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Flashcards in Magnesium and Potassium Deck (31):
1

normal Mg level

1.8-2.5

2

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

BONES

3

What is the major regulator of Mg in the body?

kidneys

4

What are some GI causes of hypomag?

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

5

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

ALCOHOLISM

6

What renal causes of hypomag?

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

7

Symptoms of hypomag

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)
3. ECG changes (prolonged QT, T-wave flattening, torsades eventually :(

8

Treatment hypomag?

mild - oral (Mg oxide)
severe - parenteral (Mg sulfate)

9

Causes of HYPERmag

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

10

Clinical features of HYPERmag

- 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

11

Treatment of hypermag

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

12

Normal K

3.5 - 5.0

13

Causes of hypokalemia

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)

14

Clinical features of hypokalemia

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

15

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

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

16

What ECG changes can you see with HYPOkalemia

flattened T waves -> inverted, U waves

17

How to work up hypokalemia

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

18

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

- decreased K intake
- laxative abuse
- excessive sweating

19

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

GI causes
- diarrhea
- fistula
- villous adenoma

20

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

RTA, DKA, acetazolamide, ureterosigmoidostomy

21

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

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

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

22

How to treat hypokalemia

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

23

What can cause pseudohyperkalemia

- prolonged use of tourniquet without fist clenching
- hemolyzed sample that wasn't processed quickly enough

24

Clinical features of hyperkalemia

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

25

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

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

K>6

26

How to treat hyperkalemia

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)

27

How to work up hyperkalemia

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

28

What are some conditions/meds that will cause redistribution hyperkalemia

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

29

hyperkalemia, normal renal function, low aldosterone

hyporeninemic hypoaldosteronism, Addison's disease, ACE inhibitors

30

hyperkalemia, normal renal function, high aldosterone

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

31

hyperkalemia, decreased renal function

TREAT RENAL RAILURE