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#1
03-02-2012
 USMLE Forums Addict Steps History: Not yet Posts: 175 Threads: 18 Thanked 63 Times in 48 Posts Reputation: 73
Weight calculation

A 70-kg (154-lb) man on a fixed NaCl intake
(200 mmol/day) is given daily injections of a
potent mineralocorticoid hormone for 4 days. He
has free access to water and consumes his usual
caloric intake. Excretion of NaCl is as follows:
Day NaCl (mmol)
1 30
2 90
3 180
4 200
Assuming that 1 L of 0.9% saline contains 150
mmol of NaCl and weighs 1 kg, how much will
this patient weigh (in kg) at the end of day 4?
(A) 66
(B) 68
(C) 70
(D) 72
(E) 74

#2
03-02-2012
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,353 Threads: 94 Thanked 877 Times in 507 Posts Reputation: 890

D) 72

200x4 = 800 --- total intake in 4 days

total clearence is 30+90+180+200 = 500

800 - 500 = 300

300/150 = 2kg
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#3
03-02-2012
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Quote:
 Originally Posted by DocSikorski D) 72 200x4 = 800 --- total intake in 4 days total clearence is 30+90+180+200 = 500 800 - 500 = 300 300/150 = 2kg
thanks alot , I had no idea how to solve this but u added the 2 to his original wt .???

#4
03-02-2012
 USMLE Forums Addict Steps History: Step 1 Only Posts: 122 Threads: 45 Thanked 57 Times in 34 Posts Reputation: 67

Quote:
 Originally Posted by DocSikorski D) 72 200x4 = 800 --- total intake in 4 days total clearence is 30+90+180+200 = 500 800 - 500 = 300 300/150 = 2kg
Stupid question here, but would you not lose 2 lbs so 68?
#5
03-02-2012
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 1,353 Threads: 94 Thanked 877 Times in 507 Posts Reputation: 890

Quote:
 Originally Posted by gear2d Stupid question here, but would you not lose 2 lbs so 68?
NaCl would drag the water with it. (he has access to water)By the same deal as Aldosterone causes hypertension
So you pump the guy up! =)
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#6
03-02-2012
 USMLE Forums Addict Steps History: Step 1 Only Posts: 122 Threads: 45 Thanked 57 Times in 34 Posts Reputation: 67

Quote:
 Originally Posted by DocSikorski NaCl would drag the water with it. (he has access to water)By the same deal as Aldosterone causes hypertension So you pump the guy up! =)
I must be out of it. You are correct. I kept thing excretion and forgot that of that 800 that 300 was still in him.

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