Lippincott's Anesthesia Review: 1001 Questions and Answers

Chapter 4. Patient Monitoring

Darren Hyatt, Ala Nozari, and Edward Bittner

    1.   To help encourage universal quality and safety practices, the ASA has adopted and mandates the use of all the following monitors during general anesthesia, except

          A.   An oxygen analyzer

          B.   Capnography

          C.   Continuous visual display of an ECG

          D.   A peripheral nerve stimulator

    2.   Current ASA standards require that during anesthesia, systemic blood pressure and heart rate be evaluated at least every

          A.   3 minutes

          B.   5 minutes

          C.   7 minutes

          D.   10 minutes

    3.   Lead II of an ECG is represented by placing the

          A.   Positive electrode on the right arm and the negative electrode on the left leg

          B.   Negative electrode on the right arm and the positive electrode on the left leg

          C.   Positive electrode on the right arm and the negative electrode on the left arm

          D.   Negative electrode on the right arm and the positive electrode on the left arm

    4.   During the course of a complicated cardiac case, the surgeon informs you that he is worried about damage to the right coronary artery in a patient with a right-dominant coronary system. During reperfusion, you are looking for signs of ischemia, and are most interested in leads

          A.   V1–V3

          B.   V4–V6

          C.   II, III, and AvF

          D.   I and AvL

    5.   Use of lead V5 alone on ECG results in the detection of _____ (%) of ischemic episodes:

          A.   35

          B.   55

          C.   75

          D.   95

    6.   You are taking over a case from another anesthesia provider with a patient in the beach chair position and a history of moderate carotid artery disease. You are told during pass-off that the patient’s blood pressures have consistently been 90/50 mm Hg. You notice the blood pressure cuff on the left arm is one or two sizes small and barely stays on the patient. A blood pressure cuff that is too small will

          A.   Incorrectly underestimate the true blood pressure

          B.   Incorrectly overestimate the true blood pressure

          C.   Randomly both over- and underestimate the true blood pressure

          D.   Not give an incorrect blood pressure, but will be uncomfortable in an awake patient

    7.   When performing the oscillometric method to measure blood pressure, for example, when you do not have a stethoscope or automated blood pressure cuff, it is important to remember that you will not be able to measure the

          A.   Systolic blood pressure

          B.   Diastolic blood pressure

          C.   Mean arterial pressure

          D.   Diastolic or mean arterial blood pressure

    8.   The diastolic blood pressure recorded with an automated blood pressure cuff using the oscillometric method will be

          A.   Approximately 10 mm Hg higher when compared to direct arterial measurement

          B.   Approximately 10 mm Hg lower when compared to direct arterial measurement

          C.   Equal to direct arterial measurement

          D.   Random and unreliable

    9.   When measuring blood pressure manually and listening for Korotkoff sounds, the diastolic blood pressure is measured at the onset of

          A.   Phase 1

          B.   Phase 2

          C.   Phase 3

          D.   Phase 5

  10.   You are preparing for an emergent mitral valve repair that will need to be done on cardiopulmonary bypass (CPB). While on CPB

          A.   A pulse oximeter can be used to monitor oxygen saturation

          B.   A noninvasive blood pressure cuff can be used to monitor perfusion pressures

          C.   An arterial line can be used to measure perfusion pressures

          D.   None of the above

  11.   The incidence of distal ischemia resulting from arterial cannulation is less than

          A.   10%

          B.   1%

          C.   0.1%

          D.   0.01%

  12.   When considering the advantages and disadvantages of different sites for arterial cannulation such as radial, ulnar, femoral, brachial, and dorsalis pedis, the

          A.   Radial artery provides the principal source of blood to the hand

          B.   Cannulation of ulnar artery is commonly associated with damage to the median nerve

          C.   Dorsalis pedis artery is commonly used during emergencies and low-flow states

          D.   Cannulation of the femoral artery risks local and retroperitoneal hematoma

  13.   Systolic blood pressures are generally higher and diastolic blood pressures are generally lower in which of the following conditions?

