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  #1  
Old 03-21-2012
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Neuro Thirst, Headache, and Nausea after Neurosurgery!

NOTE: this is a USMLE Consult-"inspired" question, so look away if you plan on using USMLE Consult as a measure of your progress.


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A 25-year-old woman undergoes neurosurgery for a subarachnoid hemorrhage after being involved in a motor vehicle collision. Thirty hours after the surgery, she has extreme thirst, headache, and nausea.
Laboratory results:

Blood Studies
White Blood Cell: 5.3*10^3mm3
Red Blood Cell: 4.3* 10^6mm3
Hemoglobin: 9.6 gm/dL
Hematocrit: 28.1
Platelets: 277*10^3mm3
Sodium: 131.mEq/L
Potassium: 4.3 mEq/L
Chloride: 104 mEq/L
CO: 2104 mEq/L
Blood urea nitrogen: 9 mg/dL
Creatinine: 0.6 mg/dL
Blood glucose: 99 mg/dL
Calcium: 9.2 mg/dL
Total Protein: 7.3 gm/dL
Albumin: 4.4 gm/dL
Bilirubin: 0.7 mg/dL
Alkaline phosphatase: 120 IU/L
ALT: 33 IU/L
AST: 16 IU/L

Urinary Data
Volume (since operation): 20 mL
Osmolality: 70 mOsm
pH: 6.0
Specific Gravity: 1.010
Ketones: Negative
Glucose: Trace
Blood: Negative
Protein: Trace
Nitrite: Negative
Leukocyte esterase: Negative


Which of the following is the most likely explanation for her condition?

A. Increased extracellular fluid volume
B. Increased extracellular fluid acid
C. Increased extracellular fluid potassium
D. Increased urinary fluid volume
E. Increased urinary fluid acid
F. Increased urinary fluid potassium

(please explain your choice).
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Last edited by Dr.NickRiviera; 03-21-2012 at 09:17 AM.
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  #2  
Old 03-21-2012
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i will go with C. Increased extracellular fluid potassium
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Old 03-21-2012
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I would go with A) Increased extracellular fluid volume.


However, hemorrhage is an ISOTONIC loss of fluid therefore the osmolarity and Na+ concentration are not changed. The fluid from intracellular compartment moves into the extracellular compartment and can be considered as increased blood or RBC volume.
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Old 03-21-2012
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I guess A...an example of brain surgery causing injury to neurohyphisis..i guess..
So intense thirst..and SIADH..urinary output less..its just a guess,,there are two three findings here which go against my guess though..
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Old 03-21-2012
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Ill go with C

mechanical trauma .. RBCs lysis .... potassium leakage out of RBCs .. !
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Old 03-21-2012
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Default Answer = A

the answer is A.

she developed SIADH after her surgery.
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Old 03-21-2012
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my explanation was way off .. but i guess i got the right answer
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Old 03-22-2012
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Default How bout D.I

How about option D, could it be Diabetes inspidis due 2 damage 2 d relevant structure durin da surgery?

I got 3 points in my favor & 2 against.
points in favor-Thirst, low urinary specific gravity & low urine osmolality
points against it-low serum Sodium & low hematocrit.
can some1 enlighten me wid these?
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Old 03-22-2012
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Urine osmolarity is waaaay low for SIADH

How can we explain that ? !
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Old 03-22-2012
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Its expansion of ECF volume. @ reasons...as previous author mentioned SIADH due to brain tempering in neurosurgery also after major surgery you have increased ADH secretion by default...so SIADH in response to surgical stress and brain trauma..if you have nausea and headache think of increased ICP
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  #11  
Old 03-22-2012
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Quote:
Originally Posted by Joanna View Post
Urine osmolarity is waaaay low for SIADH

How can we explain that ? !
I'm thinking urine Osmolarity would be: 70 mOsm / 20 ml
which is 3500 mOsm/l
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  #12  
Old 03-22-2012
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Yaaaaaaaaaaaaay
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  #13  
Old 03-23-2012
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Default contradictions....

@ BritneySpears,
Urine osmolality does not depend on d quantity, but depends on the body weight (kgs).
In short u donít expect a low osmolality on a small sample, & a high osmolality on a large sample. Rather u expect a low osmolality in babies & high osmolality in adults as normal levels. (ie.depends on body weight)

Low urine output (just 20 ml in 30 hrs post surgery), low serum Sodium, low hematocrit means it could be SIADH

But d contradicting points are
1)One must be thirsty, when there is excess fluid loss from d body (as in Diabetes insipidis), not in SIADH when u Ďve already retained so much of water.

2)In SIADH u should have high urine osmolality & specific gravity as you concentrating the urine limitlessly due to excess ADH. But here ví ve low urine osmolality & specific gravity
Maybe they are errors while framing d qstn. Perhaps Dr.NickRiviera could explain them.
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  #14  
Old 03-23-2012
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^Are you sure you are referring to my post and not Joanna's...? and I think you are agreeing with her...

Anywho... I have been reading and according to a random source: low urine Osmolarity is possible if SIADH happens in a situation of hypovolemia (as in probable this case: motor vehicle accident)

I cannot confirm this though
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Electrolytes-, Nervous-System-, Pathology-, Step-1-Questions

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