Trulearn Questions 3

Question 1

State the pKa and Lipid Solubility for the Following

1. Alfentanil
2. Morphine
3. Sufentanil
4. Fentanyl
   * What is the octanol-water partition coefficient?

Answer 1

Remember the lipid solubility of an opioid is a prime determinant of the onset and duration of action of the drug as it affects how easily the drug is able to cross cellular (lipid) membranes.

Lipid solubility is represented by the octanol-water partition coefficient (λow); the higher the λow, the higher the lipid solubility.

A unique characteristic of alfentanil relative to other opioids is its significantly lower pKa resulting in a very high fraction of the drug existing in the nonionized form. Coupled with its moderate lipid solubility, this allows alfentanil to very rapidly cross the blood-brain barrier and have an ultra-short onset of action. The plasma-brain equilibration half-time of alfentanil is 0.9-1.1 minutes compared to 6.2 minutes for sufentanil, 4.7-6.4 minutes for fentanyl, and 139 minutes for morphine.

Question 2

An alteration of which parameter MOST significantly stimulates the carotid body chemoreceptors?

Answer 2

Carotid body chemoreceptors are primarily responsive to reductions in arterial partial pressure of oxygen (PaO2).

Explanation: The carotid bodies are located at the bifurcation of the common carotid arteries bilaterally and contain afferent glossopharyngeal nerve branches that become stimulated in response to reductions in PaO2. Once the PaO2 falls below 60-65 mm Hg, neural activity increases to augment minute ventilation. Once the PaO2 increases to above 65 mm Hg, the neural input to the central respiratory centers ceases. Ventilation then falls again until the decrease in PaO2 surpasses this threshold again.

• The carotid bodies are not stimulated by changes in arterial oxygen saturation (SaO2) or arterial oxygen content (CaO2).
• Alterations in arterial partial pressure of carbon dioxide (PaCO2) do not stimulate the carotid body receptors sufficiently to produce changes in minute ventilation.
• The carotid body chemoreceptors do show some response to reductions in pH, however, the response is minor

Question 3

Regarding coronary venous anatomy; the following veins run with which coinciding arteries?

1. Great Cardiac Vein
2. Anterior Cardiac Vein
3. Middle Cardiac Vein

Mnemonic: “You cant LaRP w/o GAM GAMs”

Answer 3

1. The great cardiac vein courses along the atrioventricular groove and with the left anterior descending coronary artery
2. The anterior cardiac vein is located with the RCA and receives drainage from the right ventricle.
3. The middle cardiac vein is usually associated with the posterior descending coronary artery (PDA), which more commonly arises from the right coronary artery (RCA) and less commonly, from the left circumflex (LCx) coronary artery.

LAD = GCV

RCA = ACV

PDA = MCV

Coronary venous drainage ultimately converges in the coronary sinus, which subsequently empties into the posterior right atrium. While 85% of coronary blood flow to the left ventricle empties into the coronary sinus, 15% will eventually drain via Thebesian veins into the atrial and ventricular cavities.

Question 4

How does Cardiac Output affect FA/FI for inhalational anesthestics?

Answer 4

In general: The HIGHER the Cardiac Output the SLOWER the rate of induction (FA/FI): THIS IS ESPECIALLY SO FOR SOLUBLE VOLATILE ANESTHETICS

Uptake of volatile anesthetics is directly proportional to cardiac output, solubility, and alveolar-to-venous partial pressure difference. Greater uptake into blood may imply faster distribution within the body, but this means the partial pressure of anesthetic in the blood is lower. This, in turn, causes the gas to take longer to reach an equilibrium between the alveoli and the brain thereby slowing induction. Variation in cardiac output will have limited effect on FA/FI rate of rise during the initial transfer for insoluble agents (e.g. desflurane) as compared to soluble agents since they have decreased blood uptake and thus faster induction.

Question 5

State the function of the following receptors:

1. Alpha 1
2. Alpha 2 (Pre-synaptic)
3. Alpha 2 (Post synaptic)
4. Beta 1
5. Beta 2 (Pre-synaptic)
6. Beta 2 (Post synaptic)
7. DA1

Answer 5

1. Alpha 1 (Gq)
   
   1. Contriction of peripheral vascular smooth muscle
   2. Constriction of renal vasculature
   3. Inotropism of myocardium
   4. Gluconeogenesis & Glycogenolysis
2. Alpha 2 Pre synaptic (Gi)
   
   1. Inihibition of NE release in vascular smooth muscle
   2. Inhibition of CNS activity
   3. Decrease MAC
3. Alpha 2 Post synaptic
   
   1. Coronary constriction
   2. Inihibit insulin release
   3. Decrease bowel motility
   4. Analgesia
4. Beta 1 (Gs)
   
   1. Inotropism and Chronotropism
   2. Renin Release
   3. Coronary Relaxation
5. Beta 2 (pre-synaptic) (Gs)
   
   1. Accelaerate endogenous NE release
6. Beta 2 (Post-synaptic)
   
   1. Inotropism and Chronotropism
   2. Relaxation of Vascular Smooth Muscle
   3. Bronchial Smooth Muscle Relaxation
   4. Relaxation of Renal Vessels
   5. Gluconeogenesis & Glycogenolysis
   6. Shift K intracellularly
7. Dopamine 1 (Gs)
   
   1. Renal, coronary, & mesenteric vasodilation
   2. Natiuresis & Diuresis
   3. Renin Release

Question 6

Damage to the following structures would lead to what physiologic effects

1. Damage to the preoptic anterior hypothalamus
2. Damage to the paraventricular and supraoptic nuclei
3. Damage to Broca’s Area

Answer 6

1. Damage to the preoptic anterior hypothalamus can impair thermoregulation and temperature homeostasis.
2. The paraventricular and supraoptic nuclei, located in the medial tuberal region of the hypothalamus, contain neurosecretory neurons whose axons extend into the posterior pituitary gland. These neurons are responsible for production and secretion of oxytocin and vasopressin. Damage to these nuclei may accordingly lead to hypotension and diuresis if vasopressin (antidiuretic hormone) production is impaired.​
3. Expressive or Broca aphasia results from damage to the Broca area in the frontal lobe. The Broca area is supplied by the middle cerebral artery and is unlikely to be affected in this patient. Patients with expressive aphasia typically understand language but are unable to speak fluently.

Question 7

Indications for FFP

1.

2.

3.

4.

5.

6.

Answer 7

Question 8

When is pulmonary vascular resistance the lowest?

Answer 8

In normal healthy adults, PVR is lowest when breathing at normal tidal volumes, with a nadir at functional residual capacity (FRC). Increasing or decreasing lung volumes beyond FRC and normal tidal volumes results in an increase in PVR, creating a U-shaped curve, illustrated below. This general relationship exists for both normal breathing and positive-pressure breathing.

Question 9

Which vertebrae is identified for a stellate ganglion block?

Answer 9

C: The transverse process of C6 is the major landmark for stellate ganglion blockade.

The stellate ganglion is the fusion of the inferior cervical and first thoracic sympathetic ganglia. It receives preganglionic sympathetic fibers from T1-T6. Stellate ganglion blocks are commonly used to diagnose and treat complex regional pain syndrome (CRPS) of the upper extremity. The location of the stellate ganglion is in the neck generally anterior to the C7 vertebral body. Directly superior to the ganglion is the transverse process of C6, which is referred to as the Chassaignac tubercle (or carotid tubercle). Because of its prominence and proximity to the stellate ganglion, the Chassaignac tubercle is often used as the landmark to perform the block.

The anterior approach to the stellate ganglion block is performed in the supine position. The practitioner palpates the Chassaignac tubercle, generally at the level of the cricoid just lateral to the trachea. The needle is then placed there and advanced until it hits the tubercle. You then direct medially and inferiorly and withdraw 1-2 mm and inject (after negative aspiration for blood). This procedure may also be performed with fluoroscopic guidance, which would require recognition of the C6 transverse process by radiograph. Development of Horner syndrome in the patient generally designates a successful block, but is not the most useful sign as cephalad spread of the local anesthetic can cause this syndrome. Ipsilateral temperature changes are the most reliable for block success.

Other potential side effects associated with this block include pneumothorax, phrenic nerve paralysis, accidental vertebral artery injection leading to seizures, brachial plexus injury, and intrathecal injection. The patient should, therefore, be closely monitored during and immediately after performing the block.

Question 10

Which of the following phases on the capnograph would BEST display an acute or chronic obstructive pattern?

Answer 10

A slow rate of rise in the B-C phase would be indicative of an obstructive pulmonary pattern.

Question 11

Define the Following

1. MAC- Awake
2. MAC- Aware
3. MAC- Bar

Answer 11

1. The MAC-awake is the MAC value at which voluntary reflexes (e.g., a patient will no longer open his or her eyes to command, shouting, or shaking) and perceptive awareness are lost. It varies between 15-50% of standard MAC
2. Concentration at which patients lose awareness. The loss of awareness and recall typically occurs at 0.4-0.5 standard MAC (D). Isoflurane likely has the most recall-blocking activity and nitrous oxide the least. Current ASA guidelines recommend maintaining at least 0.7 MAC during general anesthesia to significantly reduce the risk of awareness.
3. The MAC value that blunts adrenergic responses to noxious stimuli (MAC-BAR) is 50% higher than standard MAC

Question 12

Characterize the following receptors - what type of ion channels are they linked to? What drugs stimulate them?

