We all can take things for granted. Certainly I do all of the time: like Gravity, or that a post-menarche female will have a urinary pregnancy test done, or that the kid with altered mental status will have a finger stick glucose level. Unfortunately, when you aren’t explicit, important issues can be missed. For instance, in the past we have discussed several important conditions that can be associated with a life threatening electrolyte derangement (ex, Rhabdomyolysis, Congenital Adrenal Hyperplasia, Massive PRBC transfusion, Failure to Thrive, Hypertensive Crisis, Sinus Bradycardia), but we weren’t explicit about one of the fundamental and critical treatment plans. Let’s rectify this oversight by reviewing the management of Hyperkalemia in Children:

Hyperkalemia: Basics

• Potassium (K+) is required for normal transmembrane voltage gradients. (ugh, remember that in class?) [Long, 2018]
  • Particularly important in muscle and nerve cells!
  • All muscle cells (skeletal, cardiac, smooth) use the voltage gradients for action potentials.

• Hyperkalemia is commonly encountered.
  • ~10% of all patients admitted from the ED. [Long, 2018]
  • Moderate to severe hyperkalemia was found in 12% of PICU patients. [Cummings, 2014]

• Hyperkalemia can develop due to:
  • Decreased Excretion
    • Acute or Chronic Renal Failure
    • Kidney transplant rejection
    • Obstructive uropathies (Kids with Kidney Stones, Urinary Retention)
    • Adrenal Gland Disorders
  • K+ Shift to Vascular Compartment
    • Acidosis – like in DKA
    • Tissue Injury – Crush Injury, Rhabdomyolysis
    • Hemolysis – as can happen with blood transfusions
  • Exogenous Source 
    • Medications (especially if concurrent renal impairment)
      • ACE Inhibitors
      • Potassium-Sparing Diuretics
        • Spironolactone
        • Triamterene
        • Trimethoprim-sulfamethoxazole (oh, look, another reason to not like bactrim).
        • Yasmin (birth control)
      • NSAIDs
    • K+ containing IV Fluids! (good old fashioned iatrogenic hyperkalemia!)
    • Hyperkalemia from increased intake of K+ is rare if kidneys are functional. (So eat all of those bananas!)
  • Spurious Lab Error
    • Especially an issue in children.
    • Hemolysis found in 24% of hyperkalemic results in PICU patients. [Cummings, 2014]
    • Tiny catheters, tight tourniquets, fists being cleanched, and samples that are “milked” out of the patient will potentially lead to hemolysis in the test tube and cause artificially elevated K+ level. [Long, 2018]

Hyperkalemia: Symptoms

• Symptoms are NOT reliable to determine who requires therapy.
  • Symptoms can be vague.
    • Weakness, Fatigue, Paresthesias, Diarrhea
  • Can be dramatic also – Paralysis, Decreased DTRs

• The main concern is the critical symptom of cardiac dysrhythmia!

Hyperkalemia: Management

• See an elevated K+ level… check that Blood Pressure!
  • May require a manual BP reading.
  • May help you discern whether a child has undiagnosed renal disease. [Hollander, 2016]

• Potassium level is important, but not the deciding factor.
  • Often texts will described Hyperkalemia as Mild, Moderate, and Severe. [Long, 2018]
    • Mild – 5.5-6.5 mEq/L
    • Mod – 6.5-7.5 mEq/L
    • Sev – > 7.5 mEq/L
  • Often the levels that “define” these categories differ between references.
  • The rate at which the K+ level is changing may be more important the the absolute level.
  • Management decision based on K+ level alone is not advised. [Long, 2018]

• The ECG is useful, but not the entire story.
  • ECG manifestations include:
    • Peaked T waves
    • PR prolongation, decreased P wave amplitude
    • QRS widening, increased R wave amplitude
    • Loss of P waves
    • Conduction blocks (AV blocks, LBBB, RBBB)
    • Sine Wave
    • Asystole
    • Sinus Bradycardia
    • And anything “Bizarre” looking – Amal Mattu taught me that!
  • Often ECG manifestations are taught as occurring in a step-wise fashion as the K+ level increases…
    • This is not the case. [Long, 2018]
    • A patient can progress from normal ECG to v-fib.
    • ECG changes are more common when the K+ level is changing rapidly.
  • ECG findings should not be the sole determinant of management plans. [Long, 2018]