          A.   The further you are from the heart when using a direct arterial measurement

          B.   The closer you are to the heart when using a direct arterial measurement

          C.   When using an automated noninvasive blood pressure cuff compared to a direct arterial measurement

          D.   When recording from an over dampened arterial tracing

  14.   While taking care of a patient, you notice that the arterial monitor transducer has slipped off its stand and is hanging approximately 30 cm lower than where it was originally leveled. This would correspond to a blood pressure reading that is

          A.   30 mm Hg lower than the actual pressure

          B.   30 mm Hg higher than the actual pressure

          C.   22 mm Hg lower than the actual pressure

          D.   22 mm Hg higher than the actual pressure

  15.   An important consideration in using the subclavian approach for central venous access includes the

          A.   Ease of compressibility if a hematoma or laceration develops

          B.   Lower risk of pneumothorax when compared to internal jugular approach

          C.   Ability of the vessel to remain patent in the setting of hypovolemia

          D.   Increased risk of damaging the brachial plexus when compared to internal jugular approach

  16.   When interpreting a CVP waveform, the end of systole best coincides with the

          A.   A wave

          B.   C wave

          C.   V wave

          D.   X decent

  17.   When interpreting a CVP waveform, the beginning of systole is best represented by the

          A.   A wave

          B.   C wave

          C.   V wave

          D.   X decent

  18.   After placing a central line in an unstable patient in the ICU, you notice the initial CVP tracing shows very prominent C–V waves. If an echocardiogram was then obtained, you might expect to find

          A.   Cardiac tamponade

          B.   Significant tricuspid regurgitation

          C.   Atrial fibrillation

          D.   AV dissociation

  19.   You receive a patient from the emergency department with multiple stab wounds to the upper abdomen. The patient is unstable, and needs to emergently come to the operating room with minimal to no time for fluid resuscitation. After placing a central line, you notice loss of the Y descent on the CVP tracing, as well as universally elevated filling pressures. If you were to then do an echocardiogram, you might expect to find which of the following?

          A.   Cardiac tamponade

          B.   Significant tricuspid regurgitation

          C.   Descending thoracic aortic dissection

          D.   AV dissociation

  20.   The risk of complication from pulmonary artery catheter placement is less than

          A.   0.05%

          B.   0.5%

          C.   5%

          D.   15%

  21.   Insertion of a pulmonary artery catheter can be beneficial in the management of all of the following cases, except

          A.   Helping to determine cardiogenic versus noncardiogenic pulmonary edema

          B.   Following cardiac output in an unstable patient with acute-onset tricuspid regurgitation

          C.   Following the response to therapy in a patient with severe pulmonary hypertension

          D.   Following response to therapy in an unstable septic patient using mixed venous oxygen tension

  22.   During placement of a pulmonary artery catheter, you are watching the pressure tracing, as shown. At the point indicated by the arrow, the catheter tip is located in the

images

Figure 4-1.

          A.   Right atrium

          B.   Right ventricle

          C.   Pulmonary artery

          D.   Wedge position

  23.   The tip of a pulmonary artery catheter typically enters the pulmonary artery at approximately

          A.   15 to 25 cm

          B.   25 to 35 cm

          C.   35 to 45 cm

          D.   45 to 55 cm

  24.   Typical mixed venous oxygen tension in a healthy adult is

          A.   25 mm Hg

          B.   40 mm Hg

          C.   55 mm Hg

          D.   75 mm Hg

  25.   A pulmonary artery catheter is placed to help guide management of hypotension. Cardiac output is found to be markedly decreased with low central venous, pulmonary artery, and pulmonary artery occlusion pressures. Systemic vascular resistance is moderately elevated. Of the options listed below, the most beneficial intervention at this time would be to

          A.   Administer volume

          B.   Begin diuresis

          C.   Start an infusion of milrinone

          D.   Start an infusion of epinephrine

  26.   A pulmonary artery catheter is placed to help guide management of an obese patient with a known history of poorly controlled obstructive sleep apnea who is admitted with refractory hypotension. Cardiac output and pulmonary artery occlusion pressures are markedly decreased, while central venous and pulmonary artery pressures are markedly increased. Of the options listed below, the most beneficial intervention at this time would be to

