
  3. A decrease in capillary hydrostatic pressure
  4. An increase in interstitial hydrostatic pressure

Explanation

Starling forces determine transcapillary fluid flux: hydrostatic pressure pushes fluid out, and plasma oncotic pressure pulls it back in. A fall in plasma oncotic pressure, as in hypoalbuminemia, reduces the inward force and favors filtration into the interstitium. The same result follows from a rise in capillary hydrostatic pressure or a fall in interstitial hydrostatic pressure.

Question 21Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

The effect-site equilibration rate constant, ke0, describes:

  1. the fraction of drug bound to plasma proteins
  2. the speed of conversion of a prodrug to its active metabolite
  3. the rate of equilibration between plasma and the effect site Correct answer.
  4. the rate of drug elimination from the plasma compartment

Explanation

ke0 governs how quickly drug concentration in the biophase follows plasma concentration. A small ke0 means slow equilibration and prominent hysteresis between plasma concentration and observed effect, so peak effect lags peak plasma level. This is why propofol and opioids have delayed onset and offset of maximal clinical effect relative to their plasma kinetics.

Question 22Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

If the extracellular potassium concentration rises, the resting membrane potential of a ventricular myocyte will:

  1. hyperpolarize due to increased sodium-potassium ATPase activity
  2. become less negative, moving closer to threshold Correct answer.
  3. remain unchanged because sodium conductance dominates
  4. become more negative with no change in threshold

Explanation

Resting membrane potential is set largely by the potassium gradient, described by the Nernst relationship. Raising extracellular potassium reduces that gradient, so the potential becomes less negative and approaches threshold, increasing excitability and the risk of arrhythmia. In the heart this manifests as slowed conduction and peaked T waves, then widening of the QRS as hyperkalemia worsens.

Question 23Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

For a drug with a high hepatic extraction ratio, low oral bioavailability is explained mainly by:

  1. extensive first-pass hepatic metabolism Correct answer.
  2. rapid renal excretion of unchanged drug
  3. poor dissolution in the gastrointestinal tract
  4. high plasma protein binding alone

Explanation

When the extraction ratio approaches one, nearly all drug delivered to the liver is removed during a single pass, so only a small fraction of an oral dose reaches the systemic circulation. Bioavailability is therefore low and variable, and hepatic blood flow becomes a major determinant of clearance. High protein binding alone does not limit metabolism of such drugs because the unbound fraction is efficiently extracted.

Question 24Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

The ED95 of a neuromuscular blocking drug is:

  1. the dose producing 95% receptor occupancy at the motor endplate in vivo
  2. the dose that reduces twitch height by 95% in every patient
  3. the dose that is 95% likely to cause histamine release
  4. the dose producing 95% of maximal twitch depression in a population Correct answer.

Explanation

ED95 is a population dose-response value: the dose that produces 95% of the maximal effect on evoked twitch height in the studied population. It is estimated from the cumulative dose-response curve rather than from individual responses. Intubating doses are typically about two times the ED95 to ensure reliable conditions and a reasonable duration of action.

Question 25Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Which statement about the alveolar gas equation is correct?

  1. Alveolar oxygen tension is independent of barometric pressure at altitude
  2. The respiratory quotient is defined as oxygen consumption divided by carbon dioxide production per minute
  3. Alveolar oxygen tension falls as alveolar carbon dioxide rises at a fixed respiratory quotient Correct answer.
  4. A normal alveolar-arterial oxygen gradient excludes significant shunt

Explanation

The alveolar gas equation states that alveolar oxygen tension equals inspired oxygen tension minus alveolar carbon dioxide tension divided by the respiratory quotient. Breathing room air, replacement of oxygen by carbon dioxide therefore lowers alveolar oxygen tension, and the effect is exaggerated when the respiratory quotient falls. The equation also shows why alveolar oxygen tension drops with altitude as barometric pressure decreases.

Question 26Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Minimum alveolar concentration (MAC) of a volatile anesthetic is best defined as the alveolar concentration that:

  1. abolishes explicit recall in 50% of patients during a painful surgical incision
  2. produces unconsciousness in 50% of patients within one minute
  3. prevents movement in 50% of subjects given a standard noxious stimulus Correct answer.
  4. lowers mean arterial pressure by 50% at steady-state anesthesia

Explanation

MAC is the median alveolar concentration at which half of patients do not move in response to a standardized noxious stimulus. It compares potency among volatile agents and is not defined by recall, blood pressure, or induction speed.