1. GABA- A
2. GABA- B
3. Glycine
4. NMDA

Answer 12

1. GABAA receptors, when active, allow Cl- to enter neurons and hyperpolarize the cell. Propofol is a useful induction agent because it produces a quick reliable onset of general anesthesia. Several other medications target the GABAA receptor including etomidate and benzodiazepines. Benzodiazepines directly activate the GABAA receptor.
2. GABAB receptors are linked to potassium channels. The most common GABAB receptor agonist medication is baclofen. Baclofen is used to treat muscle spasticity from spinal and supraspinal pathology.
3. The Glycine receptor is linked to a chloride channel. Alcohol is an agonist of the glycine receptor, whereas caffeine is an antagonist of the glycine receptor.
4. The NMDA receptor contains a calcium channel that is inhibited by several different medications. Ketamine is the prototypical anesthetic agent that affects the NMDA receptor. PCP and nitrous oxide also antagonize the NMDA receptor. Antagonism of the NMDA receptor can cause anesthesia without producing respiratory depression. NMDA is also related to the development of chronic pain.

Question 13

Draw an anesthesia circle system, what are the 3 requirements?

1.

2.

3.

Answer 13

1. Must have uni-drectional valves on inspiratory and expiratory limbs
2. FGF cannot be between patient and expiratory valve
3. APL cannot be between patient and inspiratory valve

Question 14

Characteristics associated with difficult mask ventilation

1.

2.

3.

4.

5.

6.

Answer 14

1. age >55
2. OSA or Snoring
3. Previous head/neck surgery, radiation
4. Lack of teeth
5. Beard
6. BMI >26

Question 16

Neck circumference >43 cm is a predictor of what in terms of airway management?

Answer 16

It has been documented that a neck circumference >43 cm has higher sensitivity and specificity as a predictor of difficult intubation in obese patients.

Question 17

What are the STOP BANG Criteria?

Answer 17

0-2 = Low risk

2-4 = Moderate risk

>5 = High Risk

Question 18

What is the Apnea Hypopnea Index?

Answer 18

Question 19

Give Some examples of

1. ASA 1
2. ASA 2
3. ASA 3
4. ASA 4
5. ASA 5
6. ASA 6

Answer 19

• Key Points
  
  • ASA 2 = Pregnancy and BMI 30 - 40
  • ASA 3 = > 3 months of MI, CVA, or Stent; ESRD on HD; BMI >40
  • ASA 4 = <3 months of MI, CVA, or Stent; ESRD NOT on HD

Question 20

This drug is associated with yellow-green vision problems

Answer 20

DIGOXIN

Question 21

Receptor site that causes Coronary Constriction?

Coronary dilation?

Answer 21

1. Alpha 2
2. Beta 1

Question 22

Where in the SNS is acetylcholine release?

Answer 22

1. Pre and post ganglionic neuron site of synapse
2. Erector Pilli
3. Sweat Glands
4. Enterochromaffin cells (modified post-ganglionic nerve cells)

Question 23

Drugs that reduce pseudocholinesterase activity and prolong succinylcholine

mnemonic: the “EN -PC-MEPO”

Answer 23

1. Echothiophate
2. Neostigmine
3. Phenelzine
4. Cyclophosphamide
5. Metoclopromide
6. Esmolol
7. Pancuronium
8. Oral contraceptives

Question 24

Factors that increase closing capacity

mnemonic: “ACLS-SO”

Factors that decrease FRC

Mnemonic: “PANGOS”

Answer 24

1. Age, Chronic Bronchitis, LV Failure, Smoking, Surgery, Obesity
2. Pregnancy, Ascites, Neonates, Obesity, Supine

Question 25

What part of a Sarcomere is Calcium dependant?

Answer 25

• THICK FILAMENT
  
  • ​Calcium dependant interaction
• Thin filament
  
  • Actin/tropomyosin complex

Question 26

Endotracheal tubes safe for laser surgery

1.

2.

3.

4.

Answer 26

1. Red Rubber Tubes
2. Silicone Based Wrapped in Aluminum
3. Stainless steel spiral ETT
4. Soft white rubber tubes wrapped in copper foil

Question 27

Differential Blockade of Local Anesthetics based on nerve fiber types from Greatest to Least

Answer 27

Sympathetic > Pain/Sensory > Motor

Sympathetics: most sensitive to local anesthetic agents (2-4 levels beyond motor)

Pain/touch: moderately sensitive (2-3 levels beyond motor)

Motor fibers: least sensitive

The expression differential blockade is used to describe how neuraxial anesthesia progresses and recovers in a predictable manner. For example, sensation to cold is lost early and thus can be used to evaluate the progression of the block. Differential blockade with local anesthetics results in sympathetic blockade first, followed by pain/sensory blockade, then motor blockade last. This is (at least in part) explained by differential susceptibility of nerve fibers to local anesthetics being A-delta, A-gamma > A-alpha, A-beta > C.

Investigative efforts have been directed at explaining such differential blockade based on the susceptibility of certain fiber types to local anesthetic blockade. In vitro studies where local anesthetic concentration is allowed to equilibrate, and fiber stimulation is standardize, clearly show that unmyelinated C fibers are the most resistant to local anesthetic action. Whereas myelinated A fibers are most sensitive and that amongst the myelinated A-fibers the smaller ones such as A-delta and A-gamma are more sensitive than the large ones such as A-alpha and A-beta. This could explain why pinprick sensation (A-delta) is lost before (and recovers after) touch sensation (A-beta).

However, the fiber type model is somewhat simplistic and does not explain all clinical observations, including why sympathetic tone is lost before touch sensation. Likely there are other factors that are important in vivo, for example:

1) Use-dependency dictates that nerves stimulated at higher frequencies are inhibited more.
2) Longitudinal and radial diffusion will create different concentrations of the drug along the nerve.
3) More than one fiber type participate in one nerve modality, for example sympathetic efferents travel through both B fibers (preganglionic) and C fibers (postganglionic).

Question 28

Diagram a standard bell curve.

What % of values lie within 1, 2, and 3 standard deviations of the mean?

Answer 28

Question 29

What is Train of Four ratio?

What do return of twitches 1 - 4 indicate?

Answer 29

• The TOF ratio is the ratio of the height of the 4th twitch (T4) to the height of the 1st twitch (T1). It was previously taught that a T4:T1 ratio of 0.75 typically guarantees (1) a sustained head lift for 5 seconds, (2) the ability to generate a vital capacity of 15-20 ml/kg, (3) an effective cough to clear secretions, and (4) a negative inspiratory force of -25 cm H2O. There are multiple devices available to assess TOF (e.g., electromyography, mechanomyography, acceleromyography). The TOF ratio (not count) is considered the current gold standard for assessing neuromuscular blockade. Unfortunately, the quantitative “direct palpation” method of counting the number of twitches is too commonly used. This method cannot determine if the TOF ratio is ≥ 0.9, which is the current requirement for determining recovery from neuromuscular blockade. Clinical tests alone are not adequate to evaluate if a TOF ratio of ≥ 0.9 has been achieved. Modern force mechanomyography (MMG) is able to assess for a TOF ratio ≥ 0.9 and acceleromyography (AMG) is able to assess for a TOF ratio ≥ 1.0. MMG is typically cumbersome and difficult to setup, thus AMG is more commonly used.
• A T4:T1 height ratio of 0.75 typically guarantees (1) a sustained head lift for 5 seconds, (2) the ability to generate a vital capacity of 15-20 ml/kg, (3) an effective cough to clear secretions, and (4) a negative inspiratory force of -25 cm H2O.
• When assessing the degree of neuromuscular blockade using TOF stimulation after nondepolarizing NMBD administration:
  
  • 1 palpated twitch indicates >90% suppression.
  • 2 palpated twitches indicate 80-90% suppression.
  • 3 palpated twitches indicate 70-80% suppression.
  • 4 palpated twitches indicate up to 65-75% suppression.
  • Palpation of twitches using TOF testing cannot detect the percentage of receptors bound at < 65%.

Question 30

Phase 2 blockade with succinylcholine is characterized as?

What is the difference between phase 1 and phase 2 blockade in terms of:

1. Cause
2. Single twitch response
3. T4:T1 Response
4. 1 Hz Twitch
5. Post - Tetanic Potentiation
6. Effect of Anticholinesterases
7. Physiology

Answer 30

• Phase II blockade with Sch is characterized by
  
  • marked fade to both tetanus and TOF stimulation
  • post-tetanic potentiation, prolonged recovery
  • and the ability to antagonize the blockade with anticholinesterase drugs.

Question 31

What happens to vital capacity with the initiation of labor epidural?

Answer 31

it INCREASES

Labor pain can cause low tidal volumes due to pain. Epidural anesthesia can provide a segmental sensory blockade that can improve respiratory function by decreasing the incidence of low tidal volumes secondary to pain splinting and allow for larger maximal breaths. This effect is seen even in parturients who are not in active labor, with the administration of epidural anesthesia improving both forced vital capacity and forced expiratory volume in one second (FEV1) when compared to baseline. The lungs receive innervation from the sympathetic system via T2 to T7 and the parasympathetic system via vagal efferent and afferent nerves and consequently lumbar epidural analgesia direct effect on the muscles that impact pulmonary function in healthy patients.

Question 32

Storage time of

1. PRBCS
2. FFP
3. Cryoprecipitate
4. Platelets

Answer 32

1. 42 Days
2. 1 Year
3. 1 year
4. 5 days

Question 33

Why is it safer for adult to donate liver to child as compared to another adult?

