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USMLE Step 2 — Lesson 1: Cardiology: Myocardial Infarction
Internal Medicine HighlightsConrad Fischer, MD
Maimonides Medical Center
Residency Director
Cardiology
Myocardial Infarction
Differential of Chest Pain
A 52-year-old man comes to the ER with 1 hour of severe chest pain on exertion. He
is nauseated and diaphoretic with slight shortness of breath. The pain does not
change with respiration or bodily position. Exam shows normal vitals, clear
lungs, no murmurs, and no tenderness.
Changes With Respiration
Pneumonia
Pneumothorax
Pulmonary embolus
Pleuritis
Pericarditis
All can give fever - so can MI.
Changes With Position
Pericarditis only
when lying back causes more pain
Changes With Palpitation
Costochondritis only
EKG shows 2 mm of ST segment elevation in V2-V4
Anything 1 mm in 2 electrically connected leads is sufficient for diagnosing acute MI
II, III F: Inferior wall
: Anterior Wall
I,L, : Lateral wall
What would you do next?
Cardiac Enzymes
Do not answer enzyme testing next:
Takes too long to obtain results
Treatment should be initiated first
Won't be positive yet
Won’t change what to do, regardless of results (positive or negative) at this time
Cardiac Enzymes
Begins to
ElevateLasts
CPK-MB 4-6 hr 2 days
Troponin 4-6 hr 1-2 wk
Myoglobin 1-4 hr s
LDH 12-24 hr s
LDH currently is not useful. Never answer it.
Best Answers:
Which has the best sensitivity, but poor specificity?
Myoglobin
Which has the best specificity?
Troponin
CPK-MB is sensitive and specific, but not as sensitive as myoglobin or as specific as
troponin.
Treatment of Acute MI in ALL Patients
Decrease
Mortality
Time
Dependa
nt
Aspirin YES (25%) YES
Nitrates ?? ?
Morphine (Analgesics) ?? ?
Thrombolytic YES (25%) YES
-Blockers YES (10-20%) NO
Special Circumstances
Angioplasty
o Patients with major bleeding or risk of bleeding
o Patients who can’t receive thrombolytics for any reason
o Patients failing thrombolytics and progressing to hemodynamic instability
o Equal in efficacy to thrombolytics
Special Circumstances
ACE Inhibitor
o Patients with decreased left ventricle function or CHF
Lidocaine
o Never as prophylaxis
o All patients who develop major vertricular arrhythmias (ventricular
tachycardia or fibrillation)
Pacemakers
Anything slow or that could become slow
Third-degree AV block
Mobitz II second degree block
Left bundle branch block
USMLE Step 2 — Lesson 2: Cardiology: Congestive Heart Failure
Cardiology
Congestive Heart Failure
Congestive Heart Failure/Pulmonary Edema
A 67-year-old woman comes to the ER with 1-2 hours of severe shortness of breath.
She has a history of two MIs in the past. She comes with a pizza in one hand and a
bag of Doritos in the other, and she is chewing a sausage. Her respiration rate is 34;
BP, 130/82; and PUD, 18. Jugulovenous distention is present. Chest: rales to apices.
Heart:3/6 systolic murmur at Apex 1. S3 gallop. Abd: Enlarged liver.3+ Edema of
lower extremities to mid-thigh.
What would you do next?
