Potassium Balance: Hypokalemia & Hyperkalemia — Comprehensive Study Notes

Hypokalemia Overview

  • Definition: hypokalemia is a serum potassium level below 3.5 mEq/L3.5\ \text{mEq/L} (mmol/L).
  • Key principle: most potassium (K⁺) is inside cells; small changes in extracellular potassium cause large changes in cell membrane excitability. This imbalance can be life-threatening because every body system is affected.
  • Major idea: both actual deficits and relative deficits can cause hypokalemia.
  • Box 13.6: Common Causes of Hypokalemia
    • Actual Potassium Deficits
    • Inappropriate or excessive use of drugs: diuretics\text{diuretics}, corticosteroids, increased secretion of aldosterone, Cushing syndrome
    • Gastrointestinal losses: diarrhea, vomiting, wound drainage (especially GI), prolonged nasogastric suction, heat-induced excessive diaphoresis
    • Kidney-related: kidney disease impairing reabsorption of potassium
    • Relative Potassium Deficits
    • Alkalosis
    • Hyperinsulinism
    • Hyperalimentation
    • Total parenteral nutrition
    • Water intoxication
    • IV therapy with potassium-poor solutions
  • Pathophysiology consequences
    • Low serum potassium levels reduce excitability of cells; excitable tissues (nerve, muscle) become less responsive to normal stimuli.
    • Gradual potassium loss may be asymptomatic until loss is extreme.
    • Rapid reduction of serum potassium causes dramatic changes in function.
    • Actual depletion vs. relative depletion:
    • Actual depletion: potassium loss is excessive or intake is inadequate to match normal loss.
    • Relative hypokalemia: normal total body potassium but abnormal distribution between fluid spaces or dilution by excess water; can occur during rapid insulin infusions (insulin increases Na⁺/K⁺-ATPase activity, pushing K⁺ into cells).
  • Magnesium interaction
    • Potassium levels are linked to magnesium in both extracellular and intracellular compartments; low magnesium often accompanies hypokalemia.

Assessment and Recognition (Interprofessional Collaborative Care)

  • Key cues to recognize hypokalemia:
    • Age considerations: older adults have decreased urine concentrating ability, increasing potassium loss; more likely to use diuretics.
    • Drug history: diuretics, corticosteroids, beta-adrenergic agonists/antagonists can increase renal potassium loss.
    • Dietary and supplement history: use of potassium-containing supplements (e.g., potassium chloride) or foods high in potassium (bananas, citrus, raisins, meat).
    • Diseases: adrenal gland and kidney diseases can cause potassium loss.
    • Nutrition history: assess typical day’s intake to identify risk.
    • Respiratory changes: metabolic acidosis can cause respiratory muscle weakness and shallow respirations; assess breath sounds, effort, color, rate/depth.
  • Nursing Safety Priority Action Alert
    • Assess respiratory status of a patient with hypokalemia at least every 2 hours because respiratory insufficiency and cardiac dysrhythmias are major causes of death from hypokalemia.

Signs and Symptoms (Musculoskeletal, Cardiovascular, Neurologic, GI)

  • Musculoskeletal changes
    • Skeletal muscle weakness; stronger stimulus needed to initiate contraction; may be too weak to stand
    • Weak hand grasps; reduced deep tendon reflexes (hyporeflexia)
    • Severe hypokalemia can cause flaccid paralysis
    • Assess muscle weakness and patient’s ability to perform ADLs
  • Cardiovascular changes
    • Irregular heartbeat due to dysrhythmia; palpate peripheral pulses; pulse often thready and weak
    • Pulse rate ranges from very slow to very rapid; often irregular
    • ECG changes: ST segment depression and a prominent U wave ((\text{ST depression}, \; \text{U wave}))
    • Monitor for conduction changes associated with hypokalemia
    • Orthostatic hypotension may occur; measure blood pressure in lying, sitting, standing positions
  • Neurologic changes
    • Altered mental status; irritability and anxiety → lethargy → acute confusion → coma with progression
  • Gastrointestinal changes
    • Decreased GI smooth muscle contractions; decreased peristalsis
    • Bowel sounds hypoactive; nausea, vomiting, constipation, abdominal distention common
    • Severe hypokalemia can cause paralytic ileus (absence of peristalsis)
  • Laboratory data
    • Confirm hypokalemia: serum potassium value below 3.5 mEq/L3.5\ \text{mEq/L}
  • ECG and dysrhythmias
    • Hypokalemia-associated ECG changes: ST-segment depression, flat or inverted T waves, increased U waves
    • Dysrhythmias can be life-threatening

