Magnesium and Potassium

Question 1

normal Mg level

Answer 1

1.8-2.5

Question 2

Where is 2/3rds of magnesium located in the body?

Answer 2

BONES

Question 3

What is the major regulator of Mg in the body?

Answer 3

kidneys

Question 4

What are some GI causes of hypomag?

Answer 4

• malabsorption, steatorrhea (MCC)
• fistulas
• nonadequate intake (bad TPN, prolonged fasting)

Question 5

What kind of subtstance abuse is a common cause of hypomag?

Answer 5

ALCOHOLISM

Question 6

What renal causes of hypomag?

Answer 6

• SIADH
• diuretics
• Bartter syndrome
• drugs: gentamicin, amphotericin B, CISPLATIN!!!
• renal transplant

Question 7

Symptoms of hypomag

Answer 7

1. marked neuromuscular and CNS HYPERirritability (twitching, weakness, tremors, hyperreflexia, seizures, AMS)
2. hypocalcemia (due to decreased release of PTH when Mg is low)
3. hypokalemia (Mg and K follow each other)
4. ECG changes (prolonged QT, T-wave flattening, torsades eventually :(

Question 8

Treatment hypomag?

Answer 8

mild - oral (Mg oxide)

severe - parenteral (Mg sulfate)

Question 9

Causes of HYPERmag

Answer 9

1. renal failure (MCC)
2. burns/trauma/surgical stress
3. excessive intake (laxatives/antacids/Mg sulfate during pre-eclampsia) while kidney isn’t working as well
4. rhabdomyolisis
5. adrenal insufficiency

Question 10

Clinical features of HYPERmag

Answer 10

• progressive loss of DTR (CLASSICALLY FIRST SIGN)
• nausea, weakness
• facial paresthesias
• ECG changes that resemble hyperkalemia (increased PR, QRS widening, peaked T waves, sinusoidal pattern)
• somnolence -> coma -> death from resp/card arrest

Question 11

Treatment of hypermag

Answer 11

• withhold any Mg administration
• IV calcium gluconate
• saline/furosemide
• dialysis or intubation if needed

Question 12

Normal K

Answer 12

3.5 - 5.0

Question 13

Causes of hypokalemia

Answer 13

1. GI losses (vomiting, diarrhea, excessive sweating, malabsorption, laxatives/enemas)
2. Renal losses (diuretics, Bartter syndrome renal tubular/parenchymal disease, primary/secondary hyperaldosternoism, excessive glucocorticoids)
3. drugs - Bactrim, amphotericin B, epinephrine (watch out for hypokalemia in trauma patients, since hypokalemia can occur due to increased epinephrine levels)

Question 14

Clinical features of hypokalemia

Answer 14

1. arrhythmias (prolongs normal cardiac conduction)
2. muscular weakness, fatigue, paralysis, muscle cramps
3. decreased DTR
4. paralytic ileus
5. polyuria/polydipsia
6. n/v

Question 15

You should always monitor K levels when giving a patient what cardiac medication?

Answer 15

DIGOXIN!!!!!

esp when giving it for CHF (since these patients are also on diuretics)…potentially could WORSEN the hypokalemia and makes patient more vulnerable to digoxin toxicity

Question 16

What ECG changes can you see with HYPOkalemia

Answer 16

flattened T waves -> inverted, U waves

Question 17

How to work up hypokalemia

Answer 17

check K level -> r/o lab error, redistribution (insulin, epi, metabolic alkalosis) -> check urine K -> check ABG

Question 18

hypokalemia, urine K< 20 = extrarenal loss, normal acid base

Answer 18

• decreased K intake
• laxative abuse
• excessive sweating

Question 19

hypokalemia, urine K < 20=extrarenal loss, metabolic acidosis

Answer 19

GI causes

• diarrhea
• fistula
• villous adenoma

Question 20

hypokalemia, urine K > 20 = renal loss, metabolic acidosis

Answer 20

RTA, DKA, acetazolamide, ureterosigmoidostomy

Question 21

hypokalemia, urine K > 20 = renal loss, metabolic alkalosis

Answer 21

FIX THE DAMN METABOLIC ALKALOSIS THAT’S WHAT’S MAKING HIM HYPOKALEMIC

remember alkalosis - shifts K into cells
acidosis - pulls K out of cells

Question 22

How to treat hypokalemia

Answer 22

oral KCl (safest method)  or IV KCl (max 10meq/hr in peripheral, 20meq/hr in central line) (when more severe, but this also burns!!)
- administer 10 mEq of KCl to raise K up 0.1 pts

treat underlying disorder, also make sure to correct any coexisting hypomag since Mg and K go together

Question 23

What can cause pseudohyperkalemia

Answer 23

• prolonged use of tourniquet without fist clenching

- hemolyzed sample that wasn’t processed quickly enough

Question 24

Clinical features of hyperkalemia

Answer 24

• arrhythmias
• muscle weakness, flaccid paralysis (rare)
• decreased DTR
• n/v, intestinal colic, diarrhea, resp failure

Question 25

Sequence of ECG changes in hyperkalemia and what value do you see ECG changes become prominent?

Answer 25

peaked T waves -> QRS widening -> PR prolongation -> loss of P waves -> sinewave pattern -> Vfib!!!!! K>6

Question 26

How to treat hyperkalemia

Answer 26

1. protect the heart! (give CALCIUM GLUCONATE to stablilizes myocardium, decreases excitability)...but watch out if giving digoxin (hypercalcemia predisposes patient to digoxin toxicity) 2. shift K back into cells (INSULIN does this, but also give GLUCOSE to prevent hypoglycemia, also SODIUM BICARB) 3. remove excess K (kayexalate prevents reabsorption in colon, HD in intractable K or in renal failure, furosemide)

Question 27

How to work up hyperkalemia

Answer 27

r/o spurious/pseudohyperkalemia, r/o redistribution, check renal function, check aldosterone

Question 28

What are some conditions/meds that will cause redistribution hyperkalemia

Answer 28

metabolic acidosis, insulin deficiency, B blockers, succinylcholine, digitalis overdose

Question 29

hyperkalemia, normal renal function, low aldosterone

Answer 29

hyporeninemic hypoaldosteronism, Addison's disease, ACE inhibitors

Question 30

hyperkalemia, normal renal function, high aldosterone

Answer 30

``` K sparing diuretics (spirinolactone,amiloride, triamterene) tubular disorders (sickle cell nephropathy, SLE, amyloidosis) ```

Question 31

hyperkalemia, decreased renal function

Answer 31

TREAT RENAL RAILURE