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Comment of the Week

After the cuff is tied, the cells and tissue distal to the cuff will continue consuming ATP (ATP->ADP), but no fresh blood will be delivered to “clear” what will be an accumulating amount of ADP and other metabolites. ADP (=Adenosine) is itself a proxy of consumption and drives vasodilation of arteries! (Evolution is smart!) Increasing ADP/Adenosine in a “local environment” is a signal to the body that a lot of consumption is occurring there; thus, arteries and arterioles naturally dilate to increase blood flow rates and “sweep away” metabolic byproducts.

          —drdoom, nbme24/Block 3/Question#2

Lol of the Week

Which of the following reasons is why this question is bull?

1) Using the word "cyclic" instead of tricyclic for clarity

2) Knowing all of epidemiology of all drugs

3) having to reason out that anticholinergic effects are probably the worst over alpha1 or H1 effects to no certainty.

4) The crippling depression of studying for days-to-weeks on end to probably do average on the test.

          —seagull, nbme22/Block 2/Question#36

Help your fellow humans! (see more)

neovanilla asks:
The crux of the question is asking, if the patient feels decreased pain (which is driven by opioid molecules; that's why opioids are administered as painkillers), then how do you stop the inhibition? An opioid antagonist (naloxone is the only one that is an antagonist) help answer!
neovanilla  wrong answers: b-endorphin - an endorphin and ACTH hormone (similar to ACTH, POMC) that can bind to the µ-opioid receptor Enkephalin - a neurotransmitter involved in the indirect basal ganglia pathway (along with GABA); it can also bind to delta-opioid receptors Morphine - an opioid agonist (used for pain relief) Oxycodone - Another opioid agonist (~same potency as morphine)
dartosfascia asks:
Why would you give GMCSF to someone with AML?? Isn't the whole goal of treatment to knock out the granulocytes? I feel like giving someone GMCSF after they were JUST treated for AML is asking for a relapse but what the hell do I know. help answer!
drdoom  The problem in AML (acute myeloid leukemia) is that precursor cells “get stuck” on their way to becoming (mature) granulocytes. Giving GM–CSF “pushes” them toward a more differentiated state and, because they divide as they mature, the cells become vulnerable to drugs that disrupt cell division (replication): “Granulocyte–macrophage colony-stimulating factor (GM–CSF) can stimulate proliferation of leukemic blasts and sensitize these cells to the cytotoxic effects of S-phase–specific drugs.” https://www.nature.com/articles/2402368
sammyj98 asks:
maybe I overthought this one, but doesn't she have free air in the bottom left? Or is that the bottom of the pleural space... help answer!
ibestalkinyo  That's probably the most inferior portion of the right lung
pg32 asks:
Can anyone explain why the lipase concentration is so high if there is an issue with LPL in hyperchylomicronemia? help answer!
garima  due to pancreatitis
neovanilla  ELI5?
jinzo asks:
A - nucleus ( with nucleolus inside ) B - mitochondria C - RER ( you can see attached ribosomes ) D - ?? may be lysosomes E - glycogen granules help answer!
rainlad asks:
How do we explain the bruit in this case? Also why isn't it left artery aneurysm? That seems like it would better explain the bruit help answer!
gdupgrant  The bruit is basically just turbulent flow, which is most commonly caused by artery narrowing. I was just reading https://emedicine.medscape.com/article/463015-clinical on renal artery aneurysm and it looks like most of the hypertension is actually related to a pre aneurysm stenosis, so i think stenosis is the "better" answer, esp. since the pt has like every risk factor for stenosis. To be honest I had not ever really thought about RAA for this case because bruit over RA has been drilled into my head as renal artery stenosis, but i apprecaite seeing how this is a super reasonable answer - just the stenosis is "more likely"
rainlad asks:
would we be worried about using G-CSF given that he has acute leukemia? would it stimulate growth of his cancer cells? help answer!
suckitnbme  I think we're assuming that we eradicated the leukemia with the chemo. However at the same time a lot of normal stem cells were also killed off so we give GCSF to help recovery especially since they have an infection.
drbravojose asks:
FA 2019 p156 Does anyone know how to differentiate the picture labeled Trypanosoma brucei and cruzi? help answer!
footballa  This question is likely not important for two reason: They're both Trypansomastigotes, so of course they look almost the same. You can differentiate these two species clinically as they have very little clinical similarity in patient presentation. For these reasons there's little to no reason you would be expected to differentiate these two species by histology alone
readit asks:
Why is is not pseudo aneurysm? "Aortic pseudoaneurysms typically occur as a result of trauma +/- intervention, a considered subset of traumatic aortic injury in the majority of cases. They can be acute or chronic." https://radiopaedia.org/articles/aortic-pseudoaneurysm?lang=us help answer!
readit  *same goes for saccular aneurysm, which also is usually 2/2 trauma
samsam3711  In the question stem there is no indication of trauma so it would be hard to just assume that
almondbreeze  see my comment above for marfan syndrome. might help
ilovemypuppies2295 asks:
What makes this coxsackie virus over Adenovirus? Both cause myocarditis which would be seen on autopsy? Is it just more common to get coxsackie? help answer!
drdoom  the general consensus appears to be that Coxsackie is more common than Adenovirus, but i haven’t come across any papers or textbooks that would agree (they only mention “Coxsackie” and “Adenovirus” as associations with myocarditis)
bharatpillai  there specifically is a question on uworld in which a young woman gets viral myocarditis with sore throat and the answer to that is adenovirus. i think thats why many people (including me) got it wrong :(
qfever asks:
Does anyone know what are A, C, D? For C not sure if it's pointing to the ribosomes on RER. (I'm assuming E is glycogen granules based on a comment below!) help answer!
lilyo asks:
Anyone have an idea on how to approach this question? help answer!
gdupgrant  So the thing i think they tried to catch people on was that the SMV Joins with the splenic to become the portal vein and the IMV feeds into the splenic vein. And they want you to know that cecum is midgut, so drained by the SMV. so my approach was automatically eliminate any answer that included IMV or Splenic vein and that left me with only Ileocolic → superior mesenteric → portal → right hepatic branch of the portal
poisonivy asks:
can we consider the overdose as a suicidal attempt? if so... wouldn't she be considered as without decision-making capacity? help answer!
