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Hypokalemia: The right way of Potassium deficit repletion

“Hypokalemia treatment consists of two arms: Treatment of the underlying cause and Potassium replacement therapy, this summary will discuss how to properly and effectively replete potassium deficits
  • Hypokalemia treatment consists of two arms:
    • Treatment of the underlying cause
    • Potassium replacement therapy
  • Potassium can be replaced orally/ enterally or intravenously.

    The severity of Hypokalemia

    • Mild hypokalemia if K 3-3.5 Meq/L.
    • Moderate hypokalemia if K 2.5-3 Meq/L.
    • Severe or critical if K < 2.5 Meq/L or any hypokalemia with symptoms. (arrhythmias, marked muscle weakness, or rhabdomyolysis).

    Hypokalemia-induced EKG changes

  • All hypokalemic patients should get an EKG and placed on telemetry, this is particularly important in moderate-severe hypokalemia.
  • Hypokalemia produces a wide range of EKG changes:
    • QT prolongation.
    • ST depression.
    • U waves.
    • PAC or PVC.
    • Sinus bradycardia.
    • Atrioventricular block.
    • Paroxysmal atrial or junctional tachycardia.
    • Ventricular tachycardia or fibrillation.
  • The following patients are at highest risk of these arrhythmias
    • Patients on digoxin, antiarrhythmic drugs, and other QT-prolonging drugs.
    • Patients with CAD, CHF, or structural heart diseases.
    • Patients with a history of previous arrhythmias.

 

Potassium level targets

  • 3.5 Meq/L for all patients including those at risk of arrhythmia!
  • 3 Meq/L for renal failure patients, whether acute or chronic.
  • 5-5.3 Meq/L for DKA/NKHH while on insulin drip.
  • The target of 4 meq/L in cardiac patients and those at risk of arrhythmia isn’t necessary.
  • Spurious hypokalemia is way less frequent compared to spurious hyperkalemia but can happen with extreme leukocytosis or when the blood sample sits for long before running the test.

 

Treatment

  • Magnesium level should always be checked and corrected if low.
  • Treat the underlying cause: Is hypokalemia due to K loss, redistribution, or both?

 

Potassium deficit

  • The vast majority of potassium in the body is located intracellularly (IC). Thus, most of the total body potassium deficit represents deficient intracellular potassium.
  • The serum K level represents the potassium level in the extra-cellular fluid.
  • A small drop in ECF potassium likely represents a large deficit in the IC potassium.
  • The total body potassium is proportional to the muscle mass and body weight. Muscle mass decreases with age.

Kdeficit (mmol) = (Knormal lower limit – Kmeasured) x kg body weight x 0.4

Daily potassium requirement is around 1 mmol/Kg body weight. 

Amount to be given = Kdeficit + Daily potassium requirement

  • This equation is a rough estimate only and should be used, only, in hypokalemia due to potassium loss whether renal or extra-renal losses. If there’s an issue with potassium redistribution, this estimate may not be as accurate as in DKA.

 

Oral vs IV Potassium

  • Potassium preparations are available for oral and IV administration.
  • Mild and moderate hypokalemia should be treated with oral potassium only unless there’s a contraindication to the enteral route, then IV potassium can be used instead.
  • IV potassium supplements should be reserved for severe or symptomatic hypokalemia.

 

Oral potassium

  • Cheaper.
  • Safer.
  • Raise K level slowly.
  • Larger doses.
  • The risk of acute hyperkalemia is small.

 

IV potassium

  • More expensive.
  • Irritates the veins/phlebitis.
  • Raise K level quickly.
  • Smaller doses.
  • May cause acute hyperkalemia

 

Potassium preparations

  • Potassium chloride (KCL):
    • Is the most widely used one
    • Available in IV and oral preparation.
    • Pills and liquid
  • Potassium Bicarbonate:
    • Available in oral form only
    • An optimal choice for hypokalemia and Non-anion gap metabolic acidosis
  • Potassium citrate:
    • Available in oral form only.
    • Citrate is metabolized into bicarb in the body.
    • An optimal choice for hypokalemia and Non-anion gap metabolic acidosis.
  • Potassium acetate:
    • Available in IV form only.
    • Metabolized into bicarb.
    • An optimal choice for hypokalemia and Non-anion gap metabolic acidosis.
  • Potassium phosphate:
    • Available in oral and IV forms.
    • Can be considered when hypokalemia and hypophosphatemia exist together.

 

Patients selection:

  • Hypokalemia + Non-anion gap metabolic acidosis (Diarrhea, RTA 1,2):
    • Potassium bicarbonate.
    • Potassium Citrate.
    • Potassium acetate (IV only).
  • Hypokalemia + Hypophosphatemia:
    • Potassium phosphate.
  • All other hypokalemias:
    • Potassium chloride.

     

Potassium administration

  • Replace potassium deficit in divided doses (reduce the dose in Renal failure).
  • A 120 meq deficit, for example, can be replenished with KCL 40 meq every 8 hours x 3 doses.
  • IV potassium:
    • Infuse at 10 meq/hour in Mild-moderate hypokalemia (Use only if the enteral route is contraindicated).
    • Infuse at 20 meq/hour in severe or symptomatic hypokalemia.
    • Infuse at 20-40 meq/hour in DKA/NKHH to quickly raise potassium to a safe level (3.3 meq/L)  to start the insulin drip.
    • In Cardiac arrest due to hypokalemia, 10-20 meq can be infused over 3-5 minutes, and this is the only time we give potassium that fast.
    • If the patient keeps losing the pulse, potassium can be infused at a rate of 60 meq/hour.
    • Use precautions in renal failure patients, the amount and the rate of infusion should be probably reduced by 25-50%, frequent monitoring is the key.
    • Rates of 20 meq/hour and above should be given via a central line. If a central line isn’t available, split the amount and give it via multiple peripheral lines.

 

Monitoring:

  • All patients should be on telemetry.
  • For mild hypokalemia, repeat K with the next morning’s labs.
  • For moderate hypokalemia, repeat K in 6-8-12 hours.
  • For severe hypokalemia, monitor potassium every 2-4 hours.
  • For potassium infused >=40 meq/hour, monitor every 60 minutes.
  • Potassium level should not be obtained directly from a line where potassium is being infused, this will give you falsely elevated potassium.
  • Potassium supplements are provided until we achieve our target K-level
  • Replete magnesium if magnesium deficiency exists.
  • Potassium-sparing diuretics should be considered in hypokalemia secondary to other types of diuretics.
  • The underlying problem should undergo simultaneous treatment.

 

 

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