Stanford's Clinical Pre Flashcards
According to ASA Standard I, what is the minimum requirement for anesthesia personnel?
A) Presence during induction only
B) Presence throughout the conduct of all anesthetics
C) Availability for consultation by phone
D) Presence only for general anesthesia cases
Answer: B
Rationale: ASA Standard I specifies that qualified anesthesia personnel must be present throughout the conduct of all types of anesthesia to ensure patient safety.
Which of the following is evaluated continually according to ASA Standard II?
A) Patient’s oxygenation, ventilation, circulation, and temperature
B) Only oxygenation and ventilation
C) Only circulation
D) Patient’s comfort and pain levels
Answer: A
Rationale: ASA Standard II requires continual evaluation of oxygenation, ventilation, circulation, and temperature during anesthesia.
or oxygenation monitoring, which of the following devices is used to assess inspired gas in an anesthesia machine?
A) EKG
B) Capnograph
C) FiO2 analyzer
D) Thermometer
Answer: C
Rationale: The FiO2 analyzer monitors inspired gas and oxygen concentration levels during anesthesia.
When using mechanical ventilation, what alarm setting must be activated according to ASA standards (select 2)?
A) Heart rate alarm
B) Low Oxygen saturation alarm
C) Disconnection alarm
D) Blood pressure alarm
Answer: B & C
Rationale: The disconnection and low Oxygen Sat alarms must be activated when the patient is mechanically ventilated to detect accidental disconnections.
Which of the following circulatory monitoring techniques is NOT part of the continuous circulatory assessment requirement?
A) Pulse oximetry
B) Pulse tracing
C) A line tracing
D) Blood pressure every 15 minutes
Answer: D
Rationale: Blood pressure should be checked at a minimum of every 5 minutes, not 15, as part of circulatory assessment.
The fractional oxygen saturation (S𝑝𝑂2) includes which of the following?
A) Only oxyhemoglobin (O2Hb)
B) O2Hb, deoxyhemoglobin (Hb), MetHb, and COHb
C) Only MetHb and COHb
D) Only deoxyhemoglobin (Hb)
Answer: B
Rationale: Fractional oxygen saturation accounts for all forms of hemoglobin including O2Hb, deoxyhemoglobin (Hb), MetHb, and COHb
In pulse oximetry, light absorption at 660 nm predominantly measures which type of hemoglobin select 2?
A) Oxyhemoglobin
B) Carboxyhemoglobin
C) Deoxyhemoglobin
D) Methemoglobin
Answer: C & D
Rationale: Light at 660 nm (red light) is primarily absorbed by deoxyhemoglobin.
he AC component of the pulse oximeter measures:
A) Venous blood flow
B) Pulsatile arterial blood
C) Capillary blood
D) Non-pulsatile tissue absorption
Answer: B
Rationale: The AC (alternating current) component corresponds to the pulsatile arterial blood, which changes with each heartbeat.
Which of the following can cause falsely elevated SpO2 readings? (Select 2)
A) Anemia
B) Carboxyhemoglobin
C) Methemoglobinemia
D) Cyanide poisoning
Answers: B, D
Rationale: Carboxyhemoglobin and cyanide poisoning can both lead to falsely high SpO2 readings. Anemia affects the amount of hemoglobin but does not directly alter the SpO2
reading.
Methemoglobinemia typically results in what change to the SpO2reading when MetHb levels are high?
A) SpO2 approaches 100%
B) SpO2 approaches 0%
C) SpO2 remains around 85%
D) SpO2 shows extreme variability
Answer: C
Rationale: High levels of methemoglobin cause the SpO2
reading to approximate 85%, regardless of true oxygenation.
What are the recommended treatments for methemoglobinemia? (Select 2)
A) Methylene blue
B) Vitamin C
C) Epinephrine
D) Albuterol
Answers: A, B
Rationale: Methylene blue is the primary treatment. Vitamin C may also help, particularly in patients with G6PD deficiency who cannot tolerate methylene blue.
What abnormality is commonly seen on an arterial blood gas (ABG) in patients suffering from cyanide poisoning? (Select 2)
A) Low partial pressure of oxygen (PaO2)
B) Normal partial pressure of oxygen with falsely elevated oxygen saturation readings
C) High lactate levels indicating lactic acidosis
D) Low bicarbonate levels
Answers: B, C
Rationale: Cyanide poisoning disrupts cellular respiration, leading to tissue hypoxia. This can result in normal oxygen levels in the blood despite a falsely high oxygen saturation reading. High lactate levels are common due to impaired aerobic metabolism.
A patient undergoing surgery has a stable oxygen saturation reading of 85% despite increasing the fraction of inspired oxygen. An arterial blood gas shows a normal partial pressure of oxygen. What is the most likely diagnosis?
A) Low blood volume (hypovolemia)
B) High levels of methemoglobin in the blood (methemoglobinemia)
C) Blockage of a lung artery (pulmonary embolism)
D) Carbon monoxide poisoning
Answer: B
Rationale: Methemoglobinemia causes a constant oxygen saturation reading of around 85%, regardless of actual oxygenation levels, due to altered hemoglobin that cannot carry oxygen effectively.
During a house fire, a patient is brought to the hospital with an oxygen saturation reading of 99% but is showing severe signs of respiratory distress. Which conditions should be considered in this patient? (Select 2)
A) High levels of methemoglobin (methemoglobinemia)
B) High levels of carboxyhemoglobin (carboxyhemoglobinemia)
C) Cyanide poisoning from smoke inhalation
D) Severe asthma attack
Answers: B, C
Rationale: Carboxyhemoglobin can falsely elevate the oxygen saturation reading, giving a misleading impression of good oxygenation. Cyanide poisoning is also a risk in smoke inhalation cases and can cause severe tissue hypoxia despite normal blood oxygen readings.
What is the first-line treatment for a patient diagnosed with cyanide poisoning?
A) Methylene blue
B) Atropine
C) Hydroxocobalamin (Vitamin B12a)
D) Sodium bicarbonate
Answer: C
Rationale: Hydroxocobalamin is the preferred treatment for cyanide poisoning. It binds to cyanide to form cyanocobalamin, which is then excreted by the body.
A patient shows an oxygen saturation reading of 100% after being resuscitated from smoke inhalation, but they continue to have symptoms of severe hypoxia, such as confusion and low blood pressure. What is the most likely cause of the discrepancy between the oxygen saturation reading and the patient’s clinical presentation?
A) Methemoglobinemia
B) Carboxyhemoglobinemia
C) Cyanide toxicity
D) Pulmonary embolism
Answer: B
Rationale: Carboxyhemoglobin, which forms from carbon monoxide exposure during smoke inhalation, can falsely elevate oxygen saturation readings, masking the true hypoxic state of the patient.
