General Surgery · Year 3 · from General Surgery

Case 2: Hyperkalemia in Surgical Patient

Patient Demographics

• Age: 68 years
• Sex: Male
• Occupation: Retired electrician

Chief Complaint

"Routine lab check before hernia surgery."

History of Present Illness

The patient is scheduled for elective inguinal hernia repair tomorrow. He presents for preoperative laboratory evaluation. He feels well with no acute complaints. His only symptom is the reducible right groin bulge he has had for 6 months.

Past Medical History

• Chronic kidney disease stage 4 (baseline creatinine 3.8 mg/dL, GFR 18)
• Type 2 diabetes mellitus
• Hypertension
• Peripheral vascular disease

Medications

• Lisinopril 40 mg daily
• Spironolactone 25 mg daily
• Insulin glargine 20 units at bedtime
• Metoprolol 50 mg twice daily

Physical Examination

• Vitals: BP 138/82 mmHg, HR 64 bpm, regular
• General: Well-appearing male in no distress
• Cardiovascular: Regular rate and rhythm, no murmurs
• Abdomen: Soft, non-tender, right inguinal hernia reduces easily
• Extremities: No edema, diminished dorsalis pedis pulses bilaterally

Laboratory Results

• Potassium: 6.8 mEq/L (CRITICAL VALUE)
• Sodium: 136 mEq/L
• Chloride: 108 mEq/L
• Bicarbonate: 18 mEq/L
• BUN: 62 mg/dL
• Creatinine: 4.2 mg/dL (slightly above baseline)
• Glucose: 142 mg/dL

EKG Findings

• Heart rate 62 bpm
• Peaked T waves (most prominent in V2-V4)
• Widened QRS complex (120 ms)
• Flattened P waves
• No sine wave pattern

Risk Factors for Hyperkalemia

1. Chronic kidney disease (decreased excretion)
2. ACE inhibitor (lisinopril) - reduces aldosterone
3. Potassium-sparing diuretic (spironolactone)
4. Diabetes (insulin deficiency impairs K+ shift into cells)
5. Possible tissue injury/hemolysis (verify not pseudohyperkalemia)

Emergency Management

Immediate Actions:

1. Cardiac monitor placed
2. Repeat potassium drawn (verify not hemolyzed) - confirmed 6.7 mEq/L
3. Surgery cancelled

Treatment Protocol for Severe Hyperkalemia (K+ >6.5 with EKG changes):

Step 1: Cardiac Membrane Stabilization (immediate)

• Calcium gluconate 10% 1 ampule (10 mL) IV over 2-3 minutes
• Onset: 1-3 minutes
• Duration: 30-60 minutes
• Repeat if EKG abnormalities persist
• Does NOT lower potassium

Step 2: Shift Potassium Intracellularly (minutes)

• Regular insulin 10 units IV + D50W 25g IV
• Onset: 15-30 minutes
• Duration: 4-6 hours
• Expected K+ decrease: 0.5-1.0 mEq/L
• Monitor glucose hourly

Step 3: Additional Shift Therapy

• Albuterol 10-20 mg nebulized
• Onset: 15-30 minutes
• Duration: 2-4 hours
• Additive effect with insulin

Step 4: Potassium Elimination

• Loop diuretic (furosemide 40 mg IV) - limited effect with CKD stage 4
• Sodium polystyrene sulfonate 30g PO (onset 2-6 hours)
• Patiromer or sodium zirconium cyclosilicate (newer agents)
• Hemodialysis - definitive treatment for refractory hyperkalemia

Response to Treatment

Disposition

• Admitted for observation and ongoing potassium management
• Nephrology consultation obtained
• Medications adjusted:
• Lisinopril reduced to 10 mg
• Spironolactone discontinued
• Low-potassium diet education
• Surgery rescheduled in 1 week after potassium optimized
• Repeat labs showed K+ 4.8 mEq/L on adjusted medications

Teaching Points

1. Always verify hyperkalemia is not pseudohyperkalemia (hemolysis)
2. EKG changes indicate cardiac toxicity requiring emergent treatment
3. Calcium stabilizes membranes but does not lower potassium
4. Insulin + glucose provides rapid shift into cells
5. Definitive treatment requires potassium elimination
6. Review all medications that contribute to hyperkalemia
7. CKD patients on ACE-I and K+-sparing diuretics at high risk

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