Electrolytes Flashcards
The major cation of extracellular fluid is…
Sodium.
___% of sodium is reabsorbed in the kidney tubules.
85.
Reference range of sodium.
135 - 145 mmol/L.
Conditions associated with decreased sodium levels (hyponatremia).
(1) Diabetic acidosis; (2) Diarrhea; (3) Addison’s Disease; (4) Renal tubular disease.
Conditions associated with increased sodium levels (hypernatremia).
(1) Cushing’s syndrome; (2) Dehydration; (3) Hyperaldosteronism (increased renal reabsorption); (4) Insulin treatment of uncontrolled diabetes.
Method used for sodium measurement.
Ion-selective electrode (ISE).
A direct ISE reading of sodium uses a diluted or undiluted sample?
Undiluted.
A indirect ISE reading of sodium uses a diluted or undiluted sample?
Diluted.
Pseudohyponatremia is defined and caused by…
Pseudohyponatremia an a false decrease of sodium levels that is caused by high levels of triglycerides or protein.
↑↑ protein/triglycerides; ↓ sodium.
The major cation of intracellular fluid is…
Potassium.
Reference range of potassium.
3.5 - 4.0 mmol/L.
What preanalytical factors may cause a false increase in potassium (pseudohyperkalemia)?
(1) Hemolysis; (2) EDTA contamination.
Hypo- or hyperkalemia may cause what conditions?
Heart arrhythmias and/or neuromuscular symptoms.
Hypokalemia conditions include…
(1) Insulin injections; (2) alkalosis; (3) GI losses (vomiting or diarrhea); (4) Hyperaldosteronism; (5) Cushing’s syndrome.
Hyperkalemia conditions include…
(1) Diabetic acidosis (metabolic); (2) Intravascular hemolysis; (3) Severe burns; (4) Renal failure; (5) Addison’s disease.
Testing method for potassium…
Ion-selective electrode.
Major anion of extracellular fluid is…
Chloride.
The function of chloride is…
Maintains hydration, osmotic pressure, and the normal anion-cation balance.
Reference range of chloride.
98 - 106 mmol/L.
Chloride levels generally trend the same direction as ___.
Sodium.
Hypochloremia conditions include…
(1) Diabetic acidosis (excessive acid production); (2) Chronic pyelonephritis; (3) Prolonged vomiting; (4) Aldosterone deficiency.
Hyperchloremia conditions include…
(1) Prolonged diarrhea (excess bicarbonate loss); (2) Renal tubular acidosis; (3) Adrenocortical hyperfunction.
Testing method for chloride is…
Ion-selective electrode.
Sweat chloride testing is elevated in what condition?
Cystic fibrosis; >60 mmol/L.
Describe the anion gap.
Calculation that reflects that differences between unmeasured cations and anions; used as analytical QC for measuring all electrolytes.
If abnormal gaps for multiple patients, suspect problem with electrolyte measurements.
What are the major unmeasured cations for the anion gap calculation?
Calcium, magnesium, and potassium.
What are the major unmeasured anions of the anion gap calculation?
Albumin, sulfate, and phosphate.
What is the calculation of the anion gap WITH potassium?
[(Na)+(K)]-[(Cl)-(HCO3)]
What is the calculation of the anion gap WITHOUT potassium?
(Na) - (Cl) + (HCO3)
Reference range of anion gap (with K).
10-20 mmol/L.
Reference range of anion gap (without K).
7-16 mmol/L.
An increased anion gap is indicative of an increased concentration of what three unmeasured anions?
(1) Ethanol; (2) Ketones; (3) Lactic acid.
A increased anion gap is indicative of an decreased concentration of what two unmeasured cations?
Low serum Mg and Ca.
A decreased anion gap is indicative of a decreased concentration of what unmeasured anion?
Albumin.
A decreased anion gap is indicative of an increased concentration of what three unmeasured cations?
Mg, Ca, and Lithium therapy.
Define osmolality.
The measure of total concentration of dissolved particles in a solution.
Osmolality can be measured directly using what two testing methods?
Freezing point depression and vapor pressure depression.
What is the equation to determine calculated osmolality?
2Na + (Glucose/18) + (BUN/2.8)
A measured osmolality is 10x higher than calculated osmolality indicates the presence of what?
Exogenous unmeasured anions (methanol, ethanol, ketone bodies, etc).
The function of magnesium is…
Calcium channel blocking agent (affects heart).
Magnesium is increased in…
Renal failure.
Magnesium is decreased in…
(1) Cardiac disorders; (2) Diabetes mellitus; (3) Diuretics, alcohol, and other drugs.
Testing methods used for magnesium determination.
Atomic absorption and colorimetric method.
Function of calcium is…
Combines with phosphate in bone.
What three hormones control calcium levels?
(1) PTH; (2) Calcitonin; (3) Vitamin D
Hypercalcemia conditions include…
(1) Hyperparathyroidism; (2) Cancer with bone metastasis; (3) Multiple myeloma; (4) Renal failure.
Hypercalcemia conditions include…
(1) Hypoparathyroidism; (2) ↓ serum albumin; (3) ↓ vitamin D.
Testing methods for calcium include…
(1) Atomic absorption spectroscopy (reference method); (2) Colorimetric method (common); (3) ISE.
What preanalytical factor may cause a false decrease in calcium?
EDTA contamination.
In cases of Tetany, suspect ___ first, then magnesium of potassium.
Calcium.
The majority of phosphate in the body is expressed as phosphorous; laboratory measures ___ only.
inorganic phosphorus (PO4).
Phosphorous has an inverse relationship with ___.
Calcium; as Calcium ↑, phosphorous ↓.