Which two wavelengths of light are primarily used in pulse oximetry to determine oxygen saturation? (Select 2)
A) 450 nm
B) 660 nm
C) 850 nm
D) 940 nm
nswers: B, D
Rationale: Pulse oximeters use red light at 660 nm and infrared light at 940 nm to differentiate between oxyhemoglobin and deoxyhemoglobin.
What does it mean if a pulse oximeter shows a reading of 85% when the patient is not connected to the device?
A) The patient is severely hypoxic
B) The ratio of light absorption at 660 nm and 940 nm is equal (1:1)
C) The device is malfunctioning
D) The patient’s hemoglobin is fully saturated
Answer: B
Rationale: When the ratio of light absorption at 660 nm and 940 nm is equal (1:1), the pulse oximeter defaults to a reading of 85%. This can happen when the sensor is disconnected or when there is interference from certain types of hemoglobin (e.g., methemoglobin).
Which of the following factors can cause a falsely low oxygen saturation reading on a pulse oximeter? (Select 2)
A) Blue nail polish
B) Anemia
C) Methylene blue dye
D) High ambient light
Answers: A, C
Rationale: Blue nail polish and methylene blue dye can interfere with the light absorption used by pulse oximeters, leading to falsely low readings. Anemia typically does not affect the oxygen saturation measurement directly.
What condition is often clinically apparent when a patient has 5 grams per deciliter of desaturated hemoglobin?
A) Hypothermia
B) Hypovolemia
C) Cyanosis
D) Hypoglycemia
Answer: C
Rationale: Cyanosis becomes visible when there is approximately 5 grams per deciliter of desaturated hemoglobin, resulting in a bluish discoloration of the skin.
What is an advantage of using a modified 3-electrode EKG system?
A) Provides better detection of atrial dysrhythmias
B) Allows monitoring of anterior wall ischemia
C) Offers full 12-lead analysis
D) Reduces sensitivity for ischemic changes
Answer: B
Rationale: The modified 3-electrode system places the left arm lead in the V5 position to better detect anterior wall ischemia.
Which EKG lead is considered the best for detecting P waves and sinus rhythm?
A) Lead I
B) Lead II
C) Lead III
D) aVR
Answer: B
Rationale: Lead II is most commonly used to detect P waves and assess sinus rhythm due to its alignment with the heart’s electrical axis.
In a 5-electrode EKG system, which combination of leads is most sensitive for detecting ischemic changes?
A) Lead I and Lead III
B) Lead II and aVR
C) V1 and V4
D) V4 and V5
Answers: D
Rationale: The addition of V4 and V5 leads in a 5-electrode system improves sensitivity for detecting ischemic changes.
What is the main measurement derived by automated noninvasive blood pressure (NIBP) devices?
A) Systolic blood pressure (SBP)
B) Mean arterial pressure (MAP)
C) Diastolic blood pressure (DBP)
D) Pulse pressure
Answer: B
Rationale: Automated NIBP devices primarily measure mean arterial pressure (MAP) and then calculate systolic and diastolic pressures using algorithms.
Which of the following could result from using a blood pressure cuff that is too small for the patient’s arm?
A) Falsely low blood pressure reading
B) Falsely high blood pressure reading
C) Accurate blood pressure measurement
D) Inability to detect diastolic pressure
Answer: B
Rationale: Using a cuff that is too small can result in a falsely high blood pressure reading because the cuff exerts more pressure than necessary.
Which of the following is an indication for invasive blood pressure monitoring? (Select 2)
A) Routine outpatient surgery
B) Rapid blood sampling requirements
C) Hemodynamic instability
D) Low-risk procedures
Answers: B, C
Rationale: Invasive blood pressure monitoring is indicated when frequent blood sampling is needed or when the patient is hemodynamically unstable.
How does blood pressure change when the patient’s head is elevated by 10 centimeters?
A) Increases by 10 mm Hg
B) Decreases by 7.4 mm Hg
C) Increases by 7.4 mm Hg
D) Remains unchanged
Answer: B
Rationale: According to the mnemonic provided (pH 7.410), elevating the head by 10 centimeters results in a decrease of blood pressure by approximately 7.4 mm Hg.
Which mnemonic can help remember the relationship between changes in height and changes in blood pressure?
A) pH 7.410
B) ABG 7.250
C) MAP 65.00
D) O2 Sat 98%
Answer: A
Rationale: The mnemonic “pH 7.410” is used to remember that a pressure change of 7.4 mm Hg corresponds to a height change of 10 centimeters.
In a patient positioned in the Beach chair (sitting) position with a blood pressure reading of 120/80 mm Hg on the leg, what would be the approximate blood pressure at the level of the brain if the brain is 60 cm higher than the cuff?
A) 90/60 mm Hg
B) 110/70 mm Hg
C) 75/35 mm Hg
D) 130/85 mm Hg
Answer: C
Rationale: For every 10 cm height difference, blood pressure decreases by approximately 7.4 mm Hg. A 60 cm difference results in a substantial decrease in pressure, bringing the brain’s blood pressure closer to 75/35 mm Hg.
When positioning an arterial line transducer for a neurosurgical procedure, where should the transducer be leveled?
A) At the level of the patient’s heart (phlebostatic axis)
B) At the level of the patient’s knees
C) At the level of the patient’s head (circle of Willis)
D) At the level of the patient’s feet
Answer: C
Rationale: In neurosurgical cases, the transducer should be leveled at the patient’s head (circle of Willis) to accurately reflect cerebral perfusion pressure.
What effect does lowering the arterial line transducer below the level of the patient’s heart have on the blood pressure reading?
A) It decreases the reading
B) It does not change the reading
C) It increases the reading
D) It measures venous pressure instead
Answer: C
Rationale: Lowering the transducer below the heart level results in a falsely elevated blood pressure reading due to hydrostatic pressure.
As you move further from the aorta, which of the following changes can be observed in arterial line tracings? (Select 2)
A) Increased systolic pressure
B) Decreased dicrotic notch
C) Narrower pulse pressure
D) Higher dicrotic notch
Answers: A, B
Rationale: Moving further from the aorta results in an increased systolic pressure (Amplification) and a later (lower) dicrotic notch. Pulse pressure widens, not narrows, with distance from the aorta.
What is the clinical significance of the delayed dicrotic notch in arterial line tracings seen further from the aorta?
A) It indicates reduced cardiac output
B) It is caused by reflected pressure waves
C) It signifies valve dysfunction
D) It indicates venous congestion
Answer: B
Rationale: The delayed dicrotic notch is due to reflected pressure waves as the pulse wave travels further from the central aorta.
Which of the following can be used as a reliable indicator of fluid responsiveness in a mechanically ventilated patient?
A) Mean arterial pressure
B) Pulse pressure variation
C) Capillary refill time
D) Systolic blood pressure
Answer: B
Rationale: Pulse pressure variation is a dynamic indicator of fluid responsiveness, particularly in patients who are mechanically ventilated.
What effect does deep inspiration have on pulse pressure and stroke volume in a healthy patient?