          A.   Administer volume

          B.   Begin diuresis

          C.   Start an infusion of milrinone

          D.   Start an infusion of epinephrine

  27.   Normal systemic vascular resistance ranges between ______ (dynes)(s)/cm5:

          A.   50 and 150

          B.   300 and 600

          C.   900 and 1500

          D.   1800 and 2100

  28.   Normal pulmonary vascular resistance ranges between ______ (dynes)(s)/cm5:

          A.   50 and 150

          B.   300 and 600

          C.   900 and 1500

          D.   1800 and 2100

  29.   The cardiac index in a healthy adult ranges between ______ L/min/m2:

          A.   0.8 and 1.2

          B.   1.4 and 2.0

          C.   2.2 and 4.2

          D.   4.4 and 6.0

  30.   Serious complications with transesophageal echocardiography (TEE), such as oral or pharyngeal injury or esophageal rupture, have an incidence as high as

          A.   0.01%

          B.   0.1%

          C.   1%

          D.   10%

  31.   When evaluating regurgitant lesions with transesophageal echocardiography, the Nyquist limit should be set between ______ cm/s:

          A.   30 and 40

          B.   40 and 50

          C.   50 and 60

          D.   60 and 70

  32.   When evaluating flow at a specific point during echocardiography, you would use

          A.   Continuous-wave Doppler

          B.   Pulse-wave Doppler

          C.   Color Doppler

          D.   Pulse-wave or continuous-wave Doppler

  33.   Pulse oximetry illuminates tissue samples with two wavelengths of light in order to calculate oxygen saturation. These wavelengths are ______ nm:

          A.   540 and 780

          B.   660 and 940

          C.   720 and 960

          D.   480 and 720

  34.   The accuracy of pulse oximetry can be significantly reduced by all of the following, except

          A.   Intravenous bolus of methylene blue

          B.   Intravenous bolus of heparin

          C.   Severe acidosis

          D.   Low blood flow

  35.   A patient with carboxyhemoglobin will have a pulse oximetry reading that

          A.   Converges around a saturation of 85%

          B.   Converges around a saturation of 65%

          C.   Converges around a saturation of 45%

          D.   Varies widely

  36.   A patient with methemoglobinemia will have a pulse oximetry reading that

          A.   Converges around a saturation of 85%

          B.   Converges around a saturation of 65%

          C.   Converges around a saturation of 45%

          D.   Varies widely

  37.   For the removal of a complex spinal cord tumor, the surgeon expresses concern of damage to the anterior spinal artery. The monitoring that would be helpful to determine viability of the anterior spinal cord intraoperatively would include

          A.   Electroencephalography

          B.   Motor-evoked potentials

          C.   Somatosensory-evoked potentials

          D.   Bispectral index or Sedline monitoring

  38.   A sudden drop in somatosensory-evoked potentials (SSEPs) would cause you to be worried about

          A.   Damage to the anterior spinal artery

          B.   Damage to the posterior spinal arteries

          C.   An insufficient depth of anesthesia

          D.   The inadvertent administration of a neuromuscular blocking agent

  39.   During cervical spine surgery for the resection of an intradural mass, the patient begins to cough. The concentration of isoflurane is subsequently increased. With respect to somatosensory-evoked potential (SSEP) monitoring, you would expect

          A.   Amplitude and latency to decrease

          B.   Amplitude and latency to increase

          C.   Amplitude to decrease and latency to increase

          D.   Amplitude to increase and latency to decrease

  40.   While monitoring somatosensory-evoked potentials, an increase in amplitude is noted. Of the options listed below, the most likely medication to have caused this increase in amplitude would be

          A.   Etomidate

          B.   Propofol

          C.   Midazolam

          D.   Sevoflurane

  41.   If somatosensory-evoked potentials change significantly, the anesthesia provider should consider

          A.   Increasing blood pressure

          B.   Hyperventilating the patient

          C.   Cooling the patient

          D.   Hemodilution

  42.   In the capnogram below, the segment that correlates with the exhalation of anatomic dead space is represented by points

images

Figure 4-2.

