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EHPLE Anesthesia study materials
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EHPLE Anesthesia practice questions

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Question 1Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

During direct laryngoscopy, which laryngeal cartilage is the unpaired midline structure that forms the anterior prominence of the larynx and is the site of attachment for the vocal ligaments?

  1. Thyroid cartilage Correct answer.
  2. Cricoid cartilage
  3. Arytenoid cartilage
  4. Corniculate cartilage

Explanation

The thyroid cartilage is a single midline shield-shaped structure whose anterior angle forms the laryngeal prominence, and its inner surface anchors the vocal ligaments at the vocal process region. The cricoid is a complete ring below it, while arytenoid and corniculate cartilages are paired and posterior.

Question 2Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

A patient's oxygen saturation falls during one-lung ventilation. Which physiologic mechanism primarily explains the hypoxemia?

  1. Increased dead space ventilation in the ventilated lung
  2. Increased intrapulmonary shunt through the non-ventilated lung Correct answer.
  3. Reduced oxygen content of inspired gas mixture
  4. Diffusion limitation across the alveolar membrane

Explanation

Blood perfusing the collapsed, non-ventilated lung receives no oxygen and returns to the left atrium desaturated, creating a true right-to-left shunt. Hypoxic pulmonary vasoconstriction reduces but does not abolish this shunt, so shunt fraction is the dominant determinant of oxygenation during one-lung ventilation.

Question 3Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Propofol produces hypnosis mainly by which molecular action?

  1. Antagonism of NMDA glutamate receptors
  2. Potentiation of GABA-A receptor chloride currents Correct answer.
  3. Blockade of voltage-gated sodium channels
  4. Agonism at alpha-2 adrenergic receptors

Explanation

Propofol binds GABA-A receptors and enhances chloride conductance, hyperpolarizing neurons and producing hypnosis. Ketamine acts at NMDA receptors, local anesthetics block sodium channels, and dexmedetomidine is the alpha-2 agonist.

Question 4Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

A 70 kg patient receives 100 mg of a drug with a volume of distribution of 50 L. What is the approximate plasma concentration, assuming immediate complete mixing?

  1. 20 mg/L
  2. 5 mg/L
  3. 0.5 mg/L
  4. 2 mg/L Correct answer.

Explanation

Concentration equals dose divided by volume of distribution, so 100 mg divided by 50 L equals 2 mg/L. This relationship is the basis for calculating loading doses from a target concentration.

Question 5Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which nerve is at greatest risk of injury during interscalene brachial plexus block, producing ipsilateral hemidiaphragmatic paresis?

  1. Phrenic nerve Correct answer.
  2. Recurrent laryngeal nerve
  3. Suprascapular nerve
  4. Long thoracic nerve

Explanation

The phrenic nerve lies on the anterior scalene muscle within the interscalene space and is frequently blocked, causing hemidiaphragmatic paresis in a high proportion of patients. Recurrent laryngeal and long thoracic nerves are not the characteristic targets of this complication.

Question 6Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

According to Poiseuille's law, how does halving the internal radius of an intravenous cannula affect laminar flow at a constant pressure gradient?

  1. Flow falls to one-eighth of the original value
  2. Flow falls to one-sixteenth of the original value Correct answer.
  3. Flow falls to one-half of the original value
  4. Flow falls to one-quarter of the original value

Explanation

Laminar flow is proportional to the fourth power of radius, so reducing radius by half multiplies flow by (1/2)^4, which is one-sixteenth. This explains why small-bore cannulas require much higher pressure to achieve the same infusion rate.

Question 7Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which change in the oxygen-hemoglobin dissociation curve is produced by hypothermia?

  1. A decrease in maximum oxygen carrying capacity
  2. An increase in the P50 value
  3. A rightward shift, decreasing hemoglobin oxygen affinity
  4. A leftward shift, increasing hemoglobin oxygen affinity Correct answer.

