Electrolytes and Lab Values:

Implications for Nursing Practice

 

Sodium (Na+) Sodium levels can be measured by blood sampling or 24hour urine collection. Sodium is the major cation in the extracellular space (outside the cell). Remember, taking a blood sample is akin to measuring the Na+ concentration in the extracellular environment, as circulation is extracellular. Sodium is an integral and vital component of nervous impulse transmission, muscular contraction, and the movement of glucose, insulin and amino acids.

  Along with chloride, sodium contributes to the physiological movement of water. Sodium and water levels are closely interrelated.

HYPONATREMIA

 

Some of the Factors precipitating hyponatremia: 

(serum Na+ less than 135mEq/L)

  • Decreased dietary intake of sodium 
  • Diuretics and various other drugs 
  • Sodium-free IV fluids 
  • Diarrhea 
  • Vomiting or NG aspiration 
  • Excessive oral or IV "H2O" intake
  • Ascites 
  • Peripheral edema 
  • Chronic renal insufficiency 
  • Excessive sweating
Signs and symptoms of hyponatremia:

(remember, Na+ is an integral part of nervous transmission, therefore…you may see symptoms of altered nervous transmission)

  • Confusion 
  • Lethargy 
  • Coma 
  • Stupor

HYPERNATREMIA

 

Some of the factors precipitating hypernatremia:

(usually associated with conditions of fluid loss)

  • Excessive fluid losses (sweating, thermal burns) 
  • Decreased fluid intake 
  • Excessive dietary or IV intake
  • Diabetes insipidus
Signs and symptoms of hypernatremia:
  • Dry mucous membranes 
  • Thirst 
  • Agitation, confusion 
  • Fatigue 
  • Restlessness 
  • Hyperreflexia 
  • Convulsions

Potassium (K+) Potassium levels can be measured by blood sampling or 24hour urine collection. Potassium is a major intracellular cation (within the cells). The difference in concentration between the intracellular environment (150mEq/L) and the extracellular environment (4mEq/L) is vitally important in maintaining the electrical potential of the membrane of the cell.

HYPOKALEMIA

Factors precipitating hypokalemia:
  • Alkalosis
  • Decreased dietary or IV intake
  • Diarrhea or vomiting/diuretics
  • Licorice ingestion!
  • Insulin or glucose administration
  • Calcium administration
  • Aldosterone (increases renal losses)
 Signs and symptoms of hypokalemia:
  • (related to decreased contractility of smooth, skeletal and cardiac muscle)
  • Weakness/paralysis
  • hyporeflexia
  • ileus
  • increased sensitivity to digoxin
  • dysrhythmias (flattened t waves, u waves)  

 

Magnesium - (Normal adult findings = 1.2 - 2.0 mEq/L)

 

Magnesium is an intracellular cation, bound to ATP and therefore an essential component of most metabolic processes. About half of physiologic magnesium is found in bone. Magnesium is also an integral part of carbohydrate and protein metabolism. Neuromuscular functioning is dependent upon magnesium, as are many organ functions. The intracellular elements of magnesium, calcium and potassium are closely linked in terms of physiologic levels so that, reductions in one of the elements corresponds to a reduction in the other elements.

 

HYPOMAGNESEMIA

 

Factors precipitating hypomagnesemia (levels below 1.2mEq/L):

 Malnourishment (either due to malabsorption or maldigestion)

  • Chronic alcoholism
  • Pancreatitis
  • Prolonged IV infusion without Mg++
  • Diabetic acidosis
  • Chronic renal disease (as Mg++ is reabsorbed in the renal tubule)
  • Hypoparathyroidism
  • Hyperthyroidism
  • Hyperaldosteronism
  • Related to toxemia of pregnancy
 Signs and symptoms of hypomagnesemia:

Related to CNS and neuromuscular hyperactivity.

  • Weakness
  • Irritability
  • Tetany
  • ECG changes
  • Delirium
  • Convulsions

 

 

HYPERMAGNESEMIA

Factor precipitating hypermagnesemia (levels above 2.5mEq/L):

 Mostly associated with increased ingestion (such as with Mg++ containing antacids)

  • Renal insufficiency
  • Uncontrolled diabetes
  • Hypothyroidism
  • Addison's disease 
 Signs and symptoms of hypermagnesemia:

Assess for these when administering IV Magnesium sulfate!

  • Flushing/Sweating
  • EKG changes similar to hyperkalemia
  • Lowered BP
  • Decreased deep tendon reflexes
  • Respiratory depression

 

Calcium - Normal adult blood findings:

TOTAL = 9.0 - 10.5 mg/dl or 2.25- 2.75 mmol/L

IONIZED = 4.5 - 5.6mg/dl or 1.05 - 1.30 mmol/L

(Values for elderly and child slightly decreased)

Calcium is either bound to protein (albumin mostly) or exists in an ionized form in the blood. The proportion of bound calcium to ionized is about 50:50. As calcium is bound to albumin, the levels of calcium will fluctuate along with serum albumin levels. That is, if the patient has a low albumin level (such as may be seen with malnourishment) the calcium level will also be low.

