Tải bản đầy đủ

2011 BRS3

Board Review Session III
Thursday, August 18, 2011
Questions with Answers and Rationales
30. A transthoracic, 2-dimensional, short-axis image of the right and left ventricles is
shown in the Figures below. Figure A represents diastole and Figure B represents systole.
The arrow shows the interventricular septum.
Which of the following diagnoses is most likely present in this patient?
a. Large pericardial effusion
b. Ventricular septal defect
c. Left ventricular infarction
d. Pulmonary embolism

31. A 19-year-old woman is febrile, tachypneic, and tachycardic, with acute-onset pain of
the right side of her neck and diffuse swelling of the right side of the face. She has
hypotension, acutely impaired renal function, and a platelet count of 100,000/µL.
Doppler ultrasonography reveals thrombophlebitis of the right internal jugular vein.
Blood cultures grow gram-positive cocci in pairs and chains. The patient is intubated
because of airway obstruction, and dopamine is begun for refractory hypotension.
Which of the following interventions is most likely to affect the patient’s outcome?
a. Anticoagulation
b. Removal of the thrombosed vein

c. Administration of rtPA
d. Tracheostomy

32. An intensivist is called to the echocardiography lab to evaluate a 44-year-old man
who was undergoing a transesophageal echocardiogram. The patient had been diagnosed
with Staphylococcus aureus endocarditis, and was being evaluated for the presence of


vegetations on his valves. Shortly after the procedure, the patient developed severe
shortness of breath. His oxygen saturation was 75%, and he was intubated emergently.
He appears cyanotic and his arterial blood gas specimen is dark in color, with pH of 7.37
and PaO2 of 258 mm Hg.
Which of the following is the most likely cause of this man's low oxygen saturation?
a. Air embolus
b. Antibiotic toxicity
c. Topical anesthetic spray
d. Laboratory error
e. Carbon monoxide

33. A 70-year-old woman experiences a drop in blood pressure 6 days after a right total
hip replacement. With the exception of severe osteoarthritis for which she was taking
ibuprofen as an outpatient, her medical history is unremarkable. She had been recovering
well from her surgery, which was uncomplicated, with minimal blood loss and a
postoperative hemoglobin level of 11 mg/dL, and was about to be discharged. Aside from
pain around the surgical site, which was treated with IV and oral opioids, she has
reported mild nausea, abdominal bloating, and back and flank pain, which were believed
to be a result of constipation from the pain medications. Laxatives provided no relief.
Two days ago, her hemoglobin level decreased to 9.5 mg/dL but has been stable since
that time. Currently, she is alert and pleasant but easily confused with questioning. She
has a BP of 90/45 mm Hg after 2 L of normal saline during the past 2 hours and her
temperature is 38°C (100.4°F). Her only medications are subcutaneous enoxaparin, 70
mg/day, and warfarin, 5 mg/day.
Which of the following is the most important intervention at this time?
a. IV dexamethasone
b. Piperacillin/tazobactam, vancomycin, and 2 L of 0.9% normal saline
c. Transfusion of 2 units of packed red blood cells
d. Changing from enoxaparin to unfractionated heparin

34. A 49-year-old man who is nonadherent with his therapy for essential hypertension
presents to the emergency department with a BP of 250/160 mm Hg; pink, frothy sputum;
severe hypoxemia; and pulmonary edema on chest radiograph. Which of the following
physiologic targets is most appropriate as a therapeutic target?
a. Decreasing left ventricular end-diastolic pressure
b. Decreasing intravascular volume
c. Decreasing pulmonary artery pressure
d. Increasing ejection fraction


35. A 45-year-old man with an acute, severe asthma attack is admitted to the ICU. He has
a history of hypertension and glaucoma. Chest radiography reveals hyperinflation. His
medical therapy in the emergency department included multiple doses of aerosolized
albuterol as well as IV methylprednisolone, 125 mg. Peak expiratory flow rate is
unimproved at 80 L/min (personal best = 450 L/min).
Which of the following is most appropriate as additional medical therapy?
a. Nebulized ipratropium by face mask
b. IV magnesium sulfate
c. Broad-spectrum antibiotics targeting community-acquired respiratory pathogens
d. Inhaled corticosteroids