Do Not Answer Lab Tests
CXR:Congestion of vasculature, enlarged heart, effusion
Arterial blood gas: Hypoxia, respiratory alkalosis
EKG: Sinus tachycardia
Echocardiogram (never used in acute cases): decreased ejection fraction, mitral
regurgitation, abnormal motion of anterior and, inferior walls
Radionuclide ventriculogram:(MUGA) – never use acute scan, most accurate
method of assessing ejection fraction
Treatment of Pulmonary Edema
Sit the patient upright
Give Oxygen
Treatment of Pulmonary Edema
First Step: Preload reduction
Diuretics – any loop diuretic intravenously
Morphine
Nitrates
Second Step: Only if preload reduction is ineffective
Positive inotropes
Dobutamine
Amrinone
Treatment of Pulmonary Edema
Third Step: Afterload reduction
Ace inhibitors - IV
Nitroprusside
Congestive Heart Failure
Treatment when the patient has been stabilized
Ace inhibitors
Diuretics
Digoxin
Blockers (carvedilol or metoprolol)
Blockers
Reduce mortality
Increase ejection fraction
Improve symptoms
USMLE Step 2 — Lesson 3: Infectious Diseases: Intro. to Antibiotics
Infectious Deseases
Introduction to Antibiotics
Introduction to Antibiotics
The organisms that cause diseases have largely not changed
The antibiotics that go with the organisms change
The most important aspect of infectious diseases: ascribe the antibiotics that go
with each group of organisms
Think in terms of groups of antibiotics
Gram-positive Cocci: Staphylococcus and Streptococcus
Penicillins:
o Oxacillin
o Cloxacillin
o Dicloxacillin
o Nafcillin
Gram-positive Cocci: Staphylococcus and Streptococcus
With mild penicillin allergy
First-generation cephalosporins:
o Cefazolin
o Cephalexin
o Cephradine
o Cefadroxil
Gram-positive Cocci: Staphylococcus and Streptococcus
With severe penicillin allergy
Clindamycin
Macrolides (erythromycin, clarithromycin, azithromycin): Used for minor, non-life-
threatening infections
Vancomycin, Synercid, Linezolid: Used for gram-positive infections with life-
threatening allergy to penicillin and methicillin-resistant Staphylococcus
Gram-negative Bacilli
For E. coli, Proteus, Enterobacter, Klebsiella, Morganella, and Pseudomonas, ALL of
following provide >90% coverage:
Aminoglycosides (gentamicin, tobramycin, amikacin)
Aztreonam
Quinolones (ciprofloxacin, levofloxacin)
Gram-negative Bacilli
For E. coli, Proteus, Enterobacter, Klebsiella, Morganella, and Pseudomonas, ALL of
following provide >90% coverage:
Carbapenems (imipenem, meropenem)
Extended-spectrum penicillins (piperacillin, ticarcillin, azlocillin, mezlocillin)
Third-generation cephalosporins (especially ceftazidime)
Fourth-generation cephalosporins (especially cefepime)
Second-generation cephalosporins (eg, cefoxitin, cefotetan, cefuroxime)
Good for gram-positive coverage like first-generation cephalosporins
Good for gram-negative coverage but NOT for Pseudomonas
Cefoxitin and cefotetan are good for anaerobes
Anaerobes
Oral anaerobes (anything above the diaphragm)
Clindamycin
Penicillin (any penicillin EXCEPT the Ox/Clox/Diclox/Naf group)
Abdominal anaerobes (below the diaphragm)
Metronidazole
Imipenem
Second-generation cephalosporins
Beta-lactam/ Beta-lactamase inhibitor combinations
Antivirals
Herpes simplex and varicella
Acyclovir, valacyclovir, famciclovir
Herpes simplex, and varicella AND Cytomegalovirus
Ganciclovir, foscarnet, cidofovir
Antivirals
Influenza
Oseltamivir, zanamivir
Amantadine, rimantadine: Becoming archaeologic
Hepatitis B
Lamivudine or interferon
Hepatitis C
Interferon and ribavirin in combination
Antifungals
Life-threatening infections (eg, endocarditis, meningitis, fungemia)
Amphotericin
Candida infections
Azoles
Fluconazole, ketoconazole, itraconazole
Onychomycosis
Terbinafine, itraconazole
Griseofulvin is as useful as a rotary telephone
USMLE Step 2 — Lesson 4: Central Nervous System Infections
Infectious Deseases
Central Nervous System Infections
Central Nervous System Infections
A 48-year-old man comes to the ER with 1 day of fever, headache, nausea.
What could this be?
ANY of the CNS infections can present with fever, headache, and nausea. To determine which one, the question will provide the following clues:
Meningitis
The patient also has photophobia and nuchal rigidity (stiff neck) on exam.
Encephalitis
The patient is disoriented confused and lethargic with difficulty thinking.
ANY of the CNS infections can present with fever, headache, and nausea. To determine which one, the question will provide the following clues:
Abscess
The patient has focal neurological deficits found on examination.
Note: There is considerable overlap between these diseases. If the question state
that he has a stiff neck AND confusion/lethargy AND focal findings, then neither you
nor anyone else could determine the precise diagnosis.
Which patients require a CT scan of the head BEFORE lumbar puncture?
Focal findings
Papilledema
Altered mental status
If CT is required before lumbar puncture, ALWAYS answer give treatment (ceftriaxone) before the lumbar puncture:
Treatment is more important than the specific diagnosis
Cell count, chemistry (protein level), gram-stain, and bacterial antigen testing can
still give the diagnosis if the antibiotics sterilize the culture
Meningitis
Diagnostic testing on lumbar puncture: Everything depends on the specific question
asked!
MOST SPECIFIC test is CULTURE
MOST SENSITIVE test is PROTEIN
NEXT BEST or BEST INITIAL test on CSF is CELL COUNT. (Cell count is not as
specific as culture or as sensitive as protein level but it is the best combination of
both.)
Cultures
In general, “culture” is the answer to the
“What is the BEST - Most Accurate - Most Likely to lead to specific diagnosis” type
of question.