A) It decreases pulse pressure and stroke volume
B) It increases pulse pressure but decreases stroke volume
C) It decreases stroke volume and increases pulse pressure
D) It has no effect on pulse pressure or stroke volume
Answer: A
Rationale: Deep inspiration reduces venous return to the heart, leading to decreased stroke volume and, consequently, a decrease in pulse pressure.
Which phase of the capnography waveform corresponds to the alveolar plateau, where the carbon dioxide concentration represents the patient’s maximal alveolar CO2 level?
A) Phase I
B) Phase II
C) Phase III
D) Phase IV
Answer: C
Rationale: Phase III of the capnography waveform is the alveolar plateau, reflecting the maximal alveolar carbon dioxide concentration (End-tidal CO2).
Which of the following can lead to an increased end-tidal carbon dioxide (ETCO2) reading? (Select 2)
A) Hyperventilation
B) Hypoventilation
C) Increased metabolic rate
D) Decreased cardiac output
Answers: B, C
Rationale: Hypoventilation and an increased metabolic rate can lead to elevated end-tidal CO2 levels due to reduced CO2 elimination and increased production, respectively.
What is a common cause of a sudden drop to near-zero in the end-tidal carbon dioxide reading during surgery?
A) Hyperthermia
B) Disconnection of the breathing circuit
C) Increased dead space
D) Excessive sedation
Answer: B
Rationale: A sudden drop to near-zero ETCO2 is commonly caused by a disconnection in the breathing circuit, interrupting CO2 detection.
Which of the following conditions can cause an upward sloping capnography waveform (upsloping phase)?
A) Hyperventilation
B) Bronchospasm
C) Hypotension
D) Pulmonary embolism
Answer: B
Rationale: An upward sloping capnography waveform suggests airway obstruction, commonly seen in conditions like bronchospasm or chronic obstructive pulmonary disease (COPD). Larger alpha angle.
What is a likely cause of a sudden drop to near-zero in end-tidal CO₂ (ETCO₂) during cardiopulmonary resuscitation (CPR)?
A) High-quality chest compressions
B) Recovery of spontaneous circulation (ROSC)
C) Esophageal intubation
D) Increased ventilation rate
Answer: C
Rationale: A sudden drop in ETCO₂ to near-zero often indicates esophageal intubation, as the carbon dioxide from the lungs is not being detected.
During CPR, a sudden increase in ETCO₂ from 10 mm Hg to 35 mm Hg is most indicative of what event?
A) Ineffective chest compressions
B) Hyperventilation
C) Recovery of spontaneous circulation (ROSC)
D) Massive pulmonary embolism
Answer: C
Rationale: A sudden increase in ETCO₂ during CPR is a strong indicator of ROSC, as effective circulation returns carbon dioxide to the lungs.
Which of the following can cause a decrease in ETCO₂ due to reduced carbon dioxide production? (Select 2)
A) Hyperthyroidism
B) Hypothyroidism
C) Neuromuscular blockade
D) Increased metabolic rate
Answers: B, C
Rationale: Both hypothyroidism and neuromuscular blockade can lead to decreased carbon dioxide production, resulting in lower ETCO₂ readings.
A patient experiences a sudden drop in ETCO₂ during surgery. Which of the following should be considered first as a potential cause?
A) Circuit sampling line disconnect
B) Hyperventilation
C) Malignant hyperthermia
D) Cardiac tamponade
Answer: A
Rationale: A sudden drop in ETCO₂ often points to a mechanical issue such as disconnection of the sampling line.
During laparoscopic surgery, an intubated patient in Trendelenburg position shows a decrease in oxygen saturation from 100% to 95% and an increase in ETCO₂ from 35 to 40 mm Hg. What is the most likely cause?
A) Decreased diaphragmatic excursion
B) Pneumothorax
C) Carbon dioxide embolism
D) Compression of the vena cava
Answer: A
Rationale: In Trendelenburg position, the diaphragm is pushed upward, reducing lung capacity and causing decreased diaphragmatic excursion, leading to an increase in ETCO₂.
Which capnography waveform pattern is most consistent with a sample line leak?
A) Gradual upsloping trace
B) Sudden drop to baseline
C) Prolonged expiratory phase
D) Oscillating baseline
Answer: B
Rationale: A sudden drop in the capnography trace to baseline suggests a sampling line disconnect or leak, interrupting the detection of exhaled carbon dioxide.
Which of the following conditions is suggested by a capnography waveform with a prolonged expiratory plateau (Phase III)?
A) Normal ventilation
B) Emphysema
C) Hyperventilation
D) Sample line obstruction
Answer: B
Rationale: A prolonged expiratory plateau is commonly seen in patients with obstructive lung disease, such as emphysema, due to delayed exhalation.
Make sure to increase the expiratory time or you might start to see the baseline start to climb, ie not reaching zero.
Which temperature monitoring site provides the most accurate reflection of the patient’s core temperature?
A) Axillary
B) Tympanic membrane
C) Pulmonary artery
D) Skin
Answer: C
Rationale: The pulmonary artery temperature is considered the gold standard for core temperature measurement, closely reflecting the body’s true core temperature.
Tympanic membrane is a decent estimation of core body temp and can be used as well.
What is a potential consequence of using a rectal temperature probe in a patient with reduced lower extremity blood flow?
A) Overestimation of core temperature
B) Underestimation of core temperature
C) Accurate temperature reading
D) Increased risk of infection
Answer: B
Rationale: Reduced blood flow to the lower extremities may cause underestimation of core temperature when using a rectal probe due to poor perfusion.
According to the capnography clinical pearl, how much should the end-tidal carbon dioxide level increase per minute during apnea?
A) 1 mm Hg
B) 2 mm Hg
C) 3 mm Hg
D) 6 mm Hg
Answer: D
Rationale: The clinical pearl states that during apnea, ETCO₂ is expected to increase by 6 mm Hg after the first minute and by approximately 3 mm Hg every minute thereafter.
Which monitoring device is used to assess the depth of anesthesia?
A) Central venous pressure (CVP) monitor
B) Intracranial pressure (ICP) monitor
C) BIS monitor or Sedline
D) Foley catheter
Answer: C
Rationale: The BIS monitor or Sedline is used to monitor the depth of anesthesia by assessing the patient’s brain activity.
What is a primary indication for using a pulmonary artery (PA) catheter during surgery?
A) Assessing intracranial pressure
B) Monitoring central venous pressure only
C) Measuring continuous cardiac output and hemodynamic status
D) Detecting air embolism
Answer: C
Rationale: The PA catheter is used for advanced hemodynamic monitoring, including continuous cardiac output measurement.
Which of the following is the best choice for monitoring if there is a high risk of air embolism during surgery?
A) Esophageal stethoscope
B) Precordial Doppler
C) Foley catheter
D) Sedline
Answer: B
Rationale: The precordial Doppler is highly sensitive for detecting air embolisms, making it the preferred monitoring device in high-risk cases.
