Glossary of IM Renal Potassium USMLE 2

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Nomal range of Potassium
3.3 - 5.5

(below is hypoK; above is hyperK)
Difference b/t Periodic paralysis of HypoK vs. HyperK
HypoK - presents in teens

HyperK - presents in infancy
What heart drug causes a greater toxicity if patient goes into HypoK?

How is this avoided?

- check K+ regularly
(4)* general ways we can lose potassium (become HypoK)
1. Cellular shift + undetermined mechanisms
2. Inc renal excretion
3. GI losses
4. Sweating
Cellular shift + undetermined mechanisms of HypoK
A Deadly VIBe:

1. Alkalosis
2. Digoxin toxicity correction (w/ digibind)
3. Vitamin B-12
4. Insulin
5. Beta-adrenergics
in Alkalosis, how does each 0.1 increase in pH affect K+?
decreases serum K+ by 0.5 mEq/L
What does insulin do to K+?
drives it into the cells
Etiology of HypoK due to Increased renal excretion mechanisms
1. Cushings (Inc Mineralcorticoid activity)
2. HypoMagnesium
3. Bartter's syndrome
4. Osmotic diuresis (mannitol)
5. Renal tubular acidosis
6. Medications
JG-cell hyperplasia causing increased renin/aldosterone, met alkalosis, HypoK, muscle weakness and tetany; seen in young adults
Bartter's syndrome
(3) GI loss causes of HypoK
1. Vomiting; nasogastric suction

2. Diarrhea; laxative abuse

3. Inadequate dietary intake (anorexia)
Impaired gastric motility, nausea, vomiting, muscle weakness (to paralysis), rhabdomyolysis, atrial + ventricular arrhythmias
What is the Tx for urgent HypoK? (2)

What works faster?

What type of patient must be monitored closely?
give IV + oral potassium simultaneously

- oral works faster

- monitor pt w/ renal failure
At what level should K+ be peri-MI to prevent arrhythmias?
K+ > 4.0
IV infusion of K+ should not exceed what number/hour?

How much does that raise serum K+?
IV no more then 20 mEq/hr

Increases K+ by 0.25 mEq/L
what diagnostic procedure should be performed on patients w/ moderate or severe HyperK?
Stat EKG
The only Tx of HyperK (aside from dialysis) that removes K from the body
MCC of HyperK in lab results

What should be done?
falsely elevated measurement due to hemolysis

Re-run lab test
(4)* causes of ICF to ECF potassium shifting causing HyperK
Heavy exercise


Insulin deficiency

Digitalis toxicity
(3) causes of an increased potassium load causing HyperK
IV potassium supplements

K+ medications

Increased cellular breakdown
Causes of decreased potassium excretion causing HyperK
(3 renal and 3 drugs)*
Renal failure;
Obstructive uropathies;
Aldosterone deficiency / ACEi;
K-sparing diuretics
N/V/D; muscle cramps, weakness, areflexia, tetany, confusion; respiratory insufficiency; arrhythmias, cardiac arrest
EKG changes when potassium equals:
1. 6.5 - 7.5 (3)
2. 7.5 - 8.0 (2)
3. 10 - 12

What does it lead to? (3)
1. Tall, peaked T-waves; short QT; prolonged PR

2. QRS widening; Flat P-wave

3. QRS degrades into SIN wave

leads to: V-fib, complete heart block or asystole
HyperK is most common with what (2) causes
Renal failure

muscle breakdown
What are the Tx of HyperK in order of Stabilize, Shift, Remove?*
Can Get In A Bad K Day:

Stabilize - Calcium

Shift - Glucose + Insulin; Albuterol; Bicarbonate

Remove - Kayexalate; Dialysis
When is calcium contraindicated for HyperK?
if patient is on Digoxin

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