Synonym/Acronym
serum, urine K+.
Rationale
To evaluate fluid and electrolyte balance related to potassium levels toward diagnosing disorders such as acidosis, acute kidney injury, chronic kidney disease, and dehydration and to monitor the effectiveness of therapeutic interventions.
This Core Lab Study describes an essential mineral and electrolyte that is included in the Electrolyte panel, Comprehensive Metabolic panel (CMP), General Health panel, and Hypertension panel. Panels are used as general health and targeted screens to identify or monitor conditions such as bone disease, diabetes, hypertension, kidney disease, liver disease, or malnutrition.
Patient Preparation
There are no food, fluid, activity, or medication restrictions unless by medical direction. Instruct the patient not to clench and unclench the fist immediately before or during blood specimen collection. Urine from an unpreserved random or timed specimen is collected in a clean plastic collection container. As appropriate, provide the required urine collection container and specimen collection instructions.
Normal Findings
Method: Ion-selective electrode.
Blood
| Serum Potassium | Conventional and SI Units |
|---|
| Newborn | 3.2–5.5 mEq/L or mmol/L |
| 7–29 days | 3.4–6 mEq/L or mmol/L |
| 1–5 mo | 3.5–5.6 mEq/L or mmol/L |
| 6–12 mo | 3.5–6.1 mEq/L or mmol/L |
| Child–18 yr | 3.8–5.1 mEq/L or mmol/L |
| Adult–older adult | 3.5–5.3 mEq/L or mmol/L |
| Anion Gap | Conventional and SI Units |
| Child or adult | 8–16 mmol/L |
Note: Value ranges may vary depending on the laboratory. Serum values are 0.1 mmol/L higher than plasma values, and reference ranges should be adjusted accordingly. It is important that serial measurements be collected using the same type of collection container to reduce variability of results from collection to collection.
Older adults are at risk for hyperkalemia due to the decline in aldosterone levels, decline in kidney function, and effects of commonly prescribed medications that inhibit the renin-angiotensin-aldosterone system.
Urine
| Age | Conventional Units | SI Units (Conventional Units × 1) |
|---|
| 6–10 yr | | |
| Male | 17–54 mEq/24 hr or mmol/24 hr | 17–54 mmol/24 hr |
| Female | 8–37 mEq/24 hr or mmol/24 hr | 8–37 mmol/24 hr |
| 10–14 yr | 18–58 mEq/24 hr or mmol/24 hr | 18–58 mmol/24 hr |
| Adult–older adult | 26–123 mEq/24 hr or mmol/24 hr | 26–123 mmol/24 hr |
Note: Reference values depend on potassium intake and diurnal variation. Excretion is significantly higher at night.
Potassium excretion declines in older adults due to the decline in aldosterone levels, decline in kidney function, and effects of commonly prescribed medications that inhibit the renin-angiotensin-aldosterone system.
Blood: Adults and Children
- HypokalemiaLess than 2.5 mEq/L or mmol/L (SI: Less than 2.5 mmol/L)
- HyperkalemiaGreater than 6.2 mEq/L or mmol/L (SI: Greater than 6.2 or mmol/L)
Blood: Newborns
- HypokalemiaLess than 2.8 mEq/L or mmol/L (SI: Less than 2.8 mmol/L)
- HyperkalemiaGreater than 7.6 mEq/L or mmol/L (SI: Greater than 7.6 mmol/L)
Timely notification to the requesting health-care provider (HCP) of any critical findings and related symptoms is a role expectation of the professional nurse. A listing of these findings varies among facilities.
Consideration may be given to verification of critical findings before action is taken. Policies vary among facilities and may include requesting immediate recollection and retesting by the laboratory or retesting using a rapid point-of-care testing instrument at the bedside, if available.
Symptoms of hyperkalemia include irritability, diarrhea, cramps, oliguria, difficulty speaking, and cardiac dysrhythmias (peaked T waves and ventricular fibrillation). Continuous cardiac monitoring is indicated. Administration of sodium bicarbonate or calcium chloride may be requested. If the patient is receiving an IV supplement, verify that the patient is voiding.
Symptoms of hypokalemia include malaise, thirst, polyuria, anorexia, weak pulse, low blood pressure, vomiting, decreased reflexes, and electrocardiographic changes (depressed T waves and ventricular ectopy). Replacement therapy is indicated.
(Study type: Blood collected in a gold-, red-, red/gray-, or green-top [heparin] tube; related body system: Circulatory, circulatory/hematopoietic, digestive, endocrine, respiratory, and urinary systems.)
