Overview
Definition:
Hyperkalemia is defined as a serum potassium concentration above the normal range, typically > 5.5 mEq/L in children
Severe hyperkalemia (> 6.5 mEq/L) can lead to life-threatening cardiac arrhythmias by altering the resting membrane potential of cardiac myocytes, making them less negative and thus less excitable.
Epidemiology:
Hyperkalemia is a common electrolyte disturbance in pediatric intensive care units (PICUs), affecting up to 10-20% of critically ill children
Causes vary with age, including renal failure, certain medications (e.g., ACE inhibitors, potassium-sparing diuretics), metabolic acidosis, rhabdomyolysis, and hemolysis.
Clinical Significance:
Understanding the electrocardiographic (EKG) manifestations of hyperkalemia is crucial for prompt diagnosis and management in pediatric patients, as it directly predicts the risk of fatal cardiac events
Timely administration of calcium is a critical intervention to stabilize the cardiac membrane and prevent arrhythmias.
Clinical Presentation
Symptoms:
Often asymptomatic in mild to moderate cases
In severe hyperkalemia: Weakness or paralysis, typically starting in the lower extremities and ascending
Paresthesias
Palpitations
Shortness of breath.
Signs:
Normal or bradycardic heart rate
Irregular pulse
Hypotension
Weak peripheral pulses
Absence of edema or ascites unless related to underlying renal disease.
Diagnostic Criteria:
Diagnosis is primarily based on serum potassium levels
EKG findings are critical for assessing immediate cardiac risk
Reference pediatric cardiology guidelines for potassium thresholds and associated EKG changes.
Diagnostic Approach
History Taking:
Inquire about recent onset of decreased urine output, use of medications affecting potassium balance (ACE inhibitors, ARBs, potassium supplements, NSAIDs, potassium-sparing diuretics like spironolactone, trimethoprim-sulfamethoxazole), conditions causing cell lysis (trauma, burns, rhabdomyolysis, tumor lysis syndrome), and underlying renal or endocrine disorders.
Physical Examination:
Assess vital signs, focusing on heart rate and rhythm
Examine for signs of volume overload (edema) or dehydration
Palpate pulses
Assess neurological status for weakness or paralysis
Examine for any signs of trauma or skin breakdown.
Investigations:
Serum potassium level (critical)
Serum electrolytes (sodium, chloride, bicarbonate)
Blood urea nitrogen (BUN) and creatinine to assess renal function
Glucose to rule out pseudohyperkalemia or diabetic ketoacidosis
Arterial blood gas (ABG) to assess for metabolic acidosis
Complete blood count (CBC) to assess for hemolysis or polycythemia
Creatine kinase (CK) if rhabdomyolysis is suspected
Electrocardiogram (EKG) is mandatory for all suspected cases of significant hyperkalemia.
Differential Diagnosis:
Pseudohyperkalemia (due to hemolysis during blood draw or prolonged tourniquet time)
Hypokalemia
Other causes of arrhythmias (e.g., hypocalcemia, hypomagnesemia, drug toxicity).
Ekg Changes And Calcium Indications
Ekg Changes Mild:
Mild hyperkalemia (5.5-6.5 mEq/L): Peaked T waves (narrow and tented) in precordial leads (V1-V3)
PR interval may be prolonged.
Ekg Changes Moderate:
Moderate hyperkalemia (6.5-8.0 mEq/L): Further PR interval prolongation, flattening of P waves, QRS widening.
Ekg Changes Severe:
Severe hyperkalemia (> 8.0 mEq/L): Merging of ST segment and T wave to form a sine wave pattern
Development of bradycardia, idioventricular rhythms, ventricular tachycardia, or asystole
Loss of P waves.
Calcium Indications:
Calcium administration is indicated for any EKG changes suggestive of cardiac membrane depolarization (peaked T waves, widened QRS, etc.), regardless of serum potassium level, especially if the patient is symptomatic or potassium is > 6.5 mEq/L
It acts as a membrane stabilizer, antagonizing the effects of potassium on the cardiac myocyte resting potential.
Management
Initial Management:
Immediate discontinuation of potassium-containing fluids and medications
Frequent EKG monitoring
IV access
Obtain STAT serum potassium.
Medical Management Calcium:
Calcium chloride (10% solution): 0.2 mL/kg IV over 2-5 minutes
Maximum dose of 10 mL
Calcium gluconate (10% solution): 0.5-1.0 mL/kg IV over 2-5 minutes
Maximum dose of 10 mL
Use calcium chloride for faster onset and higher ionized calcium concentration, especially in cardiac arrest
Calcium gluconate is less irritating to veins
Repeat doses every 5-10 minutes if EKG changes persist.
Medical Management Potassium Lowering:
Insulin and glucose: Regular insulin (0.1 units/kg IV) followed by D50W (0.5-1 g/kg IV) to drive potassium into cells
Albuterol (salbutamol) nebulization: 2.5-5 mg in 3 mL saline inhaled over 10 minutes
Sodium bicarbonate: 1-2 mEq/kg IV if severe metabolic acidosis is present (use with caution)
Diuretics: Furosemide (loop diuretic) IV if renal function is preserved to promote potassium excretion
Kayexalate (sodium polystyrene sulfonate): Oral or rectal, exchanges potassium for sodium, slower onset
Hemodialysis: Definitive treatment for refractory hyperkalemia, especially in renal failure.
Supportive Care:
Continuous cardiac monitoring
Mechanical ventilation may be needed for respiratory compromise due to muscle weakness
Management of the underlying cause of hyperkalemia.
Complications
Early Complications:
Cardiac arrhythmias: Ventricular fibrillation, asystole, cardiac arrest
Neurological deficits from severe weakness.
Late Complications:
Recurrence of hyperkalemia if underlying cause is not addressed
Chronic renal insufficiency if hyperkalemia is due to progressive kidney disease.
Prevention Strategies:
Careful monitoring of potassium levels in at-risk patients
Judicious use of medications affecting potassium
Prompt recognition and management of conditions leading to hyperkalemia
Patient and family education regarding dietary potassium restrictions if indicated.
Prognosis
Factors Affecting Prognosis:
The presence and severity of EKG changes
The rapidity of diagnosis and treatment
The underlying cause of hyperkalemia
The presence of co-existing medical conditions.
Outcomes:
With prompt and appropriate management, especially calcium administration for cardiac protection and measures to lower potassium, the prognosis is generally good
However, severe, untreated hyperkalemia can be rapidly fatal.
Follow Up:
Close monitoring of serum potassium levels until normalized
Follow-up to address the underlying cause of hyperkalemia to prevent recurrence
Renal function assessment.
Key Points
Exam Focus:
Remember the stepwise EKG changes of hyperkalemia: Peaked T waves -> PR prolongation/P wave flattening -> QRS widening -> Sine wave -> Asystole
Calcium administration is a membrane stabilizer, not a potassium-lowering agent.
Clinical Pearls:
Always check an EKG in any child with suspected significant hyperkalemia or symptoms suggestive of it
Differentiate between calcium chloride and calcium gluconate based on urgency and venous access
Prioritize emergent potassium-lowering strategies if EKG changes are severe or patient is unstable.
Common Mistakes:
Delaying EKG interpretation or calcium administration in the presence of critical EKG changes
Forgetting to administer glucose with insulin when treating hyperkalemia
Attributing cardiac symptoms solely to other causes without considering hyperkalemia
Not addressing the underlying etiology of hyperkalemia.