Answer 33

• A child requires less donor liver volume than an adult; accordingly, an adult liver donor may undergo the less technically challenging left hepatectomy.

Question 34

A 65-year-old man is intubated in the ICU with respiratory failure. He developed pneumonia more than 7 days after being admitted for management of a sacral decubitus ulcer. Which of the following would be the MOST appropriate for initial empiric antibiotic treatment?

A) ampicillin sulbactam

B) Cefepime + Ciprofloxacin + Linezolid

C) Piperacillin-Tazobactam + Levofloxacin

D) Ertapenem

Answer 34

Correct Answer: B

The American Thoracic Society (ATS) and Infectious Disease Society of America (IDSA) 2016 guidelines recommend starting empiric antimicrobial coverage based on clinical severity, multi-drug resistant (MDR) organisms, and the timing of the onset of pneumonia. Identifying the risk factors for MDR organisms is important to determine the appropriate antibiotic management.

• *The risk factors for MDR ventilator-associated pneumonia are:**
• Five or more days of hospitalization at the time of occurrence
• Prior intravenous antibiotic use within 90 days
• Septic shock at the time of occurrence
• Acute respiratory distress syndrome or acute renal replacement therapy prior to the occurrence

This patient is at risk for a multi-drug resistant organism because his pneumonia occurred more than 5 days after being in the hospital. If the prevalence of MRSA and MDR organisms is unknown, the recommended antibiotic regimen is one including coverage against methicillin-resistant Staphylococcus aureus (MRSA) and two anti-pseudomonal agents. If the prevalence of MRSA is known to be less than 10%, then coverage against methicillin-sensitive Staphylococcus aureus (MSSA) is recommended instead of MRSA coverage. The following are appropriate regimens for treatment of MDR VAP with MRSA prevalence > 10% or unknown prevalence (always refer to your local protocols and patient-specific factors for final dosing recommendations):

MRSA coverage
- Vancomycin 15 mg/kg IV every 8-12 hours
OR
- Linezolid 600 mg IV every 12 hours

PLUS

Antipseudomonal non-β-lactam-based agents
Antipseudomonal penicillins
- Piperacillin-tazobactam 4.5 g IV every 6 hours
OR
Cephalosporins
- Cefepime 2 g IV every 8 hours
- Ceftazidime 2 g IV every 8 hours
OR
Carbapenems
- Imipenem 500 mg IV every 6 hours
- Meropenem 1 g IV every 8 hours
OR
Monobactams
- Aztreonam 2 g IV every 8 hours

PLUS

Antipseudomonal non-β-lactam-based agents
Fluoroquinolones
- Ciprofloxacin 400 mg IV every 8 hours
- Levofloxacin 750 mg IV every 24 hours
OR
Aminoglycosides
- Amikacin 15-20 mg/kg IV every 24 hours
- Gentamicin 5-7 mg/kg IV every 24 hours
- Tobramycin 5-7 mg/kg IV every 24 hours
OR
Polymyxins
- Colistin 5 mg/kg IV load followed by a maintenance dose which is based on creatinine clearance

The IDSA recommends avoiding aminoglycosides and colistin if alternative agents are available.

Answer A: Ampicillin-sulbactam would be an appropriate empiric drug regimen to start on a patient with no risk factors for MDR organisms. This patient has risk factors for MDR organisms, so ampicillin-sulbactam alone is not appropriate.

Answer C: This patient is at high risk for MRSA and needs an additional antibiotic such as linezolid or vancomycin added to piperacillin/tazobactam + levofloxacin.

Answer D: Ertapenem would be an appropriate empiric drug regimen to start on a patient with no risk factors for MDR organisms. This patient has risk factors for MDR organisms, so ertapenem alone is not appropriate.

Bottom Line: Risk factors for multi-drug resistant pathogens causing ventilator-associated pneumonia include: five or more days of hospitalization at the time of pneumonia onset, prior intravenous antibiotic use within 90 days, septic shock at the time of occurrence, and acute respiratory distress syndrome or acute renal replacement therapy prior to onset. Patients presenting with ventilator-associated pneumonia with any of these risk factors need to be treated empirically with two anti-pseudomonal antibiotics and coverage against MRSA.

TrueLearn Insight : The development of ventilator associated pneumonia (VAP) conveys a poor prognosis with a mortality of two to ten times that of those without VAP.

Question 35

Advantages of for Bronchial Blocker instead of DLT

Answer 35

Advantages of using a bronchial blocker instead of a DLT include the ability for selective lobar collapse, such as in cancer patients who have had prior contralateral pulmonary resection and require selective ipsilateral lobar blockade in order to improve oxygenation and facilitate surgical exposure. Additionally, patients that have had prior oral or neck surgery with challenging airways may better tolerate a bronchial blocker since these patients may not anatomically accommodate larger DLTs. Patients with tracheostomies also require bronchial blockers for lung isolation. Similarly, children < 12 years old generally cannot accommodate even a small DLT; bronchial blockers or selective main stem intubation with a single lumen tube may allow lung separation in this age group. Lastly, when postoperative mechanical ventilation is anticipated (e.g. following prolonged thoracic procedures with upper airway edema), bronchial blockers through a standard single-lumen endotracheal tube have the advantage of not requiring the endotracheal tube to be exchanged, as would be the case with a DLT.

Question 36

What is pH stat management during Cardiopulmonary bypass and what are some advantages/disadvantages to using it?

Answer 36

There are two methods (pH-stat and alpha-stat) by which acid-base status may be managed during cardiopulmonary bypass (CPB), where hypothermia plays a major role in reducing the cerebral metabolic demands. Core body temperature may drop to as low as 17°C during cases of deep hypothermic circulatory arrest (DHCA).

Hypothermia plays a major role in reducing cerebral metabolic demands during CPB. There is a natural “alkaline drift” with hypothermia owing to the increase in gas solubility and reduction of the PaCO2. The two methods of managing acid-base balance during CPB are noted as pH-stat and alpha-stat management. A pH-stat management technique corrects the alkaline drift by maintaining a neutral pH during hypothermia. Alpha-stat management allows the natural alkaline drift to occur without correction.

During pH-stat management, CO2 is added to the oxygenator or the CPB “sweep” may be reduced (the sweep mechanism removes CO2 from the CPB circuit). The addition of CO2 to the circuit increases total body CO2 in order to maintain pH neutrality despite the continuous reduction in core temperature.

Advantages of pH-stat management include increased speed of homogenous cerebral cooling through cerebral vasodilatation, reduced cerebral metabolic rate of oxygen demand (CMRO2) while providing increased cerebral blood flow (CBF), and improved oxygen delivery to tissue by counteracting the leftward shift of the oxyhemoglobin curve typical of alkalosis. Disadvantages of pH-stat management include an increased delivery of embolic load to the brain as a result of the cerebral vasodilatation as well as loss of cerebral autoregulation. Outcome data support the use of pH-stat management during congenital heart surgery as a result of the homogeneous brain cooling.

Question 37

Which of the follwing have been used safely in multiple sclerosis (MS) patients

A) Epidural Anesthesia

B) General Anesthesia

C) Spinal Anesthesia

D) Succinylcholine

Answer 37

Epidural anesthesia and other regional anesthetic techniques with local anesthetics used in low concentrations have been used safely in multiple sclerosis (MS) patients without any reported significant exacerbations of symptoms.

Multiple sclerosis is an autoimmune disorder that results in demyelination of central nervous system neurons leading to secondary nerve conduction failure. It is primarily noted in women between the ages of 20-40 and 45-60 and is caused by genetic and environmental factors. Patients can present with a range of symptoms including paresthesias, muscle weakness, and sensory disturbances.

Depending on their preoperative status, MS patients may need extended postoperative care due to exacerbated muscle weakness which may include respiratory musculature resulting in respiratory insufficiency.

Answer B: General anesthesia and surgery (in general) have been associated with exacerbations of MS symptoms during the perioperative period secondary to increased physical and emotional stress.

Answer C: There have been reports associating spinal anesthetics with MS symptom exacerbations. Of the options, epidural anesthesia has not been associated with exacerbations. If spinal anesthesia is preferred, such as for cesarean section, a risk versus benefit discussion should take place with the patient prior to choosing a specific anesthetic strategy.

Answer D: Depolarizing muscle relaxants (succinylcholine) must be used cautiously or avoided as there is an increased chance of fatal cardiac arrhythmias secondary to succinylcholine-induced hyperkalemia from MS-induced denervation or misuse myopathy.

Bottom Line: Patients with MS are susceptible to an exacerbation of their symptoms in the perioperative period caused by surgery and the use of general or spinal anesthesia. Succinylcholine should be used cautiously or avoided. Extended postoperative care may be required with emphasis on managing respiratory insufficiency.

Question 38

According to the 2011 American Heart Association guidelines for pediatric advanced life support, what is the MOST appropriate intervention for a 4-year-old male with a HR of 180, QRS duration of 0.11 seconds, and delayed capillary refill?

A) Adenosine

B) Synchronized Cardioversion

C) Unsynchronized Defibrillation

D) Vagal Maneuvers

Answer 38

Wide complex tachycardia with evidence of cardiopulmonary compromise should be treated with synchronized cardioversion (0.5-1 J/kg).

Cardiopulmonary compromise may be represented by hypotension, acute change in mental status, or clinical signs of shock. Wide complex QRS is defined as greater than 0.09 seconds duration in children. If the patient with a wide complex tachycardia is hemodynamically stable without evidence of cardiopulmonary compromise then adenosine may be administered. The AHA also recommends consultation for possible amiodarone or procainamide administration.