Electrolytes dissociate into electrically charged ions when dissolved. Cations, including potassium, carry a positive charge. Body fluids contain approximately equal numbers of anions and cations, although the nature of the ions and their mobility differ between the intracellular and extracellular compartments. Both types of ions affect the electrical and osmolar functions of the body. For additional information regarding osmolality, refer to the study titled “Osmolality, Blood and Urine.” Electrolyte quantities and the balance among them are controlled by oxygen and carbon dioxide exchange in the lungs; absorption, secretion, and excretion of many substances by the kidneys; and secretion of regulatory hormones by the endocrine glands. Potassium also helps maintain acid-base equilibrium, and it has a significant and inverse relationship to pH: A decrease in pH of 0.1 increases the potassium level by 0.6 mmol/L.
Potassium is the most abundant intracellular cation with a number of essential functions to include transmission of electrical impulses in heart and skeletal muscle and participation in enzyme reactions that transform glucose into energy and amino acids into proteins. Potassium balance occurs in a relatively small range. For example, small disruptions of either an excess or deficit of potassium can result in significant changes in normal heart rhythms. Sufficient potassium levels are largely dependent on dietary intake; potassium is excreted, but not reabsorbed, by the kidneys. Management of potassium levels is also related to the actions of the aldosterone-renin-angiotension system. For additional information related to the regulation of potassium levels by hormones, refer to the studies titled “Aldosterone” and “Renin.” A way to remember that potassium is intracellular and sodium is extracellular is to use the mnemonic “electrolyte pies,” where we know that potassium is the major intracellular cation, and the major extracellular cation is sodium.
Regulating electrolyte balance is one of the major functions of the kidneys. In normally functioning kidneys, urine potassium levels increase when serum levels are high and decrease when serum levels are low to maintain homeostasis. The kidneys respond to alkalosis by excreting potassium to retain hydrogen ions and increase acidity. In acidosis, the body excretes hydrogen ions and retains potassium. Analyzing these urinary levels can provide important clues to the functioning of the kidneys and other major organs. Urine potassium tests usually involve timed urine collections over a 12- or 24-hr period. Measurement of random specimens also may be requested.
Abnormal potassium levels can be caused by a number of contributing factors, which can be categorized as follows:
- Altered Renal Excretion: Normally, 80% to 90% of the body’s potassium is filtered out through the kidneys each day (the remainder is excreted in sweat and stool); kidney disease (the most common cause of increased potassium levels) can result in abnormally high potassium levels.
- Altered Dietary Intake: A severe potassium deficiency can be caused by an inadequate intake from food sources or medications administered orally or by IV.
- Altered Cellular Metabolism: Damaged red blood cells (RBCs) release potassium into the circulating fluid, resulting in increased potassium levels.
The anion gap is a calculated value often reported from a set of electrolytes (sodium, potassium, chloride, and carbon dioxide) and is used most frequently as a clinical indicator of metabolic acidosis. The most common causes of an increased gap are lactic acidosis and ketoacidosis. The concept of estimating electrolyte disturbances in the extracellular fluid is based on the principle of electrical neutrality. The formula includes the major cation (sodium) and anions (chloride and bicarbonate) found in extracellular fluid. The anion gap is calculated as follows: 
anion gap = sodium – (chloride + HCO3-). Some laboratories may include potassium in the calculation of the anion gap. Calculations including potassium can be invalidated because minor amounts of hemolysis can contribute significant levels of potassium leaked into the serum as a result of cell rupture.
Because bicarbonate (HCO3–) is not directly measured on most chemistry analyzers, it is estimated by substitution of the total carbon dioxide (TCO2) value in the calculation. The anion gap is also widely used as a laboratory quality-control measure because low gaps usually indicate a reagent, calibration, or instrument error.
