Let's Break It Down! A Case of Hypokalemia-Induced Rhabdomyolysis

Introduction: Severe hypokalemia can result in life-threatening complications such as fatal dysrhythmias and respiratory muscle paralysis. It is the most common, but often unrecognized, electrolyte-induced cause of rhabdomyolysis. Case Description: A 54-year-old female presented with 6 months of progressive paresthesias, generalized weakness, and fatigue. Her medical history included depression, fibromyalgia, GERD, HLD, IBS, and left breast cancer. Review of systems was positive for anorexia, palpitations, myalgias, and chronic diarrhea. Medications were Anastrozole, Atorvastatin, Cyclobenzaprine, Omeprazole, and Paroxetine. She denied the use of herbal medications, alcohol, or illicit drugs. Vital signs revealed HR 141, BP 150/63, SpO2 98%, T 36.8oC, and Wt 101 kg. Physical exam revealed a fatigued woman with dry mucous membranes, an irregular cardiac rhythm without murmurs, clear breath sounds, abdomen soft and non-distended, 4/5 strength in the distal bilateral upper extremities, soft compartments, and no dermatological lesions. An ECG revealed frequent PVCs with bigeminy. She was treated with IV fluids, potassium, and magnesium with subsequent ECG normalization. During her hospitalization, her symptoms resolved with electrolyte repletion in conjunction with nephrology input. Her FeNa was 0.1%. Her TTKG was 2. Discussion: Hypokalemia-induced rhabdomyolysis occurs from cellular potassium depletion, causing vasoconstriction and skeletal muscle ischemia. Our patient had severe hypokalemia causing muscle breakdown and dysrhythmias from chronic diarrhea and anorexia. She had risk factors for other causes of non-traumatic rhabdomyolysis. She was on the lowest dose of Atorvastatin, which has a dose-dependent risk of myotoxicity. Anastrozole and Omeprazole are CYP3A4 inhibitors, however, her Anastrozole dose was reduced and Omeprazole is a weak inhibitor.