em_goldman  People who are suicidal still have decision-making capacity; it's not equivalent to advanced dementia or other situations where decision making is impaired. Laws vary by state; I know in my state that the maximum time for holding someone against their will is 48 hours unless a court has deemed them incompetent and designated another person as their legal decision maker, including people who are actively suicidal. My understanding of the law as a layperson is that her living will was signed along with people bearing witness to the fact that she was the one who signed it, and it was what she wanted. Ethics aside, it would be almost impossible to prove that she legally initiated a DNR in a state of suicidality that was intense enough to interfere with her decision-making capacity in that moment.
mahitha asks:
Can anyone PLZZ explain how lymes disesa has memory problems and depressed mood? help answer!
drdoom  Chronic inflammation, and the persistent elaboration of cytokines that go along with it, can cause all sorts of unusual and nonspecific problems, including cognitive compromise. (Just imagine how you might feel if you had low-grade fever for, say, a decade.) Patients who have suffered significant cardio- or cerebrovascular “events” report depressed mood following the event. My guess is that the memory problems can be from chronic inflammation or as a result of spirochete vasculitis which, over time, results in a kind of vascular dementia (“multi-infarct”). You see spirochete vasculitis (of the thoracic aorta), as well as vascular dementia, in another famous spirochete, Treponema pallidum, the culprit behind Syphilis.
mrglass asks:
Why would this not be acute transplant rejection leading to ARDS? The creatinine is elevated, and I see any reason why it would be elevated beyond rejection help answer!
sammyj98  I selected the same. I think part of the question wanted us to recognize that the pt was not receiving CMV prophylaxis (hinted that they are getting TMP-SMX but no Gancyclovir) so they're at really high risk for CMV specifically. UpToDate: •Universal prophylaxis with valganciclovir or ganciclovir is typically given to patients at risk for cytomegalovirus (CMV) reactivation (eg, seropositive recipients and those with seropositive donors). The duration of therapy often depends on the type of organ transplanted, the risk status of the patient, and individual institutional practice. Some transplant centers prefer to use a pre-emptive approach (eg, routine CMV viral load monitoring within initiation of treatment when reactivation becomes evident) for specific patient populations. (See 'Cytomegalovirus' above.)
brookly_ asks:
I thought bulimia give rise to metabolic alkalosis ...can someone elaborate ? help answer!
drdoom  Remember, bulimia itself does not mean “purging”; it means “ox-hunger”. It is purging (e.g., intentional vomiting, laxative abuse, diuretic abuse, excessive exercise, or extreme fasting) which creates metabolic disturbance. The type of disturbance depends on your preferred route of “exit”.
divya asks:
okay but where in the question is it asking whether it's intention to treat or per protocol or as treated??? are we to assume its ITT if they don't mention anything or the part of the question that says "primary analysis" the giveway to ITT?? help answer!
kpjk  I had the same doubt. I think if we were to consider "per protocol" then answer would have to be a mash of options A and B. There is no option that would be right for per protocol
mikay92 asks:
Did anyone else find this question painfully poorly written? I spent so long just trying to figure out what the heck they were asking. It's as if they don't want us to do well... help answer!
drdoom  I don’t think the NBME ever “intends” to write an ambiguous or poorly worded stem. What they want to do is write questions whose response choices are not “blatantly obvious” but which do have a single, “most correct” choice. That’s actually surprisingly difficult! If the correct choice were “obvious”, the test would not be doing a good job assessing anyone’s ability to make subtle judgment calls (an important skill, one might argue, in the morass that is the real world); this is also the reason they eschew “buzzwords”, generally. If a stem has two or more choices that are “equally correct”, the same lapse has occurred: they would be failing to assess the capacity to make subtle judgment calls.
drdoom  All that said, please see this perfect metaphorical description of all Step 1 questions: reddit.com/r/step1/comments/4jegfu/took_step_1_wanted_to_share
blueberrymuffinbabey asks:
I got this one wrong, but based on the ITT perspective others mentioned, maybe the "in their primary analysis" part of the question is a tip off. They'd start with including them in the original groups and then do additional analysis to try and tease out the impact? IDK help answer!
diabetes asks:
how is adrenal medulla has ACH nicotinic receptor which are ligand-gated Na/k channeles ? muscarinic ACH receptors are G-protein-coupled receptors. help answer!
gdupgrant  epinephrine acts on alpha or beta adrenergic receptors which are all G protien receptors. muscarinic receptors are also G coupled but Acetyl choline wasnt an answer choice. In the adrenal medulla the chromaffin cells are kinda like modified post ganglionic neurons and have nicotinic receptors.
diabetes asks:
can somebody explain how energy production by glycolysis increased, since aerobic glycolysis produce 32 net ATP,compare to 2 net ATP through anaerobic glycolysis ? help answer!
diabetes  i think the stem should be "energy production by an anaerobic glycolysis "
blueberrymuffinbabey  yeah that's the bit that tripped me up too. i get that there would be increased glycolysis in general to compensate for lack of TCA function but...the fact that it says "energy production by glycolysis" is kind of misleading/confusing.
medninja asks:
This question sounded like botulism, anybody knows why is tetanus? help answer!
hello36654 asks:
so why is "cessation of fast axonal transport" wrong? Don't myelinated axons, by definition, have fast conductance? So demyelinated axons would have "cessation of fast axonal transport", which is the answer A, right? help answer!
diabetes  i think it slows down ,no cessation .
gdupgrant  Because fast axonal transport refers to the transport of vesicles containing neurotransmitters or some kind of cell product up and down microtubules in the axon. It isn't related to actual electrical signal transduction.
hello36654 asks:
I understand why it's lung now, but I picked thyroid gland because often times thyroid tumors press on the parathyroid sitting above, which causes the parathyroids to secrete more Ca...can someone comment if they've read this too? help answer!
paulkarr  I personally have not read that, but I wouldn't be surprised by that fact. I think with these NBME problems though, if you can get the answer within one "step" that should be your choice. Here you can just go Squamous Cell Carcinoma with a direct action on serum calcium levels (via PTHrP). Thyroid requires a few more steps, (assuming your statement is true) so in the eyes of NBME, it ain't gonna be the right choice. Always follow the "KISS" logic!