Explanation

Hypothermia reduces the metabolic rate and increases hemoglobin affinity for oxygen, shifting the curve left and lowering P50 so that unloading at tissues is impaired. A rightward shift is produced by factors such as acidosis, hyperthermia, and raised 2,3-DPG.

Question 8Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

A patient with severe aortic stenosis is induced for general anesthesia. Which hemodynamic change is most dangerous because it can precipitate myocardial ischemia?

  1. A fall in systemic vascular resistance with reduced coronary perfusion pressure Correct answer.
  2. A rise in heart rate with increased diastolic filling time
  3. A fall in left ventricular end-diastolic pressure
  4. A rise in systemic vascular resistance with reduced cardiac output

Explanation

In aortic stenosis the hypertrophied left ventricle depends on adequate diastolic aortic pressure for coronary perfusion. Vasodilation lowers systemic vascular resistance and perfusion pressure while reflex tachycardia further reduces diastolic time, worsening ischemia.

Question 9Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which receptor mediates the bradycardia produced by neostigmine when it reverses neuromuscular blockade?

  1. Nicotinic receptors at the neuromuscular junction
  2. Alpha-1 adrenergic receptors
  3. Beta-1 adrenergic receptors
  4. Muscarinic M2 receptors at the sinoatrial node Correct answer.

Explanation

Neostigmine inhibits acetylcholinesterase, increasing acetylcholine at both nicotinic and muscarinic sites. The excess acetylcholine acts on cardiac M2 receptors to slow the sinoatrial node, which is why an antimuscarinic such as glycopyrrolate is co-administered.

Question 10Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which structure must be punctured first when performing a spinal anesthetic via the midline approach at L3-L4?

  1. Dura mater
  2. Ligamentum flavum Correct answer.
  3. Pia mater
  4. Arachnoid mater

Explanation

The needle passes through skin, subcutaneous tissue, supraspinous and interspinous ligaments, and then the ligamentum flavum before reaching the epidural space and dura. The dura and arachnoid are penetrated after the flavum, and the pia lies on the spinal cord.

Question 11Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

A volatile agent with a low blood-gas solubility coefficient has which characteristic?

  1. High potency requiring low inspired concentration
  2. Slow equilibration with brain tissue and slow onset
  3. Rapid equilibration with brain tissue and fast onset Correct answer.
  4. Increased metabolism by hepatic enzymes

Explanation

Blood-gas solubility determines how much agent must dissolve in blood before alveolar partial pressure rises. A low solubility coefficient means alveolar and arterial partial pressures rise quickly, so induction and recovery are fast, as with desflurane.

Question 12Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

In the Frank-Starling relationship, which change occurs when left ventricular end-diastolic volume increases within the physiologic range?

  1. Stroke volume increases due to greater actin-myosin overlap and calcium sensitivity Correct answer.
  2. Stroke volume decreases due to reduced ejection fraction
  3. Heart rate decreases due to decreased sympathetic tone
  4. Myocardial oxygen consumption decreases

Explanation

Increasing preload stretches sarcomeres toward optimal length, enhancing calcium sensitivity and cross-bridge formation so that stroke volume rises. This relationship underpins the use of fluid loading to improve cardiac output in the responsive patient.

Question 13Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which is the correct definition of minimum alveolar concentration (MAC)?

  1. The blood concentration at which 50 percent of patients lose consciousness
  2. The alveolar concentration at which 95 percent of patients remain hemodynamically stable
  3. The inspired concentration required to prevent recall
  4. The alveolar concentration at which 50 percent of patients do not respond to surgical incision Correct answer.

Explanation

MAC is defined as the end-tidal alveolar concentration of an inhaled anesthetic at one atmosphere that prevents movement in response to a standardized surgical stimulus in 50 percent of patients. It is a population measure of potency, not a guarantee of amnesia or stability.