HOWEVER:Don’t answer, “Wait for the cultures before initiating treatment.”
Meningitis
A 48-year-old man comes to the ER with 1 day of fever, headache, and nausea. He
has photophobia and a stiff neck. He has no focal neurological deficits or
papilledema and is fully oriented and alert. Lumbar puncture shows an elevated
protein, cell count of 3,502, and a negative gram stain. Culture is sent.
Which type of meningitis is this?
Cell Count on CSF
Any type of meningitis can cause an elevated cell count; the differential on the cell count
gives more specific information.
Neutrophils – Bacterial:
Streptococcus pneumonia: most common
Neisseria: look for a rash, particularly a petechial rash in the presentation
Haemophilus: particularly in children, although greatly diminished because of
vaccination
Treatment of Bacterial Menigitis
Cell Count on CSF
Lymphocytes (look for these specific features):
Rocky Mountain spotted fever: rash on wrists/ankles, moving centrally towards the
body
Lyme: Facial palsy, target lesion rash (erythema migrans)
Cryptococcus: HIV+ patients with <100 CD4 cells
TB: Very high protein in CSF,and very low glucose, TB in lungs
Viral: Everything negative; no particular association. Exclude the other causes
Treatment of Bacterial Meningitis
A 48-year-old man comes to the ER with 1 day of fever, headache, nausea. He has
photophobia and a stiff neck. He has no focal neurological deficits or papilledema
and is fully oriented and alert. Lumbar puncture shows an elevated protein, cell
count of 3,502, and a negative gram stain. Culture is sent. The differential shows
92% neutrophils.
What is the best initial therapy?
Treatment of Bacterial Meningitis
What is the best intial therapy?
Ceftriaxone unless T-cell immune deficit present.
Ceftriaxone AND Ampicillin if there is steroid use, neutropenia, pregnancy
lymphoma, leukemia, HIV or if the patient is elderly or a neonate. Ampicillin covers
Listeria.
Treatment of Bacterial Meningitis
A 48-year-old man comes to the ER with 1 day of fever, headache, nausea. He has
photophobia and a stiff neck. He has no focal neurological deficits or papilledema
and is fully oriented and alert. Lumbar puncture shows an elevated protein, cell
count of 3,502, and a negative gram stain. Culture is sent. The differential shows
92% neutrophils.
What is the best initial therapy?
Treatment of Bacterial Meningitis
What is the best intial therapy?
Ceftriaxone unless T-cell immune deficit present.
Ceftriaxone AND Ampicillin if there is steroid use, neutropenia, pregnancy
lymphoma, leukemia, HIV or if the patient is elderly or a neonate. Ampicillin covers
Listeria.
USMLE Step 2 — Lesson 5: PPD Testing
Infectious Diseases
PPD Testing
PPD Testing
When to use the PPD? What's it for?
To screen the asymptomatic: do not use as primary method for diagnosing TB in acutely
symptomatic patients
What is considered a positive PPD?
>10 mm induration, not erythema in most patients; >5 mm in HIV+ patients and
close contacts
Always get CXR after a positive PPD
Treatment for a positive PPD means INH alone
Treat all PPD+ patients if the risk of developing TB is greater than risk of hepatitis from the
isoniazid:
ANY recent (past 2 years) converter
ANYONE with severe immune deficiency (eg, HIV, steroid use, leukemia, diabetes,
lymphoma)
ANYONE <35 years old
What is the effect of BCG on these recommendations?
BCG has NO effect on these recommendations.
Which of the following patients should receive isoniazid prophylactic therapy?
A 19-year-old, HIV- woman entering college with 8 mm of induration and a negative
test last year.
Which of the following patients should receive isoniazid prophylactic therapy?
A 32-year-old, HIV- physician from India who received BCG as a child and has never
been tested before. She has 12 mm of induration at health screening before starting
an internship in the US.
Which of the following patients should receive isoniazid prophylactic therapy?
A 47-year-old HIV+ man who had never been tested before and has 7 mm of
induration.
A 95-year-old, HIV-, female nursing home resident who was PPD- last year and has
11 mm of induration this year.
Which of the following patients should receive isoniazid prophylactic therapy?
A 3,725-year-old Egyptian mummy who was PPD- last year and is PPD+ this year.
Which of the following patients should receive isoniazid prophylactic therapy?
The 19-year-old woman: NO
The 32-year-old physician: YES
The 47-year-old-HIV+ man: YES
The 95-year-old nursing home resident: YES
The 3725-year-old Eqyptian mummy:
YES, YES, YES!
USMLE Step 2 — Lesson 6: HIV
Infectious Diseases
HIV
HIV
A 37-year-old man comes to your office after having been recently diagnosed with
HIV. He has no symptoms. His physical examination is normal. His CD4 count is
575, and his viral load is 1,000.