Recent comments (see more)

... powerfulgarbage made a comment on nbme21/block2/q#2 (A 4-year-old girl is conscious but unable to breathe...)
 +0  upvote downvote
submitted by powerfulgarbage(0)

There was a uworld Q on this. The duration of action of Succinylcholine is determined by its metabolism by plasma cholinesterase. Some people are homozygous for an abnormal plasma cholinesterase, aka "pseudocholinesterase" or "butyrylcholinesterase" (BCHE). People with a homozygous BCHE mutation have delayed metabolism of succinylcholine, mivacurium, heroin, and cocaine.

In these patients, paralysis from succinylcholine can last for hours and you have to maintain them on mechanical ventilation until they can breath on their own

... powerfulgarbage made a comment on nbme21/block1/q#14 (A 21-year-old man is brought to the emergency...)
 +0  upvote downvote
submitted by powerfulgarbage(0)

FA 2020, page 127:

Encapsulated bacteria are opsonized and then cleared by spleen. Asplenic patients have decreased opsonizing ability and an increased risk for severe infections.

They need vaccines to protect against Neisseria meningitidis, Streptococcus Pneumoniae, Haemophilus influenza

mnemonic: "No Spleen Here"

regardless I got this one wrong because of a 50/50 guess between strep and e. coli. I guess they wanted you to recognize that he was at risk for S. pneumonia sepsis and therefore needed to be vaccinated, whereas there's not much you can do to protect him from E. coli other than wash your hands lol

... neovanilla made a comment on nbme20/block2/q#23 (Which of the following changes in the cardiovascular...)
 +0  upvote downvote
submitted by neovanilla(0)

The way I approached the question was to consider what happens 1. When you grow from a baby to a child, and 2. when you grow from a teenager to an older adult. Whatever remained true between both of them was the right answer.