A precordial Doppler ultrasound detects air embolisms by producing a distinctive sound pattern that changes when air enters the body:
Small air embolisms: A brief “chirp” sound
Large air embolisms: A persistent “static” sound, similar to a gramophone needle on a record
What monitoring adjunct is commonly used in neurosurgical procedures to assess cerebral oxygenation?
A) Transesophageal echocardiogram (TEE)
B) Cerebral oximetry (NIRS)
C) Central venous pressure (CVP) monitor
D) Foley catheter
Answer: B
Rationale: Near-infrared spectroscopy (NIRS) is used for cerebral oximetry to monitor brain oxygen levels, especially in neurosurgical cases.
Near-infrared spectroscopy (NIRS) is a non-invasive technique that measures cerebral oxygenation by using infrared light to penetrate the head and scalp and measuring the absorption of light by tissue chromophores:
1. Light penetration
NIRS uses light in the near-infrared range of 700–1000 nanometers (nm) that can pass through skin, bone, and other tissues.
2. Light absorption
The amount of infrared light absorbed by tissue depends on the concentration of oxygenated and deoxygenated hemoglobin (HbO2 and HbR).
3. Data analysis
The device uses a modified version of the Beer-Lambert law to calculate the concentration of hemoglobin species from the relative absorption of light at different wavelengths.
NIRS can be used to monitor cerebral oxygenation during surgery and in the hospital bed. It can help detect oxygen deficiency in the brain, and can be used to guide therapy to reverse oxygenation issues. NIRS can also be used to monitor cerebral blood flow (CBF) and volume, and cerebral venous oxygen saturation.
Which of the following phases is NOT typically a part of the pharmacokinetics of inhalational anesthetic agents?
A) Uptake
B) Distribution
C) Filtration
D) Elimination
Answer: C
Rationale: The four main phases of pharmacokinetics for inhalational anesthetics are uptake (absorption into the bloodstream), distribution (to the site of action like the CNS), minimal metabolism, and elimination (primarily via exhalation). Filtration is not a phase in this context.
What is the primary goal of administering an inhalational anesthetic agent?
A) To achieve high blood concentration
B) To achieve a partial pressure of the agent in the alveoli that equilibrates with the CNS
C) To maximize metabolism in the liver
D) To maintain constant heart rate
Answer: B
Rationale: The goal is to produce a partial pressure of the anesthetic gas in the alveoli that equilibrates with the central nervous system (CNS), allowing the gas to exert its anesthetic effect. Partial pressure, not concentration, determines the anesthetic’s effect.
Which factor increases the inspired concentration (Fi) of an inhalational anesthetic?
A) High circuit absorption
B) Low fresh gas flow
C) Increased fresh gas flow
D) Decreased ventilation
Answer: C
When the fresh gas flow is increased, more of the anesthetic gas is delivered to the patient, directly increasing the inspired concentration (Fi).
What determines the alveolar concentration (FA) of an inhalational anesthetic agent? (Select 2)
A) Uptake into the blood
B) Blood solubility of the agent
C) Volume of breathing system
D) Metabolism by the liver
Answers: A, B
Rationale: The alveolar concentration (Fa) is influenced by the uptake of the gas into the blood and its solubility. Highly soluble agents are taken up by the blood more readily, reducing FA. Metabolism plays a minimal role for most inhalational anesthetics.
Which anesthetic agent would likely have the fastest rise in the ratio of alveolar concentration to inspired concentration (Fa/Fi)?
A) Halothane
B) Isoflurane
C) Desflurane
D) Nitrous oxide
Answer: C
Rationale: Desflurane has low blood solubility, allowing it to equilibrate quickly between the alveoli and blood. This results in a rapid rise in the Fa/Fi ratio, indicating faster onset.
How does increased cardiac output affect the induction speed of an inhalational anesthetic agent?
A) It speeds up induction
B) It has no effect on induction
C) It slows down induction
D) It only affects intravenous agents
Answer: C
Rationale: Increased cardiac output increases the amount of anesthetic taken up by the blood, effectively “removing” the agent from the alveoli and slowing the rise of Fa. This delays the onset of the anesthetic effect, particularly for more soluble agents.
Which type of shunt delays the onset of poorly soluble inhalational agents the most?
A) Left-to-right shunt
B) Right-to-left shunt
C) Atrial septal defect
D) Patent ductus arteriosus
Answer: B
Rationale: A right-to-left (mainstem intubation) shunt bypasses the alveoli, reducing the effective delivery of inhalational agents. This has a more significant impact on poorly soluble agents, which rely on alveolar ventilation for rapid uptake.
A mainstem intubation can cause a right-to-left shunt because the endotracheal tube is positioned beyond the carina, only oxygenating one lung. This results in oxygen-poor blood from the non-ventilated lung diluting the oxygen levels of blood returning to the left ventricle.
Why does low cardiac output predispose patients to overdose of inhalational anesthetics, especially with soluble agents?
A) It decreases alveolar ventilation
B) It increases blood solubility of the agent
C) It results in a faster rise in the Fa/Fi ratio
D) It enhances the metabolism of the agent
Answer: C
Rationale: Low cardiac output reduces the amount of anesthetic taken up by the blood, allowing the alveolar concentration (Fa) to rise rapidly, especially for soluble agents. This can lead to faster onset and potential overdose.
Soluble Agents:
Soluble agents (e.g., halothane, isoflurane) have high blood solubility, meaning a larger amount of the agent is absorbed into the blood. This normally slows the rise of the alveolar concentration (Fa) because the gas is “taken up” by the blood rather than staying in the alveoli.
Impact of Cardiac Output on Soluble Agents:
Low Cardiac Output:
When cardiac output is low, blood flow is reduced, so there is less blood available to take up the anesthetic agent, especially if the agent is highly soluble. This means that even soluble agents, which normally are absorbed extensively into the blood, will stay in the alveoli longer.
As a result, the alveolar concentration (Fa) rises more quickly because there is less “sink effect” from the blood. This can lead to a faster onset and potentially an overdose, especially if the patient cannot compensate for the rapid rise in the agent’s effect.
What is the primary effect of the second gas phenomenon when using nitrous oxide with a volatile anesthetic agent?
A) It decreases the uptake of the second gas
B) It delays the onset of the second gas
C) It accelerates the onset of the second gas
D) It has no impact on the second gas
Answer: C
Rationale: The second gas effect refers to the ability of a rapidly absorbed gas like nitrous oxide to increase the concentration of a co-administered volatile agent in the alveoli, accelerating its onset.
What does a slower rise in the ratio of alveolar concentration to inspired concentration (Fa/Fi) indicate about an anesthetic agent?
A) High blood solubility
B) Low potency
C) Fast induction
D) Low tissue uptake
Answer: A
Rationale: A slower rise in the Fa/Fi ratio indicates high blood solubility, meaning the anesthetic is being absorbed into the blood more extensively, reducing the alveolar concentration and slowing induction.