Which medications are appropriate for this patient?
None for this patient: CD4>500, viral load <20,000
Antiretroviral Medications and their most common adverse effects
Nucleoside reverse transcriptase inhibitors
Zidovudine (anemia)
Didanosine (pancreas, neuropathy)
Stavudine (pancreas, neuropathy)
Zalcitabine (pancreas, neuropathy)
Lamivudine
Protease inhibitors: hyperlipidemia, hyperglycemia
Nelfinavir
Ritonavir
Indinavir
Saquinavir
Amprenavir
When to start therapy?
CD4 < 500 or viral load > 20,000
What to start?
Any two reverse transcriptase inhibitors AND any protease inhibitor
A 37-year-old man comes to your office after having been recently diagnosed with
HIV. He has no symptoms. His physical examination is normal. His CD4 count is
575, and his viral load is 1,000.
NONE for this patient: CD4 >500, viral load <20,000
A 37-year-old man comes to your office after having been recently diagnosed with
HIV. He has no symptoms. His physical examination is normal. His CD4 count is
275, and his viral load is 1,000.
What medications are appropriate?
Any two nucleosides AND a protease inhibitor
A 37-year-old man comes to your office after having been recently diagnosed with
HIV. He has no symptoms. His physical examination is normal. His CD4 count is
575, and his viral load is 71,000.
What medications are appropriate for this patient?
Any two nucleosides AND a protease inhibitor
A 37-year-old man comes to your office after having been recently diagnosed with
HIV. He has no symptoms. His physical examination is normal. His CD4 count is
175, and his viral load is 31,000
Any two nucleosides AND a protease inhibitor AND . . .
Pneumocystis Prophylaxis: when the CD4 <200
Trimethoprim/Sulfamethoxazole(first choice) Dapsone Atovaquone
A 37-year-old man comes to your office after having been recently diagnosed with
HIV. He has no symptoms. His physical examination is normal. His CD4 count is
45, and his viral load is 31,000.
Any two nucleosides AND a protease inhibitor +
trimethoprim/sulfamethoxazole AND . . . Mycobacterium avium complex
prophylaxis: when the CD4 <50
Azithromycin (once a week)
A 37-year-old man comes to your office after having been recently diagnosed with
HIV. He has no symptoms. His physical examination is normal. His CD4 count is 5,
and his viral load is 371,000
.
Any two nucleosides AND a protease inhibitor AND
trimethoprim/sulfamethoxazole AND azithromycin AND…
NOTHING!!
USMLE Step 2 — Lesson 7: Hematology: Microcytic Anemia
Hematology
Microcytic Anemia
Microcytic Anemia
A 32-year- old woman presents with several weeks of fatigue. She complains of
nothing else. Initial CBC reveals an hematocrit of 28%.
Symptoms of anemia are largely based on severity not etiology. Iron
deficiency with hematocrit of 28% will give the same symptoms and the
anemia of chronic disease, folate deficiency, thalassemia, etc, with
hematocrits of 28%.
A 32-year-old woman presents with several weeks of fatigue. She complains of
nothing else. Initial CBC reveals hematocrit of 28%. The other portions of the CBC
are normal, and the MCV is 70 (normal 80-100).
What is the most likely diagnosis?
After determining that the patient has anemia, the next most useful step is to
determine the cell size. This is the next easiest clue as to the etiology of the
anemia.
Low MCV Iron deficiency
Anemia of chronic disease (can also be normocytic)
Sideroblastic
Thalassemia
High MCV Vitamin B12 deficiency
Folate deficiency
Alcohol
Drug toxicity
Normal MCV
Hemolysis
A 32-year-old woman presents with several weeks of fatigue. She complains of
nothing else. Initial CBC reveals an hematocrit of 28%; other portions of the CBC
are normal, and MCV is 70 (normal 80-100).
What is the next best step in the management of this microcytic patient? (ie:
What is the best initial diagnostic test?)
What is the next best step in the management of this microcytic patient?
Iron Studies Iron deficiency: low ferritin, high iron binding capacity
Chronic disease: high ferritin, low iron binding capacity
Sideroblastic: high serum iron
Thalassemia: normal iron studies
After the iron studies, how would you address other questions about the specifics of the various low MCV anemias? (“What is the most accurate diagnostic test?”)
Iron Deficiency High red cell distribution of width (RDW)
What is the most specific test? Bone marrow for stainable iron.
Sideroblastic anemia What is the most specific test? Prussian blue stain for ringed sideroblasts
Thalassemia What is the most specific test? Hemoglobin electrophoresis
What is the best therapy for this patient?