Right answer: The resting BP of a newborn is 65/40 (google), while that of a 1-month old is 95/60. The average adult is higher, with the American Heart Association citing (absurdly, IMO) that "normal" is <120/<80. Nevertheless, the trend is that BP increases as we age, whether we are newborns or old people.

Wrong answers: Development of coronary atherosclerosis: Perhaps due to the American diet it can be argued that the development of atherosclerosis is almost inevitable as you become an older adult. Certainly not true as a baby --> child.

Development of mitral stenosis: Similar reasoning as coronary atherosclerosis; you MAY develop it as an adult (not nearly as common as a buildup of atherosclerotic plaques), but sure, let's say that it can happen. Not true as a baby --> child.

Increased basal heart rate: The opposite is actually true. The basal heart rate of a newborn can easily exceed 150, and that's considered normal. As we age, this heart rate goes down.

Increased cardiac muscle mass: This one was the hardest to work through. It is true that as we age from a baby --> child our heart grows in size. But if we tweak our assumption from before with the American diet, and instead put our patient on a more moderate diet, realistically his heart shouldn't increase in size too much, at least to the point of cardiomegaly.

Increased compliance of arteries: As we become older adults, the compliance of arteries decreases and stiffness increases (careful not to confuse arteries with lungs, which actually do increase in compliance as we age!)

... neovanilla made a comment on nbme20/block2/q#39 (A 29-year-old man comes to the physician because of...)
 +0  upvote downvote
submitted by neovanilla(0)

Reason why it's not E: While it's true that mycoplasma pneumoniae uses sterols for its cell membrane, it's the lack of a target for amoxicillin (peptidoglycan) that renders it ineffective. Classic test technique where they include a right answer but isn't the correct answer

... thirdaid made a comment on nbme22/block1/q#31 (A 60-year-old woman comes to the physician because...)
 +0  upvote downvote
submitted by thirdaid(0)

The initial presentation looks like cancer: weight loss and progressive dyspnea over the course of months in a heavy smoker. Then, the question describes extra-pulmonary symptoms and a paraneoplastic syndrome.

More acutely, there is development of edema of the face and jugular venous distention. Because this is localized to upper body, we should think of a mechanical obstruction to venous flow as opposed to some cardiogenic reason. This is an extra-pulmonary symptom of lung cancer.

[ Superior Vena Cava Syndrome caused by the medial spreading of the tumor. Can be exacerbated in the physical exam by asking patient to raise both arms. ]

Finally, there is a single highlighted lab value -> hyponatremia. Small cell lung cancer can release inappropriate levels of antidiuretic hormone -> SIADH. ADH will retain water and decrease sodium concentration possibly leading to cerebral edema and seizures.

[ Syndrome of Inappropriate ADH (due to small cell carcinoma, a neuroendocrine tumor of the lung) decreases sodium concentration. Paraneoplastic syndrome. ]

In SketchyPath: SVC syndrome is the red balloon near the mediastinum ship and SIADH is the guy trying to carry the water cooler and getting water all over himself.

... thirdaid made a comment on nbme22/block1/q#48 (A 1-year-old boy is found to have an impairment of...)
 +0  upvote downvote
submitted by thirdaid(0)

Phagocytes need to produce hydrogen peroxide from oxygen to be able to undergo the oxidative burst that will kill bacteria.

Hydrogen peroxide can come from:

  • A reaction catalyzed by NADPH oxidase (missing in Chronic Granulomatous Disease)
  • Production of hydrogen peroxide by own infecting bacteria

Hydrogen peroxide can be degraded by catalase in catalase-positive organisms. Without hydrogen peroxide there is no creation of hydroxyl halide radicals and no destruction of the pathogen.

There are two catalase positive organisms in the answers: E. coli and S. aureus. We are more commonly in contact with S. aureus and it is the more common pathogen so that's the answer.

... carotidmassage made a comment on nbme21/block1/q#17 (A 7-year-old girl is brought to a clinic in a...)
 +0  upvote downvote
submitted by carotidmassage(0)

1-letter-abbreviation-accurate mnemonic for essential amino acids:

"MLK eradicated HIV FTW"

M = Methionine

L = Leucine

K = Lysine

H = Histidine

I = Isoleucine

V = Valine

F = Phenylalanine

T = Threonine

W = Tryptophan

P.S. It's MLK Day in the U.S. so perfect time to learn about Martin Luther King Jr.'s biochemistry/infectious disease side hustle.

... moxomonkey made a comment on nbme23/block3/q#17 (A 24-year-old woman comes to the physician because...)
 +1  upvote downvote
submitted by moxomonkey(3)

the lack of Howell jolly bodies in asplenic patients is suggestive of accessory spleen