HY USMLE Q #394 – Pathology / Internal medicine — Transcript

Full transcript

1. 0:00how's it going guys so this is a
2. 0:01challenging question for both step one
3. 0:02and step two it's a bit fact tweety uh
4. 0:05we could discuss this for 45 minutes but
5. 0:07i'm not gonna waste our [ __ ] time
6. 0:08okay we're not gonna discuss superfluous
7. 0:10horseshit that has no relevance to your
8. 0:12score so before we get started please
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12. 0:18underscore medical mehlman underscore
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16. 0:25now start the [ __ ] question so 55
17. 0:28year old dude he has rheumatoid
18. 0:29arthritis and diabetes and he's on a
19. 0:31bunch of meds lisinopril metformin
20. 0:32glybenclimide simvastatin aspirin he
21. 0:35drinks four beers every evening vitals
22. 0:37are within normal limits and he's got an
23. 0:39abdominal brewery and his serum studies
24. 0:42are shown so
25. 0:44you will have the normal lab values
26. 0:46available to you on the exam but you
27. 0:48have to take your [ __ ] training
28. 0:49wheels off okay you're gonna be a doctor
29. 0:51learn your [ __ ] lab values stop your
30. 0:53crying
31. 0:54so his sodium is normal at 140 the range
32. 0:56is 135 to 145 potassium normal at 3.8
33. 1:00the range is 3.5 to 5. chloride should
34. 1:03be 95 to 105. his is quote-unquote
35. 1:06elevated at 108. i say quote-unquote
36. 1:08elevated because if your chloride is out
37. 1:10of the normal range it doesn't mean
38. 1:13anything for usmle almost always okay
39. 1:16it's just we make note that 95 to 105 is
40. 1:19what is what we'd expect
41. 1:21but it doesn't matter if your chloride
42. 1:24is uh low or high on usmle
43. 1:26so bicarb is low at 20 no equivalence
44. 1:29per liter normal range 22-28 glucose is
45. 1:32impaired fasting he's got diabetes we
46. 1:34don't expect his glucose to be normal
47. 1:37okay but
48. 1:3872-99 is what we expect for fasting 100
49. 1:41to 125 is impaired fasting glucose 126
50. 1:44or greater on two separate occasions for
51. 1:46fasting is diabetes medicine he's
52. 1:47already diagnosed with diabetes so the
53. 1:49question's asking the most likely
54. 1:50explanation of these findings and you
55. 1:51say well what am i [ __ ] looking at
56. 1:53like what do you mean what findings well
57. 1:55he's got low bicarb okay that's what
58. 1:57he's got here which would be a metabolic
59. 1:59acidosis
60. 2:01so we say well what could cause his
61. 2:03metabolic acidosis i mean he's on
62. 2:05various medications lisinopril and ace
63. 2:07inhibitor can cause hyperkalemia it can
64. 2:10cause a dry cough
65. 2:11uh doesn't classically cause metabolic
66. 2:13acidosis in theory if you're inhibiting
67. 2:15ras you could retain protons distally
68. 2:18not classically associated with
69. 2:20metabolic acidosis metformin causes
70. 2:22lactic acidosis i mean this is a known
71. 2:24thing okay so this would decrease your
72. 2:26bicarb we're not jumping to conclusions
73. 2:28yet we're just uh
74. 2:30making contemplations so metformin can
75. 2:33cause lactic acidosis glycomide i'd say
76. 2:3699 of students seeing this clip have no
77. 2:38[ __ ] idea what that is this is uh
78. 2:40similar to glyburide it's a sulfonylurea
79. 2:44which is an insulin secretog
80. 2:46libenclamide is classically known in the
81. 2:49literature for causing hypoglycemia
82. 2:52very [ __ ] rarely used okay but when
83. 2:55we consider the notion of sulfonylureas
84. 2:58inducing hypoglycemia glybenclimide is
85. 3:02the quote unquote famous one for doing
86. 3:04that
87. 3:05statins i mean obviously hepatotoxicity
88. 3:07myosinus aspirin can cause
89. 3:10a mixed respiratory alkalosis metabolic
90. 3:13acidosis as well as tinnitus
91. 3:15so
92. 3:16we just go through our answers here
93. 3:18choice alcohol use wrong [ __ ] answer
94. 3:20there's no reason to assume it alcohol
95. 3:23could cause lactic acidosis
96. 3:25uh and we say is this lactic acidosis
97. 3:28right i mean it's a separate answer
98. 3:29choice here and so as i pre-faced with i
99. 3:32was going to cut to the chase so why
100. 3:34don't i just [ __ ] do that right
101. 3:37we need to calculate anion gap
102. 3:40so anion gap on usmili is going to be
103. 3:44you add the chloride in the bicarb okay
104. 3:47you take that number in this case 128
105. 3:50and then you subtract it from the sodium
106. 3:54and in this case that would be 12.