Question 14Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

A patient receiving a large dose of morphine develops delayed respiratory depression with normal initial recovery. Which pharmacokinetic property of morphine best explains this?

  1. Extensive renal excretion of unchanged drug
  2. Very high lipid solubility
  3. Rapid ester hydrolysis in plasma
  4. Enterohepatic recirculation of the glucuronide metabolite Correct answer.

Explanation

Morphine undergoes glucuronidation, and morphine-6-glucuronide is an active metabolite that undergoes enterohepatic recirculation, prolonging opioid effects. Low lipid solubility also slows brain penetration, so delayed rather than immediate depression can occur.

Question 15Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which nerve supplies sensation to the anterior two-thirds of the tongue?

  1. Glossopharyngeal nerve
  2. Lingual nerve Correct answer.
  3. Hypoglossal nerve
  4. Vagus nerve

Explanation

The lingual nerve, a branch of the mandibular division of the trigeminal nerve, carries general sensation from the anterior two-thirds of the tongue. Taste is carried by the chorda tympani, while the glossopharyngeal nerve supplies the posterior third.

Question 16Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which parameter is most useful for confirming that a neuromuscular monitor shows adequate recovery of the train-of-four ratio before extubation?

  1. A train-of-four ratio greater than 0.9 Correct answer.
  2. A post-tetanic count of one
  3. A train-of-four count of two
  4. A single twitch response to stimulation

Explanation

A train-of-four ratio above 0.9 indicates adequate recovery of neuromuscular function and is associated with safe airway reflexes and reduced postoperative pulmonary complications. Counts and post-tetanic counts reflect deeper degrees of blockade.

Question 17Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which statement about the anatomy of the epidural space is correct?

  1. It ends at the level of the second lumbar vertebra
  2. It contains fat, venous plexuses, and lymphatics and extends from the foramen magnum to the sacral hiatus Correct answer.
  3. It is bounded anteriorly by the ligamentum flavum
  4. It is a potential space containing cerebrospinal fluid

Explanation

The epidural space lies between the dura and the vertebral canal wall and contains fat, venous plexuses, and lymphatics, extending from the foramen magnum to the sacral hiatus. Cerebrospinal fluid is within the subarachnoid space, not the epidural space.

Question 18Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which change in acid-base status most increases the fraction of an acidic drug that is un-ionized and able to cross lipid membranes?

  1. Increase in protein binding
  2. Addition of a buffer at neutral pH
  3. Acidification of the environment Correct answer.
  4. Alkalinization of the environment

Explanation

For a weak acid, lowering the pH shifts the equilibrium toward the un-ionized, lipid-soluble form, which diffuses across membranes more readily. Alkalinization increases ionization and traps the drug in aqueous compartments.

Question 19Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which mechanism best explains the rapid offset of action of remifentanil?

  1. Hepatic cytochrome P450 metabolism
  2. Redistribution into adipose tissue
  3. Renal glomerular filtration of unchanged drug
  4. Hydrolysis by nonspecific plasma esterases Correct answer.

Explanation

Remifentanil is an ester that is hydrolyzed by nonspecific plasma and tissue esterases to inactive metabolites, so its context-sensitive half-time remains short regardless of infusion duration. Hepatic and renal pathways are not the main determinants of its offset.

Question 20Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which lung volume cannot be measured by simple spirometry?

  1. Inspiratory reserve volume
  2. Tidal volume
  3. Residual volume Correct answer.
  4. Expiratory reserve volume

Explanation

Residual volume is the air remaining after maximal expiration and cannot be exhaled, so it cannot be measured by spirometry. It requires techniques such as helium dilution, nitrogen washout, or body plethysmography.

Question 21Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

A patient with cirrhosis and ascites requires a non-depolarizing neuromuscular blocker. Which agent has the most prolonged duration because of its dependence on hepatic and renal elimination?

