March 26 - NBME

Question 1

Blood gas in chronic bronchitis

Answer 1

Lung is poorly ventilated due to mucus plugging and shunting resulting in low pO2 and high pCO2. Bicarb goes up to compensate for respiratory acidosis.

Question 2

Methylphenidate

Answer 2

Ritalin. CNS stimulant for ADHD and narcolepsy

Question 3

Sertraline

Answer 3

SSRI

Question 4

T4/5 dermatome

Answer 4

nipple

Question 5

T10 dermatome

Answer 5

umbilicus

Question 6

L1 dermatome

Answer 6

inguinal area

Question 7

L4 dermatome

Answer 7

anterior knee

Question 8

S1/2 dermatome

Answer 8

back of thigh (via sciatic nerve)

Question 9

Alcoholic hepatitis: pathophysiology and pathology

Answer 9

Pathophysiology: Oxidative damage due to increased CYP450 resulting in increased ROS and increased toxic metabolites. Inflammation due to endotoxins from the gut going to the liver via the portal tract.

Pathology: centered around the portal vein. Mallory bodies are classic due to increased acetaldehyde which causes lipid peroxidation and cytoskeletal damage. Body is intracellular accumualtion of intermediate filaments

Question 10

Gout vs pseudogout crystals

Answer 10

Gout: negatively birefringent monosodium urate crystals
Pseudogout: positively birefringent calcium pyrophosphate crystals

Question 11

Calcium kidney stones

Answer 11

Can be calcium oxalate or calcium phosphate. Radioopaque stones. Most commonly formed due to increased urine Ca++ with normal serum Ca++.

Can also be seen due to increased oxalate. In Crohns or gastric bypass, fat that doesn’t get absorbed binds Ca++ leaving oxalate free to be absorbed. Vitamin C abuse also increases oxalate.

Question 12

Struvite kidney stones

Answer 12

Ammonium, magnesium, and phosphate stones. Seen in the setting of a UTI with urease positive bacteria (proteus, staph, kelbsiella). These bacteria create alkaline urine that allows them to form.

Can form staghorn calculi: stone material precipitates out and forms cast of renal pelvis and calcies. These require surgery; failure to treat forms a nidus for recurrent infection.

Question 13

Uric acid kidney stones

Answer 13

Causes: increased uric acid such as in gout, leukemia, myeloproliferative disease. Acidic urine

Radiolucent stones that are not visible on x-ray. Form in distal tubule and collecting duct which have the lowest pH. Treated medically, not surgerically

Question 14

Cystine stones

Answer 14

Seen in kids with cystinuria who cannot absorb cystine in their tubules. Can form staghorn calculi

Question 15

Ascites treatment

Answer 15

Spironolactone is first line: gets at the pathophysiology of inappropriate RAAS activation due to perceived volume depletion.

Add loop diuretic if ineffective

Question 16

Pseudohyponatremia

Answer 16

Caused by hyperglycemia: increased glucose in the blood pulls water into the vasculature, diluting out sodium

Question 17

Hypocalcemia presentation

Answer 17

muscle spasms/tremor/tetany
increased blood pressure
arrhythmias
confusion
seizures

Question 18

Hypercalcemia presentation

Answer 18

N/V, anorexia, increased thirst
confusion to acute psychosis
kidney and biliary stones
bone pain and muscle weakness
polyuria leading to dehydration

Question 19

Fibromuscular dysplasia

Answer 19

Narrowing and weakness of blood vessels. Risk of dissection and aneurysm. Classically a string of beads appearance of renal vein in middle aged woman. Causes HTN and renal bruit

Question 20

NSAID nephropathy

Answer 20

Prostaglandins dilate the afferent arteriole. Angiotensin II is still constricting the efferent, so RPF goes down.

Question 21

Normal saline

Answer 21

0.9% saline

Question 22

Omeprazole interactions

Answer 22

CYP450 inhibitor: increases levels of many drugs, decreases activation of clopidogrel

Decreases stomach acidity which decreases azole absorption

Question 23

Glucocorticoids: mechanisms

Answer 23

1. inhibits NFkappaB decreasing production of inflammatory cytokines
2. inhibits formation of inflammatory mediators by inhibiting phospholipase A2 and COX
3. Decreases adhesion molecules, decreasing leukocyte emigration
4. Decreases T cell activation via inhibition of cytokine production

Question 24

Classification of burns

Answer 24

First degree: only epidermis; skin red and dry
Second degree: epidermis and dermis; skin red, moist, blistering, very painful
Third degree: extends to hypodermis; painless; patchy appearance

Question 25

Glue sniffing symptoms

Answer 25

Dizziness, loss of coordination, slurred speech, hallucinations

Question 26

Vascular supply to female pelvis

Answer 26

Uterine a, vaginal a, and internal pudendal all branch off of internal iliac a. Internal pudendal gives rise to inf rectal and supplies the clitoris/penis and labia/scrotum

Question 27

Phases of clinical trials

Answer 27

I: small number of healthy people; assess safety
II: small number with the disease; assess efficacy
III: large number randomly assigned; assess if better than what’s already on the market
IV: post-market surveillance; look for long term outcomes/side effects