          A.   A to B

          B.   A to C

          C.   C to D

          D.   D to E

  43.   In the capnogram (Fig. 4-2), the segment correlating with inspiration is represented by points

          A.   A to B

          B.   A to C

          C.   C to D

          D.   D to E

  44.   Capnography can help detect all of the following, except

          A.   Endobronchial intubation

          B.   Esophageal intubation

          C.   Bronchospasm

          D.   Pulmonary embolism

  45.   The capnograph depicted in Figure 4-3 is most likely a result of

images

Figure 4-3.

          A.   Pulmonary embolism

          B.   Bronchospasm or airway obstruction

          C.   Esophageal intubation

          D.   Elimination of neuromuscular blockers

  46.   Approximately 30 minutes after the induction of general anesthesia in a healthy adult patient, you notice that core body temperature has dropped by a full degree Celsius. This is most likely due to

          A.   Conduction

          B.   Convection

          C.   Redistribution

          D.   Radiation

  47.   According to the American Society of Anesthesiologists, temperature monitoring is

          A.   Always required

          B.   Never required, but recommended

          C.   Required for all general anesthetics, however not required for sedation

          D.   Up to the discretion of the anesthesia provider

  48.   Detrimental effects of hypothermia include all of the following, except

          A.   Increasing cerebral oxygen consumption

          B.   Increasing surgical site infections

          C.   Impairment of platelet function

          D.   Increasing the duration of action of muscle relaxants

  49.   During a complex mitral valve replacement, it is determined that the patient will benefit from brief protective hypothermia. Of the options listed below, core temperature is best measured via the

          A.   Tympanic membrane

          B.   Bladder

          C.   Nasopharnyx

          D.   Rectum

  50.   While monitoring a patient for return of neuromuscular function after using rocuronium, you notice the patient has regained four twitches using train of four stimulations. With four twitches on train of four stimulations, the patient may still have blockage of acetylcholine receptors of up to

          A.   25%

          B.   50%

          C.   75%

          D.   90%

CHAPTER 4 ANSWERS

    1.   D.   ASA standards mandate the use of pulse oximetry, capnography, an oxygen analyzer in the breathing system, disconnect alarms, a visual display of an ECG, systemic blood pressure and heart rate monitoring, and temperature monitoring (when clinically indicated) for all cases. The use of a peripheral nerve stimulator is not a mandated monitor.

    2.   B.   During the delivery of anesthesia, the current standard of care is to measure systemic blood pressure and heart rate every 5 minutes at a minimum. The clinical scenario and phase of the operation may mandate more frequent monitoring, which is up to the judgment of the anesthesia provider.

    3.   B.   Lead I correlates with the placement of the negative electrode on the right arm and the positive electrode on the left arm. Lead II correlates with the placement of the negative electrode on the right arm and the positive electrode on the left leg. Lead III correlates with the placement of the negative electrode on the left arm and the positive electrode on the left leg.

    4.   C.   The understanding of coronary anatomy and regions of ischemia on an ECG is fundamental. The right coronary artery provides perfusion to the inferior of the heart in approximately 80% of patients who are considered to be right-dominant (the posterior descending artery is supplied by the right coronary artery in a right-dominant system). This inferior distribution is represented by leads II, III, and AvF. The anterior wall is supplied by the left anterior descending artery, and is represented roughly by leads V1–V4. The lateral wall of the heart is supplied primarily by the left circumflex artery, and is represented by I, AvL, V5, and V6.

    5.   C.   The use of the V5 lead results in the detection of 75% of ischemic episodes. This can be increased to 90% with the addition of the V4 lead, and up to 96% with the addition of leads II and V4.

    6.   B.   A properly-sized noninvasive blood pressure cuff should encompass 40% of the circumference of the arm. A cuff that is too small will result in a reading that is incorrectly high, whereas a cuff that is too large will result in a lower-than-accurate pressure. This is particularly worrisome in this patient when considering her cerebral perfusion pressure, since she already has a history of carotid artery disease and is in the beach chair position.