  1. Cisatracurium
  2. Succinylcholine
  3. Pancuronium Correct answer.
  4. Atracurium

Explanation

Pancuronium is eliminated largely unchanged by the kidney and metabolized in the liver, so its duration is markedly prolonged in hepatic and renal dysfunction. Cisatracurium and atracurium undergo Hofmann degradation independent of organ function, and succinylcholine is cleared by plasma cholinesterase.

Question 22Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which physical principle underlies pulse oximetry?

  1. Differential absorption of red and infrared light by oxyhemoglobin and deoxyhemoglobin Correct answer.
  2. Measurement of partial pressure of oxygen by a Clark electrode
  3. Doppler shift of ultrasound in arterial blood
  4. Detection of exhaled carbon dioxide by infrared absorption

Explanation

Pulse oximetry compares the pulsatile absorption of red and infrared light, exploiting the differing absorption spectra of oxyhemoglobin and deoxyhemoglobin. It estimates saturation rather than partial pressure and is unaffected by the Clark electrode principle.

Question 23Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which factor most increases the risk of aspiration pneumonitis during induction of anesthesia?

  1. Use of a supraglottic airway in a fasted patient
  2. Gastroesophageal reflux disease with a full stomach Correct answer.
  3. Preoperative beta-blockade
  4. Mild dehydration

Explanation

Reflux disease combined with a full stomach increases gastric volume and reduces barrier function, raising the risk of aspiration during induction. Beta-blockade and mild dehydration do not directly increase aspiration risk.

Question 24Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which statement about the neuromuscular junction is correct?

  1. Acetylcholinesterase inhibitors block nicotinic receptors
  2. Nondepolarizing blockers increase acetylcholine release
  3. Calcium entry into the nerve terminal inhibits vesicle fusion
  4. Depolarizing blockers cause prolonged depolarization and receptor desensitization Correct answer.

Explanation

Succinylcholine binds nicotinic receptors and produces sustained depolarization, which leads to receptor desensitization and flaccid paralysis. Nondepolarizing agents instead competitively antagonize acetylcholine at the receptor.

Question 25Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

A patient undergoes a rapid sequence induction with succinylcholine and develops masseter spasm and hypercarbia. Which underlying pathophysiology is most consistent with malignant hyperthermia?

  1. Deficiency of plasma cholinesterase
  2. Excessive calcium release from the sarcoplasmic reticulum via a ryanodine receptor defect Correct answer.
  3. Antibody-mediated nicotinic receptor destruction
  4. Excess acetylcholinesterase activity at the motor end plate

Explanation

Malignant hyperthermia results from a defect in the ryanodine receptor that causes uncontrolled calcium release from the sarcoplasmic reticulum, producing sustained muscle contraction, hypermetabolism, and hypercarbia. Treatment is dantrolene, which inhibits this calcium release.

Question 26Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

During direct laryngoscopy, which laryngeal structure lies most posterior and is the first cartilaginous landmark encountered after passing the vallecula?

  1. Arytenoid cartilage
  2. Cricoid cartilage
  3. Epiglottis Correct answer.
  4. Thyroid cartilage

Explanation

The epiglottis is a fibrocartilaginous flap attached to the thyroid cartilage that projects upward behind the tongue base. When the blade is placed in the vallecula and lifted, the epiglottis is displaced anteriorly and is the first laryngeal structure visualized, exposing the glottic opening behind it.

Question 27Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

A 70 kg patient receives a drug with a volume of distribution of 0.5 L/kg. Approximately what loading dose is required to achieve a plasma concentration of 4 mg/L?

  1. 140 mg Correct answer.
  2. 280 mg
  3. 1400 mg
  4. 14 mg

Explanation

Volume of distribution equals 0.5 L/kg multiplied by 70 kg, giving 35 L. The loading dose is the target concentration multiplied by volume of distribution, so 4 mg/L times 35 L equals 140 mg.

Question 28Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which gas law explains why a nitrous oxide cylinder pressure gauge remains constant until the liquid nitrous oxide is nearly exhausted?