Question 27Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

For laminar flow through a rigid tube, doubling the internal radius while keeping pressure gradient and viscosity unchanged changes flow by a factor of:

  1. 8
  2. 4
  3. 16 Correct answer.
  4. 2

Explanation

For laminar flow, Poiseuille's law gives flow proportional to the fourth power of radius when pressure gradient and viscosity are constant. Doubling the radius therefore multiplies flow by 2^4, or 16.

Question 28Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Which condition shifts the oxyhemoglobin dissociation curve to the right?

  1. Hyperventilation-induced hypocapnia
  2. Increased 2,3-diphosphoglycerate Correct answer.
  3. Fetal hemoglobin
  4. Hypothermia

Explanation

A right shift indicates reduced hemoglobin oxygen affinity, favoring oxygen unloading at tissues. Increased 2,3-DPG, acidosis, hypercapnia, and hyperthermia shift the curve right; hypothermia, hypocapnia, and fetal hemoglobin shift it left.

Question 29Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

A competitive antagonist shifts the agonist dose-response curve in which way?

  1. Upward, with an increased maximal response
  2. Downward, with a reduced maximal response
  3. Leftward, with a reduced EC50
  4. Rightward, with an unchanged maximal response Correct answer.

Explanation

A competitive antagonist competes reversibly at the same receptor, so higher agonist concentrations can overcome the block. This produces a parallel right shift in the dose-response curve with an unchanged maximal response.

Question 30Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

A patient given succinylcholine remains paralyzed for 3 hours. Which mechanism best explains this?

  1. Renal failure reduces renal clearance of succinylcholine and its active metabolites
  2. Upregulation of postsynaptic acetylcholine receptors increases sensitivity to succinylcholine
  3. Prolonged exposure produces a phase II block at the neuromuscular junction
  4. Homozygous pseudocholinesterase deficiency slows succinylcholine hydrolysis Correct answer.

Explanation

Succinylcholine is normally hydrolyzed rapidly by plasma butyrylcholinesterase (pseudocholinesterase). Homozygous atypical enzyme activity markedly prolongs paralysis after a single dose, whereas a phase II block typically follows prolonged infusion or repeated doses.

Question 31Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Air is entrained into a Venturi mask because gas flowing through a narrow constriction:

  1. becomes turbulent and raises pressure downstream
  2. increases in velocity and decreases lateral pressure Correct answer.
  3. increases in pressure and pushes room air into the mask
  4. decreases in velocity and increases lateral pressure

Explanation

According to Bernoulli's principle, the total energy of a flowing fluid remains constant, so a rise in velocity through a constriction is accompanied by a fall in lateral pressure. The low pressure at the side port entrains room air into the mask.

Question 32Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Which substance is best used to measure glomerular filtration rate because it is freely filtered and neither secreted nor reabsorbed?

  1. Albumin
  2. Inulin Correct answer.
  3. Glucose
  4. Para-aminohippurate

Explanation

Inulin is freely filtered at the glomerulus and is neither reabsorbed nor secreted by the tubules, so its clearance equals GFR. Glucose is reabsorbed, PAH is secreted, and albumin is largely retained by the filtration barrier.

Question 33Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Severe bupivacaine cardiotoxicity is most closely related to which property?

  1. Rapid hepatic metabolism to a toxic metabolite
  2. High affinity for cardiac sodium channels with slow dissociation Correct answer.
  3. Release of endogenous catecholamines causing tachyarrhythmia
  4. Selective blockade of cardiac potassium channels at therapeutic concentrations

Explanation

Bupivacaine blocks cardiac sodium channels with high affinity and dissociates slowly, which can cause profound conduction delay and ventricular arrhythmias. Intravenous lipid emulsion is used in severe toxicity.

Question 34Basic and Applied Sciences (physics, pharmacology, physiology, pathophysiology)

Cardiac output by the Fick principle is calculated as oxygen consumption divided by which value?

  1. Mixed venous oxygen saturation
  2. Alveolar-arterial oxygen gradient
  3. Arterial oxygen content alone
  4. Arteriovenous oxygen content difference Correct answer.

Explanation

The Fick principle states that oxygen consumption equals cardiac output multiplied by the arteriovenous oxygen content difference. Rearranging gives cardiac output = oxygen consumption / (arterial oxygen content − mixed venous oxygen content).

Question 35Clinical Anesthesia Practice and Anesthetic Techniques

The minimum alveolar concentration (MAC) of an inhaled anesthetic is defined as the alveolar concentration that:

  1. occupies 95% of gamma-aminobutyric acid receptors
  2. prevents movement in 50% of patients given a surgical stimulus Correct answer.
  3. equalizes arterial and brain partial pressures within one minute of administration
  4. renders 90% of patients unconscious during surgery

Explanation

MAC is the ED50 for immobility in response to a standardized noxious stimulus and is used to compare potency among volatile agents. It is not a measure of unconsciousness, receptor occupancy, or speed of equilibration.