At equilibrium, which of the following statements is true regarding partial pressures of an inhalational anesthetic agent?
A) Partial pressure in the alveoli is greater than in the blood
B) Partial pressure in the blood is less than in the CNS
C) Partial pressures in the alveoli, blood, and CNS are equal
D) Partial pressure in the CNS is higher than in the alveoli
Answer: C
Rationale: At equilibrium, the partial pressures of the anesthetic gas are equal across the alveoli, blood, and CNS, allowing the agent to exert its clinical effect consistently.
Which inhalational agent has the lowest blood-gas partition coefficient, indicating the fastest onset and recovery?
A) Isoflurane
B) Halothane
C) Desflurane
D) Sevoflurane
Answer: C
Rationale: Desflurane has the lowest blood-gas partition coefficient (0.42), meaning it is less soluble in blood. This results in a rapid rise in alveolar concentration (Fa) and faster onset and recovery.
What does the minimum alveolar concentration (MAC) of an inhalational anesthetic represent?
A) The concentration needed to achieve half-maximal metabolism
B) The concentration required to prevent movement in 50% of patients in response to a surgical stimulus
C) The concentration at which the anesthetic reaches equilibrium in the brain
D) The concentration that produces cardiovascular depression
Answer: B
Rationale: MAC is the concentration of an inhalational anesthetic that prevents movement in response to a surgical incision in 50% of patients. It is a measure of the anesthetic’s potency.
Which of the following factors would increase the rate of rise in the alveolar concentration to inspired concentration ratio (Fa/Fi) for an inhalational agent? (Select 2)
A) High cardiac output
B) Low blood-gas partition coefficient
C) Low fresh gas flow
D) Low cardiac output
Answers: B, D
Rationale: A low blood-gas partition coefficient (indicating low solubility) leads to a faster rise in Fa/Fi. Additionally, low cardiac output reduces uptake by the blood, allowing the alveolar concentration to rise more quickly.
How does increased cardiac output affect the onset of anesthesia for relatively soluble agents like isoflurane?
A) It speeds up induction
B) It has no effect on induction
C) It slows down induction
D) It only affects intravenous agents
Answer: C
Rationale: Increased cardiac output increases the uptake of soluble agents like isoflurane by the blood, slowing the rise of alveolar concentration (Fa) and delaying the onset of anesthesia.
f a patient has a high-fat content, how might this affect the pharmacokinetics of inhalational anesthetic agents?
A) It speeds up induction
B) It slows down induction
C) It decreases the minimum alveolar concentration (MAC)
D) It has no impact on pharmacokinetics
Answer: B
Rationale: High fat content increases the overall blood-gas partition coefficient, meaning more of the agent is taken up by adipose tissue. This reduces the amount available in the alveoli, slowing induction.
Which neurotransmitter receptor is most commonly associated with the action of inhalational anesthetics?
A) Dopamine receptors
B) GABA receptors
C) Serotonin receptors
D) Acetylcholine receptors
Answer: B
Rationale:GABA, NMDA, glycine receptor subunits have all been shown
to be affected
How does sevoflurane at 1 MAC affect cerebral metabolic rate of oxygen (CMRO₂) and cerebral blood flow (CBF)?
A) Increases CMRO₂ and decreases CBF
B) Decreases CMRO₂ and increases CBF
C) Increases both CMRO₂ and CBF
D) Has no effect on CMRO₂ or CBF
Answer: B
Rationale: At 1 MAC, sevoflurane decreases the cerebral metabolic rate of oxygen (CMRO₂), while the vasodilatory effects increase cerebral blood flow (CBF).
What is the effect of inhalational anesthetics on the renal system?
A) Increase renal blood flow and glomerular filtration rate (GFR)
B) Decrease renal blood flow and GFR
C) Increase GFR but decrease renal blood flow
D) Have no effect on renal function
Answer: B
Rationale: Inhalational anesthetics generally decrease renal blood flow and glomerular filtration rate .
How does a dose-dependent increase in ventilatory response to hypercapnia and hypoxemia manifest with the use of inhalational anesthetics?
A) Decreased tidal volume with preserved respiratory rate
B) Increased tidal volume with decreased respiratory rate
C) Complete abolition of the hypoxic ventilatory drive
D) Enhanced respiratory drive
Answer: A
Rationale: Inhalational anesthetics typically cause a dose-dependent decrease in tidal volume while preserving respiratory rate, leading to an overall reduction in minute ventilation.
Which of the following best describes the cardiovascular effects of halothane compared to other volatile anesthetics?
A) Halothane increases heart rate and cardiac output
B) Halothane decreases cardiac output, while others may increase heart rate
C) Halothane has no effect on the heart
D) Halothane increases cardiac output but decreases heart rate
Answer: B
Rationale: Halothane is known to decrease cardiac output, whereas other volatile anesthetics can compensate by increasing heart rate.
Which inhalational agent is more likely to maintain cerebral blood flow (CBF) without significant change at 0.5 MAC?
A) Desflurane
B) Isoflurane
C) Sevoflurane
D) Halothane
Answer: B
Rationale: Isoflurane at 0.5 MAC can counteract cerebral vasodilation, maintaining cerebral blood flow (CBF) relatively unchanged.
Least cerebral Vasodilation DOC FOR ↑ICP CASES Suppresses Lidocaine induced seizure activity
How does a high fat-blood partition coefficient affect the onset of inhalational anesthetics in obese patients?
A) It speeds up induction
B) It has no impact on onset
C) It slows down induction
D) It decreases MAC
Answer: C
Rationale: A higher fat-blood partition coefficient leads to increased uptake of the anesthetic into adipose tissue, reducing its availability in the alveoli and slowing induction.
Which property of inhalational anesthetics primarily determines their potency?
A) Blood-gas partition coefficient
B) Oil-gas partition coefficient
C) Minimum alveolar concentration (MAC)
D) Rate of metabolism
Answer: B
Rationale: The oil-gas partition coefficient is closely related to the potency of inhalational anesthetics; higher lipid solubility generally indicates greater potency.
Which of the following is a primary reason why nitrous oxide cannot achieve 1 MAC in clinical practice?
A) High lipid solubility
B) High potency
C) Low potency (MAC 104%)
D) Strong muscle relaxation properties
Answer: C
Rationale: Nitrous oxide has a MAC of 104%, indicating low potency. It cannot reach 1 MAC because it would require a concentration above 100%, which is not possible.
What is a potential complication of using nitrous oxide in patients with a pneumothorax or bowel obstruction?
A) Hypothermia
B) Diffusion into air-filled cavities, causing expansion
C) Increased cardiac output
D) Muscle relaxation
Answer: B
Rationale: Nitrous oxide can rapidly diffuse into air-filled cavities faster than it can leave, leading to expansion of spaces like pneumothorax or bowel, worsening the condition.
Why is nitrous oxide often contraindicated in patients with a risk of middle ear surgery or recent eye surgery involving a gas bubble?