Iron Deficiency Iron replacement
Ferrous sulfate tablets
Chronic Disease Correct the underlying disease
What is the best therapy for this patient?
Sideroblastic anemia Pyridoxine
Thalassemia trait No therapy
USMLE Step 2 — Lesson 8: Hematology: Macrocytic Anemia
Hematology
Macrocytic Anemia
A 32-year-old woman presents with several weeks of fatigue. Initial CBC reveals an
hematocrit of 28%.
Symptoms of anemia are largely based on the severity not the etiology. Iron
deficiency with hematocrit of 28% will give the same symptoms and the
anemia of chronic disease, folate deficiency, thalassemia, etc, with an
hematocrit of 28%.
A 32-year-old woman comes to the office with several weeks of fatigue. In addition,
she complains of a sensation of pins and needles in her hands and feet. She drinks
almost a quart of vodka per day. Initial CBC reveals an hematocrit of 28%. The MCV
is 120 (normal 80-100).
What is the next best step in the management of this macrocytic patient?
Macrocytic anemia is largely due to either vitamin or folate deficiency, although
several drug toxicities (eg, severe alcoholism, zidovudine or methotrexate use) can
do it as well. You do NOT need neurological symptoms to have anemia from
deficiency. However the presence of neurological symptoms means it cannot be
folate deficiency alone. Alcohol can give neurological symptoms as well.
Which neurological problems can occur with B12 deficiency?
Motor, sensory, psychiatric, ataxia, position, vibratory, cognitive, autonomic, sexual
ANY neurological symptom can occur with deficiency
Which is the most common neurological symptom with B12 deficiency?
Peripheral neuropathy
B12 Deficiency
What is the best intial test?
Presence of hypersegmented neutrophils and a low B12 level (NOT a Schilling test).
Folate Deficiency
What is the best initial test?
Presence of hypersegmented neutrophils and a low folate level.
Alcohol or other drug toxicity
What is the best initial test?
Absence of hypersegmented neutrophils and to exclude the B12 and folate deficiency
and look for the drug in the history.
What are the specific tests you would do to determine the specific etiology of the B12?
Elevated methylmalonic acid and elevated LDH are characteristic of deficiency.
Antibodies to intrinsic factor and an elevated gastrin level are characteristic of
pernicious anemia
Schilling’s test is the least often used but most specific way to determine precisely
how a patient is malabsorbing . Do NOT answer Schilling’s test if the case gives
you the elevated LDH, antibodies to intrinsic factor and elevated gastrin level.
What is the best therapy?
B12 deficiency: Replace the B12
Folate deficiency: Replace the folate
Drug/Alcohol toxicity: Stop the drug/alcohol
USMLE Step 2 — Lesson 9: Hematology: Hemolysis
Hematology
Hemolysis
Hemolysis
A 42-year-old man is admitted to the hospital because of weakness, fatigue, and
dark urine. On examination he appears jaundiced with scleral icterus. Initial CBC
shows an hematocrit of 28% with a normal MCV. His indirect bilirubin, LDH level and
reticulocyte count are all elevated.
What is the cause of his anemia?
All forms of hemolysis present with elevated LDH levels, reticulocyte count, and
indirect bilirubin. The dark urine can be either from hemoglobin filtered into the urine
in intravascular hemolysis or from the bilirubin alone. Sometimes the MCV can be
slightly elevated because reticulocytes are slightly larger.
Which clues in the history will tell you which type of hemolytic anemia it is?
Autoimmune:Lupus, lymphoma, leukemia, rheumatoid arthritis, viral infections,
penicillin or quinidine use
Glucose 6 phosphate dehydrogenase deficiency (G6PD): Very sudden onset,
current infection, oxidant stress from drugs (eg, dapsone, primaquine, or sulfa) or
fava bean ingestion
Which clues in the history will tell you which type of hemolytic anemia it is?
Paroxysmal nocturnal hemoglobinuria (PNH): Dark morning urine, major venous
thrombosis such as the portal vein
Hemolytic uremic syndrome (HUS): Renal failure and thrombocytopenia
Which clues in the history will tell you which type of hemolytic anemia it is?
Thrombotic thrombocytopenic purpura (TTP): Renal failure and
thrombocytopenia and neurological symptoms and fever
Hereditary spherocytosis: Splenomegaly
Which diagnostic testing is useful to distinguish between these?
All EXCEPT the hereditary spherocytosis can also give:
low haptoglobin level
hemoglobinuria
Hemosiderinuria
Hereditary spherocytosis will not give these because it is extravascular hemolysis.
Extravascular means it occurs in the spleen.
Which of the following tests is the “most specific”, “most accurate”, and “most likely to lead to a definite diagnosis” in each of these forms of anemia?