    7.   B.   When using the oscillometric method to measure blood pressure, the cuff is inflated until no oscillations on the sphygmomanometer are seen. The cuff is then slowly deflated until oscillations are seen, which represents the systolic blood pressure. As the cuff continues to be deflated, you note the point where maximal oscillations occur. This point of maximal oscillation represents the mean arterial pressure. It is not possible to measure a diastolic blood pressure with the oscillometric method.

    8.   A.   The DINAMAP (device for indirect noninvasive automatic mean arterial pressure) method for measuring blood pressure uses an automated cuff that measures oscillometric variations with reduction in cuff pressure to calculate systolic, mean, and diastolic pressures. In general, diastolic measurements with DINAMAP are about 10 mm Hg higher with automated as opposed to direct arterial measurement, whereas systolic and mean pressures tend to correlate well.

    9.   D.   Korotkoff sounds are used to interpret blood pressure when using a stethoscope and a noninvasive blood pressure cuff, and is described in 5 phases of sound. Phase 1 heralds the onset of the first sound heard and correlates with the systolic blood pressure. Phase 5 occurs at the cuff pressure at which the sound first disappears, and is the phase recommended by the American Heart Association to correspond most reliably with the diastolic heart sound. In cases where Phase 5 does not occur (the sound never fully disappears), Phase 4 is then used to represent the diastolic blood pressure, and is described as a thumping or muting of the sound just before diastole. Phases 2 and 3 have no clinical significance.

  10.   C.   Both pulse oximetry and noninvasive blood pressure cuffs require pulsatile blood flow in order to obtain measurements. These monitors will not be effective during CPB when blood flow is artificially sustained with a more continuous flow. This can also be the case with some patients on left ventricular assist devices, and venous to arterial extracorporeal membrane oxygenation devices, where pulsatile flow is minimal.

  11.   C.   Complications from arterial cannulation include distal ischemia (<0.1%), infection, and hemorrhage. Common sites for cannulation include radial, brachial, axillary, dorsalis pedis, and femoral arteries. Common indications for direct blood pressure monitoring include cardiopulmonary bypass, when wide swings in BP are expected, when rigorous control of BP is necessary, and when there is need for multiple arterial blood gas measurements.

  12.   D.   The ulnar artery is the principal source of blood flow to the hand. Hence radial artery cannulation is much more commonly used for invasive blood pressure monitoring. Cannulation of the brachial artery risks damage to the median nerve. The femoral artery is often used in emergencies, since it is a large vessel and can still be identified in low flow states. Cannulation of the femoral artery risks both local and retroperitoneal hematoma. Dorsalis pedis artery cannulation, while not ideal since it is far from the central circulation, can reliably measure mean arterial pressure.

  13.   A.   Systolic blood pressures are generally higher and diastolic blood pressures are generally lower the further you are from the heart when using direct invasive arterial measurement. For example, when comparing a dorsalis pedis arterial measurement to a femoral arterial measurement, the dorsalis pedis will record higher systolic and lower diastolic pressures compared to the femoral line. However, the mean arterial pressures will be approximately the same. A noninvasive automated blood pressure cuff will tend to correlate with systolic arterial blood pressures, but the diastolic pressure will be approximately 10 mm Hg lower when measured via the direct invasive arterial monitor. An over dampened arterial line tracing will tend to reduce systolic pressures and increase diastolic pressures.

  14.   D.   For every 30 cm in height that a transducer is moved up and down, there is a corresponding change of 22 mm Hg in the blood pressure reading (1 cm H2O = 0.74 mm Hg).

  15.   C.   Risks and benefits of different central cannulation sites are important for an anesthesia provider to understand. The internal jugular approach has good landmarks, predictable anatomy, and the convenience of being easily accessible at the head of the bed. Disadvantages include risk of carotid artery puncture, trauma to the brachial plexus, and risk of pneumothorax with lower placements. The left internal jugular vein carries the added risk of damage to the thoracic duct, and can be more difficult to pass a pulmonary artery catheter when needed. The external jugular vein can also be cannulated, and its superficial location makes it an easy target, but it can be more difficult to thread a catheter centrally. The subclavian approach has the benefit of also having good landmarks, as well as remaining relatively patent in a hypovolemic patient. The subclavian however does carry the highest risk of pneumothorax, and can be difficult to compress if a hematoma or laceration occurs.