• Treatments for Hyperkalemia are effective and have few side effects. [Long, 2018]
  • Stablize Cardiac Membranes
    • Should give first! They works quickly and can save a life.
    • Calcium: [Long, 2018]
      • Calcium Chloride
        • Has 13.6 mEq of Ca+ in 10 mL
        • Can be caustic (ie, necrosis, thrombophlebitis) to peripheral vessels.
        • Use via Central Access or during a Code (“C”hloride for Codes and Central lines)
      • Calcium Gluconate
        • Has 4.6 mEq of Ca+ in 10 mL
        • Friendly on peripheral veins, but lower Ca+ amount makes Chloride preferred if having cardiac ectopy… or you can give 3 times the amount of Ca+ gluconate.
      • Calcium onset = < 3 min
      • Calcium duration = 20-60 min (so, it buys you some time… but you may need to re-dose)
    • Hypertonic Saline: [Long, 2018]
      • Also alters electric potentials in cardiac cells.
      • May be useful therapy for those with concurrent hyponatremia.
  • Redistribute K+ into the Cells
    • Beta-Agonists
      • 10 – 20 mg of Albuterol can be nebulized and will decrease K+ in 15-30 min.
      • Duration = ~90 min.
      • Can also use IV terbutaline.
    • Insulin & Glucose
      • Insulin reliably lowers plasma K+ levels.
        • IV Regular insulin (0.1 U/kg up to 10 Units) is often used in a bolus. [Wheeler, 2016]
        • Onset of action = 15 min
        • Duration = 4-6 hrs.
        • Short-acting synthetic insulins (ex, Lispro, Insulin Aspart) may have some benefits over Regular Insulin.
          • Have shorter-half-lives and more rapidly absorbed.
          • Decreased risk for hypoglycemia
          • They are also not eliminated by kidneys, so they don’t hang around if patients with renal impairment.
      • Concern for hypoglycemia is significant! [Schafers, 2012]
        • Dose of glucose is usually given with the insulin, but insulin activity will often outlast the glucose stores.
        • Be paranoid about causing hypoglycemia. Give more than you think you need and check it often!
      • Giving insulin is difficult in children and takes time. [Arnholt, 2015]
        • It requires serial dilutions and lots of math.
        • Give other therapies first because of this.
  • Remove the K+
    • Diuretics +/- IV Fluids
      • For patient with functional kidneys who is hypervolemic or euvolemic, loop diuretics (furosemide) can be a great option. [Long, 2018]
      • If patient is hypovolemic, giving IV fluids alone can also help.
    • Dialysis
      • If patient with severe hyperkalemia or in patient without functional kidneys, the dialysis is the only real option.

• There is often debate and confusion about treatment strategies. [Chime, 2015]
  • Certainly whether to treat or not treat is made easy when the patient is critically ill, but when they appear well with vague symptoms it can be challenging.
  • Don’t be cavalier always blaming the K+ in kids on the fact it was a “difficult stick.”
  • Membrane stabilizers may afford you time to sort out the details.

• Treatment Controversies
  • Sodium Bicarbonate
    • Many treatment strategies include sodium bicarb (including ACLS).
    • In theory, alkalinization can lead to H+ and K+ exchange.
    • In practice, sodium bicarbonate does not significantly decrease K+ when pH is normal. [Long, 2018]
    • It may be helpful in the patient with metabolic academia. [Long, 2018]
  • Sodium Polystyrene Sulfonate
    • We are often asked to give this medicine.
    • I’ll be blunt, it is NOT a medicine that will be useful in the ED. [Long, 2018; Kovesdy,2017; Cochrane, 2005]
    • It is likely not useful at all.
    • It may be harmful (ex, bowel obstruction, bowel necrosis).
    • Novel potassium binders may eventually replace this defunct medicine. [Long, 2018; Kovesdy, 2017]
      • Patiromer – non absorbable synthetic polymer
      • ZS-9 – non absorbable cation exchanger that binds 9 times the amount of K+ compared to sodium polystyrene sulfonate.

Moral of the Morsel

• It’s not always a Lab Error. What are the risk factors for this being real? Double check that level, but some empiric therapy may be reasonable while awaiting confirmation.
• Consider the Whole picture. Don’t just rely on ECG or K+ level.
• Review those Medications and Fluids. Iatrogenic causes are all around.
• Triple your Gluconate! You can give as much elemental Ca+ as calcium chloride with 3 times the amount of calcium gluconate.
• Don’t waste time with things that don’t help. Save the sodium bicarb for the TCA overdose. Don’t kill the gut with a medicine that doesn’t work.

References