# Clinical Cases: Electrolyte Disorders

## 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:
1. Chronic kidney disease with acute-on-chronic kidney injury
2. Medication-induced (ACE inhibitor + potassium-sparing diuretic + trimethoprim)
3. Metabolic acidosis contributing to transcellular potassium shift

### Management
**Immediate stabilization:**
1. Calcium gluconate 1 gram IV over 2-3 minutes for cardiac membrane stabilization (immediate onset, does not lower potassium)
2. Regular insulin 10 units IV with dextrose 50% 25 grams IV for transcellular shift (onset 15-30 minutes)
3. Albuterol 10-20 mg nebulized for additional transcellular shift
4. Continuous cardiac monitoring

**Potassium elimination:**
5. Furosemide 80 mg IV for renal potassium excretion
6. Sodium polystyrene sulfonate 30 grams orally for GI potassium elimination
7. Nephrology consultation for consideration of emergent hemodialysis

**Medication adjustments:**
8. Discontinue lisinopril, spironolactone, and trimethoprim-sulfamethoxazole
9. 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
![Hyperkalemia ECG](case_01_image.jpg)

**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

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## Case 2: Severe Hyponatremia with Neurological Symptoms

### Patient Demographics
- **Age:** 58 years
- **Sex:** Female
- **Occupation:** Elementary school teacher

### Chief Complaint
"My sister is confused and had a seizure at home."

### History of Present Illness
The patient was brought to the emergency department by her sister after witnessing a generalized tonic-clonic seizure at home. For the past week, the patient has complained of progressive headache, nausea, and fatigue. Her sister notes that she has been increasingly confused over the past 2 days, with difficulty remembering conversations and appearing "not herself." The patient has a history of small cell lung cancer diagnosed 3 months ago, currently undergoing chemotherapy. She has no prior history of seizures.

### Vital Signs
- Temperature: 98.4 degrees F (36.9 degrees C)
- Blood pressure: 124/78 mmHg
- Heart rate: 82 bpm
- Respiratory rate: 16/min
- Oxygen saturation: 96% on room air

### Physical Examination
**General:** Somnolent, arousable to voice, disoriented to time and place
**HEENT:** Mucous membranes moist, no JVD
**Cardiovascular:** Regular rate and rhythm, no murmurs
**Pulmonary:** Clear bilaterally, no crackles or wheezes
**Extremities:** No edema, skin turgor normal
**Neurologic:** GCS 13 (E3V4M6), oriented to person only, no focal deficits, reflexes symmetric

### Laboratory Findings
- Sodium: 112 mEq/L (critical value)
- Potassium: 4.2 mEq/L
- Chloride: 78 mEq/L
- Bicarbonate: 24 mEq/L
- BUN: 8 mg/dL
- Creatinine: 0.6 mg/dL
- Glucose: 102 mg/dL
- Serum osmolality: 232 mOsm/kg (low)
- Urine sodium: 68 mEq/L (elevated)
- Urine osmolality: 520 mOsm/kg (inappropriately concentrated)
- TSH: 2.1 mIU/L (normal)
- Morning cortisol: 18 mcg/dL (normal)

### Diagnosis
**Severe symptomatic hyponatremia** secondary to Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) from small cell lung cancer

**Diagnostic criteria for SIADH met:**
1. Serum sodium < 135 mEq/L with serum osmolality < 275 mOsm/kg (hypotonic hyponatremia)
2. Urine osmolality > 100 mOsm/kg (inappropriately concentrated)
3. Urine sodium > 40 mEq/L
4. Clinical euvolemia
5. Normal thyroid and adrenal function
6. Known cause: small cell lung cancer (ectopic ADH production)

### Management
**Acute symptomatic hyponatremia protocol:**
1. 3% hypertonic saline 100 mL bolus over 10 minutes
2. Recheck sodium in 20 minutes
3. Repeat 3% saline bolus if symptoms persist
4. Goal: raise sodium by 4-6 mEq/L in first 2-4 hours to reverse cerebral edema

**Ongoing management:**
5. Admit to ICU for neurological monitoring
6. Check sodium every 2 hours during active correction
7. Correction rate: maximum 8-10 mEq/L in 24 hours to prevent osmotic demyelination syndrome
8. Once acute symptoms resolve, transition to fluid restriction 1-1.5 L/day
9. Oncology consultation for optimization of cancer treatment
10. Consider tolvaptan if refractory to fluid restriction

### Clinical Pearl
SIADH from small cell lung cancer represents a paraneoplastic syndrome where tumor cells ectopically produce ADH. The diagnosis requires excluding hypothyroidism and adrenal insufficiency, which can mimic SIADH. In this case, the patient's seizure and altered mental status constitute a medical emergency requiring immediate treatment with hypertonic saline. The key principle is to correct just enough to reverse acute symptoms (4-6 mEq/L) while respecting the maximum 24-hour correction rate to prevent osmotic demyelination syndrome.

### Clinical Image
![Hyponatremia Management](case_01_image.jpg)

**Image Description:** Electrocardiogram demonstrating findings that may accompany severe electrolyte disturbances, emphasizing the importance of cardiac monitoring during correction of severe electrolyte abnormalities.

**Attribution:** Image from Wikimedia Commons. Licensed under CC BY-SA 4.0. Source: https://commons.wikimedia.org/wiki/File:ECG_Hyperkalemia.jpg

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