Narrow complex tachycardia can be divided into probable sinus tachycardia versus probable supraventricular tachycardia (SVT). P-waves are present in sinus tachycardia and HR is typically less than 220/min for an infant and 180/min for children (150/min for adults). Supraventricular tachycardia has either absent P-waves or morphologically abnormal P-waves with fixed HR typically > 220 for infants and > 180 for children. Vagal maneuvers and/or adenosine are recommended as first line therapy for SVT. If adenosine is ineffective or IV/IO access is not available, then proceed with synchronized cardioversion. Sinus tachycardia therapy includes treating the cause.

Answer A: Adenosine is recommended for SVT. This patient has a wide complex tachycardia (e.g. ventricular tachycardia).

Answer C: Synchronized cardioversion is recommended for wide complex tachycardia. Unsynchronized defibrillation is recommended for ventricular fibrillation.

Answer D: Vagal maneuvers may be attempted prior to adenosine therapy in stable patients with SVT.

Bottom Line: Wide complex tachycardia with evidence of cardiopulmonary compromise should be treated with synchronized cardioversion (0.5-1 J/kg).

Question 39

Identify the Murmur

1) Low-pitched mid-diastolic rumble murmur best heard over the point of maximum impulse during exhalation.
2) Harsh systolic murmur best heard using the diaphragm of the stethoscope at the second or third intercostal space while the patient is supine and during a brief period of held expiration. The murmur will significantly decrease in intensity or even disappear during inspiration.
3) Blowing pandiastolic murmur best heard at the left and right sternal borders at the third and fourth intercostal spaces while the patient is sitting up and leaning forward. The diaphragm of the stethoscope should be used. The intensity of the murmur increases as afterload increases; this can be accomplished by having the patient hold his/her breath in deep exhalation, squat, and/or squeeze his/her hands (“hand-grip maneuver”)
4) low intensity, holosystolic or mid-systolic decrescendo murmur best heard during inspiration using the diaphragm of the stethoscope at the left sternal border at the third interspace.
5) diastolic rumble heard with the stethoscope bell on the left lower sternal border increases in intensity with inspiration

Answer 39

1) Mitral Stensosis
2) Pulmonic Stenosis
3) Aortic Regurge
4) Tricuspid stenosis

Question 40

Some causes of non-anion gap metabolic acidosis

Answer 40

1) Diarrhea
2) Saline administration
3) Hyperparathyroidism
4) Addison’s Disease
5) TPN
6) RTA

Question 41

Compared to an adolescent, a preterm infant is more responsive to which of the following interventions for hypotension on induction of anesthesia?

A) Norepinephrine

B) Epinephrine

C) Atropine

D) IV fluid bolus

Answer 41

The autonomic nervous system of newborns is not mature. It is characterized by low catecholamine stores and poor responsiveness to exogenous catecholamines. Conversely, the parasympathetic nervous system is intact in newborns and predominates. For this reason, bradycardia or hypotension in neonates is typically very responsive to atropine, a muscarinic acetylcholine receptor blocker. Throughout childhood, the sympathetic nervous system matures and assumes a larger role in regulation of cardiopulmonary physiology.

In addition, neonates have immature contractile mechanisms in their cardiac myocytes. This results in poor lusitropy - large increases in end diastolic pressure for each unit increase in end diastolic volume. As a result, increases in cardiac output are accomplished by increasing heart rate rather than increasing stroke volume.

Answers A & B: The sympathetic nervous system in neonates and infants is not mature. They have low endogenous catecholamine stores and are relatively insensitive to exogenous catecholamines. Adolescents, however, have a more mature sympathetic nervous system and will respond more briskly to exogenous catecholamines.

Answer D: Infants have immature cardiac contractile mechanisms with poor lusitropy. Their cardiac output is relatively insensitive to increased preload as their stroke volume is relatively static. Heart rate in neonates, however, is highly variable and is the major determinant of cardiac output. For this reason, increasing preload with a fluid bolus would only increase blood pressure to a small degree in the neonate and would only do so if initial preload were inadequate. In the adolescent with good lusitropy a fluid bolus would result in increased preload, stroke volume, and cardiac output.

Bottom Line: The cardiac output of the neonate is determined primarily by heart rate and their cardiac myocytes are relatively insensitive to catecholamines. Neonatal myocytes have poor lusitropy and cannot accommodate increasing preloads with increasing stroke volume. Atropine is an initial treatment option for the euvolemic neonate in response to hypotension

Question 42

True or False: Sympathetic Blocks may be beneficial for Acute Herpes Zoster NOT Post Herpetic Neuralgia

Answer 42

TRUE

Sympathetic blocks may be beneficial for acute herpes zoster infection but are NOT effective (C) for postherpetic neuralgia (PHN).

The causative agent, varicella-zoster virus (VZV), typically lays dormant in the dorsal root ganglia after initial infection (usually presenting as chickenpox in children). Immunity declines as a person ages or becomes immunocompromised, and the latent VZV can become active, resulting in herpes zoster (“shingles”).

The goal of acute herpes zoster treatment is to minimize pain and duration of the outbreak in order to reduce the risk of developing postherpetic neuralgia (PHN), but there is no conclusive data for the best treatment modality. The management of acute herpes zoster may include antivirals, corticosteroids, and/or sympathetic blocks.

Postherpetic neuralgia is defined as herpes zoster pain that persists beyond vesicular rash healing and can last 4 weeks to 6 months. The incidence of herpes zoster resulting in PHN is 16% for patients less than 60 years old but 47% for patients older than 60.

Medical management of PHN is the first modality of treatment. Pain relief begins with tricyclic antidepressants (e.g., amitriptyline, nortriptyline) (A). Anticonvulsants (e.g., gabapentin, pregabalin) (B), transcutaneous lidocaine patches (to treat allodynia) (D), topical capsaicin (E), and opiates (including controlled-release morphine) may be added to the regimen. Tramadol has also proven effective in the treatment of PHN. It is a μ-opioid receptor agonist, NMDA antagonist, and norepinephrine and serotonin reuptake inhibitor. Tramadol also has a lower addiction profile relative to opioids which makes it attractive for providers to prescribe. Medical treatment may take 2-4 weeks until symptomatic resolution. Spinal cord stimulators are also effective in PHN refractory to medical treatment.

Bottom Line: The treatment of PHN includes anticonvulsants, tricyclic antidepressants, lidocaine patches, topical capsaicin, opiates, and tramadol.

Question 43

A former 31-week premature infant with apneic and bradycardic episodes is to undergo bilateral inguinal hernia repair under general anesthesia. Which of the following statements regarding when to perform elective outpatient surgery is CORRECT?

1. No waiting required regardless of age
2. Perform surgery after 40 weeks postconceptual age
3. Perform surgery after 64 weeks of post conceptual age
4. Perform surgery after 6 months free from apnea or bradycardia episodes
5. All infants <1 year should be admitted for 23 hour post operative monitoring

Answer 43

If an infant has a history of apnea and bradycardia, it is advocated that there should be a six-month interval free from any events prior to proceeding with elective outpatient surgery.

Apnea is defined as the cessation of breathing >10 or >15 seconds (depending on source), or for any duration if accompanied by cyanosis and bradycardia. If the infant does have a history of apnea and bradycardia, it is advocated that there should be a six-month interval free from any events prior to proceeding with elective outpatient surgery. If these criteria are not met and the patient undergoes elective surgery, s/he should be admitted to a monitored unit for 12-24 hours.

Another risk factor for postoperative apnea in an infant, INDEPENDENT of postconceptual age, is anemia. Anemia is defined as hematocrit < 30%.

Regardless of the postoperative plan, some advocate the administration of a respiratory stimulant, such as IV caffeine (10 mg/kg) or aminophylline, as a prophylactic measure to prevent apneic episodes. This may be beneficial because it is unknown how detrimental these episodes of decreased brain perfusion are during the periods of bradycardia. Respiratory stimulants, however, do not replace the need for in-hospital postoperative monitoring.

Note, periodic breathing is regular breathing interrupted by short pauses or apnea lasting 5-10 seconds without cyanosis or bradycardia. This is a normal variant and may be present in both full term and preterm neonates.

Answers A & B & C: Premature infants are at risk for postoperative apnea following general anesthesia (GA) or sedation with regional anesthesia. Current recommendations to proceed with an elective outpatient procedure include waiting until 44-60 weeks postconceptual age (PCA) if the infant has NEVER experienced apnea or bradycardia.

Answer E: The exact PCA between 44-60 weeks in which monitoring is required (E) is institution and physician specific. If apneic episodes or bradycardia occur, assuming the infant’s clinical status returns to baseline, then in-hospital observation should continue for an additional 12-24 hours post-event.

Bottom Line: Postoperative in-hospital monitoring of premature infants for 12-24 hours after GA or regional anesthesia with sedation should be considered in infants before 44-60 weeks PCA without a history of apnea/bradycardia or any age in which an apnea/bradycardia event has occurred within the previous six months. Risks for postoperative apnea include GA, IV sedation, and anemia. The risk of postoperative apnea is inversely proportional to the gestational age and PCA. Being small for gestational age appears to provide some protection against postoperative apnea. General anesthesia, anemia, and PCA < 44-60 weeks at the time of surgery are all INDEPENDENT risk factors for postoperative apnea.

TrueLearn Insight : If the procedure allows, performing regional anesthesia without sedation in a former preterm infant < 60 weeks PCA has been shown to reduce the risk of postoperative apnea or bradycardia.