  1. Dalton's law
  2. Charles's law
  3. Boyle's law
  4. Henry's law Correct answer.

Explanation

Henry's law states that the amount of dissolved gas is proportional to its partial pressure above the liquid, and it governs the equilibrium between liquid and vapour in a cylinder. In a nitrous oxide cylinder, vapour pressure stays constant at a given temperature while liquid and gas coexist, so the gauge reads a plateau until only gas remains.

Question 29Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which change occurs in the cardiovascular system during the first hour of a high spinal anesthetic extending to T2?

  1. Increased venous return from venoconstriction
  2. Increased systemic vascular resistance
  3. Bradycardia from unopposed vagal tone Correct answer.
  4. Reflex tachycardia from sympathetic activation

Explanation

High neuraxial blockade interrupts cardiac sympathetic fibres arising from T1 to T4, leaving vagal tone unopposed. The combination of reduced right atrial filling from venodilation and unopposed vagal activity commonly produces bradycardia, which can progress to severe hypotension or cardiac arrest.

Question 30Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which statement about the pharmacology of atropine compared with glycopyrrolate is correct?

  1. Atropine crosses the blood-brain barrier more readily and causes more central anticholinergic effects Correct answer.
  2. Glycopyrrolate produces more marked tachycardia at equipotent doses
  3. Glycopyrrolate has a faster onset of action after intravenous injection
  4. Atropine is a quaternary ammonium compound with minimal lipid solubility

Explanation

Atropine is a tertiary amine and is therefore lipid soluble, allowing it to enter the central nervous system and produce effects such as sedation and confusion at higher doses. Glycopyrrolate is a quaternary ammonium compound that is largely excluded from the brain and has a slower onset but longer duration.

Question 31Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which mechanism best explains why a patient with renal failure has an exaggerated response to a standard dose of morphine?

  1. Accumulation of morphine-6-glucuronide Correct answer.
  2. Enhanced renal clearance of morphine-3-glucuronide
  3. Reduced plasma protein binding of morphine
  4. Increased hepatic first-pass metabolism of morphine

Explanation

Morphine is metabolized by glucuronidation to morphine-3-glucuronide and morphine-6-glucuronide, and the latter is a potent opioid agonist. In renal failure these metabolites accumulate and can cause prolonged sedation and respiratory depression even when the parent drug level is falling.

Question 32Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which feature distinguishes the blood supply of the spinal cord that is clinically relevant during aortic surgery?

  1. The spinal cord receives no radicular contributions below T6
  2. The anterior spinal artery is supplemented by the artery of Adamkiewicz, which arises variably between T8 and L1 Correct answer.
  3. The posterior spinal arteries supply the anterior two-thirds of the cord
  4. The artery of Adamkiewicz most commonly arises from the cervical vertebral artery

Explanation

The anterior spinal artery is a slender vessel that depends on radicular contributions, the largest being the artery of Adamkiewicz, which arises variably from a lower thoracic or upper lumbar intercostal or lumbar artery. Its variable origin makes the lower thoracic cord vulnerable to ischemia during aortic cross-clamping.

Question 33Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which statement about the physiology of cerebrospinal fluid is correct?

  1. Cerebrospinal fluid is produced predominantly by the ependymal lining of the lateral ventricles
  2. Cerebrospinal fluid is reabsorbed mainly through the arachnoid villi into the dural venous sinuses Correct answer.
  3. Cerebrospinal fluid is an ultrafiltrate of plasma with the same protein content as plasma
  4. Cerebrospinal fluid is produced mainly by the choroid plexus at a rate of about 500 mL per day

Explanation

Cerebrospinal fluid is formed mainly by the choroid plexus at roughly 500 mL per day and is absorbed through the arachnoid villi into the dural venous sinuses, driven by a pressure gradient. This balance determines intracranial pressure and the volume of fluid available for spinal anesthesia.