A) It triggers malignant hyperthermia
B) It provides inadequate analgesia
C) It diffuses into gas-filled spaces, causing expansion
D) It has a high risk of nephrotoxicity
Answer: C
Rationale: Nitrous oxide diffuses into closed gas-filled spaces, such as the middle ear or eye, and can expand these spaces, leading to increased pressure and potential damage.
What is the primary mechanism by which nitrous oxide may provide analgesic effects?
A) GABA receptor activation
B) NMDA receptor antagonism
C) Serotonin receptor blockade
D) Opioid receptor activation
Answer: B
Rationale: Nitrous oxide acts as an NMDA receptor antagonist, which contributes to its analgesic properties.
Which of the following statements is true regarding nitrous oxide and malignant hyperthermia (MH)?
A) Nitrous oxide is a potent trigger of MH
B) Nitrous oxide should be avoided in all patients due to MH risk
C) Nitrous oxide does not trigger MH, unlike volatile anesthetics
D) Nitrous oxide is only a mild trigger of MH
Answer: C
Rationale: Nitrous oxide is not a trigger for malignant hyperthermia, unlike other volatile anesthetics.
What is a major concern when using isoflurane related to coronary artery blood flow?
A) Coronary artery vasospasm
B) Coronary steal phenomenon
C) Myocardial infarction
D) Cardiac arrhythmia
Answer: B
Rationale: Isoflurane has been implicated in the “coronary steal” phenomenon, where dilation of normal coronary arteries diverts blood away from stenotic vessels, potentially worsening ischemia.
Which of the following effects is typically seen with isoflurane at 1 MAC?
A) Increased intracranial pressure (ICP)
B) Decreased cerebral blood flow (CBF)
C) Electrically silent EEG
D) Profound myocardial depression
Answer: A
Rationale: Isoflurane can increase CBF, especially at higher MAC levels, and may increase ICP as a result. (usually short lived and less pronounced than other agents)
EEG silent at 2 MAC
What is the most common cardiovascular effect of isoflurane?
A) Bradycardia
B) Decreased blood pressure due to vasodilation
C) Increased myocardial contractility
D) Hypertension
Answer: B
Rationale: Isoflurane commonly causes vasodilation, leading to a decrease in blood pressure.
Why is sevoflurane a preferred agent for inhalational induction, especially in pediatric patients?
A) High pungency
B) Sweet smell and non-pungency
C) Slow onset
D) High lipid solubility
Answer: B
Rationale: Sevoflurane is sweet-smelling and non-pungent, making it well-tolerated for inhalational induction, particularly in children.
What potential complication can arise from using sevoflurane with a desiccated CO₂ absorbent?
A) Formation of Compound A
B) Triggering of malignant hyperthermia
C) Increased cerebral blood flow
D) Coronary steal phenomenon
Answer: A
Rationale: Sevoflurane can form Compound A in the presence of desiccated CO₂ absorbent, which has shown nephrotoxic effects in animal studies.
How can the formation of Compound A be minimized during sevoflurane use?
A) Use of calcium hydroxide absorbent instead of barium hydroxide
B) Increasing inspired concentration
C) Decreasing fresh gas flow to less than 2 L/min
D) Avoiding volatile anesthetics
Answer: A
Rationale: Compound A formation can be minimized by using CO₂ absorbents that do not contain strong bases like barium hydroxide, opting for calcium hydroxide instead.
Which characteristic of desflurane requires it to be delivered via a specialized vaporizer?
A) Low MAC
B) High solubility
C) High vapor pressure and boiling point close to room temperature
D) Low cost
Answer: C
Rationale: Desflurane has a high vapor pressure and a boiling point close to room temperature, necessitating a heated, pressurized vaporizer to ensure consistent delivery.
What respiratory side effect is common when desflurane is administered to an awake patient?
A) Hypoventilation
B) Bronchodilation
C) Breath-holding and laryngospasm
D) Sedation
Answer: C
Rationale: Desflurane is very pungent and can cause airway irritation, leading to breath-holding, coughing, and laryngospasm in awake patients.
What cardiovascular response can occur with a rapid increase in desflurane concentration?
A) Hypotension
B) Bradycardia
C) Tachycardia and hypertension
D) Myocardial depression
Answer: C
Rationale: Rapid increases in desflurane concentration can trigger a sympathetic response, resulting in tachycardia and hypertension. Blunt with some fent
Here’s a Select 2 question incorporating the provided answer choices:
Question:
Which of the following strategies or mechanisms are related to heat loss and temperature management during general anesthesia? (Select 2)
A) Redistribution of heat as vasodilation causes blood to shift from core to periphery, followed by radiation as a major form of heat loss
B) Use of desiccated CO₂ absorbents to minimize heat loss
C) Using low fresh gas flows during anesthesia to help maintain body temperature and reduce water loss
D) Avoiding volatile anesthetics to preserve thermoregulation
E) Increasing inspired oxygen concentration to reduce convection heat loss
Answers: A, C
Rationale:
A: Redistribution of heat is a major mechanism of heat loss under general anesthesia, as vasodilation causes blood to move from the core to the periphery. Radiation is the primary form of heat loss after redistribution, with conduction, convection, and evaporation also contributing.
C: Using low fresh gas flows minimizes heat and water loss, helping to maintain the patient’s body temperature during general anesthesia.
B, D, E: These options do not directly relate to the key mechanisms or strategies for managing temperature during general anesthesia.
What is the primary purpose of assessing “Anesthesia” immediately after intubation?
A) To confirm endotracheal tube placement
B) To set ventilation parameters and verify volatile anesthetic delivery
C) To assess the patient’s position for surgery
D) To administer additional analgesics
Answer: B
Rationale: After intubation, it is critical to confirm proper ventilator settings and ensure the delivery of volatile anesthetics for anesthesia maintenance.
Which intervention is used to maintain patient body temperature during surgery?
A) Administering warm IV fluids
B) Applying forced-air warming devices (e.g., Bair Hugger) and using a temperature probe
C) Decreasing fresh gas flows
D) Performing ABG analysis
Answer: B
Rationale: Forced-air warming devices and temperature monitoring help prevent hypothermia during surgery.
What is the purpose of placing an orogastric (OG) tube after intubation?
A) To secure the endotracheal tube
B) To prevent airway obstruction
C) To decompress the stomach and prevent aspiration
D) To deliver volatile anesthetics
Answer: C
Rationale: An OG tube is placed to decompress the stomach and reduce the risk of regurgitation and aspiration, especially in patients undergoing prolonged procedures.
Why should a bite block be considered after intubation?
A) To prevent dental damage and protect the endotracheal tube
B) To ensure airway patency
C) To facilitate OG tube placement
D) To reduce the risk of tongue injury
Answer: A
Rationale: A bite block prevents the patient from biting down on the endotracheal tube, which could cause dental injury or damage to the tube.
Why should analgesics be redosed prior to surgical incision?