Question 44

A 44-year-old, 5’2”, 120 kg (50 kg ideal body weight) female is undergoing laparoscopic Roux-en-Y gastric bypass for morbid obesity. During the surgery, she received a total of 110 mg of rocuronium. At the end of surgery, she has two twitches in response to train-of-four stimulation at the adductor pollicis muscle. Which of the following is the MOST appropriate dose of sugammadex to administer to reverse her neuromuscular blockade at this time?

A) 100 mg

B) 200 mg

C) 240 mg

D) 480 mg

Answer 44

A dose of 2 mg/kg actual body weight is recommended for routine reversal of neuromuscular blockade (NMB) from rocuronium or vecuronium when the patient has two twitches in response to train-of-four (TOF) stimulation.

Sugammadex is a synthetic, modified γ-cyclodextrin (an 8-glucose ring) that has a large lipophilic core and eight hydrophilic side chains. It functions as a reversal agent for steroidal neuromuscular blocking drugs (rocuronium and vecuronium) since each molecule of sugammadex is capable of encapsulating and noncovalently binding one molecule of neuromuscular blocker.

Neuromuscular blockers bind to sugammadex with a high affinity and dissociate at a very low rate, therefore sugammadex allows for reversal of potentially all levels of NMB. Unlike neostigmine, there is no ceiling effect with sugammadex and NMB can be rapidly reversed even in the absence of twitches on TOF monitoring.

Currently, there are three recommended doses for sugammadex in adults (not currently FDA approved for pediatric patients) based on the clinical indication and the degree of NMB. It is important to note that sugammadex dosing is based on actual body weight. Dosing based on ideal body weight can result in under-dosing in overweight/obese patients and can place them at risk for residual neuromuscular blockade.

Answers A & B: Sugammadex dosing is based on actual body weight, not ideal body weight. Both doses (especially the 100 mg dose) will likely be inadequate to fully reverse the neuromuscular blockade and the patient could be at risk for residual neuromuscular blockade.

Answer C: A dose of 2 mg/kg actual body weight is the recommended dose in this patient based on the presence of two twitches from TOF stimulation.

Answer D: A dose of 4 mg/kg actual body weight would be appropriate if the patient had no twitches with TOF stimulation and 1-2 post-tetanic counts.

Bottom Line: There are three recommended doses for sugammadex in adults based on the clinical indication and the degree of NMB.

TrueLearn Insight : TrueLearn Insight : Use of a 16 mg/kg dose of sugammadex following rapid sequence intubation with rocuronium cannot be relied upon as a rescue solution for an unanticipated cannot intubate, cannot ventilate scenario. The management of a cannot intubate/ventilate scenario should primarily focus on facilitating airway patency, oxygenation, and ventilation per the American Society of Anesthesiologists’ difficult airway algorithm.

Question 45

Which of the following is NOT a sign of autonomic neuropathy in a diabetic patient?

a) Resting tachycardia
b) Gastroparesis
c) Dysrhytmia

D) Hypoglycemia Unawareness

E) Impaired Ventilatory responses

F) Increased Sweating

Answer 45

Diabetic autonomic neuropathy is the most common form of autonomic neuropathy and occurs in 20-40% of all insulin dependent diabetic patients. Increased sweating is not a sign of autonomic neuropathy (F). Many patients with diabetic autonomic neuropathy have diminished sweating.

The pathogenesis behind diabetic autonomic neuropathy is not completely understood but it likely occurs as a result of hyperglycemia with microvascular and/or autonomic damage. Damage to small fibers of the parasympathetic and sympathetic nervous system occurs, resulting in a variety of symptoms.

Clinical diabetic autonomic neuropathy does not develop for many years and depends on the duration of diabetes and the degree of glucose control. Symptomatic autonomic neuropathy is rare and occurs in 5% of diabetics. Cardiac autonomic neuropathy can result in a variety of symptoms. A resting tachycardia with loss of heart rate variability during deep breathing is the earliest sign (A). A later developing sign that indicates significant cardiac denervation is failure of the heart rate to respond to exercise. Dysrhythmias may be responsible for sudden cardiac death (C).

The pulmonary system can be affected and patients with diabetic autonomic neuropathy may demonstrate impaired respiratory reflexes and impaired ventilatory responses to hypoxia and hypercapnia (E). The gastrointestinal system can show a variety of signs in patients with diabetic autonomic neuropathy. Gastroparesis is present to some degree in 25% of diabetics (B) and many patients will have nausea, vomiting, early satiety, and bloating. In patients with diabetic autonomic neuropathy, loss of counter regulatory hormone responses result in lack of hypoglycemia warning signs that can create hypoglycemia unawareness (D).

Bottom Line: Signs and symptoms of diabetic autonomic neuropathy include loss of heart rate variability, resting tachycardia, dysrhythmias, impaired ventilatory responses, gastroparesis with increased risk of aspiration on induction, and unawareness of hypoglycemia.

Question 46

Which of the following has a negligible effect on somatosensory evoked potential (SSEP) amplitude?

A) Acute anemia

B) Administering a bolus dose of propofol

C) Hypothermia to or below a temperature of 32 degrees celsius

D) Increases PaCO2 to 50 mmHg

Answer 46

Hypercapnia to a level of 50 mmHg will not affect somatosensory evoked potentials (SSEPs).

Monitoring of the nervous system during surgery can be important, alerting clinicians if major changes occur while the patient is anesthetized and unable to do so themselves. Evoked potentials are a way to record electrical signals and transcribe them to a visual graph that can be interpreted. When major changes are noted the surgeon may alter the surgical plan or the anesthesia team may alter the anesthetic to optimize conditions. There are several types of evoked potentials. In the operating theater, they are used most frequently during neurosurgical, orthopedic, and vascular procedures. These modalities include motor evoked (MEP), somatosensory evoked (SSEP), brainstem auditory evoked responses (BAER), and visual evoked (VEP).

Somatosensory evoked potentials (SSEPs) involve stimulation of the peripheral sensory nerve followed by measurement of that response somewhere along the sensory pathway, most commonly in the cerebral cortex. SSEPs measure the cortical, subcortical, spinal, and peripheral components. The most frequently stimulated peripheral nerves are the median, ulnar, or posterior tibial. SSEPs test primarily the dorsal column of the spinal cord (the posterior segments). SSEPs can be used for a variety of surgeries although most commonly they are used for intracranial, spinal, and vascular surgery. What constitutes a meaningful change in waveform is not standard and may be up to the physician monitoring them. Additionally, many of the studies that helped to identify meaningful changes in SSEP were performed in animals.

SSEP use during surgery does not guarantee nerve injury is not occurring because SSEPs monitor the posterior spinal columns only. If monitoring of the anterior columns is not concurrently being performed, profound deficits can occur without a change in SSEP signals. Proper planning and determining what types of evoked potential to monitor based on patient and surgical characteristics is vital.

Multiple variables can alter evoked potential signals. It is easy to break these down into variables that lead to inadequate oxygen delivery and alterations in temperature or plasma homeostasis from either pharmacologic agents or physiologic changes. Since nerves are reliant on oxygen for metabolism, anything that alters the delivery of oxygen to the tissue will result in ischemia and the potential to cause changes in the evoked potentials. Depending on the site of monitoring and patient conditions, this can occur secondary to hypotension, decreased hemoglobin concentration causing a decline in oxygen-carrying capacity, increased intracranial pressure prohibiting adequate perfusion, and regional changes altering oxygen delivery.

Temperature changes may also alter evoked potentials. The effects of hypothermia on SSEPs are complicated and depend on the degree of temperature change. Hypothermia may not be deleterious to the nervous system but may mimic changes in SSEPs including decreased amplitude and increased latency when temperatures reach 32 degrees Celsius. Hypocapnia to a level of 20-25 mmHg did not compromise SSEP monitoring, however, did result in a small degree of shortened latency which may be secondary to changes in pH. Hypercapnia to a level of 50 mmHg has no effect on SSEPs.

Pharmacologic agents can have a profound effect on evoked potentials. Volatile anesthetics have an inhibitory effect on neurotransmission, producing a dose-dependent increase in SSEP latency and decreased amplitude. There are marked changes when minimum alveolar concentrations exceed 0.5. The major intravenous anesthetic agents affect SSEPs in variable ways depending on the specific agent used. Most barbiturates, benzodiazepines, and propofol cause a dose-dependent increase in latency and decreased amplitude. Opioids tend to have less effect except when given in bolus doses. Etomidate and ketamine tend to increase amplitude; thus ketamine may be useful to improve neuromonitoring conditions acutely. Use of neuromuscular blocking drugs is not prohibited with SSEP monitoring. It is most important when performing SSEP monitoring to try and maintain a stable anesthetic concentration so if changes are noted they can be attributed to factors outside the anesthetic.

When a change in the evoked potential is noted a series of troubleshooting events should occur. The surgeon should be notified, and a discussion should occur about recent surgical events and ways to improve perfusion. The anesthesia team should not make any changes in anesthetics, as bolusing certain medications such as opioids can alter the potentials. Finally, perfusion should be optimized by ensuring adequate blood pressure and hemoglobin concentrations.

Answer A: Anything that causes a decreased oxygen delivery to the nerve tissue can result in a change in the SSEP. This includes a decreased oxygen carrying capacity secondary to anemia.