Question 34Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which change in respiratory physiology occurs when a patient is placed in the prone position under general anesthesia?

  1. Functional residual capacity increases compared with the supine position
  2. The supine-to-prone change reduces functional residual capacity and worsens ventilation-perfusion matching Correct answer.
  3. Diaphragmatic excursion becomes more efficient because abdominal pressure is reduced
  4. The dependent lung regions become better ventilated but less perfused

Explanation

Prone positioning under anesthesia typically reduces functional residual capacity and restricts diaphragmatic movement because of abdominal pressure and chest wall support. The dependent dorsal lung regions remain well perfused but become less ventilated, worsening ventilation-perfusion matching unless lung-protective ventilation is used.

Question 35Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which best explains why a volatile anesthetic with a low blood-gas solubility coefficient produces a faster rise in alveolar concentration?

  1. It undergoes less metabolism in the liver
  2. It has a higher oil-gas solubility coefficient, increasing its potency
  3. It is taken up less avidly by blood, so alveolar partial pressure rises rapidly toward inspired partial pressure Correct answer.
  4. It diffuses more rapidly across the alveolar membrane

Explanation

The blood-gas solubility coefficient determines how much agent is absorbed from alveoli into blood. A low coefficient means less agent is taken up, so alveolar partial pressure rises quickly toward the inspired value, and induction and emergence are correspondingly fast.

Question 36Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which statement about the anatomy of the brachial plexus at the level of the first rib is correct?

  1. The plexus is formed by the anterior rami of C5 to T1 Correct answer.
  2. The cords are named according to their relation to the axillary artery
  3. The trunks divide into cords at the level of the first rib
  4. The musculocutaneous nerve arises directly from the posterior cord

Explanation

The brachial plexus is formed by the anterior rami of spinal nerves C5 to T1, which pass between the anterior and middle scalene muscles. The roots form trunks, the trunks divide into divisions behind the clavicle, and the divisions form cords around the second part of the axillary artery.

Question 37Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which mechanism explains the increased sensitivity to non-depolarizing neuromuscular blockers in a patient with myasthenia gravis?

  1. Increased release of acetylcholine from the motor nerve terminal
  2. Upregulation of postjunctional acetylcholine receptors
  3. Enhanced acetylcholinesterase activity at the endplate
  4. Reduced number of functional postjunctional acetylcholine receptors Correct answer.

Explanation

Myasthenia gravis is an autoimmune disease in which antibodies destroy or block postjunctional acetylcholine receptors. With fewer functional receptors, a given concentration of non-depolarizing blocker produces greater blockade, so these patients require reduced doses and are also at risk of postoperative respiratory failure.

Question 38Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which factor most increases the resistance to gas flow through an endotracheal tube during mechanical ventilation?

  1. Increasing the internal diameter of the tube
  2. Decreasing the length of the tube
  3. Increasing the flow rate through the tube Correct answer.
  4. Increasing the humidity of the inspired gas

Explanation

For turbulent flow through a tube, resistance rises with the square of the flow rate, so doubling flow quadruples the pressure required. Tube radius has a much larger fourth-power effect on resistance, but among the listed options increasing flow is the factor that increases resistance.

Question 39Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

Which statement about the physiology of the pulmonary circulation is correct?

  1. Pulmonary vascular resistance falls as lung volume increases from residual volume to functional residual capacity
  2. Hypoxic pulmonary vasoconstriction diverts blood away from poorly ventilated alveoli Correct answer.
  3. Pulmonary blood flow is greatest at the lung apex in the upright position
  4. Pulmonary artery pressure is normally higher than systemic arterial pressure

Explanation

Hypoxic pulmonary vasoconstriction is a local response in which small pulmonary arteries constrict when alveolar oxygen tension falls. This diverts blood from poorly ventilated regions toward better-ventilated alveoli and helps preserve arterial oxygenation during one-lung ventilation.