107. 3:56now normal anion gap is 8 to twelve
108. 4:00if you are 13 or greater your elevated
109. 4:02anion
110. 4:04mud piles are diagnoses for elevated
111. 4:06anion gap metabolic acidosis methanol
112. 4:08toxicity uremia which is renal failure
113. 4:11dka
114. 4:12fenformin some weird drug you don't need
115. 4:14to know
116. 4:15um i is iron tablets slash isoniazid l
117. 4:19lactic acidosis e ethylene glycol which
118. 4:21is antifreeze s salicylates which is
119. 4:23aspirin so those are all ana high anion
120. 4:27got metabolic acidosis 13 or greater
121. 4:29this is 12. so let's look at our answer
122. 4:32choices here again
123. 4:34lactic acidosis salicylate toxicity
124. 4:37wrong [ __ ] answers because they're
125. 4:39mud piles okay
126. 4:41glibenclamide
127. 4:43we don't have hypoglycemia here okay
128. 4:45it's just a distractor
129. 4:47when students don't know an answer they
130. 4:49choose weird sounding [ __ ] never heard
131. 4:50of glibenclamide before in my entire
132. 4:52life maybe that's right it's the wrong
133. 4:53[ __ ] answer
134. 4:54crohn disease a completely outrageous
135. 4:57answer uh but if this were a cubink and
136. 4:59we were to see stats you'd probably get
137. 5:00like four percent of people just
138. 5:02randomly choosing that for whatever
139. 5:03reason uh there's nothing about diarrhea
140. 5:05here zero reason to suspect ibd it's
141. 5:07just in there as a miscellaneous
142. 5:09distractor
143. 5:11now renal tubular acidosis
144. 5:14this is not one of the mud piles okay
145. 5:17and this is classically a normal anion
146. 5:19gap
147. 5:20metabolic acidosis
148. 5:22now this is sort of what you need to
149. 5:24know for us mla students will fixate
150. 5:28about
151. 5:29omg rta type one two four the mechanisms
152. 5:32and like you know the urine findings for
153. 5:34ph and all this [ __ ] horseshit it's
154. 5:37not my opinion it's a matter of what
155. 5:40have i observed across thousands of
156. 5:42questions on step one and step two level
157. 5:45nvme exams
158. 5:46and it's been to my observation that the
159. 5:48way usmle assesses renal tubular
160. 5:52acidosis rta is they give you a vignette
161. 5:54like this where it's it's fairly vague
162. 5:57you're not really sure what's going on
163. 5:59and then when you have to try to
164. 6:01eliminate you're going to calculate the
165. 6:03anion gap and it will be normal okay 12
166. 6:06is considered normal
167. 6:07so you eliminate the answers it's a
168. 6:09diagnosis of exclusion on usmla we've
169. 6:12eliminated lactic acidosis and
170. 6:14salicylates okay so it's aspirin we've
171. 6:16eliminated those because they're mud
172. 6:17piles we've eliminated glybenclimide
173. 6:20alcohol if anything would cause lactic
174. 6:22acidosis these are the same answer and
175. 6:23the wrong [ __ ] answer crohn's disease
176. 6:25outrageous and we're left with rta it's
177. 6:27a diagnosis of exclusion
178. 6:29okay i mean we could articulate the
179. 6:32possibility of like causes of rta i mean
180. 6:35could it be diabetes could it be things
181. 6:37like multiple myeloma children syndrome
182. 6:39fanconi
183. 6:40uh syndrome okay so
184. 6:43there's different causes but what usmle
185. 6:46cares about how they actually assess it
186. 6:48without wasting our [ __ ] time is just
187. 6:51you're gonna get a relatively vague
188. 6:53vignette
189. 6:54and you're gonna calculate the anion gap
190. 6:56as normal okay and you're left with rta
191. 6:59once again in recapitulation you're
192. 7:01going to take chloride plus bicarb add
193. 7:03them together you take that number and
194. 7:04you subtract it from sodium 8 to 12 is
195. 7:07normal if it's 13 or greater that's
196. 7:09elevated and that's going to be one of
197. 7:10the mud piles
198. 7:12you know the deal i'm going to continue
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201. 7:16and i appreciate your time that's it