Eagle_303
Forum Guru
Topics: 77
Posts: 655
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A 45-year-old woman with
Crohn’s disease and a small intestinal
fistula develops tetany during
the second week of parenteral nutrition.
The laboratory findings include
Ca 8.2 meq/L; Na 135 meq/L;
K 3.2 meq/L; Cl 103 meq/L; PO4 2.4
meq/L; albumin 2.4; pH 7.48; 38
kPa; P 84 kPa; bicarbonate 25
meq/L. The most likely cause of the
tetany is
a. Hyperventilation
b. Hypocalcemia
c. Hypomagnesemia
d. Essential fatty acid deficiency
e. Focal seizure
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| docdoc9
Forum Guru
Topics: 63
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hypomagnesemia?
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| Oussama77
Forum Junior
Topics: 9
Posts: 58
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Hey. I found and agree with answer c.
Answer: c- Hypomagnesemia. (Schwartz, 7/e, pp 64-66) Magnesium Deficiency is common in malnourished patients and patients with large gastrointestinal fluid losses. The neuromuscular effects resemble those of calcium deficiency - namely, paresthesia, muscle spasm and ultimately tetany. The cardiac effects are more like those of hypercalcemia. An electrocardiogram therefore provides a rapid means of differentiating between hypocalcemia and hypomagnesemia. Hypomagnesemia also causes potassium wasting by the kidney. Many hospital patients with refractory hypocalcemia will be found to be magnesium deficient.
Often this deficiency becomes manifest during the response t parenteral nutrition when normal cellular ionic gradients are restored.
A normal blood pH and arterial Pco2 rule out hyperventilation. The serum calcium in this patient is normal when adjusted for the low albumin. Hypomagnesemia causes functional hypoparathyroidism, which can lower serum calcium and thus result in a combined defect.
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| dr.wad
Forum Senior
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Posts: 350
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adjusted ca level ..
serum ca + 0.8 * albumin deficit
in this case 8.2 + 0.8 * 1= 9.2 mg/dl
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| nightflight1945
banned
Topics: 32
Posts: 920
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Hyperventilation is the most probable cause. It causes ALKALOSIS (PH=7.48) and reduces the amount of ionized Ca.
Oussama77 : The Blood PH of 7.48 is not Normal at all. Normal Blood PH is : 7.4 +/- 0.02-0.05
The corrected Ca is : 8.2+1.6*0.8=9.5
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| tompat
Forum Elite
Topics: 39
Posts: 362
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yes i think hyperventilation would be the right choice as he has alkalosis and total calcium level is already low because of the low albumin. even though we correct the calcium level more of it will be bound to albumin cuz of more negative charge due to alkolosis.
he also has low PO2 -84 k pa if i m inferring it right.
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| ngaybinhyen
Forum Guru
Topics: 23
Posts: 657
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Would a PCO2 of 38 fit Hyperventilation? pH and HCO3 are heading same direction too.
I'd go for Mg
-t.
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| paheli
It'sAllAboutGoodKarma
Topics: 197
Posts: 2,720
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C
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| WaqasQureshi
Forum Senior
Topics: 5
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yes hypomagnesemia does cause tetany
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| ngaybinhyen
Forum Guru
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Eagle, is the answer C?
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| zx_stien
Forum Senior
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Posts: 164
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the answer is C hypomagnesemia.
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| priya11
Forum Junior
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hey good one!!
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| drms
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Posts: 947
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A
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