The ionized form of calcium is unaffected by levels of albumin. There are several methods for measuring the level of ionized calcium, which may or may not be available depending upon the availability of lab equipment.

 

HYPOCALCEMIA

Factors precipitating hypocalcemia:

CRITICAL VALUE < 6mg/dl (may lead to tetany)

 Hypoalbuminemia

  • Intestinal malabsorption and chronic Malnutrition states (alcoholism)
  • Renal failure
  • Rhabdomyolysis and large blood losses
  • Alkalosis
  • Acute pancreatitis (due to saponification of fat)
  • Rickets and Vitamin D deficiency
  • Osetomalacia
  • Hyperphosphatemia secondary to renal failure
  • Some drugs: aspirin, anticonvulsants, loop diuretics, magnesium salts, estrogens, albuterol. And oral contraceptives
 Signs and symptoms of hypocalcemia:

 

Hypocalcemia likely linked with hyperphosphatemia

  • Severe hypocalcemia may lead to tetany (levels below 6 mg/dl)
  • Altered mental status
  • Cardiac arrythmias
  • Muscular spasms and cramping in the extremities
  • Chvostek's sign (facial muscle spasm on tapping the area over the facial nerve)
  • Hyperreflexia
  • Bronchospasm, laryngospasm, strider
  • Seizures
  • Paresthesia around the mouth
  • Signs and symptoms may be masked by underlying pathology

HYPERCALCEMIA

Factors precipitating hypercalcemia:

Most commonly caused by hyperparathyroidism, which leads to increased intestinal absorption, decreased renal excretion and increased bone resorption of calcium.

Malignancy is the next most common cause of hypercalcemia by either tumor metastasis to the bone destroying the bone or by cancer induced parathormone-like action.

Vitamin D intoxication

 Signs and symptoms of hypercalcemia:

Signs and symptoms may be seen due to primary disease or causative agent.

  • Agitation, personality changes
  • Anorexia, nausea, vomiting
  • Bone pain
  • Confusion, coma
  • Hyporeflexia, lethargy, weakness
  • Cardiac conduction changes
  • Thirst

 Calcium levels may be measured by 24 hour urine collection as well with normal findings varying with the patient's diet.

"Normal diet" values = 100 - 300mg/day or 2.50 - 7.50 mmol/day ; "Low calcium diet" values = 50 - 150 mg/day or 1.25 - 3.75 mmol/day

 

 

Chloride - Normal serum findings = 90 - 110 mEq/L or 98 - 106 mmol/L

 

Chloride is the major extracellular anion. It is secreted by the stomach mucosa as hydrochloric acid (HCl) aiding in digestion. Chloride acts as a buffer and aids in maintaining acid-base balance and takes part in the exchange of oxygen and carbon dioxide from hemoglobin in red blood cells. As carbon dioxide increases, bicarbonate moves from the intracellular to the extracellular space while chloride moves into the cell to maintain electrical neutrality. Chloride shifts follow sodium shifts so hypochloremia is usually accompanied by hyponatremia.

 

HYPOCHLOREMIA

Factors precipitating hypochloremia:

 May occur with hypokalemia, as potassium is lost as potassium chloride.

  • Low salt diet
  • Chronic respiratory acidosis
  • Prolonged diarrhea, vomiting, gastric suctioning
  • Diaphoresis
  • Drugs: that cause kidneys to preferentially excrete chloride such as thiazide diuretics

Drugs: aldosterone, bicarbonates, corticosteroids, loop diuretics

 Signs and symptoms of hypochloremia:

As shifts in chloride parallel shifts in sodium, you will see symptoms of hyponatremia as well as the following: 

  • Muscle weakness
  • Twitching
  • Tetany
  • Slow, shallow respirations
  • Respiratory arrest

  HYPERCHLOREMIA

Factors precipitating hyperchloremia:
  • Fluid losses, dehydration
  • Renal tubular acidosis
  • Excessive infusion of normal saline
  • Eclampsia
  • Multiple myeloma
  • Kidney dysfunction
  • Metabolic acidosis
  • Hyperventilation and respiratory alkalosis
  • Anemia
  • Hyperparathyroidism
  • Cushing's syndrome
  • Drugs: acetasolamide, ammonium chloride, androgens, estrogens, hydrochlorothiazide, methyldopa, NSAIDs.
 Signs and symptoms of hyperchloremia:

 As shifts in chloride parallel shifts in sodium, the patients will show signs and symptoms of hypernatremia as well as the following:

 

  • Lethargy
  • Weakness and confusion
  • Deep and laboured breathing

 

 

 

 Bibliography

Bove, Lisa Anne (1996) Restoring electrolyte balance: Sodium and Chloride, RN, January, (pp. 25 – 29).

Pagana, Kathleen Deska & Pagana, Timothy James (1997) Mosby’s Diagnostic and Laboratory Test Reference-3rd edition Mosby, St.Louis.

 

Glossary of terms:

Aldosterone -

Anion

Cation

Extracellular

Hyponatremia

Intracellular

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