Interventions (Take Actions)

  • Goals of therapy
    • Prevent potassium loss, increase serum potassium, ensure patient safety
    • Use drug therapy and nutrition therapy to restore normal potassium levels
  • Nursing priorities
    • Ensure adequate gas exchange
    • Prevent patient falls and injury from potassium administration
    • Monitor patient response to therapy
    • Review nursing care activities (Box 13.2 in course material)
  • Pharmacologic therapy
    • Potassium supplements: most commonly potassium chloride\text{potassium chloride}, potassium gluconate, or potassium citrate
    • Dose and route depend on degree of loss
  • Intravenous potassium (severe hypokalemia)
    • Potassium is given IV for severe hypokalemia; available in different concentrations; high-alert due to concentrated electrolyte
    • Safety measures: before infusion, confirm dilution; conjugate with National Patient Safety Goals (NPSG)
    • NPSG: concentrated potassium must be diluted and added to IV solutions only in the pharmacy by a registered pharmacist; vials of concentrated potassium should not be in patient care areas
    • Infusion details: must be diluted and infused slowly; recommended rate 5 to 10 mEq/hr5\ to\ 10\ \text{mEq/hr}; never given by IV push; not administered IM or subcutaneously (tissue irritant; phlebitis risk)
    • IV site care: assess hourly; check for burning or pain at site; document and report infiltration immediately; stop infusion and notify provider if infiltration occurs
  • Oral potassium administration
    • Available as liquids or solids; taste can be strong/unpleasant; can mix with liquids to improve palatability; take with meals to reduce GI upset; do not take on an empty stomach
  • Additional notes
    • Review boxed care activities (Box 13.2) for comprehensive nursing actions

Special Considerations: Pharmacology and Safety

  • Diuretics and potassium loss
    • High-ceiling (loop) diuretics (e.g., furosemide\text{furosemide}, bumetanide\text{bumetanide}) and thiazide diuretics increase renal potassium loss; these are avoided in patients with hypokalemia
    • Potassium-sparing diuretics (e.g., spironolactone\text{spironolactone}) may be used to increase urine output without increasing potassium loss
  • Nutrition and safety
    • Nutrition therapy involves collaboration with a Registered Dietitian Nutritionist (RDN) to increase dietary potassium intake
    • Foods rich in potassium help prevent ongoing loss; supplementation may be needed to restore levels
  • Mobility and respiratory safety
    • Implement falls precautions for patients with muscle weakness; use gait belt when ambulating; ensure help is available
    • Monitor respiratory status hourly in severe hypokalemia; assess oxygen saturation and ability to cough; ABG assessment when available
  • Physical signs of hypoxia
    • Pallor or cyanosis of face, mucosa, nail beds; ABG findings of hypoxemia or hypercapnia indicate poor gas exchange

Hyperkalemia Overview

  • Definition: hyperkalemia is a serum potassium level higher than 5.0 mEq/L5.0\ \text{mEq/L} (mmol/L).
  • Effect on body systems: even small increases above normal can affect excitable tissues, especially the heart; rapid rises are particularly dangerous
  • Prevalence and risk factors
    • Hyperkalemia is rare in individuals with normal kidney function; most cases occur in patients under medical treatment
    • Greatest risk in chronically ill, debilitated, older adults, and those taking potassium-sparing diuretics
  • Box 13.7: Common Causes of Hyperkalemia
    • Actual Potassium Excesses
    • Overingestion of potassium-containing foods or medications: salt substitutes, potassium chloride
    • Rapid infusion of potassium-containing IV solutions, bolus IV potassium injections
    • Transfusions of whole blood or packed cells
    • Adrenal insufficiency
    • Kidney failure
    • Potassium-sparing diuretics
    • ACE inhibitors (ACEIs)
    • Angiotensin receptor blockers (ARBs)
    • Relative Potassium Excesses
    • Tissue damage
    • Acidosis
    • Hyperuricemia
    • Uncontrolled diabetes mellitus

Assessment and Recognition (Interprofessional Care)

  • Key cues
    • Age and kidney function: kidney function declines with aging
    • Drug history: especially potassium-sparing diuretics, ACEIs, ARBs
    • Nutrition history: intake of potassium-rich foods; use of salt substitutes (high in potassium)
    • Cardiac symptoms: palpitations, skipped beats; muscle twitching; leg weakness; tingling or numbness in hands/feet/face
    • Bowel habits: diarrhea

Signs and Symptoms (Cardiovascular, Neuromuscular, GI)