Autoimmune: Coombs test
G6PD: G6PD level
PNH: Sugar-water and Ham’s test
HUS: Finding renal failure and thrombocytopenia with hemolysis; no specific test
TTP:Finding renal failure, thrombocytopenia, and neurological symptoms and fever
with hemolysis; no specific test
Hereditary spherocytosis:Spherocytes on the smear AND an osmotic fragility test
Which of the following is the best intitial therapy and most definitive therapy?
Autoimmune:: Initially, steroids; with life-threatening hemolysis, IV immunoglobulin;
recurrent, splenectomy
G6PD:Avoid the oxidant stress
PNH:Steroids
HUS:Initially, spontaneous resolution; with life-threatening disease, plasmapheresis
TTP:Plasmapheresis
Hereditary spherocytosis:Splenectomy
USMLE Step 2 — Lesson 10: Nephrology: Acute Renal Failure
Nephrology
Acute Renal Failure
An 87-year-old woman with a history of gout and osteoarthritis is found on the floor
of her apt. by her family. It is not clear how long she has been on the floor. She uses
NSAIDs for joint pain. In the ER she is found to be confused. Her temperature is 102
F, pulse is 117, and systolic BP blood is 92; rales are heard on lung examination.
She has a head CT with contrast to evaluate her confusion and receives penicillin
and gentamicin for her pneumonia. She has no urine output since admission. On
hospital day 2 her BUN and creatinine begin to rise.
How many causes of renal failure can you identify in this patient?
The first step in evaluating a patient with acute renal failure is to determine whether
there is a problem inside the kidney (tubules, glomeruli, vascular) or with the
perfusion of the kidney (prerenal) or drainage out of the kidney (postrenal).
The fever, tachycardia, relatively low BP, and the fact that she was found on
the floor are all sufficient suggestions of pre-renal azotemia.
The best initial tests to determine whether it is pre-renal azotemia is as follows:
Pre-renalAcute Tubular
NecrosisBUN/
Creatinine
Ratio
> 20:1 10.1
Urine Sodium Low < 20 High > 40
Urine
Osmolality
High >
500Low < 350
To exclude post-renal azotemia (obstruction to drainage OUT of the kidney) the following are useful:
Physical examination to detect enlarged bladder
Ultrasound to look for bladder size and hydronephrosis
Urinary catheter placement
Do NOT assume that the decreased urine output described is from the renal failure. The
renal failure could simply be from decreased urine output and obstruction.
Intra-renal Damage (ATN)
Damage to the kidney could affect tubules, glomeruli, or vasculature. It is NOT very
useful to think of the diseases as cortical or medullary. Glomerular diseases, eg,
lupus, Goodpasture, Alport syndrome, Berger disease, or even post-streptococcal
disease, are unlikely to occur this acutely and without other history of systemic
disease. The same is true of vascular diseases, eg, polyarteritis nodosa, Wegener
granulomatosis, TTP, HUS, or Henoch Schonlein purpura.
Intra-renal Damage (ATN)
Acute renal failure such as this is most often from tubular diseases, which are most
often from various toxins combined with possible ischemia from hypoperfusion.
How many different toxins can you identify in this case?
An 87-year old woman with a history of gout and osteoarthritis is found on the
floor of her apartment by her family. It is not clear how long she has been on the
floor. She uses NSAIDs for joint pain. In the ER she is found to be confused. Her
temperature is 102 F, pulse is 117, and systolic BP blood is 92; rales are seen on
lung examination. She has a heat CT with contrast to evaluate her confusion and
receives penicillin and gentamicin for her pheumonia. She has no urine output
since admission. On hospital day 2 her BUN and creatinine began to rise.
You could simply say that the tubular diseases are from toxins. However,
since the answers to questions concerning initial and best tests and
treatments are different, they must be subdivided so they can be addressed
individually.
Direct Toxins
Gentamicin acts directly as a toxin to the kidney's tubule. Other drugs include
amphotericin, cisplatin, NSAIDs, and cyclosporine. Contrast agents also act in the
same way.
Best test: Exclude other causes of renal failure. There is no test to determine the
specific etiology of any toxin-mediated organ toxicity. Biopsy will NOT determine the
specific agent.
Direct Toxins:
Best therapy: Stop the offending agent. There is no specific therapy to reverse ANY
toxin-mediated organ damage beyond this. Dialysis does NOT reverse the damage;
it supports the patient while waiting for the kidneys to come back to life on their own.
Allergic Interstitial Nephritis:
Penicillin causes damage to the kidney, as it causes an allergic reaction against the
kidney tubule. Other drugs include sulfa drugs, allopurinol, phenytoin, rifampin and
NSAIDs.
