In a patient with severe systolic dysfunction (ejection fraction 19%) on milrinone and diuretics who developed worsening altered mental status, had a negative head CT, an ammonia level of 67 µmol/L, and was started on lactulose, what are the optimal next steps in management?

This patient's altered mental status is unlikely to be hepatic encephalopathy and requires urgent investigation for alternative causes, particularly given the cardiac context and normal ammonia level.

Critical Reassessment Needed

The ammonia level of 67 µmol/L is essentially normal (reference range typically 15-80 µmol/L), making hepatic encephalopathy an unlikely primary diagnosis. While lactulose has been started, this patient's clinical picture demands a broader differential diagnosis given the severe cardiac dysfunction and recent fall.

Immediate Next Steps

1. Identify and Treat Precipitating Factors

The guidelines emphasize that altered mental status in cardiac patients requires systematic evaluation for multiple etiologies 1:

• Infection workup: Complete blood count with differential, C-reactive protein, chest X-ray, urinalysis with culture, blood cultures. Sepsis is a leading cause of altered mental status in critically ill patients (20.7% in cirrhotic patients, likely higher in cardiac patients) 2

• Metabolic derangements:

  • Recheck electrolytes (sodium, potassium, calcium, magnesium)
  • Hyponatremia is common with diuretics and can cause altered mental status 3
  • Hypokalemia should be corrected, especially given recent diuretic changes 1, 3
  • Assess renal function (BUN, creatinine)

• Cardiac causes:

  • Cardiogenic shock with EF 19% can cause cerebral hypoperfusion
  • Milrinone can cause arrhythmias (ventricular ectopy, nonsustained VT) that may compromise cerebral perfusion 4, 5
  • Check continuous telemetry for arrhythmic events
  • Assess blood pressure trends - hypotension reduces cerebral perfusion

2. Medication Review

Critically evaluate milrinone 4:

• Milrinone causes arrhythmias in high-risk populations and can worsen mental status through hemodynamic instability
• Monitor for excessive blood pressure drops
• Consider dose adjustment if hypotension or arrhythmias present

Review all medications for:

• Benzodiazepines (consider flumazenil if suspected) 1
• Opioids (consider naloxone if suspected) 1
• Other sedating medications

3. Reassess Lactulose Appropriateness

With normal ammonia, lactulose may be harmful 3:

• Excessive lactulose causes dehydration and electrolyte disturbances
• Can worsen hyponatremia through fluid losses
• May cause hypokalemia, predisposing to arrhythmias in this cardiac patient 4

Consider discontinuing or reducing lactulose unless ammonia rises or clear evidence of hepatic dysfunction emerges.

4. Cardiac-Specific Hyperammonemia Consideration

While ammonia is normal now, severe heart failure can cause hyperammonemic encephalopathy through hepatic and intestinal hypoperfusion 6. However, this typically presents with elevated ammonia levels. The current normal level argues against this mechanism.

Diagnostic Algorithm

If focal neurological deficits develop: Repeat head CT immediately (current CT was negative but done before worsening) 7, 2

If no focal deficits: Routine repeat head imaging has low yield 2. Focus on:

1. Infection screening (cultures, imaging)
2. Metabolic panel (electrolytes, renal function)
3. Cardiac monitoring (telemetry, blood pressure)
4. Medication reconciliation

Common Pitfalls to Avoid

• Assuming hepatic encephalopathy with normal ammonia: The ammonia level of 67 is not elevated. Hepatic encephalopathy guidelines emphasize ammonia has high negative predictive value 7

• Over-treating with lactulose: In the absence of hyperammonemia, aggressive lactulose can cause harm through dehydration, electrolyte disturbances, and worsening cardiac function 3

• Missing cardiac causes: With EF 19% on milrinone, arrhythmias and hypoperfusion are critical considerations. Milrinone's proarrhythmic effects are well-documented 4, 5

• Overlooking infection: Sepsis and metabolic abnormalities account for 35.4% of altered mental status in critically ill patients 2

Specific Management Based on Findings

If infection identified: Appropriate antibiotics 1

If hyponatremia (Na <130): Fluid restriction to 1-1.5L/day, reduce or stop diuretics, correct hypokalemia 3

If hypotension: Consider reducing milrinone dose, hold further diuretics, assess volume status 4

If arrhythmias on telemetry: Adjust milrinone dose, correct electrolytes (especially potassium and magnesium) 4

If ammonia rises above 80-100 µmol/L: Then consider lactulose 30-45 mL every 1-2 hours until 2-3 soft stools daily, with goal to titrate to 2-3 soft stools per day 1, 8. Consider adding rifaximin 550 mg twice daily for improved outcomes (76% vs 44% recovery at 10 days) 1