Ch_6 - Nephrology

Question 1

What are normal Mg2+ levels in blood?

Answer 1

1.8 - 2.5 mg/dL

Question 2

Where is most Mg in the body? How much about?

Answer 2

2/3 is in bones, 1/3 is intracellular, 1% is extracellular

Question 3

What are the influences on Mg excretion?

Answer 3

Hormones - Insulin, Glucagon, PTH, Calcitonin, ADH, and steroids

Question 4

About what % of Mg is absorbed in GIT?

Answer 4

30-40% normally, more when Mg levels are low.

Question 5

What is the major regulator of Mg levels?

Answer 5

The kidneys! - has great capacity to reabsorb Mg

Question 6

Hypomagnesemia makes what e- disturbances difficult to treat?

Answer 6

Hypokalemia and Hypocalcemia

Question 7

What are the causes of hypoMg?

Answer 7

GI causes (in)
Alcoholism
Renal causes (out)
Other: postparathyroidectomy, DKA, thyrotoxicosis, lactation, burns, pancreatitis, cisplatin

Question 8

What are the GI causes for hypoMg?

Answer 8

1. Malabsorption, steatorrheic causes (MCC)
2. Prolonged fasting
3. Fistulas
4. Pts receiving TPN w/o Mg supplements

Question 9

What are the renal causes of hypoMg?

Answer 9

1. SIADH
2. Diuretics
3. Barrter’s syndrome
4. Drugs: Gentamicin, Amphotericin B, Cisplatin
5. Renal transplant

Question 10

Clinical features of hypoMg?

Answer 10

1. Neuromuscular and CNS hyperirritability
2. Hypocalcemia sx
3. Hypokalemia sx
4. EKG changes - prolonged QT interval, T wave flat, and ultimately Torsades.

Question 11

Treatment of mild hypoMg

Answer 11

PO Mg (MgO)

Question 12

Treatment of severe hypoMg

Answer 12

parenteral Mg (MgSO4)

Question 13

T/F Physical exam can tell you the etiology of AKI

Answer 13

False, labs can.

Question 14

What two lab studies must be done for most (if not all) AKIs?

Answer 14

U/A and U/S

Question 15

kidney injury is an emergency in which situations? [5]

Answer 15

1. Hyperkalemia
2. metabolic Acidosis
3. Pericarditis (uremia)
4. Fluid Overload
5. Encephalopathy/AMS

Question 16

When AEIOU are present, what do you need to do? [3]

Answer 16

1. make sure resident/attending are informed
2. Arrange for dialysis
3. get EKG for hyperkalemia

Question 17

What do you need to check in the labs for AKI?

Answer 17

Check BUN/Cr ratio first

Question 18

If BUN/Cr > 20:1, what is the likely cause of the AKI?

Answer 18

Pre-renal azotemia; decreased renal perfusion

Question 19

If BUN/Cr ratio is 10:1, what is the likely cause of the AKI?

Answer 19

Intra-renal

Question 20

With suspected kidney injury, which tests should be done?

Answer 20

1. BMP – always repeat and never make decision on 1 reading
2. U/A
3. Renal U/S
4. Uosm, Una, protein:creat ratio

Question 21

Usefulness of 24-hr urine protein in a kidney injury pt?

Answer 21

useless

Question 22

What does rhabdomyolysis show on dipstick?

Answer 22

+ for blood (but no RBCs!!!)

Question 23

What is pre-renal azotemia?

Answer 23

abnormal perfusion to the kidney. The kidney itself is normal and would fxn normally if transplanted into another person

Question 24

BUN:Cr ratio is often ? in pre-renal azotemia?

Answer 24

increased BUN reabsorption leads to > 20:1

Question 25

Common causes of pre-renal azotemia?

Answer 25

Dehydration/Hypovolemia
Hypotension of any kind
CHF, esp after Lasix and diuretics 
Hypoalbuminemia
RAS

Question 26

Classic example of pre-renal azotemia with HTN

Answer 26

Renal artery stenosis