- 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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