  • Cardiovascular changes
    • Cardiac symptoms include bradycardia, hypotension, tall peaked T waves, prolonged PR intervals, flat or absent P waves, wide QRS complexes
    • Ectopic beats; complete heart block, asystole, ventricular fibrillation in severe cases
  • Neuromuscular changes
    • Two-phase: early skeletal muscle twitching and paresthesias; then weakness; progress to flaccid paralysis; respiratory muscles affected only at lethal levels
  • Gastrointestinal changes
    • Increased GI motility with diarrhea and hyperactive bowel sounds; frequent, watery stools
  • Laboratory data
    • Hyperkalemia defined as potassium level > 5.0 mEq/L5.0\ \text{mEq/L}
    • If due to dehydration: elevated other electrolytes, hematocrit, and hemoglobin
    • If due to kidney failure: elevated creatinine and BUN, decreased pH, and normal/low hematocrit and hemoglobin

Interventions (Take Actions)

  • Primary goals
    • Reduce serum potassium, prevent recurrences, ensure patient safety
  • Drug therapy and excretion strategies
    • Agents to reduce potassium: increase excretion (diuretics that promote potassium loss) or shift potassium into cells; calcium, insulin, and other measures may be used depending on urgency and kidney function
    • Patiromer binds potassium in the GI tract to decrease absorption; other binders include Kayexalate (sodium polystyrene sulfonate) and sodium zirconium cyclosilicate
  • Immediate measures
    • Stop potassium-containing infusions and withholding oral supplements; collaborate with an RDN to select low-potassium foods
    • Move potassium from ECF to cells temporarily (cellular shift) via insulin; IV dextrose with insulin is common; solutions are hypertonic and given via central line or high-flow vein to avoid local irritation
    • Cardiac monitoring during treatment; compare with prior ECGs to track changes
  • Invasive and additional strategies (depending on severity and kidney function)
    • Calcium gluconate or calcium chloride intravenously to stabilize cardiac membrane
    • Insulin + glucose to shift potassium into cells
    • Beta-2 agonists (e.g., albuterol) via nebulizer to promote intracellular potassium shift
    • Sodium bicarbonate to correct acidosis and shift potassium into cells
    • Loop diuretics to enhance potassium excretion if kidney function is intact
    • Hemodialysis in severe cases or when kidney function is compromised
    • Dietary restrictions and stopping potassium-containing products
    • Treat underlying causes (medication adjustments, management of comorbid conditions)
  • Monitoring and safety
    • Continuous ECG monitoring and serial serum potassium measurements during treatment
    • Rapid Response if signs of instability occur (e.g., heart rate < 60 beats/min or characteristic EKG changes with tall, peaked T waves)
  • Patient and family education
    • Diet and drug label reading to identify potassium content; avoid salt substitutes containing potassium

Potassium Roles and Importance (Summary of Key Functions)

  • Major intracellular electrolyte: intracellular concentration ≈ 150−160 mEq/L150{-}160\ \text{mEq/L}
  • Cellular function: maintains resting membrane potential; essential for transmission/conduction of nerve impulses, normal cardiac rhythms, and contraction of skeletal and smooth muscles
  • Electrolyte balance: works with sodium to regulate cellular fluid distribution
  • Enzyme activation: involved in various enzymatic reactions
  • Acid-base balance: contributes to pH homeostasis
  • Muscle function: essential for proper muscle contraction and relaxation
  • Heart function: crucial for maintaining normal cardiac rhythms and preventing arrhythmias
  • Blood pressure regulation: influences vascular smooth muscle tone

Takeaway: Why Potassium Balance Matters

  • Maintaining proper K⁺ balance is vital for nervous and cardiovascular system function, gas exchange, muscle activity, and overall homeostasis.
  • Both low and high potassium levels have broad, potentially life-threatening implications; close monitoring and timely interventions are essential in clinical settings.

Quick Reference: Key Numeric Thresholds and Actions

  • Hypokalemia definition: \text{K⁺} < 3.5\ \text{mEq/L}
  • Severe hypokalemia may necessitate IV replacement at 5 to 10 mEq/hr5\text{ to }10\ \text{mEq/hr} with dilution and caution
  • Hyperkalemia definition: \text{K⁺} > 5.0\ \text{mEq/L}; risk rises rapidly beyond 6−7 mEq/L6{-}7\ \text{mEq/L} or higher if rapid
  • Intracellular potassium concentration (typical): 150−160 mEq/L150{-}160\ \text{mEq/L}
  • Potassium movement into cells with insulin: often used with IV glucose for quick temporary reduction of serum K⁺
  • Common IV or oral therapy options and roles summarized in the sections above

End of notes