Disorders of Potassium: Physiology Flashcards
What is the predominant intracellular cation in the body?
Potassium (( K^+ ))
High intracellular concentration of ( K^+ ) is crucial for cellular functions.
What is the normal intracellular concentration of potassium in mEq/L?
140–150 mEq/L
In blood, normal concentration is 3.5–5 mEq/L.
What is kaliuresis?
K^+ excretion in the urine
It parallels dietary intake.
What are the three mechanisms of potassium reabsorption in the proximal tubule?
- Solvent drag
- Diffusion
- Active transcellular transport
What percentage of filtered potassium is reabsorbed by the proximal tubule?
60–80%
This occurs before reaching the distal nephron.
Which segments of the distal nephron participate in potassium secretion?
- Distal convoluted tubule
- Connecting tubule
- Cortical collecting duct
What factors influence potassium excretion?
- Dietary ( K^+ ) intake and plasma ([K^+])
- Urine flow rate and ( Na^+ ) delivery
- Hormones
- Acid–base balance
- Anions
- Diuretics
Define hypokalemia.
Plasma ([K^+] < 3.5 , ext{mEq/L})
Normal plasma ([K^+]) is generally between 3.6 and 4.9 mEq/L.
What is the prevalence of hypokalemia in peritoneal dialysis patients?
5.4 to 27.9%
This is higher than in individuals with normal kidney function.
What are the five major categories of causes of hypokalemia?
- Dietary
- ( K^+ ) uptake by cells (transcellular)
- Kidney loss
- Gastrointestinal loss
- Skin loss
What is the mechanism behind familial hypokalemic periodic paralysis?
Movement of ( K^+ ) from extracellular fluid to intracellular fluid
It is an autosomal dominant condition.
What is the gold standard for diagnosing familial hypokalemic periodic paralysis?
Genetic test in the context of symptoms
What are the clinical manifestations of hypokalemia?
- Skeletal muscle: weakness, tetany, cramps, paralysis
- Smooth muscle: ileus, constipation, urinary retention
- Cardiovascular: abnormal EKG changes, arrhythmias, hypertension
What is the preferred treatment for mild-to-moderate hypokalemia?
Oral KCl (40–80 mEq/day)
Severe hypokalemia may require immediate intravenous treatment.
True or False: Hyperthyroidism or high carbohydrate intake can precipitate paralytic attacks in hypokalemic periodic paralysis.
True
Fill in the blank: The primary route for potassium excretion is the _______.
kidney
What is the normal range for plasma potassium concentration in mEq/L?
3.5–5 mEq/L
What is the consequence of pseudohypokalemia?
Can present with false hypokalemia due to ( K^+ ) uptake by leukocytes in leukemia
