frontal
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Q.1 After an emergency repair of a ruptured aortic aneurysm, a 66 yr old man has a urine output of 35 mL in 4 hours; a Foley cath. is still in place. He received 14 units of blood during the op. His temp: 100 F, BP: 104/68, pulse: 126/min. Examination shows diffuse peripheral edema. Heart sounds-normal, lungs- clear, JVP-normal, abdomen-soft. Labs:
Hematocrit: 27% Serum: Na: 143 mEq/L; K: 5 mEq/L, Urine Na: 6 mEq/L
Which of the foll. is the most likely cause of the oliguria? A)heart failure B) Hypovolemia C) Occluded Foley D) Renal artery thrombosis E) Transfusion reaction.
Q.2 Two hours after an uneventful cholecystectomy, a 50 yr old woman has ventricular extrasystoles and a decrease in systolic BP from 110 to 90. ABG analysis on room air shows: pH-7.30, pCO2- 52 mm 52mmHg, pO2-58mmHg. What is the most likely cause of these findings?
A. ALVEOLAR HYPOVENTILATION
B. OCCULT HEMORRHAGE
C. PRIMARY CARDIAC IRRITABILITY AND FAILURE
D. PRIMARY HYPOXEMIA CAUSED BY ANESTHETIC GASES
E. PULMONARY EMBOLUS.
Please explain what option 'C' is about. If possible, please give an explanation for your answer. I've the answers but no explanation.
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| frontal
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No replies?
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| chemamr
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they are hard man!
i will guess, ok?.
1) E? (or d?)
2) D?
not sure, really.
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| DrS
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Q1 is pretty straightforward. The oliguria and presence of urinary Na of 6 are suggestive of prerenal acute renal failure. The history of a ruptured aortic aneurysm with the transfusion of 14 pints of blood obviously suggest that he was obviously severely hypovolaemic which is the most likey cause of his prerenal failure.
Regarding Q2 i'm sorry really cant help you out. No idea what PRIMARY CARDIAC IRRITABILITY AND FAILURE is!!! 
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| chemamr
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1) if itīs a severe hypovolemia: why is there edema?, why is the JVP normal?
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| ARJ
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E) Transfusion reaction
D. PRIMARY HYPOXEMIA CAUSED BY ANESTHETIC GASES
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| chemamr
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well frontal, you have 2 people saying itīs : 1) E; 2) D.
which is the answer? 
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| DrS
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chemamr: he is not hypovolemic now! He was hypovolaemic during surgery which has caused prerenal acute renal failure. That is the cause of his oliguria.
Renal artery thrombosis would not cause oliguria if the other kidney was normal, and transfusion reactions usually occur immediately after transfusion and would have features like fever rashes etc...but i guess its possible. But going from the history I feel hyovolemia is the more likely answer.
Q2 could be either A or D not really sure
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| chemamr
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thank you for your explanation DrS 
letīs wait for the answer and explanation by frontal
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| mani
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1. hypovolemia that led to ARF
2. C due to anesthetic agents
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| frontal
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The answers given are- hypovolemia and alveolar hypoventilation. DrS did a good job on the first one. Any explanation for the edema?
These are usmle questions guys, so we had better know them. Explanation is not available with the answer, but if I find one in the books, I'll surely post.
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| DrS
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Yes frontal, the edema is a real problem in this question, as the BP and tachycardia would suggest that his intravascular compartment is compromised. And in addition if his edema was due to volume overload then his JVP should be elevated as well. Therefore this does not fit the clinical picture?! The usual cause of peripheral edema in the presence of a normal JVP is hypoproteinemia of some cause, however there is no reason to suggest this either.
Anyway I came to the answer by a method of elimination as well as going by the fact that "common things are common" and the commnest cause for oliguria following major surgery is hyovolemia. However the edema and normal JVP do not go together in this situation and indeed is a mystery. Hopefully someone else can shed some light on this issue.
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| chemamr
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 Good work guys!
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