36. A 55-year-old woman is receiving assist-control volume ventilation for an
exacerbation of chronic obstructive pulmonary disease. She has dyssynchronous
breathing, ie, she is “fighting the ventilator.” Ventilator set rate is 14/min and total rate is
22/min. Flow over time is shown in the waveform Figure.
Which of the following interventions is most likely to relieve dyssynchrony?

a. Decreasing peak inspiratory flow rate
b. Switching to decelerating inspiratory flow waveform
c. Increasing set ventilator rate to 20/min
d. Positioning patient with left side down
e. Increasing ventilator-set positive end-expiratory pressure


37. The ECG shown in the Figure was recorded in a 45-year-old man in the surgical ICU
12 hours after he underwent a partial colectomy for cancer. He is awake and
hemodynamically stable, complaining only of a rapid heartbeat. Which of the following
is the most appropriate intervention?

A. Adenosine, 6-mg IV bolus
B. Adenosine, 12-mg IV bolus
C. Procainamide, 1-g IV infusion over 50 minutes
D. Esmolol, continuous IV infusion
E. Diltiazem, continuous IV infusion

38. The rhythm strip shown in the Figure was recorded in a 75-year-old woman in the
surgical ICU. She has a history of severe aortic stenosis and heart failure, with a left
ventricular ejection fraction of 20%, and underwent aortic valve replacement 2 days
earlier. She is hemodynamically stable but still intubated and sedated. Which of the
following is the most appropriate management?


A. Lidocaine bolus and infusion
B. Amiodarone bolus and infusion
C. Esmolol continuous IV infusion
D. Diltiazem continuous IV infusion
E. No antiarrhythmic drug

39. A 52-year-old woman with a long-standing history of asthma develops pneumonia
with fevers and severe dyspnea. Her long-term medications include inhaled
beclomethasone and aerosolized albuterol. She is admitted to the ICU and treated with
supplemental oxygen, aerosolized albuterol, levofloxacin, aminophylline, and
methylprednisolone. On the second ICU day, the patient reports palpitations and mild
chest discomfort. HR has increased from 90 to 188/min, and her ECG is shown in the
Figure below. BP is 110/70 mm Hg, RR is 18/min, and temperature is 38°C (100.4°F).
She continues to have diffuse wheezing bilaterally. Serum theophylline level is 14
µg/mL. Carotid sinus massage bilaterally has no effect on the rhythm.
In addition to discontinuing theophylline, which of the following pharmacotherapies is
most appropriate to administer?


Formatted: Italian (Italy)

a. Lidocaine
b. Metoprolol
c. Flecainide
d. Adenosine
e. Verapamil

40. Which of the following conditions represents an absolute contraindication to
fibrinolysis?
a. Diabetic retinopathy
b. Stroke within 6 months
c. Warfarin therapy with international normalized ratio of 1.9
d. Cardiopulmonary resuscitation
e. Age older than 80
41. A 17-year-old man falls through the ice in a lake and is submerged for 35 minutes.
His core temperature is 28°C (82.4°F) by rectal thermistor on arrival to the hospital. He is
intubated with no spontaneous respirations and the cardiac monitor shows asystole.
Which of the following is the most appropriate management plan?
a.Confirm asystole and absence of clinical brainstem activity and pronounce the patient
dead.


b. Institute CPR and active core rewarming measures for 20 minutes and cease if no
response.
c. Institute CPR and active core rewarming measures to 32°C (89.6°F) before assessing
resuscitation status.
d. Institute CPR and active core rewarming measures but discontinue if potassium level is
greater than 10 mEq/L.

