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