  16.   C.   In the CVP waveform depicted below, the A wave represents atrial contraction, the C wave represents bulging of the tricuspid valve into the atrium during the beginning of systole, the X decent occurs during systole and corresponds to atrial relaxation, the V wave represents filling of the atrium while the tricuspid valve is closed, and the Y descent occurs when the tricuspid valve opens and the atrium starts to empty.

images

Figure 4-4.

  17.   B.   In the CVP waveform depicted in Figure 4-4, the A wave represents atrial contraction, the C wave represents bulging of the tricuspid valve into the atrium during the beginning of systole, the X decent occurs during systole and corresponds to atrial relaxation, the V wave represents filling of the atrium while the tricuspid valve is closed, and the Y descent occurs when the tricuspid valve opens and the atrium starts to empty.

  18.   B.   During systole in a patient with tricuspid regurgitation, part of the ejected volume flows backward into the atrium. Instead of seeing a small C wave that normally represents the bulging of the tricuspid valve, a much larger C wave would be seen as blood flows retrograde into the right atrium and toward the transducer. This retrograde blood flow would continue throughout the systole, and would, therefore, also increase the V wave size, since this is a systolic component of the CVP trace. During cardiac tamponade, there will be elevated pressures throughout the entire waveform, as well as loss of the Y descent. In patients with atrial fibrillation, there will be a loss of the A wave, since there is no longer a uniform atrial contraction, and an overall increase in the C wave size, since filling pressures elevate to compensate and improve ventricular filling. With AV dissociation, there are large and exaggerated A waves (often called “cannon” A waves), which represent atrial contraction against a closed tricuspid valve.

  19.   A.   See the answer explanation of Question 18. It would be highly unlikely to have elevated filling pressures in a bleeding trauma patient who has not yet been resuscitated. Aortic dissections can cause cardiac tamponade, but only if they involve the aortic root and then extend into the pericardium.

  20.   B.   While the incidence of complications is infrequent, some of the complications can carry severe morbidity and mortality risks. In addition to universal complications associated with central line placement, some additional pulmonary artery catheter complications include dysrhythmias (most common), catheter knotting, cardiac valve injury, pulmonary artery rupture, development of complete heart block in a patient with preexisting left bundle branch block, pulmonary thromboembolism or air embolism, bacteremia, endocarditis, and sepsis.

  21.   B.   As well as knowing some valuable indications, it is important to know some of the limitations of a pulmonary artery catheter before subjecting a patient to risks. For example, the measurement of cardiac output in patients with tricuspid regurgitation or ventricular septal defects is inaccurate due to dilution of the injectate. Pulmonary artery occlusion pressure can also inaccurately represent left ventricular end diastolic pressure in patients with mitral stenosis, left atrial myxomas, pulmonary venous obstruction, elevated alveolar pressures, and decreased left ventricular compliance. Other common errors in measurement that are not patient dependent can include an inaccurate volume or temperature of the injectate solution.

  22.   B.   A pulmonary artery catheter is placed while monitoring the pressure changes measured at the tip of the catheter. The first section shows a traditional CVP waveform measured in the right atrium. As the catheter is advanced, a systolic step-up is seen when entering the right ventricle, a diastolic step-up when entering the pulmonary artery, and a return to a traditional CVP waveform when entering the wedge position.

images

Figure 4-5.

  23.   C.   The tip of the pulmonary artery catheter typically enters the pulmonary artery at around 35 to 45 cm. This can vary from patient to patient, especially with patients at the extremes of height.

  24.   B.   Mixed venous oxygen tension can provide valuable information on the balance between oxygen consumption and delivery. Typical mixed venous oxygen tension in a healthy adult is 40 mm Hg, yielding a saturation of approximately 75%. Reduction in oxygen delivery can be due to a reduction in oxygen content per deciliter leaving the left ventricle, or a reduction in overall cardiac output. Increased oxygen consumption (low mixed venous oxygen) occurs during periods of elevated metabolic states, such as during vigorous exercise or sepsis.