42. A 60-year-old woman with non–small cell lung cancer undergoes bronchoscopy with
topical anesthetic for placement of a stent in the right bronchus. At the end of the
procedure, oxygen saturation drops from 98% to 85% by pulse oximetry, and she
becomes cyanotic and confused. A nonrebreather mask is placed, but oxygen saturation
remains at 85%. Arterial blood gas measurement reveals pH of 7.46, PaCO2 of 32 mm Hg,
and PaO2 of 300 mm Hg.
Which of the following is the most appropriate intervention?

a. Obtain spinal CT with pulmonary embolism protocol.
b. Administer IV methylene blue.
c. Intubate the patient.
d. Administer IV thiosulfate.
e. Obtain a chest radiograph.

43. A 40-year-old woman is admitted to the hospital with probable immune
thrombocytopenic purpura. She has some petechiae on her lower extremities and
ecchymoses in areas of mild trauma. Her platelet count is 5,000/µL and prothrombin
time/partial thromboplastin time is normal. She is started on prednisone, 80 mg/day. On
the second hospital day, she slips and falls, sustaining a femoral neck fracture. Surgical
repair is required in the next several days.
Which of the following is the most appropriate intervention to increase the platelet count
prior to surgery?
a. Platelet transfusion
b. Splenectomy
c. IV immunoglobulin
d. Rituximab
e. Danazol

44. A 78-year-old woman with hypertension and congestive heart failure is found
comatose and hypotensive in her apartment without air conditioning after 4 days of
outside temperatures of 38°C (100°F). She is intubated by paramedics and given a 500-


mL bolus of normal saline. On arrival at the hospital, BP is 80/40 mm Hg, HR is
130/min, RR is 14/min with manual ventilation, and rectal temperature is 41.9°C
(107.5°F). Arterial blood gas results on 100% FIO2 show a pH of 7.20, PaCO2 of 37 mm
Hg; and PaO2 of 270 mm Hg.
Which of the following statements is correct?
a. Significant dehydration is likely.
b. A lactic acidosis due to anaerobic muscle metabolism is present.
c. Heart rate should be slowed pharmacologically to improve hemodynamic status.
d. Dopamine should be administered to improve blood pressure.
e. A pulmonary artery catheter should be inserted to guide therapy.

45. A 35-year-old woman is found in her car with the ignition on and brought to the
hospital. She is unresponsive and intubated for airway protection. Her BP is 96/54 mm
Hg, HR is 115/min, RR is 12/min, and temperature is 36.1°C (97°F). Physical
examination reveals obtundation, tachycardia, and basilar rales. Pupils are 3 mm and
sluggishly reactive. Arterial blood gas analysis shows pH of 7.27, PaCO2 of 35 mm Hg,
and PaO2 of 365 mm Hg on 100% oxygen. There is an anion gap of 18, normal osmolar
gap, and a negative result for serum ethanol. Carboxyhemoglobin level is 15%. ECG
shows nonspecific ST-segment changes. Salicylate and acetaminophen levels are
pending.
Which of the following interventions is most likely to benefit this patient?
a. Administering flumazenil
b. Increasing respiratory support to decrease PaCO2 to 30 mm Hg
c. Hemodialysis
d. Continuing 100% oxygen
e. Administering hyperbaric oxygen

46. A 45-year-old man with alcohol dependence is brought to the hospital after being
found behind a building during a rainstorm. His core body temperature is 28°C (82.4°F).
The monitor shows an HR of 30/min. Carotid pulse is weak, and blood pressure is
unobtainable. The patient is intubated, and heated oxygen and IV fluids are initiated.
Which of the following interventions is indicated as initial therapy?
a. Administration of atropine
b. Administration dopamine
c. Chest compressions
d. Transthoracic pacing
e. Application of forced-air rewarming blanket


47. A 20-year-old man with hemophilia A sustains significant chest wall trauma in a
motor vehicle collision. After thoracostomy for a right pneumothorax, he has bloody
output from the chest tube. He has received transfusions multiple times in the past and is
known to have inhibitors to factor VIII.
Which of the following treatments should be administered?
a. Recombinant factor VIII
b. Cryoprecipitate
c. Factor XI concentrate
d. Recombinant factor VIIa
e. Fresh frozen plasma


