Internal Medicine · Year 3 · from Internal Medicine
Case 1: Severe Hyperkalemia with ECG Changes
Patient Demographics
- Age: 72 years
- Sex: Male
- Occupation: Retired postal worker
Chief Complaint
"I feel weak and my heart is racing funny."
History of Present Illness
The patient presents to the emergency department with progressive generalized weakness over the past 2 days. He reports feeling increasingly fatigued, with difficulty climbing stairs and rising from a seated position. He also describes a sensation of his heart "skipping beats." Past medical history includes type 2 diabetes mellitus, hypertension, chronic kidney disease stage 4 (baseline creatinine 3.2 mg/dL), and heart failure with reduced ejection fraction. Current medications include lisinopril 40 mg daily, spironolactone 25 mg daily, metoprolol succinate 50 mg daily, and metformin 500 mg twice daily. He was recently started on trimethoprim-sulfamethoxazole for a urinary tract infection 5 days ago.
Vital Signs
- Temperature: 98.6 degrees F (37.0 degrees C)
- Blood pressure: 158/92 mmHg
- Heart rate: 48 bpm, irregular
- Respiratory rate: 18/min
- Oxygen saturation: 97% on room air
Physical Examination
General: Alert, appears uncomfortable, no acute distress Cardiovascular: Bradycardic, irregular rhythm, no murmurs, JVP elevated to 10 cm Pulmonary: Clear to auscultation bilaterally Extremities: 1+ pitting edema bilaterally, no cyanosis Neurologic: Generalized muscle weakness 4/5 in all extremities, reflexes diminished throughout
Laboratory Findings
- Sodium: 138 mEq/L
- Potassium: 7.8 mEq/L (critical value)
- Chloride: 108 mEq/L
- Bicarbonate: 18 mEq/L
- BUN: 68 mg/dL
- Creatinine: 4.1 mg/dL (baseline 3.2)
- Glucose: 142 mg/dL
- Magnesium: 2.1 mg/dL
- Calcium: 8.8 mg/dL
Electrocardiogram Findings
- Heart rate: 48 bpm
- Rhythm: Sinus bradycardia with first-degree AV block
- Peaked T waves in precordial leads
- Widened QRS complex (140 ms)
- Loss of P wave amplitude
- PR interval prolonged (280 ms)
Diagnosis
Severe hyperkalemia with ECG changes secondary to:
- Chronic kidney disease with acute-on-chronic kidney injury
- Medication-induced (ACE inhibitor + potassium-sparing diuretic + trimethoprim)
- Metabolic acidosis contributing to transcellular potassium shift
Management
Immediate stabilization:
- Calcium gluconate 1 gram IV over 2-3 minutes for cardiac membrane stabilization (immediate onset, does not lower potassium)
- Regular insulin 10 units IV with dextrose 50% 25 grams IV for transcellular shift (onset 15-30 minutes)
- Albuterol 10-20 mg nebulized for additional transcellular shift
- Continuous cardiac monitoring
Potassium elimination:
- Furosemide 80 mg IV for renal potassium excretion
- Sodium polystyrene sulfonate 30 grams orally for GI potassium elimination
- Nephrology consultation for consideration of emergent hemodialysis
Medication adjustments:
- Discontinue lisinopril, spironolactone, and trimethoprim-sulfamethoxazole
- Hold metformin given acute kidney injury
Clinical Pearl
This case illustrates the "perfect storm" of hyperkalemia: chronic kidney disease combined with multiple medications that impair potassium excretion (ACE inhibitor, potassium-sparing diuretic, trimethoprim) plus an acute kidney injury that further compromises the kidney's ability to excrete potassium. The ECG changes (peaked T waves, widened QRS, prolonged PR) represent a medical emergency requiring immediate calcium gluconate for cardiac stabilization before addressing potassium elimination.
Clinical Image
Image Description: Electrocardiogram demonstrating classic findings of severe hyperkalemia including peaked T waves, widened QRS complex, and diminished P wave amplitude.
Attribution: Image from Wikimedia Commons. Licensed under CC BY-SA 4.0. Source: https://commons.wikimedia.org/wiki/File:ECG_Hyperkalemia.jpg