Question 36Clinical Anesthesia Practice and Anesthetic Techniques

Succinylcholine produces skeletal muscle relaxation primarily through which mechanism?

  1. inhibition of presynaptic acetylcholine release
  2. blockade of voltage-gated sodium channels in the motor nerve
  3. competitive antagonism at postsynaptic nicotinic acetylcholine receptors
  4. sustained depolarization of the motor end plate Correct answer.

Explanation

Succinylcholine is a depolarizing neuromuscular blocker that binds nicotinic receptors and maintains depolarization, preventing further end-plate potentials. This persistent depolarization produces flaccid paralysis until the drug is hydrolyzed by plasma cholinesterase.

Question 37Clinical Anesthesia Practice and Anesthetic Techniques

According to standard ASA preoperative fasting guidelines, clear liquids may be ingested until how long before elective anesthesia?

  1. 3 hours
  2. 1 hour
  3. 2 hours Correct answer.
  4. 6 hours

Explanation

Clear liquids empty rapidly from the stomach, and current ASA guidance permits them up to 2 hours before elective anesthesia. Longer intervals apply to breast milk, infant formula, light meals, and fatty meals.

Question 38Clinical Anesthesia Practice and Anesthetic Techniques

Cricoid pressure (Sellick maneuver) is primarily applied to:

  1. facilitate passage of the tracheal tube through the glottis
  2. improve oxygenation during bag-mask ventilation
  3. decrease the risk of laryngospasm during induction
  4. reduce the risk of pulmonary aspiration of gastric contents Correct answer.

Explanation

Cricoid pressure compresses the upper esophagus against the vertebral body, aiming to occlude the esophageal lumen and limit passive regurgitation. It does not reliably improve ventilation or intubating conditions and may worsen the view at laryngoscopy.

Question 39Clinical Anesthesia Practice and Anesthetic Techniques

Normal end-tidal carbon dioxide (EtCO2) in a healthy spontaneously breathing adult is approximately:

  1. 35–45 mmHg Correct answer.
  2. 65–75 mmHg
  3. 20–30 mmHg
  4. 50–60 mmHg

Explanation

EtCO2 normally approximates arterial PaCO2 and is typically 35–45 mmHg in a healthy adult. Values outside this range suggest hypoventilation, hyperventilation, or a change in dead space or metabolism.

Question 40Clinical Anesthesia Practice and Anesthetic Techniques

For cesarean delivery under spinal anesthesia, the sensory block should typically be established to which dermatome level?

  1. T10
  2. T2
  3. T4 Correct answer.
  4. T8

Explanation

A sensory level of T4 is generally required to block visceral pain from uterine manipulation and peritoneal traction during cesarean delivery. Higher levels increase the risk of maternal hypotension and respiratory compromise.

Question 41Clinical Anesthesia Practice and Anesthetic Techniques

A Mallampati class III oropharyngeal view is characterized by visualization of:

  1. soft palate, fauces, and uvula
  2. soft palate, fauces, uvula, and tonsillar pillars
  3. soft palate and base of uvula only Correct answer.
  4. hard palate only

Explanation

Mallampati class III shows only the soft palate and the base of the uvula, indicating reduced oropharyngeal space. Class I shows the tonsillar pillars, class II shows the uvula, and class IV shows only the hard palate.

Question 42Clinical Anesthesia Practice and Anesthetic Techniques

Pulse oximetry estimates arterial oxygen saturation by measuring:

  1. differential light absorption by oxyhemoglobin and deoxyhemoglobin Correct answer.
  2. the total arterial oxygen content, including bound and dissolved oxygen
  3. the fraction of carboxyhemoglobin in arterial blood
  4. the partial pressure of dissolved oxygen in arterial blood

Explanation

Pulse oximeters compare light absorption at two wavelengths to estimate the ratio of oxyhemoglobin to deoxyhemoglobin in pulsatile arterial blood. They do not directly measure PaO2, oxygen content, or carboxyhemoglobin.

Question 43Clinical Anesthesia Practice and Anesthetic Techniques

A patient has a train-of-four count of 2 after rocuronium administration. Which sugammadex dose is recommended for reversal?