Answers and Rationale:
30. Correct Answer: D. Pulmonary embolism
Rationale: The transthoracic echocardiographic images demonstrate flattening of the
interventricular septum and a D-shaped left ventricle consistent with right ventricular
pressure or volume overload. Pressure and volume overload of the right ventricle lead to
distortion of left ventricular geometry and abnormal motion of the intraventricular
septum. The flattening of the interventricular septum leads to a D-shaped left ventricle.
This may occur with volume overload, as occurs with atrial septal defect, and also with
pressure overload, as occurs with primary pulmonary hypertension, acute chronic
thromboembolic disease, and cor pulmonale.
31. Correct Answer: B. Removal of the thrombosed vein
Rationale: This patient has typical clinical findings of Lemierre syndrome. Removal of
the thrombosed vein is indicated. Lemierre syndrome is an uncommon complication of
peritonsillar abscess defined by thrombophlebitis of the internal jugular vein with or
without septicemia. Treatment includes antibiotics and surgical drainage of any purulent
collection. Anticoagulation is controversial, and not all patients should be anticoagulated.
Administration of rtPA is not part of the treatment regimen.
32. Correct Answer: C. Topical anesthetic spray
Rationale: This patient has methemoglobinemia due to topical anesthetic spray. The
patient on whom the vignette is based had an oxygen saturation gap of 24% (calculated
minus observed). Co-oximetry showed a methemoglobin level of 51% and a hemoglobin
level of 11 g/dL. Thus, only 49% of his hemoglobin was able to carry and offload oxygen
because 51% of his hemoglobin was in the methemoglobin form. This situation can be
rapidly reversed by methylene blue.
Erythrocytes are normally exposed to oxidative stress that transforms the oxygencarrying ferrous ion (Fe2+) of the heme group to the oxidized ferric group (Fe3+). This
methemoglobin form binds a water molecule rather than oxygen. The normal
cytochrome-b5 and NADPH-dependent methemoglobin reductase pathways normally
maintain methemoglobin levels less than 1%. Exposure to exogenous oxidizing drugs can
overwhelm this balance, however. Patients with more than 1.5 g/dL of methemoglobin
will appear cyanotic.
Healthy patients can generally tolerate methemoglobin levels <15%. However, like
carbon monoxide poisoning, higher levels result in headache, fatigue, dizziness, syncope,
and ultimately dysrhythmias, coma, and death. There is a long list of drugs that can cause
this:
Benzocaine spray
Cetacaine spray