Question 40Basic Sciences Relevant to Anesthesia (Anatomy, Physiology, Pharmacology, Physics)

A patient with chronic obstructive pulmonary disease has a raised bicarbonate and a normal arterial pH. Which interpretation of the acid-base status is most appropriate?

  1. Mixed metabolic acidosis and respiratory alkalosis
  2. Chronic respiratory acidosis with metabolic compensation Correct answer.
  3. Metabolic alkalosis with respiratory compensation
  4. Acute respiratory acidosis with no renal compensation

Explanation

A normal pH with an elevated arterial carbon dioxide and a raised bicarbonate indicates chronic respiratory acidosis in which the kidneys have retained bicarbonate over days to weeks. The compensation returns pH toward normal without fully correcting the carbon dioxide, which distinguishes chronic from acute respiratory acidosis.

Question 41Preoperative Assessment and Patient Optimization

A 68-year-old man scheduled for elective hip arthroplasty takes clopidogrel for a drug-eluting coronary stent placed 4 months ago. What is the most appropriate preoperative management?

  1. Substitute warfarin bridging until the day of surgery
  2. Stop clopidogrel 5 days before surgery and proceed as planned
  3. Defer surgery and consult cardiology about the ongoing dual antiplatelet therapy Correct answer.
  4. Proceed with surgery without interrupting clopidogrel

Explanation

Elective surgery should be postponed in a patient still within the recommended duration of dual antiplatelet therapy after a drug-eluting stent, because premature interruption risks stent thrombosis. The decision to stop or continue antiplatelet therapy requires cardiology input rather than unilateral surgical scheduling. Bridging with warfarin does not substitute for antiplatelet effect.

Question 42Preoperative Assessment and Patient Optimization

Which preoperative finding most strongly predicts difficult mask ventilation in an adult?

  1. Thyromental distance of 7 cm
  2. Mallampati class I
  3. Age under 40 years
  4. Body mass index greater than 30 kg/m2 Correct answer.

Explanation

Obesity is one of the strongest independent predictors of difficult mask ventilation, along with age over 55, beard, edentulous state, and history of snoring. Mallampati class and thyromental distance relate more to difficult laryngoscopy. Younger age is not a recognized risk factor.

Question 43Preoperative Assessment and Patient Optimization

A patient with cirrhosis (Child-Pugh class C, MELD 22) is being assessed for elective cholecystectomy. Which statement best reflects preoperative risk?

  1. Coagulation studies are the only preoperative parameter that matters
  2. Child-Pugh class C predicts markedly increased perioperative mortality and warrants deferral or optimization Correct answer.
  3. Child-Pugh class has no bearing on anesthetic planning
  4. MELD score is irrelevant to perioperative risk in hepatobiliary surgery

Explanation

Child-Pugh class C cirrhosis carries a high perioperative mortality, particularly with major abdominal surgery, and elective procedures should generally be deferred or optimized. MELD also predicts perioperative risk and complements Child-Pugh. Coagulation alone does not capture the multisystem dysfunction of cirrhosis.

Question 44Preoperative Assessment and Patient Optimization

Which preoperative test is routinely indicated before cataract surgery under topical anesthesia in an otherwise healthy adult?

  1. Resting electrocardiogram
  2. Complete blood count
  3. Chest radiograph
  4. No routine preoperative testing Correct answer.

Explanation

Low-risk procedures such as cataract surgery under topical anesthesia do not require routine preoperative testing in healthy patients. Testing should be guided by history, comorbidity, and the planned anesthetic. Routine ECG, CBC, and chest radiograph add cost without improving outcomes in this population.

Question 45Preoperative Assessment and Patient Optimization

A 55-year-old with obstructive sleep apnea (apnea-hypopnea index 35) is scheduled for outpatient knee arthroscopy. Which factor most favors an inpatient or monitored setting?