Keys to recognizing this as the cause of the renal failure are fever and rash,
although these do not have to be present.
Allergic Interstitial Nephritis:
Best initial test: Measure blood and urinary eosinophils. IgE levels are not
sufficiently sensitive. Renal biopsy is the most accurate test but should seldom, if
ever, be used.
Best initial therapy: Stop the medications. Very severe cases can be treated with
steroids.
Crystals:
Uric acid crystals from the gout as well as from oxalate crystals from ethylene glycol
ingestion can also damage the tubules. Look for gout or ethylene glycol ingestion in
the history.
Best initial test: Urinalysis to look for crystals.
Therapy: Either allopurinol for gout or ethanol infusion for the ethylene glycol
ingestion.
Pigments:
Myoglobin from rhabdomyolysis and hemoglobin from hemolysis are directly toxic to
the tubule. The fact that this patient was found lying on the floor of her apartment is
suggestive of rhabdomyolysis. Clues to pigments as the cause of the renal failure
are hemolysis or muscle breakdown, as dark urine, on history.
Pigments:
Best initial tests: EKG to exclude signs of life-threatening hyperkalemia and
urinalysis to show dipstick positive for blood with no RBCs on the microscopic
examination.
Most accurate and specific tests: Myoglobin in urine and elevated CPK level in
blood for rhabdomyolysis.
Best initial therapy: Hydration and alkalinization of the urine with bicarbonate.
USMLE Step 2 — Lesson 11: Nephrology: Hyponatremia
Nephrology
Hyponatremia
A 59-year-old man with a history of lung cancer 1 cm from his carina is admitted to
the hospital because of mild confusion, which has developed over the past several
days. His sodium level is 119 (normal 135-145)
What is the etiology of his hyponatremia?
The first step in evaluating hyponatremia is to determine the volume status of the patient.
Hypervolemic (presence of rales, edema, jugulovenous distention):
o Congestive heart failure
o Nephrotic syndrome
o Cirrhosis
The first step in evaluating hyponatremia is to determine the
volume status of the patient.
Hypovolemic (orthostasis, dry mucous membranes, decreased skin turgor):
o GI fluid loss
o Urinary loss, diuretics
o Skin losses, sweating, fever, burns
The above also require replacement with free water to drive sodium down
The first step in evaluating hyponatremia is to determine the volume status of the patient.
Normal volume:
Addison’s disease does not require free water to drive the sodium down.
Psychogenic polydipsia
Pseudohyponatremia
Syndrome of inappropriate antidiuretic hormone (SIADH)
Hypothyroidism
A 59-year-old man with a history of lung cancer 1 cm from his carina is admitted to
the hospital because of mild confusion, which has developed over the past several
days. His sodium level is 119 (normal 135-145). Physical examination reveals
normal skin turgor and no orthostasis, edema, or rales.
What is the best initial test?
If a normal person’s sodium were suddenly driven below normal, the body’s
response would be to immediately shut off all ADH secretion, allowing the maximal
amount of free water to be released. The normal response would be to maximally
dilute the urine. The normal response to hyponatremia would be to have a urine
osmolality at the lowest possible amount. The range of urine osmolarity is 50-1200
mOsm/kg. The normal response would be urine osmolarity around 50 mOsm/kg and
urine osmolality less than serum osmolarity. Urine sodium should also be low.
The best initial test is the
urine osmolality
A 59-year-old man with a history of lung cancer 1 cm from his carina is admitted to
the hospital because of mild confusion, which has developed over the past several
days. His sodium level is 119 (normal 135-145). Physical examination reveals
normal skin turgor and no orthostasis, edema, or rales. His serum osmolality is
250 mOsm/kg (normal 280-300), urine osmolality is 425 mOsm/kg and urine
sodium is 42 mEq/L.
What is the best therapy for this patient?
The urine osmolality in this patient is higher than the serum osmolality. Combined
with a high urine sodium level this is confirmatory of SIADH. We do not use ADH
levels.
Therapy for SIADH is divided as follows:
Mild, asymptomatic hyponatremia: Fluid restriction to 1/L/day
Moderate hyponatremia with mild or moderate neurological symptoms: Saline
infusion and loop diuretic
Severe hyponatremia with severe symptoms: 3% hypertonic saline sometimes
combined with diuretic
What are the complications of changing sodium levels too rapidly?
(>1-2 mEq/L/hr)
Too rapid a RISE => central pontine myelonolysis
Too rapid a DROP => cerebral edema
The patient described above has his sodium corrected by normal saline infusion and
a diuretic. His neurological symptoms resolve.
What is the next best step in his management?