  25.   A.   In the clinical scenario, low central venous, pulmonary artery, and pulmonary artery occlusion pressures support the diagnosis of hypovolemia. Increasing intravascular volume would be the most beneficial intervention at this time.

  26.   C.   The patient’s history and clinical scenario suggest right heart failure due to pulmonary hypertension. Milrinone may be beneficial in decreasing pulmonary vascular resistance as well as increasing cardiac output.

  27.   C.   Interpreting physiologic data from a pulmonary artery catheter and guiding therapy requires having an intimate knowledge of baseline values. On average, normal physiologic vascular resistance falls between 900 and 1500 (dynes)(s)/cm5.

  28.   A.   Normal pulmonary vascular resistance ranges between approximately 50 and 150 (dynes)(s)/cm5.

  29.   C.   Normal cardiac index in a healthy adult ranges between 2.2 and 4.2 L/min/m2. Cardiac index is often used over cardiac output in estimating cardiac function, since it is more reliable with extremes of height.

  30.   B.   Serious complications with TEE have been reported in approximately 0.1% of cases, or approximately 1 in 1,000 patients. Strict contraindications to TEE include but are not limited to esophageal spasm, esophageal stricture, esophageal laceration, esophageal perforation, and esophageal diverticulum. Relative contraindications include but are not limited to upper GI bleed, dysphagia or odynophagia, mediastinal radiation, large diaphragmatic hernias, atlantoaxial disease, and difficult intubation due to possibility of unintentional extubation with probe manipulation.

  31.   C.   The current guidelines recommend a Nyquist limit of 50 to 60 cm/s when evaluating regurgitant lesions. Setting the limit to low could result in overestimating the regurgitant lesion, and setting the limit to high could result in underestimating the regurgitant lesion.

  32.   B.   Pulse-wave Doppler is used to capture flow at a specific point. During pulse-wave Doppler, a single crystal is used to both emit and receive ultrasound energy, and the location of the signal can be calculated. Continuous-wave Doppler, on the other hand, uses two separate crystals to send and receive ultrasound energy. This allows the echo machine to detect higher velocities and energy shifts; however, the exact location of the signal cannot be determined. Color-wave Doppler is used to examine regurgitant lesions.

  33.   B.   Pulse oximetry uses two wavelengths of light to calculate oxygen saturation. These wavelengths are 660 nm of red light (well absorbed by oxygenated hemoglobin) and 940 nm of infrared light (well absorbed by deoxygenated hemoglobin).

  34.   B.   The accuracy of pulse oximetry can be affected by many factors. These include but are not limited to low blood flow conditions, patient movement, ambient light, dysfunctional hemoglobin molecules, dyes such as methylene blue and indigo carmine, and altered relationships in the hemoglobin dissociation curve (severe acidosis). Intravenous heparin bolus is not known to distort the accuracy of pulse oximetry.

  35.   D.   Many different clinical situations will cause pulse oximetry to read in characteristic patterns. Methemoglobinemia absorbs both wavelengths of light and tends to converge around a saturation of 85%. Carboxyhemoglobin only absorbs red light, but not infrared light, and can vary widely in saturation readings. Methylene blue, a common dye used during surgery, tends to cause saturations to converge around 65%.

  36.   A.   Many different clinical situations will cause pulse oximetry to read in characteristic patterns. Methemoglobinemia absorbs both wavelengths of light and tends to converge around a saturation of 85%. Carboxyhemoglobin only absorbs red light, but not infrared light, and can vary widely in saturation readings. Methylene blue, a common dye used during surgery, tends to cause saturations to converge around 65%.

  37.   B.   The corticospinal tracts responsible for motor function travel along the anterior spinal cord, and can be monitored using motor-evoked potentials. Sensory tracts, on the other hand, travel along the posterior spinal cord, and can be monitored using somatosensory-evoked potentials. Electroencephalography is commonly used to measure cerebral activity during neurovascular surgeries, such as carotid endarterectomies, looking for decreased cerebral blood flow. Bispectral index or Sedline monitoring is somewhat controversial, but is used to monitor the adequacy of depth of anesthesia.