A) To maintain hemodynamic stability during intubation
B) To optimize postoperative pain control
C) To ensure adequate pain management during the surgical stimulus
D) To prevent respiratory depression
Answer: C
Rationale: Redosing analgesics before the surgical incision ensures adequate pain control during the surgical stimulus, reducing the risk of intraoperative hemodynamic instability.
When should antibiotics be administered in relation to surgical incision?
A) After the incision is made
B) Immediately after intubation
C) Within one hour before the incision
D) During emergence from anesthesia
Answer: C
Rationale: Administering antibiotics within one hour before the incision is critical for preventing surgical site infections.
What should be assessed regarding “Access” after intubation? (Select 2)
A) Whether there is adequate IV access for the procedure
B) Placement of an arterial line if required for hemodynamic monitoring
C) Bilateral breath sounds for tube placement confirmation
D) Positioning of the patient’s arms and legs
Answers: A, B
Rationale: Ensuring adequate IV access and placing an arterial line (if indicated) are key steps to prepare for medication administration and advanced hemodynamic monitoring during surgery.
Why is it important to reassess the positioning of the patient’s arms and legs after intubation?
A) To confirm endotracheal tube placement
B) To prevent nerve injuries and ensure comfort during the procedure
C) To reduce the risk of hypothermia
D) To allow better ventilation
Answer: B
Rationale: Proper positioning helps prevent nerve injuries (e.g., brachial plexus or ulnar nerve compression) and ensures patient safety during long surgical procedures.
Under what circumstances should a baseline arterial blood gas (ABG) analysis be performed after intubation?
A) For all patients undergoing surgery
B) Only for patients with suspected acid-base disturbances or critical illness
C) For patients receiving volatile anesthetics
D) To verify oxygen saturation
Answer: B
Rationale: ABG analysis is typically reserved for patients with suspected acid-base disturbances, respiratory failure, or other critical conditions where baseline values are clinically relevant
What key information does a baseline ABG provide in a post-intubation scenario?
A) Cerebral oxygenation
B) Confirmation of volatile anesthetic delivery
C) Acid-base status and adequacy of ventilation
D) Electrolyte concentrations
Answer: C
Rationale: A baseline ABG provides critical information about the patient’s acid-base status and adequacy of ventilation, ensuring proper respiratory management.
What is the primary function of a vaporizer in modern anesthetic machines?
A) To cool the anesthetic agent
B) To mix fresh gas flow with liquid anesthetic
C) To create a saturated vapor in equilibrium with the liquid anesthetic
D) To humidify the gas delivered to the patient
Answer: C
Rationale: Vaporizers create a saturated vapor by allowing liquid anesthetic to evaporate until it reaches equilibrium. This vapor is then mixed with fresh gas flow and delivered to the patient.
How does fresh gas flow interact with the vaporizer in an anesthetic machine?
A) It absorbs the anesthetic vapor, becoming saturated with anesthetic gas
B) It cools the vaporizer chamber
C) It directly delivers the liquid anesthetic to the patient
D) It removes excess anesthetic vapor from the chamber
Answer: A
Rationale: Fresh gas flow passes through the vaporizer, absorbing anesthetic vapor to create a mixture that is delivered to the patient.
What is the definition of saturated vapor pressure (SVP)?
A) The pressure at which the anesthetic agent becomes solid
B) The maximum partial pressure of a vapor at a given temperature when the liquid and vapor phases are in equilibrium
C) The total pressure of the carrier gas and anesthetic vapor
D) The pressure required to evaporate the anesthetic agent
Answer: B
Rationale: SVP is the maximum pressure exerted by a vapor in equilibrium with its liquid phase at a given temperature.
Why is SVP important in the delivery of volatile anesthetics?
A) It determines the solubility of the anesthetic in blood
B) It influences the partial pressure of the anesthetic in the carrier gas
C) It affects the metabolism of the anesthetic
D) It regulates the temperature of the vaporizer
Answer: B
Rationale: The SVP dictates the partial pressure of the anesthetic gas in the carrier gas, which is essential for achieving the desired anesthetic concentration delivered to the patient.
What happens to the concentration of anesthetic vapor delivered to the patient when the concentration control dial is increased?
A) It decreases the fresh gas flow
B) It increases the volume of vapor entering the carrier gas
C) It decreases the volume of vapor entering the carrier gas
D) It bypasses the vaporizer completely
Answer: B
Rationale: Increasing the concentration control dial increases the amount of anesthetic vapor mixed with the fresh gas flow, raising the concentration delivered to the patient.
What effect would a sudden decrease in room temperature have on the SVP of a volatile anesthetic?
A) SVP would increase, delivering more anesthetic to the patient
B) SVP would decrease, delivering less anesthetic to the patient
C) SVP would remain unchanged
D) The vaporizer would stop functioning
Answer: B
Rationale: SVP is temperature-dependent. A decrease in room temperature lowers the SVP, reducing the partial pressure of anesthetic vapor delivered to the patient.
What is the purpose of the bypass chamber in a vaporizer?
A) To heat the anesthetic vapor
B) To prevent over-saturation of the carrier gas
C) To allow a portion of the fresh gas to bypass the vaporizing chamber
D) To store excess anesthetic vapor
Answer: C
Rationale: The bypass chamber ensures that a portion of the fresh gas bypasses the vaporizing chamber, mixing with saturated vapor to achieve the desired anesthetic concentration.
What could happen if a vaporizer designed for one agent is used with a different volatile anesthetic?
A) The anesthetic concentration would be delivered accurately
B) The vaporizer would automatically adjust for the different SVP
C) The delivered anesthetic concentration could be inaccurate, leading to overdose or underdose
D) The vaporizer would stop functioning
Answer: C
Rationale: Vaporizers are calibrated for specific agents based on their SVP. Using the wrong agent can lead to significant errors in the concentration delivered to the patient.
Answer: B
Rationale: This equation calculates the volume of anesthetic gas (VA) delivered by the vaporizer into the fresh gas flow.
Answer: B
Rationale: This equation calculates the total percentage concentration of volatile anesthetic delivered to the patient relative to the combined flow of fresh gas and anesthetic vapor.
How does increasing fresh gas flow (FGF) affect the percentage of volatile anesthetic delivered?
A) It increases the percentage of anesthetic delivered
B) It decreases the percentage of anesthetic delivered
C) It has no effect on the percentage of anesthetic delivered
D) It directly increases the patient’s uptake of anesthetic
Answer: B
Rationale: Increasing FGF dilutes the anesthetic vapor in the carrier gas, reducing the overall percentage of volatile anesthetic delivered to the patient.
Given an SVP of 240 mmHg for sevoflurane, a total pressure (PT) of 760 mmHg, and a carrier gas volume (VC) of 1 L, what is the calculated volume of anesthetic gas (VA)?
A) 0.316 L
B) 0.240 L
C) 1.000 L
D) 0.760 L
Why does the vaporizer dial for sevoflurane or isoflurane remain the same (e.g., 2% for 1 MAC) when used at higher altitudes like Denver?