Nitroprusside
Primaquine


Chloroquine
Dapsone
Lidocaine
33. Correct Answer: A. IV dexamethasone

Silver nitrate
Sulfonamides
Herbicides, pesticides

Rationale: Adrenal hemorrhage is an important but uncommon cause of adrenal
insufficiency in the ICU. Adrenal hemorrhage associated with severe sepsis is classically
associated with disseminated Neisseria species infection but may also be caused by
Pneumococcus, Pseudomonas species, and Haemophilus influenzae type B. Cardiac
disease, coagulopathy, anticoagulant therapy, thromboembolism, bums, and trauma may
predispose patients to adrenal hemorrhage. It typically occurs during the first or second
postoperative week, closely following initiation of anticoagulant therapy. Abdominal,
back, flank, or chest pain; nausea; vomiting; fever; mental status changes; orthostatic
hypotension; and a sudden drop in hematocrit are common findings. The hemodynamic
crisis usually occurs 1 to 3 days after the initial hemorrhage. No information is given in
the question that would lead to a source of infection, nor is there evidence of hypoxemia,
chest pain, or shortness of breath, which makes septic shock and pulmonary embolism
unlikely. The decrease in hemoglobin occurred 2 days ago and hemoglobin level has been
stable since that time. No information is given to support a change in hemodynamic
status at the time of the drop in hemoglobin, making hemorrhage an unlikely cause of this
patient's hypotension.
34. Correct Answer: A. Decreasing left ventricular end-diastolic pressure
Rationale: The scenario presented is the typical presentation for high-pressure
pulmonary edema associated with uncontrolled severe hypertension in a patient with
preexisting essential hypertension. These patients typically have normal or even
increased left ventricular ejection fraction with thick ventricles and diastolic dysfunction.
Their mortality risk is from hypoxemia related to high pulmonary capillary pressure that
is directly related to elevated left ventricular end-diastolic pressure. Treatment is targeted
to decrease left ventricular end-diastolic pressure and includes both preload and afterload
reduction. Vasodilatation and venodilatation are the optimal treatments. Diuresis is often
counterproductive for management as most of these patients have decreased intravascular
volume.
35. Correct Answer: B. IV magnesium sulfate
Rationale: The patient presented with severe, life-threatening asthma and has had a poor
response to the cornerstone of therapy for asthma – aggressive treatment with an inhaled
beta-adrenergic agonist. The patient has also received IV steroid therapy, which will not
work immediately. Of the additional medical therapies shown, IV magnesium sulfate is
most likely to offer additive benefit to continued inhaled beta-adrenergic agonist therapy.
Inhaled ipratropium should also be administered, but not by face mask in a patient with a
history of glaucoma because it may precipitate increases in intraocular pressure. Inhaled
corticosteroids, although shown in one study to produce a statistically significant increase
in bronchodilatation as additive therapy, are unlikely to offer significant clinical benefit.


Additionally, the data regarding meaningful clinical response is better for IV magnesium
sulfate than for corticosteroids. Antibiotics are not indicated for an asthma attack in the
absence of pneumonia
36. Correct Answer: E. Increasing ventilator-set positive end-expiratory pressure
Rationale: The waveform of flow over time demonstrates a sudden drop in expiratory
flow (short arrow) with a rebound to a higher expiratory flow before inspiratory
triggering occurs (long arrow). This sudden decrease in expiratory flow is due to the
patient’s inspiratory effort, creation of a negative pleural pressure, and failure to trigger
the next inspiration. The next inspiration is not triggered as the patient is pulling through
significant auto-positive end-expiratory pressure (PEEP). When the patient tries to inspire
during significant expiratory flow and fails, what should be end expiration is not. This is
a type of auto-PEEP that can be treated by those skilled in treating auto-PEEP in
mechanically ventilated patients by increasing set PEEP. This treatment will allow the
patient to trigger with less inspiratory effort as the ventilator senses the patient’s
triggering effort from ventilator-set PEEP.

37. Correct Answer: C. Procainamide, 1-g IV infusion over 50 minutes
Rationale: The rhythm strip shows an irregularly irregular tachycardia with variable
QRS-complex durations and morphologies. The rhythm is consistent with atrial
fibrillation with a rapid ventricular response and ventricular preexcitation in a patient
with Wolff-Parkinson-White syndrome (WPW). Patients with WPW have an accessory
pathway that connects the atrium to the ventricle, which can conduct much more rapidly
than the atrioventricular node and can present with three different types of arrhythmias:
1. Orthodromic atrioventricular reentry (AVRT) caused by macroreentry with
anterograde conduction over the atrioventricular (AV) node and retrograde conduction
over the accessory pathway: This manifests as a regular tachycardia, usually with a


