NAPLEX Question of the Week: Potassium Problems

This week's question focuses on a very common electrolyte abnormality.
NAPLEX Question of the Week: Potassium Problems

DH is a 58 year old male who was brought to ED by EMS after reporting chest pains and heart palpitations. DH has a history of hypertension and obesity. He notes that he has been using salt alternatives and training for a marathon to help lose weight. He has also been using electrolyte supplements to help with cramping. He reports being adherent to his medications, but he is worried he is having a heart attack. An EKG was performed, which showed peak T-waves. Peripheral venous access achieved in the ED.

PMH: HTN and Obesity.

Current Medications; Zestril 40 mg QD, Norvasc 10 mg QD

Pertinent Labs:

  • Na: 140 mEq/L; K: 6.8 mEq/L: Cl: 96 mEq/L; Mg: 4 mg/dL; BUN: 60 mg/dL; SCr: 4.0 mg/dL; SBG: 110 mg/dL; AST 22 U/L; ALT 28 U/L
  • Vitals: BP: 142/84 mmHg; HR: 65; RR: 19; Temp: 99.6 F
  • Weight: 95 kg; Height: 64 in
  • Troponin: 0.01 ng/mL

Based on the patient’s primary electrolyte disturbance, select the following medications that could potentially remove this electrolyte from the body.

A. Kayexalate 15g PO

B. Lasix 40 mg IV

C. Humulin R 10 Units IV

D. D50W 25g IV

E. Calcium gluconate 1g IV


Brands/Generics covered: Zestril (lisinopril), Norvasc (amlodipine); Kayexalate (sodium polystyrene sulfonate); Lasix (furosemide); Humulin R (insulin regular); D50W (Dextrose 50% water)


Hyperkalemia is an electrolyte disturbance that can present with several symptoms. These include muscle cramps or weakness, decreased cardiac contractility, peaked T-waves on EKG, depressed or absent reflexes, and oliguria or anuria. This patient had several contributing factors to his hyperkalemia, such as his hypertension regimen and supplement use. Lisinopril is an ACE inhibitor, which blocks angiotensin II. As a result, aldosterone secretion is also inhibited, and more potassium is retained in the body as opposed to excreted in the urine in exchange for sodium. 

When treating hyperkalemia, order of administration of potential agents is extremely important. It is important to assess whether EKG changes are present, as this is a sign of cardiac compromise. Typically, EKG changes can be seen with potassium levels > 5.5 mEq/L. Calcium is given as the first step to stabilize and protect the myocardium from hyperkalemia. Furthermore, is important that note that calcium gluconate was chosen for this patient scenario over calcium chloride due to the peripheral venous access. While calcium chloride would be preferred, it can cause necrosis and/or sloughing when given in smaller veins. Therefore, calcium chloride should only be administered IV via central lines. Calcium however does NOT ultimately remove potassium. 

Dextrose and Insulin are used to shift potassium intracellularly and would be given next. It is important to note that dextrose should be given prior to administrating insulin due to risk of causing hypoglycemia associated with insulin. Additionally, insulin regular is the only insulin that should be administered intravenously. If the patient’s glucose is greater than 250 mg/dL, dextrose is not needed. Insulin only temporarily addresses the issue as it as well does not remove potassium from the body. 

Kayexalate is administered to help eliminate the potassium from the body. It is a resin that exchanges sodium ions for potassium ions in the intestines. From there the bound potassium is eliminated in the stool. While the onset of kayexalate can take over 2 hours, potassium absorption in the intestines should not be ignored, as 90% of the potassium taken in is absorbed in the intestines. The delayed onset is why it is important to get this medication on board as soon as possible understanding.

Furosemide also helps eliminate potassium from body, as it increases the amount excreted in urine. However, it is important to note that if the patient is producing little to no urine, this medication may not be very useful.

Therefore the correct answers are A and B. 

NAPLEX Competencies Covered:

Area 2 (Identify Drug Characteristics), 2.1 Pharmacology, mechanism of action, or therapeutic class; Area 3 (Develop or Manage Treatment Plans), 3.5 Drug route of administration, dosage forms, or delivery systems, 3.10 Drug pharmacokinetics or pharmacodynamics, 3.11 Evidence-based practice

Congrats as many of you finish your final clinical rotations! See everyone next week.

Dr. B

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