A) The vaporizer automatically compensates by increasing the partial pressure of the anesthetic gas.
B) The vaporizer automatically increases the output volume to maintain the same partial pressure of the anesthetic gas.
C) Partial pressure is unaffected by altitude, so no compensation is needed.
D) Higher altitudes require a fixed percent concentration output, which modern vaporizers cannot adjust.
Answer: B
Rationale: Modern vaporizers adjust their output in proportion to the drop in atmospheric pressure at higher altitudes. While the volume of anesthetic vapor output increases, the partial pressure remains the same to maintain the desired anesthetic effect.
Question 2: Desflurane at High Altitudes
What must be done to adjust the desflurane vaporizer setting at higher altitudes?
A) The dial must be increased because the vaporizer delivers a fixed partial pressure.
B) The dial setting remains unchanged because the vaporizer automatically adjusts for altitude.
C) The dial must be increased because desflurane vaporizers deliver a fixed percent concentration, not a fixed partial pressure.
D) The dial must be decreased to compensate for the reduced partial pressure at altitude.
Answer: C
Rationale: Desflurane vaporizers deliver anesthetic based on a fixed percent concentration, unlike sevoflurane and isoflurane, which deliver a fixed partial pressure. At higher altitudes, the lower atmospheric pressure requires increasing the dial setting to maintain the desired partial pressure of desflurane in the alveoli. Like 12% in Denver
What does the minimum alveolar concentration (MAC) represent?
A) The concentration of anesthetic in the blood required to induce unconsciousness
B) The alveolar concentration of an anesthetic that prevents movement in 50% of patients in response to surgical incision
C) The maximum concentration of anesthetic tolerated by the patient
D) The concentration needed to prevent hemodynamic changes during surgery
Answer: B
Rationale: MAC is the alveolar concentration of an anesthetic at 1 atmosphere that prevents movement in 50% of subjects exposed to surgical incision, making it a measure of anesthetic potency.
Which property of an inhalational agent is MAC inversely related to?
A) Blood-gas partition coefficient
B) Oil-gas partition coefficient
C) Vapor pressure
D) Fresh gas flow rate
Answer: B
Rationale: MAC is inversely related to the oil-gas partition coefficient, which is a measure of lipid solubility. Higher lipid solubility corresponds to greater anesthetic potency and lower MAC.
If 0.5 MAC of isoflurane is combined with 0.5 MAC of nitrous oxide, what is the resulting MAC?
A) 0.5 MAC
B) 1.0 MAC
C) 1.5 MAC
D) 2.0 MAC
Answer: B
Rationale: MAC values are additive. Combining 0.5 MAC of one agent with 0.5 MAC of another results in a total of 1.0 MAC.
Which MAC level is required to prevent awareness in 95% of patients?
A) 0.8 MAC
B) 1.0 MAC
C) 1.2 MAC
D) 2.0 MAC
Answer: C
Rationale: At 1.2 MAC, approximately 95% of patients will not respond to surgical incision. This is based on the ED95 calculation, which accounts for individual variability in anesthetic requirements.
Which of the following agents has the lowest MAC, indicating the highest potency?
A) Desflurane
B) Halothane
C) Isoflurane
D) Nitrous oxide
Answer: B
Rationale: Halothane has the lowest MAC (0.75%) among the listed agents, indicating it is the most potent inhalational anesthetic.
Which agent has the highest MAC, indicating the lowest potency?
A) Nitrous oxide
B) Isoflurane
C) Desflurane
D) Sevoflurane
Answer: A
Rationale: Nitrous oxide has the highest MAC (104%), indicating it is the least potent inhalational agent.
The potency of an inhalational agent can be estimated by its solubility in which medium?
A) Olive oil
B) Deionized water
C) Ethylene glycol
D) Coconut water
Answer: A
Rationale: Potency correlates with solubility in olive oil, as described by the Meyer-Overton hypothesis. Lipid solubility is directly proportional to anesthetic potency.
Which of the following statements about partition coefficients is true? (Select 2)
A) Anesthetics with greater blood-gas partition coefficients have higher solubility in blood.
B) Blood-gas partition coefficient is a key determinant of the speed of anesthetic induction and recovery.
C) Oil-gas partition coefficient correlates directly with anesthetic elimination.
D) Tissue
partition coefficients are crucial in describing redistribution of chemicals in the body.
Answers: B, D
Rationale:
B: Blood-gas partition coefficient determines how quickly anesthetics equilibrate between alveoli and blood. Lower coefficients result in faster induction and recovery.
D: Tissue
partition coefficients help explain the redistribution of anesthetic agents and their movement within the body.
A is false because higher blood-gas coefficients indicate slower induction and recovery due to greater solubility in blood.
C is false because oil-gas partition coefficient correlates with potency, not elimination.
Effect of Age on MAC
At what age is MAC highest, and how does it change over time?
A) MAC is highest at birth and declines after age 20.
B) MAC is highest at 6 months and declines by approximately 6% per decade after age 40.
C) MAC is highest at 6 months and remains stable throughout life.
D) MAC is highest at birth and declines by 10% per decade after age 30.
Answer: B
Rationale: MAC peaks at around 6 months of age, reflecting increased anesthetic requirements. After age 40, MAC decreases by roughly 6% per decade due to changes in physiology, including reduced metabolic demands and brain sensitivity to anesthetics.
Which of the following medications decreases MAC?
A) Ketamine
B) Methamphetamine
C) Barbiturates
D) Tricyclic antidepressants
Answer: C
Rationale: Barbiturates decrease MAC because they have sedative and hypnotic properties, reducing the need for inhaled anesthetic to achieve the desired depth of anesthesia. Ketamine and methamphetamine increase MAC, while tricyclic antidepressants do not directly affect MAC.
Which physiologic condition increases MAC?
A) Hypothermia
B) Hypernatremia
C) Pregnancy
D) Hypoxia
Answer: B
Rationale: Hypernatremia increases MAC because it enhances neuronal excitability. Conversely, hypothermia, pregnancy, and hypoxia reduce MAC by decreasing metabolic and neurologic demands.
What is the approximate MAC value needed to prevent response to verbal or tactile stimulation (MACawake)?
A) 1.0 MAC
B) 0.4 MAC
C) 1.6 MAC
D) 0.6 MAC
Answer: B
Rationale: MACawake is typically around 0.4 MAC, representing the concentration required to prevent response to non-painful stimuli such as verbal commands and tactile stimulation.
Which condition is LEAST likely to increase the risk of intraoperative awareness?
A) Emergency damage-control laparotomy
B) Cesarean delivery under general anesthesia
C) History of opioid abuse
D) Red hair
Answer: D
Rationale: While red hair is associated with a higher MAC requirement due to mutations in the melanocortin-1 receptor, it is not a recognized risk factor for intraoperative awareness. The other conditions are linked to insufficient anesthetic delivery.
