When should Spontaneous Bacterial Peritonitis (SBP) prophylaxis be initiated in patients with cirrhosis and ascites?

When to Initiate SBP Prophylaxis in Cirrhosis with Ascites

SBP prophylaxis should be initiated in three specific high-risk patient populations: patients who have recovered from a previous episode of SBP, patients with cirrhosis and ascites with low ascitic fluid protein (<1.5 g/dL) plus impaired renal function or advanced liver failure, and patients with cirrhosis presenting with gastrointestinal bleeding. 1

Primary Prophylaxis (No Previous SBP)

Primary prophylaxis should be offered to patients with:

• Low ascitic fluid protein (<1.5 g/dL) AND one of the following:
  • Advanced liver failure (Child-Pugh score ≥9 with serum bilirubin ≥3 mg/dL)
  • Impaired renal function
  • Hyponatremia 1, 2

This recommendation is based on evidence that patients with these risk factors have significantly higher rates of developing SBP and mortality. The European Association for the Study of the Liver (EASL) guidelines strongly support this approach 2.

However, it's important to note that there is some controversy in this area. The NORFLOCIR trial showed that norfloxacin did not reduce 6-month mortality in patients with advanced cirrhosis overall, though post-hoc analyses suggested benefit in those with low ascitic fluid protein 1.

Secondary Prophylaxis (After First SBP Episode)

All patients who recover from an episode of SBP should receive prophylaxis with:

• Norfloxacin 400 mg once daily (first choice)
• Ciprofloxacin 500 mg once daily (alternative, more commonly used in UK)
• Trimethoprim-sulfamethoxazole 800/160 mg daily (another alternative) 1, 2

The evidence for secondary prophylaxis is stronger than for primary prophylaxis. In patients who survive an episode of SBP, the cumulative recurrence rate at 1 year is approximately 70% without prophylaxis 1. A randomized controlled trial showed that norfloxacin reduced the probability of SBP recurrence from 68% to 20% 1.

Prophylaxis in Gastrointestinal Bleeding

All patients with cirrhosis and ascites presenting with gastrointestinal bleeding should receive antibiotic prophylaxis:

• For severe liver disease: IV ceftriaxone
• For less severe liver disease: Oral norfloxacin or alternative quinolone 1, 2

Duration of Prophylaxis

• Secondary prophylaxis: Continue indefinitely until liver transplantation or resolution of ascites 2
• Primary prophylaxis: Continue until resolution of risk factors or liver transplantation 2

Antibiotic Selection Considerations

When selecting antibiotics for prophylaxis, consider:

1. Local bacterial resistance patterns 1, 2
2. Risk of developing resistant organisms with long-term use 1, 2
3. Potential side effects of fluoroquinolones (including rare but serious musculoskeletal and nervous system effects) 1

Monitoring During Prophylaxis

• Regular assessment for signs of infection despite prophylaxis
• Vigilance for adverse drug effects, particularly with fluoroquinolones
• Monitoring for development of resistant organisms 1

Important Caveats

1. Transplant evaluation: All patients who recover from SBP should be evaluated for liver transplantation due to poor long-term survival (30-50% at 1 year, 25-30% at 2 years) 1, 2

2. Antibiotic resistance concerns: Long-term quinolone prophylaxis may lead to resistant organisms. Patients on prophylaxis who develop infections have higher rates of gram-positive bacterial infections (79%) compared to those not on prophylaxis (67%) 2

3. Medication availability: Norfloxacin is not widely available in some countries (including the UK), so ciprofloxacin is often used as an alternative 1

4. Emerging evidence: A meta-analysis showed that antibiotic prophylaxis improves short-term survival and reduces overall infection risk in high-risk cirrhotic patients with ascites 3

By following these guidelines, clinicians can appropriately identify patients who would benefit from SBP prophylaxis while minimizing unnecessary antibiotic exposure and associated risks.