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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?
Digitalis

- 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
(5)*
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
(6)*
1. Cushings (Inc Mineralcorticoid activity)
2. HypoMagnesium
3. Bartter's syndrome
4. Osmotic diuresis (mannitol)
5. Renal tubular acidosis
6. Medications
Dx:
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)
Dx:
Impaired gastric motility, nausea, vomiting, muscle weakness (to paralysis), rhabdomyolysis, atrial + ventricular arrhythmias
HypoK
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
Kayexalate
MCC of HyperK in lab results

What should be done?
Pseudo-HyperK:
falsely elevated measurement due to hemolysis

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

Acidosis

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)*
ROB A K:
Renal failure;
Obstructive uropathies;
Beta-blockers;
Aldosterone deficiency / ACEi;
K-sparing diuretics
Dx:
N/V/D; muscle cramps, weakness, areflexia, tetany, confusion; respiratory insufficiency; arrhythmias, cardiac arrest
HyperK
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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