  1. Use of a peripheral nerve block
  2. A preoperative apnea-hypopnea index above 30 with planned postoperative opioids Correct answer.
  3. Male sex
  4. Surgery lasting 45 minutes

Explanation

Severe OSA (AHI greater than 30) combined with postoperative opioid requirements increases the risk of perioperative respiratory events and often warrants monitored or inpatient care. Regional anesthesia and short procedure duration are favorable features. Male sex alone is not a determinant of disposition.

Question 46Preoperative Assessment and Patient Optimization

Which statement about perioperative beta-blocker initiation is most consistent with current evidence?

  1. Abruptly discontinue chronic beta blockade before surgery
  2. Continue chronic beta blockade perioperatively and avoid starting high doses acutely on the day of surgery Correct answer.
  3. Initiate beta blockade only after induction of anesthesia
  4. Start high-dose beta blockade on the day of surgery in all patients

Explanation

Patients on chronic beta blockers should generally continue them perioperatively to avoid rebound tachycardia and ischemia. Acute high-dose initiation on the day of surgery has been associated with harm, including stroke and hypotension. Titrated initiation days to weeks before surgery may be considered in selected high-risk patients.

Question 47Preoperative Assessment and Patient Optimization

A patient reports anaphylaxis to penicillin. Which preoperative step best reduces the risk of a perioperative reaction?

  1. Give a test dose of penicillin in the preoperative holding area
  2. Premedicate with diphenhydramine and proceed with penicillin
  3. Obtain a detailed allergy history and select structurally unrelated antibiotics Correct answer.
  4. Give a cephalosporin routinely because cross-reactivity is negligible

Explanation

A structured allergy history clarifies the reaction type and severity and guides selection of structurally unrelated antibiotics. Routine cephalosporin use is not universally safe, as cross-reactivity depends on side-chain structure. Test dosing and antihistamine premedication do not reliably prevent anaphylaxis.

Question 48Preoperative Assessment and Patient Optimization

Which preoperative laboratory abnormality most warrants correction before elective surgery?

  1. Platelet count of 220,000/mm3
  2. Serum potassium of 2.8 mmol/L Correct answer.
  3. Hemoglobin of 12.5 g/dL
  4. Sodium of 138 mmol/L

Explanation

Severe hypokalemia increases the risk of intraoperative arrhythmias and should be corrected before elective surgery. The other values are within normal ranges and do not require intervention. Elective procedures allow time to normalize significant electrolyte disturbances.

Question 49Preoperative Assessment and Patient Optimization

A patient with severe aortic stenosis (aortic valve area 0.7 cm2) is scheduled for elective colon resection. Which statement best guides management?

  1. Defer elective surgery for cardiology evaluation and possible valve intervention Correct answer.
  2. Give a large fluid bolus preoperatively to increase cardiac output
  3. Proceed with surgery because general anesthesia is safe in aortic stenosis
  4. Avoid neuraxial anesthesia in all cases of aortic stenosis

Explanation

Severe symptomatic aortic stenosis carries high perioperative risk, and elective surgery should be deferred for cardiology evaluation and consideration of valve replacement. Maintenance of sinus rhythm, preload, and afterload is critical if surgery must proceed. Large fluid boluses may precipitate pulmonary edema in the setting of diastolic dysfunction.

Question 50Preoperative Assessment and Patient Optimization

Which preoperative measure is most effective for reducing surgical site infection in colorectal surgery?

  1. Administering prophylactic antibiotics within 60 minutes before incision Correct answer.
  2. Shaving the surgical site the night before
  3. Routine postoperative antibiotic administration for 5 days
  4. Using a drain at the surgical site

Explanation

Timely prophylactic antibiotic administration before incision, along with normothermia and glycemic control, reduces surgical site infection. Hair removal should be done with clippers immediately before surgery rather than shaving the night before. Prolonged postoperative antibiotics and routine drains do not reduce infection.