This patient’s underlying problem probably can’t be corrected; lung cancer at the
carina typically can’t be resected. Hence, as soon as the saline and diuretic therapy
is stopped the hyponatremia will recur. He will probably not be thrilled with
maintaining lifelong fluid restriction.
What is the management of chronic SIADH?
Demeclocycline to block the effect of the ADH at the level of the kidney tubule
on a chronic basis.
USMLE Step 2 — Lesson 12: Nephrology: Hyperkalemia
Nephrology
Hyperkalemia
A 27-year-old man presents to the ER at your hospital after having just taken the
physical exam to join the NY City Fire Department. As part of this exam he must do
50 push-ups followed by suddenly lifting a 175-lb bag of sand. He then has to run up
and down 3 flights of stairs and across a balance beam followed by 50 more push-
ups. He comes to see you because of severe muscle pain, muscle tenderness, and
dark urine developing over the next several hours.
What is the most important first step in his management?
The patient seems to have rhabdomyolysis on the basis of severe, sudden exertion.
Several tests are needed: CPK level, urinalysis looking for blood on dipstick, urine
microscopic exam, potassium level, and possibly urine myoglobin level. However,
you must choose the MOST URGENT test. No matter how high the CPK level is,
hyperkalemia is more immediately life-threatening. Even if the potassium level is
elevated, it is more important to know whether there are EKG abnormalities from the
hyperkalemia, which mean he will suddenly die of an arrhythmia.
The EKG shows peaked T-waves
What is the NEXT best step in management?
Calcium chloride or calcium gluconate is given intravenously
What is the NEXT best step in management?
Half normal saline infusion and bicarbonate as well as an ampule of 50% dextrose is given with insulin.
The original potassium level (on entry, before therapy) comes back at 7.9 mEq/L. His
CPK level is markedly elevated at 48,000 and the urinalysis is dipstick positive for
blood, but no RBCs are seen on microscopic exam.
What is the NEXT best step in management?
The fluid and bicarbonate infusion is continued.
Kayexalate is given orally to remove potassium from body.
Repeat potassium level 2 hours later is 6.8 mEq/L. A further level 2 hours after that
is 5.8 mEq/L.
USMLE Step 2 — Lesson 13: Emergency Medicine: Overdose
Emergency Medicine
Overdose
A 25-year-old medical student gets very depressed while preparing for USMLE Step
2. After finishing studying at midnight she takes a bottle of pills at 12:15 am in an
attempt to commit suicide. She removes the label from the bottle so no one can
determine what she took. After 12:15 she finds that her last practice test score was
87% and she will easily pass. She walks across the street to the ER at 12:30 am to
seek treatment.
What is the best initial step in the management of this patient?
Ipecac is given immediately
Gastric emptying with ipecac has limited utility because it must be given within the
first hour of management. Do NOT give ipecac with ingestions of caustic substances
since they will burn the GI tract and mouth on their way out.
Do NOT answer “toxicology screen.” This takes too long to come back to be useful
and it will not change management. No matter what pills she took, the initial answer
in the first hour of management is to empty the stomach.
Why NOT the gastric lavage?
Gastric lavage with an oropharyngeal hose is not very useful, and most awake
patients do not need this and will not tolerate it. Use gastric lavage in patients with
an acute overdose who have an altered mental status in the first hour after a pill
ingestion. You cannot give ipecac to these patients because they will aspirate.
Perform endotracheal intubation with gastric lavage to protect the airway
when the patient has altered mental status.
Do NOT lavage patients with caustic, acid or alkali ingestion.
After the ipecac, what is the NEXT best step in management?
Activated charcoal
Charcoal is useful in almost all overdoses and is not dangerous in anybody. In
addition, charcoal will even remove drug from the body that has already been
absorbed into the blood stream.
A 25-year-old medical student gets very depressed while preparing for USMLE Step
2. After finishing studying at midnight she takes a bottle of pills at 12:15 am in an
attempt to commit suicide. She removes the label from the bottle so no one can
determine what she took. At 12:30 am she finds that her last practice test score was
87% and she will easily pass. She walks across the street to the ER at 1:00 am to
seek treatment.
The patient is confused, disoriented, lethargic, sleepy, and obtunded and is not thinking so well.
What is the best initial step in the management of this patient?
Naloxone
Thiamine
Dextrose
Although you will want to intubate the patient to perform gastric
lavage, you must FIRST give the naloxone, thiamine, and dextrose. If
the patient took an opiate or is hypoglycemic she will awaken
immediately. You will NOT have to do lavage then because the
problem will have been solved.
She awakens after being given the naloxone, dextrose and thiamine.
What is the NEXT best step in management?
Activated charcoal for the same reasons as described above.
After this management, then toxicology and specific drug levels are used to
determine the specific etiology of the overdose.