Answer B: Propofol, when administered in bolus dosing, has a mild to moderate depressant effect on SSEPs. During surgery where SSEPs are monitored, it is important to obtain a relatively constant infusion of anesthetic agents, including propofol. If a bolus dose is required to obtain a deeper level of anesthetic depth, it should be communicated to the neuromonitoring team.

Answer C: The effect temperature has on SSEP waveform is variable and depends on the degree of temperature change. Hypothermia to or below 32 degrees has been shown to result in a decreased amplitude and increased latency.

Bottom Line: Anemia, PaO2, and hypothermia affect SSEPs.

TrueLearn Insight : Motor evoked potentials (MEPs) are most often used during spinal and vascular surgery; however, they can also be useful in cortical surgery. MEPs have better correlation with postoperative outcome since they are inherently more sensitive to ischemic vascular insults. Electrical stimulation in the motor cortex via electrodes placed on the scalp starts the signal and the response is recorded in the extremities.MEPs monitor the anterior spinal cord pathways which is an earlier predictor of impeding damage to the spinal cord due to the more precarious blood supply (when compared with SSEPs). Electroencephalogram (EEG) monitors the cortex only, thus it cannot provide information about any other pathways. This is why SSEPs may be used during carotid endarterectomy to monitor for subcortical ischemia.

Question 47

A patient is undergoing coronary artery bypass surgery. Intraoperatively, the surgeon has placed a catheter in the aorta to transduce the arterial pressure. Which of the following is most likely TRUE regarding the arterial pressure waveforms recorded at the proximal aorta compared to the radial artery?

A) Blunted dicrotic notch in the aorta

B) Less area under hte waveform tracing in the aorta

C) Lower systolic peak in the aorta

D) Steeper systolic upstroke in the aorta

Answer 47

Arterial waveforms will have higher systolic peaks when measured at more distal arterial sites. This occurs because of the summation of the original antegrade pressure wave generated by left ventricular contraction and the reflected pressure waves in a retrograde fashion.

Ejection of blood from the left ventricle into the aorta during systole and subsequent peripheral runoff during diastole generates an arterial pressure waveform. The waveform begins with a steep upstroke corresponding to ventricular contraction and ejection of blood into the aorta. The waveform peaks to represent maximal pressure during systolic ejection and then declines as the pressure during left ventricular ejection decreases. The decrease in pressure during systole is interrupted by the dicrotic notch, which represents closure of the aortic valve and end systole when measured in the proximal aorta. The arterial waveform measured at more distal sites, however, will have a smoother appearing notch occurring later in the cardiac cycle and is more representative of arterial wall properties and waveform reflections than aortic valve closure. The pressure then continues to decline after the dicrotic notch during diastole and reaches a nadir representing the pressure exerted by the vascular bed onto the closed aortic valve.

It is important to recognize that morphology of the arterial waveform differs based on the site of measurement. When the original waveform travels distally and encounters increased vascular resistance in the arterioles, pressure waves are generated and reflected in a retrograde fashion. Convergence of the original antegrade and retrograde waves causes distal pulse amplification. The original antegrade waveform morphology is distorted or amplified to a greater degree when measured closer to the source of the reflected wave. Therefore, the arterial waveform measured from a more distal site will display a steeper systolic upstroke, higher systolic peak, blunted dicrotic notch, lower diastolic peak, and a greater pulse pressure (see figure below).

The mean arterial pressure (MAP), however, is only slightly lower at more distal sites but still closely approximates proximal aortic pressure. The MAP displayed from invasive arterial monitoring is generated by an algorithm in the computer. It is roughly equal to the area beneath the arterial pressure waveform divided by the beat period and averaged over a series of consecutive heartbeats. The increase in systolic pressure measured at more distal sites is offset by a narrowing of the systolic pressure wave and the overall area under the waveform decreases only slightly.

Answer A: The dicrotic notch of the arterial waveform is more distinct when measured in the proximal aorta. The notch has a blunted appearance when measured at more distal sites due to a greater distance from the aortic valve.

Answer B: The area under the arterial waveform tracing is used to calculate the mean arterial pressure, and is slightly larger when measured at the aorta.

Answer C: An aortic arterial waveform has a lower systolic peak than more distal waveforms since there are fewer reflected retrograde pressure waves proximally to add to the wave amplitude.

Answer D: The systolic upstroke becomes steeper in the periphery due to distal pulse amplification.

Bottom Line: Compared to the proximal aorta, arterial waveforms measured at more distal sites have the following characteristics: higher systolic peak, steeper systolic upstroke, lower diastolic peak, blunted dicrotic notch, delayed dicrotic notch, slightly lower MAP.

Question 48

A child undergoes adenotonsillectomy for obstructive sleep apnea. The patient has persistent obstructive sleep apnea in the postoperative period. Which of the following is NOT a known predictor for this condition?

A) Age >5 years

B) History of Prematurity

C) Significant Airway Obstruction

D) Upper Respiratory tract infection 2 weels prior to surgery

Answer 48

Age < 3 years is a known predictor of respiratory compromise and obstructive sleep apnea (OSA) in pediatric patients following adenotonsillectomy (A).

More than 20% of children undergoing adenotonsillectomy to improve upper airway obstruction experience respiratory compromise in the postoperative period. Known predictors of postoperative OSA include:

• Severe OSA on polysomnography
• *- History of prematurity (B)
• Age <3 years (A)**
• Morbid obesity
• Mallampati score of 3-4
• Nasal pathology (e.g. deviated septum or enlarged turbinates)
• Neuromuscular disorders
• Craniofacial disorders and genetic disorders
• Enlarged lingual tonsils
• *- Upper respiratory infection (URI) within 4 weeks of surgery (D)**
• Cor pulmonale
• *- Systemic hypertension**
• *- Marked obstruction on inhalational induction (C)**
• Disordered breathing in the PACU
• Difficulty breathing during sleep
• Growth impairment resulting from chronic obstructed breathing

Bottom Line: Respiratory compromise and OSA is common in pediatric patients postoperatively following adenotonsillectomy. Factors predictive of postoperative respiratory compromise are numerous but include history of prematurity, age < 3 years, neuromuscular disorders, URI within 4 weeks of surgery, and nasal or craniofacial disorders.

Question 49

Which of the following associations between difficult airway management and coexisting disease is INCORRECT?

A) Difficult laryngoscopy is associated with Type 1 Diabetes

B) Pathologic C spine fusion is associated with ankylosing spondylosis

C) Soft tissue swellign is associated with hypothyroidisim

D) Subglotting stenossis is associated with trisomy 18

Answer 49

Trisomy 21 (Down syndrome), not trisomy 18 (Edwards syndrome), predisposes to subglottic stenosis. These patients can also have other features which may provide challenges to airway management such as atlantoaxial occipital joint instability, macroglossia, floppy soft palate, and enlarged tonsils and adenoids.

Answer A: Chronic hyperglycemia occurs with type 1 diabetes mellitus. This can lead to glycosylation of the joints and limited mobility. This is known as diabetic stiff joint syndrome. Glycosylation affects the atlanto occipital (AO) joint and compromises adequate neck extension. Patients with diabetic stiff joint syndrome may display the “prayer sign,” which is an inability to oppose the palmar surface of the interphalangeal joints. This sign may be suggestive of difficult laryngoscopy.

Answer B: Ankylosing spondylitis is a form of chronic inflammation of the spine (primarily cervical and lumbar), hip joints, and shoulders, usually presenting as early morning stiffness and low back pain in young men. Progressive ossification can lead to fusion of the spine. About 90% of patients with ankylosing spondylitis express the HLA-B27 antigen which is associated with Reiter’s syndrome (also known as reactive arthritis), ulcerative colitis, Crohn’s disease, and psoriasis. Imaging of the spine usually reveals a “bamboo-like” appearance. Indomethacin and other NSAIDs are the usual pain treatment of choice.

Answer C: Hypothyroidism can lead to myxedema. Severe myxedema can progress to subcutaneous swelling in the oral cavity and hypopharynx and total body swelling secondary to inappropriate ADH secretion. Changes in mental status, hyponatremia, hypothermia, and pulmonary edema may also occur.

Bottom Line: Ankylosing spondylitis may cause fusion of the cervical spine. Hypothyroidism can lead to myxedema, anasarca, and angioedema. Thyroid goiters and tracheal stenosis may cause fixed intrathoracic and extrathoracic obstruction on flow-volume loop. Type 1 diabetes mellitus may cause diabetic stiff joint syndrome and difficult laryngoscopy due to AO joint glycosylation.

Question 50

Which of the following is the LEAST indicative of fetal distress during cardiotocography monitoring?

A) Decrease in heart rate by 20 after the onset of uterine contraction

B) Fetal Heart rate varies from beat to beat by 20

C) SInusoidal fetal heart pattern

D) Fetal heart rate of 165 for about 15 minutes

Answer 50

Beat to beat variability in fetal heart rate is a normal finding (B).

Continuous fetal heart rate (FHR) monitoring is used to assess patterns that can serve as a warning for fetal hypoxia or umbilical cord compression. However, FHR monitoring has a high false positive rate. Assessment of the FHR is dependent on the baseline, and how it changes in relation to the uterine contractions. Normal FHR ranges from 120-160 beats per minutes. Tachycardia is considered to be FHR > 160, and bradycardia is < 120. If the FHR is tachycardic or bradycardic for a sustained period of time, it becomes concerning of fetal distress (D).