  38.   B.   SSEPs monitor the posterior spinal column, which would be affected by damage to the posterior spinal arteries or compression of the posterior spinal cord. A light plane of anesthesia would not cause a drop in SSEPs, nor would the administration of a neuromuscular blocking agent (the latter would hinder the use of motor-evoked potentials).

  39.   C.   Halogenated anesthetics as well as nitrous oxide (especially when combined together) can decrease amplitude and increase latency. For this reason, it is recommended to minimize the use of volatile anesthetics to below 1 MAC, or to use a total intravenous technique when monitoring SSEPs.

  40.   A.   Etomidate is known to increase the amplitude of somatosensory-evoked potentials (SSEPs), and can sometimes be dramatic. Propofol is considered to have minimal to no effect on amplitude, and is commonly used as an infusion for the maintenance of anesthesia when monitoring SSEPs. Midazolam has been shown to decrease amplitude, and this should be kept in mind when used for premedication. As discussed in the previous question, sevoflurane would be expected to decrease amplitude and increase latency of SSEPs.

  41.   A.   Medications are not the only variables that affect somatosensory-evoked potentials, as changes in physiology can also alter latency and amplitude. Amplitude decreases during episodes of hypotension, hypoxia, and hyperthermia. Latency can be increased during hypothermia, hypocarbia, and hemodilution/anemia.

  42.   A.   A to B occurs during exhalation of anatomic dead space, B to C occurs during mixing of exhaled dead space and alveolar gas, C to D reflects the exhalation of alveolar gas, with point D correlating with end-tidal carbon dioxide, and D to E represents the beginning of inspiration.

  43.   D.   A to B occurs during exhalation of anatomic dead space, B to C occurs during mixing of exhaled dead space and alveolar gas, C to D reflects the exhalation of alveolar gas, with point D correlating with end-tidal carbon dioxide, and D to E represents the beginning of inspiration.

  44.   A.   It is important to remember that capnography will show a normal capnograph and end-tidal CO2 immediately following endobronchial intubation. Anesthesia providers must be vigilant to always listen for bilateral breath sounds and observe bilateral chest rise to confirm tracheal intubation.

  45.   D.   The classic image above is commonly referred to as a curare cleft, and occurs when a patient begins to attempt inspiration during the expiratory phase of mechanical ventilation. This is one of the indications that neuromuscular function is returning.

  46.   C.   On average, core temperature declines by approximately 1 to 1.5°C after the induction of general anesthesia. This initial drop in core body temperature is primarily due to redistribution (core to periphery) from the vasodilating properties of many anesthetics. Temperature may continue to drop as processes of heat loss, such as conduction, convection, radiation, and evaporation, occur (as opposed to redistribution).

  47.   D.   The current recommendations from the American Society of Anesthesiologists state that temperature monitoring is required “when clinically significant changes in body temperature are intended, anticipated, or suspected.” In addition to considering the surgical procedure, it is also important to consider at risk populations such as the elderly, infants, burn patients, and patients with autonomic dysfunction.

  48.   A.   Uncontrolled hypothermia has many detrimental effects, including increased oxygen utilization through shivering, impaired platelet function and coagulation, delayed wound healing and increasing surgical site infections, as well as potential for serious dysrhythmias. Cerebral oxygen consumption, however, decreases by approximately 7% per degree Celsius decrease in temperature.

  49.   A.   Numerous sites can be used to monitor temperature in the operating room. Of the most common, tympanic membrane (perfused by carotid artery) and pulmonary artery measurements tend to be the best reflectors of core temperature, followed by bladder temperatures. Rectal temperatures overall tend to be a poor substitute, while axillary and skin temperatures are highly prone to error.

  50.   C.   Understanding the limitations of neuromuscular twitch monitoring devices is fundamental for an anesthesia provider. At the point the fourth twitch reappears, still up to 75% to 80% of acetylcholine receptors may be blocked. Adequate reversal (neostigmine–glycopyrrolate) should be given, and clinical signs for return of neuromuscular function should be used to gauge readiness for extubation.