narrow QRS complex, unless there is a rate-dependent or preexisting bundle-branch
block.
2. Atrial fibrillation with a rapid ventricular response: The rapid rates are due to rapid and
frequent anterograde conduction over the accessory pathway and can be fast enough to
lead to ventricular fibrillation and cardiac arrest.
3. Antidromic AVRT caused by macroreentry in the opposite direction from orthodromic
AVRT: This manifests as a regular, wide QRS-complex tachycardia that can be difficult
to differentiate from ventricular tachycardia.
Treatment of atrial fibrillation in a patient with WPW should include a drug that targets
the atrium to terminate the atrial fibrillation and the accessory pathway (made of tissue
like the ventricular myocardium rather than the AV node) to slow the ventricular rate
before atrial fibrillation termination. IV procainamide is the only drug listed that targets
both the atrium and the accessory pathway. Drugs that block the AV node have little
effect on the atrium or accessory pathway and will not convert the rhythm or slow the
ventricular rate. Furthermore, some AV nodal blocking drugs such as diltiazem could
make the patient hypotensive.
38. Correct Answer: E. No antiarrhythmic drug
Rationale: This rhythm strip shows an apparent wide-complex tachycardia (WCT)
caused by ECG artifact. No intervention is required. Clues that a recording that appears to
be a WCT actually represents artifact rather than ventricular tachycardia include:
•Patient or electrode movement during the recording
•QRS complexes, or portions of the QRS complexes and sometimes T waves, visible at
expected intervals within the artifact
•Unstable recording baseline before or after the episode
•Presence of a QRS complex at a time that would not be physiologic, such as
immediately after a QRS complex when the ventricles would be expected to be refractory
•Absence of expected QT prolongation on the first recorded beat after an apparent long
pause
The arrows shown in the figure below indicate the presence of QRS complexes that are
visible within the artifact.



39. Correct Answer: E. Verapamil
Rationale: This patient has a narrow-complex tachycardia at a rate of 188/min, with
palpitations and mild chest discomfort. No clear P waves are seen and there are diffuse
ST changes consistent with her tachycardia. The most likely diagnosis is supraventricular
tachycardia (SVT) from a reentrant focus in the atrioventricular node. If vagal maneuvers
such as carotid sinus massage are not effective, the 2 most effective treatments are
adenosine and calcium-channel blockers (verapamil or diltiazem). Both adenosine and
verapamil produce >90% success in converting SVT to sinus rhythm by interrupting the
reentry circuit in the atrioventricular nodal tissue. Because of its rapid half-life (7
seconds), adenosine has been favored clinically. However, this patient is receiving
aminophylline, a methylxanthine, which is a competitive antagonist of adenosine.
Therapeutic concentrations of theophylline totally block the exogenous adenosine effect
on the heart. Thus, adenosine should not be used in this patient. Verapamil (or diltiazem)
will not be affected by methylxanthines, and it is the drug of choice in this patient.
Of the other choices, lidocaine is a class 1b (Vaughan Williams classification)
antiarrhythmic drug that inhibits the sodium channel; it has actions on ventricular
arrhythmias but no effect on SVT. Metoprolol is a beta-blocker that would be
contraindicated in asthma with active bronchospasm. Beta-blockers are not as effective as
adenosine or calcium blockers in converting SVT. Flecainide is a class 1c antiarrhythmic
drug that may be used to prevent the recurrence of SVT, but it has little ability to convert
the acute SVT rhythm.
Additional drug interactions with adenosine deserve comment. Dipyridamole is a
nucleoside transport blocker that blocks the reuptake of adenosine, delaying clearance of
adenosine from the circulation and potentiating its effect. Smaller doses of adenosine (3mg versus 6-mg or 12-mg doses) should be used in patients taking dipyridamole. When
adenosine is administered into a central vein or to a patient with a heart transplant, the
adenosine dose should be lower than usual. Conventional doses may produce prolonged
atrioventricular nodal block or profound sinus slowing.
40. Correct Answer: B. Stroke within 6 months
Rationale: For patients presenting within 6 hours of the onset of an ST-elevation
myocardial infarction, prompt reperfusion with either fibrinolytic agents or primary
coronary intervention is indicated. The clinician should perform a focused history and
physical examination to collect sufficient information to ensure that there are no absolute
contraindications to fibrinolytic therapy before initiating treatment. Relative
contraindications impact the decision about whether fibrinolysis or primary coronary
intervention is best in a given patient, but do not rule out use of fibrinolytics. Thus,
clinicians must be able to distinguish absolute from relative contraindications to
fibrinolytic agents.
A history of hemorrhagic stroke at any time, or a nonhemorrhagic stroke within the past
year is an absolute contraindication to fibrinolytic therapy. Other absolute


