Disorders of Potassium: Hyperkalemia Flashcards
What is hyperkalemia defined as?
Plasma [K(^+)] > 5.5 mEq/L
What can hyperkalemia lead to if not treated?
It can be fatal
What are the main causes of true hyperkalemia?
- Excessive exogenous load of K(^+)* Decreased cellular uptake* Massive release following cell lysis* Decreased kidney excretion
Define pseudohyperkalemia.
A condition in which K(^+) is released from cells during venipuncture following prolonged application of a tourniquet
What are some causes of pseudohyperkalemia?
- Hemolysis of red blood cells* Increased white blood cells (>100,000 cells)* Increased platelets (>1,000,000 platelets)
What is a benign form of familial pseudohyperkalemia?
Leakage of K(^+) from blood cells in some families
What is a faster measure of circulating [K(^+)]?
Measurement of whole blood [K(^+)]
List some causes of hyperkalemia related to exogenous intake.
- Excess oral intake* High K(^+)-containing foods (fruits, salt substitutes, KCl supplements, etc.)* Herbal medications (horsetail, noni juice, dandelion, alfalfa)
What can cause K(^+) release from cell lysis?
- Gastrointestinal bleeding* Hemolysis* Exercise* Catabolic states* Red cell transfusion* Rhabdomyolysis* Tumor lysis syndrome
What is a mechanism of transcellular shift of K(^+)?
Transfer of K(^+) from ICF to ECF
What is one effect of insulin deficiency on potassium levels?
Decreased cell uptake of K(^+)
What is a condition that can cause decreased kidney excretion of K(^+)?
- Advanced kidney failure (CKD G5)* Hypoaldosteronism* Addison disease* Congenital adrenal hyperplasia* Pseudohypoaldosteronism type I
Name a drug class that decreases aldosterone synthesis.
ACE inhibitors, ARBs, and renin inhibitors
What is hyperkalemic periodic paralysis?
An autosomal dominant disorder characterized by episodic muscle weakness
What are some triggers for hyperkalemic periodic paralysis attacks?
- Exposure to cold* Rest following exercise* High K(^+) intake* Fasting* Emotional stress* Pregnancy* Glucocorticoids
What is the typical treatment for acute attacks of hyperkalemic periodic paralysis?
β2-agonists (salbutamol)
What is the relationship between serum [K(^+)] and mortality in CKD patients?
A U-shaped relationship observed; serum [K(^+)] ≤4.0 mEq/L is associated with higher mortality risk
What should be the first step in diagnosing hyperkalemia?
Check electrocardiogram (EKG)
What factors and conditions predispose to hyperkalemia?
- CKD G4-G5* Acute kidney injury* Heart failure* Diabetes* Volume depletion* Elderly subjects* Metabolic acidosis
What are some clinical manifestations of hyperkalemia?
- Muscle weakness* Paralysis* EKG changes (peaked T waves, etc.)* Hyperchloremic metabolic acidosis
What EKG changes are associated with serum [K(^+)] levels of 5.5–6.5 mEq/L?
Peaked T waves with narrow base
What is a common metabolic effect of hyperkalemia?
Hyperchloremic metabolic acidosis
Fill in the blank: The expected ( U_K/U_{Creatinine} ) ratio in hyperkalemia with normal kidney function is _______.
> 200 mEq/g or >20 mmol/mmol