Normal FHR can vary from beat to beat, and is referred to as “short-term variability” or “beat to beat variability.” The variation from one beat to another can range from 5-25 beats per minute (B). Variability in the FHR is a sign of a healthy autonomic nervous system, chemoreceptors, baroreceptors, and cardiac responsiveness. FHR becomes non-reassuring if the variability is < 5 or > 25. A decrease in FHR variability can be due to fetal sleep state, fetal acidosis, or maternal sedation from drugs.

FHR monitoring can have patterns in relation to the uterine contractions, which can be used to determine fetal well-being. Deceleration is when a sudden decrease in FHR occurs, typically by 15 beats per minute or more.

Early deceleration: deceleration starts at the same time as a uterine contraction. This is indicative of head compression and is not associated with fetal distress.

Late deceleration: deceleration starts after the onset of a uterine contraction. This is most likely due to uteroplacental insufficiency (A). The severity is determined by the magnitude of the deceleration.

Variable deceleration: deceleration starts at variable times in relation to the uterine contraction. This is due to cord compression. The compression of the umbilical cord results in a sudden increase in fetal blood pressure resulting in a reflex bradycardia. The severity of a variable deceleration is determined by its duration.

Sinusoidal FHR pattern: a smooth sine wave (no variability present). It is rare, however, is associated with high rates of fetal morbidity and mortality (C). This pattern is indicative of severe fetal anemia.

Bottom Line: Beat to beat variability of 5-25 beats/minute is part of a normal fetal heart rate.

Question 51

A patient with severe COPD is admitted to the intensive care unit in septic shock. He was recently treated for a MRSA osteomyelitis. He now may have community acquired pneumonia, or return of the osteomyelitis, but the diagnosis is unclear. Which of the following antibiotics has activity against both MRSA and Gram-negative bacteria?

A) Daptomycin

B) Linezolin

C) Tigecycline

D) Vancomycin

Answer 51

Tigecycline is a glycylcycline antibiotic that covers MRSA and Gram-negative organisms. It acts as a protein synthesis inhibitor, binding to the 30S ribosomal subunit of bacteria.

Methicillin resistant Staphylococcus aureus (MRSA) is a species of Staphylococcus aureus that is resistant to beta-lactam antibiotics including oxacillin and cefazolin. MRSA infections are a growing concern as infections can be very difficult to treat and many medication used for the treatment of MRSA are either toxic or have a very limited spectrum of activity.

• *Treatment options for hospital-associated MRSA include:
• Ceftaroline
• Daptomycin
• Linezolid
• Quinupristin/dalfopristin
• Teicoplanin
• Tigecycline
• Vancomycin**

Ceftaroline is a 5th generation cephalosporin. Ceftaroline has activity against both Gram-positive and Gram-negative bacteria. Ceftaroline is a prodrug that is converted to its active form by the body and is only available in intravenous form at this time.

Answer A: Daptomycin is a lipopeptide antibiotic used in the treatment of systemic and life-threatening infections caused by Gram-positive organisms. It is useful for MRSA, but does not cover Gram-negative organisms.

Answer B: Linezolid is an oxazolidinone antibiotic. Linezolid is bacteriostatic by inhibition of bacterial protein synthesis. Linezolid inhibits the 50S subunit of the bacterial ribosome. Linezolid is effective against a wide variety of Gram-positive organisms, including MRSA and vancomycin resistant enterococcus (VRE). However, linezolid is not effective against Gram-negative bacteria.

Answer D: Vancomycin is a glycopeptides antibiotic and is often considered the drug of choice for use in MRSA infections. Vancomycin is not orally bioavailable because of its large molecular structure. Vancomycin is only effective against Gram-positive bacteria and therefore is considered narrow spectrum (not broad spectrum).

Bottom Line: There are very few drugs with a broad spectrum of activity that are effective for use in the treatment of MRSA. Ceftaroline, tigecycline, and TMP-SMX have the broadest spectrum of activity effecting both Gram positives and some Gram negatives. Many of the other agents effective against MRSA like vancomycin, daptomycin, and linezolid are only effective against Gram-positive organisms.

TrueLearn Insight : Vancomycin resistance occurs as a result of a mutation at the end of the NAM/NAG polypeptides found in the bacterial cell wall. Normally they contain a D-alanyl D-alanine or D-ala-D-ala region. This is the area in which vancomycin binds to a bacterial cell wall. If a mutation occurs here, vancomycin becomes much less potent.

Question 52

A patient with antiphospholipid syndrome presents in labor. The patient has a confirmed diagnosis of anticardiolipin antibodies pre-pregnancy. She did not tolerate aspirin therapy previously due to gastric discomfort and has been receiving 5000 units subcutaneous heparin three times daily, with her last dose administered just now. The patient has an elevated aPTT. She requests an epidural; which of the following is MOST appropriate?

A) She cannot have an epidural placed due to elevated aPTT

B) Place the epidural at this time

C) Wait 6 hours and then place the epidural

D) Wait 12 hours and then place the epidural

Answer 52

American Society of Regional Anesthesia and Pain Medicine (ASRA) guidelines recommend waiting 4-6 hours after heparin before neuraxial block placement.

Antiphospholipid syndrome (APS) is the most common acquired thrombophilia and it is characterized by arterial and/or venous thrombosis, potential pregnancy morbidity, and the presence of at least one type of antiphospholipid autoantibody (lupus anticoagulant, anticardiolipin antibody). Autoantibodies inhibit the fibrinolytic system by binding to anticoagulants as well as activating endothelial cells, monocytes, and trophoblasts resulting in complement-mediated thrombosis.

Diagnosis of APS depends on clinical history including recurrent venous or arterial thrombosis, recurrent pregnancy loss, and laboratory evidence of autoantibodies. Laboratory evidence includes an elevated aPTT. This elevation is not caused by factor deficiency; instead, it is caused by the phospholipid-dependent coagulation alterations. Furthermore, the inhibitor is directed against the phospholipid instead of specific coagulation factors.

Parturients with APS are at a higher risk for venous and/or arterial thrombosis, pulmonary embolism, myocardial infarction, cerebral infarction, and fetal loss. Monitoring of maternal/fetal health consists of ultrasound examinations for fetal growth and placental volume. Additionally, nonstress tests are performed routinely after the 25th to 32nd week of pregnancy. Choice of delivery method depends on maternal and fetal health.

Expectant management can help improve both fetal and maternal outcome. Fetal loss most often occurs following placental infarction and most fetal deaths occur during mid to late pregnancy. Patients with higher levels of antibodies have a worse prognosis. The mainstay of treatment is anticoagulation. This entails administration of aspirin and heparin throughout pregnancy for patients that have positive autoantibodies. Low molecular weight heparin may also potentially be used but more randomized studies are needed. Neither heparin, nor low molecular weight heparin, cross the placenta.Administration of anticoagulation should continue for at least six weeks postpartum.

The conduct of anesthesia for these patients may be complex. The anesthesia provider should be aware of the potential for coexisting autoimmune disorders such as lupus. Very infrequently, antiphospholipids cause coagulation factor deficiencies and thus neuraxial anesthesia may be contraindicated. In the absence of an underlying coagulation deficit and/or anticoagulation therapy, a prolonged aPTT does not suggest a bleeding tendency and neuraxial anesthesia can be administered safely. Since most of these patients are on antiplatelet agents and anticoagulants, determining the dose and timing of the last administration is important along with weighing the risk/benefit ratio depending on the specific agents. Aspirin administration alone is not a contraindication to neuraxial anesthesia.

• *If heparin or low molecular weight heparin are given, it depends on the dose and timing as to whether neuraxial can be performed.** For subcutaneous unfractionated heparin in doses of 5000 U, given BID or TID, the latest version (4th Edition) of the American Society of Regional Anesthesia (ASRA) guidelines recommends the following time intervals:
• From last dose to neuraxial block placement: 4-6 hours
• From neuraxial block to restarting heparin: Immediately
• From last dose to removal of epidural catheter: 4-6 hours
• From catheter removal to restarting heparin: Immediately

Answer A: Patients with antiphospholipid syndrome can have an elevated aPTT, which is not secondary to factor deficiencies. This is not a contraindication to neuraxial anesthesia.

Answers B & D: The route of heparin administration will dictate when neuraxial anesthesia can be performed. In this patient, she is on 5000 U TID. The ASRA recommends that neuraxial can be performed in patients on 5000 units BID or TID after a 4-6 hour wait. If she was receiving 7500 or 10,000 U BID subcutaneous (referred to as “high dose prophylaxis”) the necessary wait would be 12 hours. If she was receiving more than 10,000 U subcutaneous per dose or more than 20,000 U subcutaneous per day (referred to as “therapeutic”) the necessary wait would be 24 hours.

Bottom Line: Pregnant patients with antiphospholipid syndrome carry a higher risk peripartum, especially for thrombotic events. A history of recent administration of antiplatelet and anticoagulants is important if a neuraxial anesthetic is planned. ASRA guidelines recommend waiting 4-6 hours after heparin before neuraxial block placement.

Question 53

Which of the following is the most effective post-thoracotomy pain management regimen that also improves ventilation?

A) Lumbar epidural with opioid

B) Patient controlled IV opioid anesthesia

C) Thoracic epidural with opioid and local anesthetic

D) Transcutaneous electricl nerve stimulation (TENS)

Answer 53

Thoracic epidural infusion with local anesthetic and opioid will provide the best pain relief of the options listed.

Thoracotomy incision results in severe post-operative pain. Pain control is critical to avoid pulmonary complications and allows patients to breathe deeper, ambulate, and cough effectively. Lack of pain control results in splinting and ineffective pulmonary toilet, resulting in atelectasis and potential respiratory decompensation and need for reintubation.

