From the EM Model

5.0 Endocrine, Metabolic, and Nutritional Disorders

5.3 Fluid and Electrolyte Disturbances

Hyperkalemia, defined as a serum potassium level of more than 5 mEq/L, is the most common electrolyte abnormality leading to life-threatening arrhythmias and cardiac arrest.¹ Hyperkalemia has vague and varied symptoms; in fact, it can be totally asymptomatic, or the initial presentation may be sudden death. The correct and early diagnosis of hyperkalemia requires attention to risk factors, especially a history of renal failure and medication that can cause potassium retention, as well as a search for ECG changes consistent with elevated potassium. Hyperkalemia can be rapidly progressive, and lifesaving interventions must be instituted at the earliest suspicion of toxicity.

Case Presentation

A 51-year-old woman with a history of diabetes mellitus, hypertension, peripheral vascular disease, and hemodialysis-dependent end-stage renal disease presents by ambulance because of dizziness, weakness, abdominal pain, vomiting, and diarrhea. Her symptoms began three days ago and have been worsening. She did not feel well enough to go to her dialysis appointment yesterday and has not been able to afford any of her medications this week.

On physical examination, the patient appears lethargic and very ill. Her initial vital signs are supine blood pressure 98/66, pulse rate 98, respiratory rate 26, oral temperature 36.7°C (98°F), and oxygen saturation 96% on room air. She has a patent airway and an unremarkable HEENT examination. Her chest examination reveals mild bibasilar crackles and normal heart sounds with a grade II/VI systolic murmur. Her abdomen is soft but diffusely tender. She has a weak radial pulse in the right arm; there is an AV fistula with a palpable thrill medial to the left biceps. Her lower extremities are cool, dry, and shiny, with 1+ pitting pretibial edema bilaterally.

By department protocol, in light of the patient’s initial vital signs and lethargy, weakness, and ill appearance, she was placed on a cardiac monitor and an ECG was performed immediately. The ECG and the rhythm on the monitor revealed a junctional tachycardia without P waves, a wide QRS, and peaked T waves. Blood wass obtained by peripheral butterfly stick, and a stat chemistry panel revealed sodium 129, potassium 8.2, chloride 88, bicarbonate 5, BUN 48, creatinine 3.9, glucose 422, and venous pH 7.11.

Hyperkalemia

Table 1 on the following page organizes five of the most common causes of hyperkalemia. A history of one of these conditions may be the lone clue to the diagnosis because symptoms do not reliably appear with any particular serum potassium level.¹