  1. 16 mg/kg
  2. 0.5 mg/kg
  3. 2 mg/kg Correct answer.
  4. 4 mg/kg

Explanation

For moderate neuromuscular blockade with a train-of-four count of 1–2, sugammadex 2 mg/kg is recommended. Higher doses are reserved for deep blockade or immediate rescue.

Question 44Clinical Anesthesia Practice and Anesthetic Techniques

Which feature best distinguishes epidural anesthesia from spinal anesthesia?

  1. Epidural anesthesia typically produces a denser motor block for the same sensory level
  2. Epidural anesthesia reliably blocks sacral roots with a single lumbar injection
  3. Epidural anesthesia carries a lower risk of local anesthetic systemic toxicity
  4. Epidural anesthesia permits catheter placement for continuous infusion Correct answer.

Explanation

An epidural catheter allows titration and continuous delivery of local anesthetic, whereas a spinal anesthetic is usually a single injection. Epidural blockade is less dense and has a higher local anesthetic dose requirement.

Question 45Clinical Anesthesia Practice and Anesthetic Techniques

A patient develops laryngospasm with oxygen desaturation after extubation. Which initial measure is most appropriate?

  1. 100% oxygen with jaw thrust and CPAP Correct answer.
  2. intravenous flumazenil to reverse sedation
  3. intramuscular epinephrine for bronchospasm
  4. immediate emergency cricothyrotomy before any airway maneuvers

Explanation

Initial management of laryngospasm includes removing the stimulus, applying 100% oxygen with jaw thrust and CPAP, and deepening anesthesia if needed. Succinylcholine is reserved for persistent severe laryngospasm, and invasive airway rescue is a last resort.

Question 46Clinical Anesthesia Practice and Anesthetic Techniques

A patient develops seizures and cardiovascular collapse after an interscalene block. Which specific therapy is indicated in addition to airway and circulatory support?

  1. sodium bicarbonate 1 mEq/kg
  2. naloxone 0.4 mg
  3. 20% lipid emulsion 1.5 mL/kg bolus Correct answer.
  4. calcium chloride 1 g

Explanation

This presentation suggests local anesthetic systemic toxicity, for which intravenous lipid emulsion is the specific antidote. A 1.5 mL/kg bolus is followed by an infusion and repeated boluses as needed.

Question 47Clinical Anesthesia Practice and Anesthetic Techniques

During one-lung ventilation, a patient becomes hypoxemic. Which initial maneuver is most appropriate?

  1. apply CPAP to the non-ventilated lung Correct answer.
  2. clamp the bronchial lumen of the non-ventilated lung
  3. reduce the inspired oxygen fraction to 0.3
  4. increase tidal volume to 12 mL/kg predicted body weight

Explanation

Applying CPAP to the non-ventilated lung improves oxygenation by allowing some gas exchange in the operative lung while the dependent lung remains ventilated. High tidal volumes increase ventilator-induced lung injury, and reducing FiO2 would worsen hypoxemia.

Question 48Clinical Anesthesia Practice and Anesthetic Techniques

The initial intravenous dose of dantrolene for an adult with malignant hyperthermia is:

  1. 1 mg/kg
  2. 0.1 mg/kg
  3. 2.5 mg/kg Correct answer.
  4. 10 mg/kg

Explanation

Dantrolene is started at 2.5 mg/kg IV and repeated until hyperthermia, rigidity, and acidosis are controlled. The maximum cumulative dose is typically 10 mg/kg, after which alternative therapy and supportive care are emphasized.

Question 49Clinical Anesthesia Practice and Anesthetic Techniques

A patient cannot be intubated and cannot be oxygenated after induction of anesthesia. Which rescue step is indicated?

  1. awaken the patient and postpone surgery
  2. insert a second supraglottic airway
  3. attempt fiberoptic intubation through the existing airway
  4. perform emergency front-of-neck airway access Correct answer.

Explanation

In a cannot-intubate, cannot-oxygenate emergency, emergency front-of-neck airway access is required to restore oxygenation. Further attempts at intubation or supraglottic rescue should not delay this lifesaving intervention.

Question 50Clinical Anesthesia Practice and Anesthetic Techniques

During neonatal resuscitation, chest compressions should begin when the heart rate remains below which threshold after 30 seconds of effective ventilation?

  1. 40 beats/min
  2. 80 beats/min
  3. 100 beats/min
  4. 60 beats/min Correct answer.

Explanation

The Neonatal Resuscitation Program recommends starting chest compressions when the heart rate is below 60 beats/min despite 30 seconds of effective positive-pressure ventilation. Compressions are coordinated with ventilations at a 3:1 ratio.