Pain-control focuses on blockade of the thoracic intercostal nerves. Effective pain control will improve ventilation, allowing increased ambulation and decreased respiratory complications. Overuse of systemic opioids can further the risk of pulmonary complications due to respiratory depression.

Thoracic epidural analgesia and paravertebral blockade have shown to be the most effective methods for post-thoracotomy pain control. These methods are more effective than intravenous patient-controlled analgesia with opioids as there is a safer side-effect profile due to lower levels of systemic opioid absorption to achieve the same pain levels. When compared to lumbar epidural analgesia, thoracic epidural analgesia has been shown to be equivalent or superior. The use of local anesthetic and opioid in the epidural infusion has shown superior pain control to the use of opioid alone. TENS is a useful adjunct to pain-control after thoracotomy but is not effective as a sole modality.

Answer A: Thoracic epidural anesthesia has been shown to provide equivalent or better pain-relief than lumbar epidural anesthesia for post-thoracotomy pain. However, epidural infusion with local anesthetic and opioid has been shown to provide better pain relief than infusion with opioid alone.

Answer B: Intravenous patient-controlled analgesia does not provide as good pain relief as thoracic epidural infusion and is associated with higher respiratory depression due to the high levels of systemic opioids needed to achieve adequate pain relief.

Answer D: The TENS unit is a useful adjunct in the management of post-thoracotomy pain, but is ineffective as a lone modality. It is a useful modality for patients who have contraindications to neuraxial anesthesia.

Bottom Line: Thoracic epidural analgesia and paravertebral blockade are considered the most effective methods of pain control in the management of post-thoracotomy pain.

Question 54

A 62-year-old female is undergoing wrist surgery with intravenous regional anesthesia (Bier block). Five minutes after the local anesthetic injection, the tourniquet malfunctions and fully deflates. The patient becomes agitated and tachycardic, but shortly thereafter suffers cardiac arrest. According to the American Society of Regional Anesthesia and Pain Medicine, which of the following BEST describes how epinephrine should be administered during advanced cardiac life support resuscitation in the setting of LA toxicity?

A) Increased dosage (>1 mg every 3-5 minutes)

B) Same Dosage (1 mg every 3-5 minutes)

C) Decreased dosage (<1 mg everyt 3-5 minutes)

D) Avoid epinephrine and substitue vasopressin

Answer 54

A significantly reduced dose of epinephrine (< 1 mcg/kg per administration) is recommended for use during advanced cardiac life support (ACLS) resuscitation in the setting of local anesthetic systemic toxicity (LAST). Vasopressin use should be avoided.

Local anesthetics, even at toxic doses, do not lead to irreversible myocardial damage. Thus, the overarching goal of treatment of LAST is ensuring adequate coronary (and systemic) perfusion and oxygenation. In 2010, the American Society of Regional Anesthesia (ASRA) and Pain Medicine published guidelines for management of LAST. The guidelines are organized into three primary sets of actions that should be taken following a known or suspected diagnosis of LAST.

First, supportive measures should be initiated including airway management and administration of 100% oxygen, with avoidance or prompt treatment of hypoxia and acidosis. Seizures, if present, should be treated with benzodiazepines. Finally, the nearest facility capable of providing cardiopulmonary bypass should be alerted since the procedure can be life-saving if lipid and vasopressor therapy fail.

Second, intravenous lipid emulsion (20%) therapy should be promptly initiated. A bolus of 1.5 mL/kg should be delivered over one minute followed by an infusion of 0.25 mL/kg/min. The infusion should be run until at least 10 minutes following restoration of cardiovascular stability. The infusion may be increased to 0.5 mL/kg/min in the setting of persistent hypotension. The bolus may be repeated up to two additional times in the setting of continued cardiovascular collapse.

Third, cardiac arrhythmias must be managed. Arrhythmias may include, but are not limited to, ventricular arrhythmias (ventricular tachycardia, ventricular fibrillation, torsades de pointes), conduction blocks, bradycardia, PEA, and asystole. In general, ACLS measures should be followed and use of certain classes of drugs should be avoided; these include local anesthetics, beta blockers, calcium channel blockers, and vasopressin. In addition, it is recommended to decrease each dose of epinephrine to < 1 mcg/kg. Amiodarone is the preferred treatment for ventricular arrhythmias.

Epinephrine by itself is highly arrhythmogenic and these effects may be even more pronounced in the setting of LAST. Animal studies have shown that lipid-only resuscitation of bupivacaine toxicity had better outcomes than epinephrine-only resuscitation due to the presence of severe arrhythmias seen in the latter. Despite this, the use of small doses of epinephrine is still recommended since epinephrine provides critical inotropic and vasopressor support.

Answers A & B & C: The dose of epinephrine in ACLS guided resuscitation of LAST should be reduced to <1 mcg/kg per dose.

Answer D: Vasopressin use should be avoided.

Bottom Line: The dose of epinephrine in ACLS guided resuscitation of LAST should be reduced to < 1 mcg/kg per dose. Vasopressin use should be avoided.

TrueLearn Insight : Propofol should NOT be used in patients with cardiovascular instability from LAST. Although propofol exists as a lipid emulsion, the lipid content is too small to provide any significant clinical benefit. However, small doses of propofol may be considered for seizure suppression in patients without cardiac compromise when a benzodiazepine is not immediately available.

Question 55

Which of the following statistical tests should be used to compare whether the incidence of postoperative vomiting differs between women ages 21-64 in the intensive care unit versus the floor unit?

a) analysis of variance
b) chi-square test
c) paired t-test
d) unpaired t-test

Answer 55

A chi-square test is used to investigate whether distributions of categorical variables differ from one another.

The distribution of a categorical variable in a sample often needs to be compared with the distribution of a categorical variable in another sample. The chi-square test is the best test to use when categorical data are being compared. It is important to emphasize here that chi-square tests may be carried out for this purpose only on the actual numbers of occurrences, not on percentages, proportions, means of observations, or other derived statistics.

There are two types of random variables and they yield two main types of data: numerical and categorical. Categorical variables yield data in categorical form that is dichotomous (binary data), nominal (qualitative data), or ordinal (ordered, ranked, or measured without a constant scale interval). Numerical variables yield data in numerical form and can be either discrete (integer scale) or continuous (constant scale). Responses to such questions as, “What is your gender?” or, “Did you experience any nausea or vomiting?” are categorical because they yield data such as, “male” or, “no”, respectively. In contrast, responses to such questions as, “How many siblings do you have?” or, “What is your blood pressure?” are numerical.

Answer A: Analysis of variance (ANOVA) is used to compare multiple variables with numerical data (either continuous or discrete). For example, measuring blood pressure ten times before and during anesthetic induction then comparing the changes between the initial measurements and those obtained during induction.

Answer C: The paired t-test is used when there is one population with respect to two variables with numerical data. For example, a study where subjects’ blood pressures are measured prior to a treatment for hypertension and the same subjects are tested again after treatment with a blood-pressure lowering medication.

Answer D: The unpaired t-test allows for comparison of two populations with respect to a single variable with numerical data. For example, a study compares the mean arterial blood pressures (single variable) of one group of patients receiving IV labetalol (first population) and a separate group receiving IV hydralazine (second population).

Bottom Line: Chi-square testing is used for comparison of two or more populations with respect to a single variable with categorical data (nominal scale).

Question 56

A researcher plans to design an experiment testing the efficacy of an antihypertensive drug in diabetic patients. The plan is to take two groups of 500 diabetic patients and measure baseline and post-treatment blood pressures for group A (the treatment group) and group B (the control group), and then compare the change in blood pressure in group A versus the change in blood pressure in group B. Which of the following would be the MOST appropriate statistical test?

A) ANOVA

B) Chi-square

C) Paired t-test

D) Unpaired t-test

Answer 56

An unpaired t-test would be the most appropriate analytic tool for this study given the sample size, two group design, and parametric data set. An unpaired t-tests is used to analyze normally distributed, non-ordinal, parametric data when two groups are compared. It essentially analyzes the change in mean values and divides this by the projected variance of the groups.

A paired t-test differs from an unpaired t-test in that comparison of the variable in question is within 1 group. So if the researcher only had one group, all of which received the antihypertensive drug, and compared baseline and post-treatment blood pressure values, a paired t-test would be appropriate as the patients serve as the test and control group simultaneously.

In this experimental design (which by the way is quite common) there are four different numbers and at least four possible comparisons. One would usually compare baseline A versus baseline B, just to make sure the groups are similar to start with. This would be done with unpaired t-test (different groups = unpaired).

One could also compare baseline A versus post-treatment A, and baseline B versus post-treatment B, which would tell you if the treatments had any effect at all or not. These two would be with paired t-test (comparison within the same group = paired).

Ultimately the most important comparison is the one this question is about (i.e. whether the antihypertensive effect of A was different from that of B). For this, the best approach is to reduce the four numbers to just two (post-minus-baseline A versus post-minus-baseline B) and compare them. This is done with the unpaired t-test since it is comparing two different groups.

Answer A: Analysis of variance (ANOVA) is used to test parametric continuous data when 3 or more groups exist.

Answer B: Chi-square is a test used to analyze ordinal data. Ordinal data allow for rank order (e.g. 1st, 2nd, 3rd, etc).

Answer C: A paired t-test would be appropriate if there were only one group (being compared or “paired” to itself).

Bottom Line: A paired t-test compares outcomes in a single group who serve as their own control, whereas an unpaired t-test compares an outcome in two different groups.