Summary of Significant Electrolytes/Minerals (Note: Bicarbonate HCO3- is not a mineral)
| Intracellular | Extracellular |
|---|
| Cation (+) Positive | Anion (-) Negative | Cation (+) Positive | Anion (-) Negative |
|---|
| K+ Potassium is the major intracellular cation | PO43-Phosphate is the major intracellular anion | Na+ Sodium is the major extracellular cation | Cl- Chloride is the major extracellular anion |
| Mg2+ (Magnesium) | | Ca2+ (Calcium) | HCO3- Bicarbonate is the second most important extracellular anion |
Potential Problems: Assessment & Nursing Diagnosis/Analysis
| Problems | Signs and Symptoms |
|---|
| Electrolytes (deficit—related to renal loss, decreased oral intake, anorexia, IV fluids or NPO status prolonged without supplement, alkalosis, potassium movement from extracellular fluid to intracellular fluid secondary to hyperinsulinism, laxative abuse, vomiting, diarrhea, excessive diaphoresis or wound drainage, potassium-wasting diuretics) | Thirst, tetany, weakness, constipation, arrhythmias, hypotension, nausea, vomiting, abdominal distention, hypoactive bowel sounds, anorexia, polyuria, mental depression, cardiac arrest, confusion, apathy, anxiety, weak thready pulse |
| Electrolytes (excess—related to renal failure, overuse of oral supplements, mismanaged use of potassium-laden IV fluids, use of potassium-sparing diuretics, multiple transfusions, cellular fluid shift, tumor lysis, metabolic acidosis) | Nausea; weak or irregular pulse; anxiety; irritability; sudden collapse; cardiac arrest; muscle weakness; fatigue; bradycardia or slowing heart rate; anxiety; pins and needles tingling (paresthesia) of the hands, feet, face, and tongue; decreased urinary output |
Before the Study: Planning and Implementation
Teaching the Patient What to Expect
- Discuss how this test can assist in evaluating electrolyte balance.
- Explain that a blood or urine sample is needed for the test. Information regarding urine specimen collection is presented with other general guidelines in Appendix A: Patient Preparation Specimen Collection.
Potential Nursing Actions
- Patients receiving digoxin or diuretics should have potassium levels monitored carefully because cardiac dysrhythmias can occur.
- Include on the urine collection container’s label the amount of urine, test start and stop times, and ingestion of any foods or medications that can affect test results.
After the Study: Implementation & Evaluation Potential Nursing Actions
Avoiding Complications
- Observe the patient for signs and symptoms of fluid volume excess related to excess potassium intake (hyperkalemia), fluid volume deficit related to active loss (hypokalemia), or risk of injury related to an alteration in body chemistry.
- Increased urine potassium levels may be associated with the formation of kidney stones. Discuss the importance of drinking a sufficient amount of water when kidney stones are suspected.
Treatment Considerations
Electrolytes: Deficit
- Interventions/actions related to electrolyte deficit include the following: Monitor and trend potassium results, electrocardiogram status, and respiratory changes. Facilitate administration of oral or IV potassium supplements. Discuss adding high-potassium foods to the diet. Discuss the importance of using potassium supplements and potassium-rich foods to offset loss from medications that deplete potassium stores (e.g., antibiotics, furosemide, insulin, laxatives, steroids, thiazides). Examine medications that may be contributing to potassium loss. Correlate potassium imbalance with disease process, nutritional intake, renal function (polyuria can result in excessive urinary excretion of potassium), and medications.
Electrolytes: Excess
- Interventions/actions related to electrolyte excess include the following: Monitor and trend potassium results, electrocardiogram status, and respiratory changes. Correlate potassium imbalance with disease process, nutritional intake, renal function (urine output should be 25 mL/hr; decreased urinary excretion may increase blood level of potassium), and medications. Collaborate with the pharmacist and HCP for appropriate pharmacological interventions and adjust medication dosage to compensate for renal impairment. Facilitate elimination of simple causal factors such as potassium-sparing diuretics (spironolactone) and oral or IV potassium supplements. Facilitate the use of ordered IV medications (calcium gluconate, insulin, glucose) or dialysis (hemodialysis, peritoneal) to manage and remove excess potassium.
Nutritional Considerations
- Educate potassium-deficient patient on dietary choices that can replace potassium stores.
- Potassium is present in all plant and animal cells, making dietary replacement simple to achieve. Foods rich in potassium are fruits and vegetables (artichokes, avocados, bananas, cantaloupe, dried fruits, kiwi, mango, dried beans, mushrooms, nuts, oranges, peaches, pears, pomegranates, potatoes, prunes, pumpkin, raisins, spinach, sunflower seeds, swiss chard, tomatoes, and winter squash), dairy products (especially milk and milk products such as ice cream, yogurt, cream, buttermilk, half & half), and meats.
- Educate patients with an excess of potassium on foods to avoid. All of the foods discussed for the potassium-deficient patient should be avoided with the inclusion of beet greens, chocolate, dried fruit, orange juice, coffee, and tea.
Clinical Judgement
- Consider how to convey the negative health repercussions of potassium excess or deficit and encourage adaptation to strategies, including dietary changes, that will improve health.
Follow-Up Evaluation and Desired Outcomes
- Acknowledges contact information provided for the U.S. Department of Agriculture’s resource for nutrition (www.myplate.gov).