contraindications include known intracranial neoplasms, active bleeding, uncontrolled
hypertension (>180/100 mm Hg), and suspected aortic dissection.
Diabetic retinopathy, oral anticoagulants at therapeutic or subtherapeutic levels, and CPR
performed for more than 10 minutes are only relative contraindications to lytic therapy.
Other relative contraindications include recent trauma or major surgery within 4 weeks,
noncompressible vascular punctures, a history of chronic severe hypertension, blood
pressure that is initially higher than 180/100 mm Hg and is subsequently controlled with
medications, and pregnancy. These conditions increase the risk of bleeding with lytics,
and so affect the decision to proceed with fibrinolytic therapy, which should be made on
a case-by-case basis. Age by itself is not a contraindication to lytics, although bleeding
risks are higher in elderly patients.
41. Correct Answer: C. Institute CPR and active core rewarming measures to 32°C
(89.6°F) before assessing resuscitation status.
Rationale: There are no absolute predictors of survival from hypothermia. In this patient,
the best approach is to assume that he can be resuscitated and institute aggressive core
rewarming along with CPR. The risk of death from hypothermia is related to age,
preexisting illnesses, nutritional status, and alcohol and drug intoxication. Clearly,
resuscitation will only be successful if cardiac arrest is due to hypothermia and not a
consequence of anoxia or other injuries. Although the treatment dictum has been that “no
one is dead until warm and dead,” clinical judgment is necessary in determining the most
appropriate treatment and termination of efforts. Neurologic status on initial examination
is not predictive of death. Poor prognostic indicators on arrival that have been identified
in studies include severe hyperkalemia greater than 10 mEq/L, which may indicate death
prior to severe hypothermia; venous pH less than 6.5; and severe coagulopathy. However,
none of these indicators in isolation is sufficiently sensitive to exclude successful
resuscitation.
42. Correct Answer: B. Administer IV methylene blue
Rationale: This patient most likely has methemoglobin induced by topical anesthetic
spray. The most significant clue is the low oxygen saturation by pulse oximetry but high
PaO2. Co-oximetry should be performed to document the methemoglobin level, but
administration of methylene blue is indicated by the clinical scenario and symptoms.
Topical anesthetics oxidize the ferrous iron of hemoglobin to the ferric iron of
methemoglobin, which is incapable of carrying oxygen. Methemoglobinemia is most
likely to occur with bronchoscopy and transesophageal echocardiography. The antidote is
IV methylene blue, administered initially as 1-2 mg/kg over 5 min (total dose 7 mg/kg).
Mild cases of methemoglobinemia (<20%-30%) may not require treatment. Methylene
blue is contraindicated in patients with glucose-6-phosphate dehydrogenase deficiency.
The scenario is not consistent with a pulmonary embolism because of the discrepancy
between pulse oximetry and arterial blood gas results. Likewise, a chest radiograph
would not provide an etiology of the low oxygen saturation. Intubation would not resolve


the methemoglobinemia in this patient. Thiosulfate is the antidote for cyanide poisoning,
which is not suggested by the clinical information.
43. Correct Answer: C. IV immunoglobulin
Rationale: Patients with immune thrombocytopenic purpura usually do not have
significant bleeding because the few platelets present are young and active in
coagulation. This patient has a comorbidity that makes urgent surgical intervention
necessary. Although steroids are the first-line treatment, platelet counts may not increase
for several days to weeks. IV immunoglobulin would be the best intervention to
accomplish a transient increase in platelets during the operative intervention. It is
administered as 0.5-1 g/kg/day along with methylprednisolone, 1 g/day. Depending on
the response, platelet transfusions may be needed at the time of surgery. Platelet
transfusions alone are unlikely to benefit this patient since they would be subject to the
same antibody destruction as endogenous platelets. Splenectomy would not be warranted.
Rituximab and danazol are options for chronic immune thrombocytopenic purpura but
would be unlikely to have a rapid effect on the platelet count.

44. Correct Answer: A. Significant dehydration is likely
Rationale: This patient presents with classic heatstroke that affects the elderly and those
with chronic medical conditions and social isolation. The syndrome usually occurs over
days, so significant dehydration is present and anhidrosis is often noted on examination.
Additional IV fluids are needed, but the amount should be individualized. As the patient
is cooled and vasodilation abates, intravascular volume overload may occur if excessive
fluids are administered, especially in the elderly with cardiac dysfunction. In contrast,
approximately 50% of exertional heatstroke victims will have profuse sweating on
examination. Exertional heatstroke develops more rapidly, and dehydration may be less
severe. The lactic acidosis in classic heatstroke is due to hypoperfusion, while it usually
results from anaerobic muscle metabolism in exertional heatstroke. The hemodynamic
status of this patient is best addressed with cooling, which should decrease heart rate and
increase the blood pressure. A pulmonary artery catheter could be considered if initial
cooling and resuscitation measures fail.
45. Correct Answer: E. Administering hyperbaric oxygen
Rationale: This patient’s presentation suggests carbon monoxide poisoning for several
reasons. She was found in the appropriate setting, the clinical findings are consistent with
carbon monoxide toxicity, and the laboratory results also support exposure to carbon
monoxide. The best confirmation of significant carbon monoxide exposure is an elevated
carboxyhemoglobin level (venous or arterial). However, the initial level may not be
helpful if a significant period of time has elapsed since exposure. Carboxyhemoglobin
levels of up to 10% can be found in people in some urban areas and in heavy smokers.
Pulse oximetry often overestimates oxygenation in the setting of carbon monoxide
toxicity, so it is not helpful in assessment. The presence of metabolic acidosis suggests


tissue hypoxia, and a lactate level is more reliable than the carboxyhemoglobin level in
determining the severity of toxicity. Although there is continued debate on the indications
for hyperbaric oxygen therapy, most clinicians would agree that the presence of
significant neurologic impairment would warrant treatment.
There is no reason to administer flumazenil since the patient is supported by mechanical
ventilation. Increasing ventilation would only alter the acid-base findings without
addressing the underlying etiology. There is no indication for dialysis in this patient.
Although 100% oxygen shortens the half-life of carboxyhemoglobin, a recent study
suggests that it is less effective than hyperbaric oxygen at reducing postexposure
cognitive deficits.
46. Correct Answer: E. Application of forced-air rewarming blanket
Rationale: In a severely hypothermic patient with a palpable pulse, efforts should be
directed to rewarming. The bradycardia is an expected consequence of hypothermia and
responds to rewarming. Medications such as atropine and dopamine are unlikely to have
any activity at such a low temperature. Chest compressions are not needed in a patient
with evidence of perfusion (ie, palpable pulse) but are indicated in patients who are
pulseless or have a nonperfusing rhythm such as ventricular fibrillation or asystole.
Transthoracic pacing is unlikely to be successful and may precipitate life-threatening
arrhythmias in the hypothermic myocardium.
47. Correct Answer: D. Recombinant factor VIIa
Rationale: One of the approved indications for use of recombinant factor VIIa is serious
bleeding in hemophiliacs with inhibitors. Factor VIIa enhances thrombin generation,
leading to hemostasis. Factor VIII in any form (cryoprecipitate, plasma-derived, or
recombinant) would be ineffective in the presence of inhibitors. Factor XI requires factor
VIII as a cofactor to activate factor X. Fresh frozen plasma does not contain significant
amounts of factor VII to allow sufficient thrombin generation.



Tài liệu bạn tìm kiếm đã sẵn sàng tải về

Tải bản đầy đủ ngay

×

×