Infection 4: Abdominal Sepsis Portal

This portal focuses on the initial approach to (suspected) abdominal bacterial infection that causes a systemic inflammatory response. This information assumes the reader has read Vol III—IN3 Sepsis in Adults. Important aspects of patient management are covered there which will not be repeated in this portal. Diverse entities besides infection can cause inflammation within the abdominopelvic region, such as pancreatitis, arterial embolization, bleeding, and infarction. Maintain a high index of suspicion for this myriad of possibilities.

Infection in the abdomen may be localized and contained, or generalized and/or uncontained. If generalized and uncontained, the term bacterial peritonitis is used, signifying infection within the greater peritoneal cavity. Two categories of bacterial peritonitis exist: primary spontaneous bacterial peritonitis and secondary peritonitis.

Spontaneous bacterial peritonitis is an acute bacterial infection of the ascitic or peritoneal fluid. Spontaneous bacterial peritonitis can occur as a complication of any disease state that is associated with ascites, such as cirrhosis, peritoneal dialysis, nephrosis, lupus, and congestive heart failure. Secondary peritonitis is due to bowel perforation, such as a ruptured appendix or ruptured diverticula, with soiling of the peritoneal cavity.

Clinical Considerations

Abdominal sepsis can present as an acute abdomen with marked abdominal pain, abdominal distension, guarding, and rebound. On the other hand, there may be few abdominal signs in geriatric patients, small children, or immunocompromised patients. A complete exam is warranted, with careful inspection of the abdomen, pelvis, and rectum. Diagnostic testing, which may be extensive in these seriously ill patients, is determined by the findings on exam.

Diagnostic paracentesis may be needed on patients with ascites; ultrasound can help to guide this procedure. If the patient has an indwelling peritoneal catheter, a sample can be drawn from it using sterile technique. Send the sample for cell count, lactic acid, pH, and culture. Inoculate blood culture bottles with 10 mL of ascitic fluid to improve the culture results. Polymorphonuclear counts in the ascitic fluid > 250 cells/cubic mm establishes the diagnosis prior to culture results.¹ Lab tests for patients with ascites should include blood and urine cultures and liver and renal chemistries.

One of the few rapid clarifying tests in the evaluation of abdominal disease is free air visible on either abdominal x-rays or under the diaphragm on the chest x-ray. If free air is seen, make a diagnosis of perforated viscus. Otherwise, advanced testing (except on patients with GI hemorrhage) is thought to delay needed emergency laparotomy.² Obtain surgical consultation early.

Fluid management is critical in these complicated patients. If more than 1 to 2 L of NS in adults or (PEDS) 10 to 20 mL/kg in children is needed, switch to Ringer’s lactate solution to avoid hyperchloremic acidosis. If administering large volumes of fluid (especially in older adults) consider obtaining central venous access ( Vol II—CIRC SKILLS 2 Central Venous Access) to measure central venous pressure ( Vol II— CIRC SKILLS 3 Central Venous Pressure Measurement) in order to guide volume replacement. Do not resort to vasopressor treatment of shock unless blood volume is restored and hypotension continues to persist. See Vol III—TRAU CARE 2 Shock.

In patients with spontaneous bacterial peritonitis, albumin IV (1.5 g/kg at the time of diagnosis and 1 g/kg on day 3) may decrease the frequency of renal impairment and mortality.³ See Vol III—IN3 Sepsis in Adults for further management considerations of sepsis.

Antibiotic therapy considerations

The following antibiotic therapy assumes a highly suspected bacterial cause in an adult with normal renal function. Knowledge of local resistance patterns is needed to determine the appropriate antibiotic chosen, and knowledge of local bacterial resistance patterns. Other antibiotic recommendations exist besides the ones that follow.

Suspected primary spontaneous bacterial peritonitis

Pathogens to consider: Enterobacteriaceae > Strep pneumo > enterococci > anaerobes (< 1%, given the high oxygen tension in peritoneal fluid).4 Options include⁴:

cefotaxime: 2 g IV every 4 to 8 hours
ticarcillin/clavulanate: 3.1 g IV every 6 hours
piperacillin/tazobactam: 3.375 g IV every 6 hours
ampicillin/sulbactam: 3 g IV every 6 hours
ceftriaxone: 2 g IV every 24 hours (PEDS: 50 mg/kg every 12 hours)

If resistant E coli or resistant Klebsiella are suspected, choose one of the following instead:

imipenem 0.5 g IV every 6 hours
meropenem 1 g IV every 8 hours

Adding an aminoglycoside (eg, tobramycin) to any of these is a consideration,⁵ although all of these with the exception of ampicillin/sulbactam act against gram-negative aerobes. In patients with pre-existing renal dysfunction, exercise caution in choosing antibiotics so there is no further compromise of their kidneys.

Suspected bacterial peritonitis in a chronic peritoneal dialysis patient⁴
(defined as >100 WBC/cubic mm; > 50% PMNs. For diagnosis: concentrate several hundred mLs of removed dialysis fluid by centrifugation, gram stain concentrate, and culture in aerobic/anaerobic bottles).

Pathogens to consider: Staphylococcus aureus, gram-negative bacilli, Staphylococcus epidermidis, pseudomonas. If there are multiple gram negatives present, consider perforation.

Consider one of the following:

vancomycin 1 g IV every 12 hours and one of the following:
cefotaxime: 2 g IV every 4 to 8 hours
ceftizoxime: 2 g IV every 4 to 8 hours
ceftriaxone: 1 to 2 g IV four times daily
vancomycin and an aminoglycoside (such as tobramycin, see below)

May use antibiotics through the catheter in selected cases (see reference).⁶

Suspected secondary bacterial peritonitis

Pathogens to consider: both gram-negative aerobic (eg, Enterobacteriaceae, Pseudomonas) and gram-negative anaerobic bacteria (eg, Bacteroides) must be covered, as well as enterococci.

Severe life-threatening disease options include one of the following:⁴

imipenem 0.5 g IV every 6 hours
meropenem 1 g IV every 8 hours
ertapenem 1 g IV four times daily
trova 300 mg IV first day four times daily, then 200 mg IV four times daily
ampicillin 2 g IV every 6 hours and metronidazole 500 mg IV every 6 hours and an aminoglycoside (see below)

Adding an aminoglycoside (eg, tobramycin) to any of the above is a consideration,⁵ although the above does act against gram-negative aerobes.

Mild to moderate disease options include one of the following:

ticarcillin/clavulanate: 3.1 g IV every 6 hours
piperacillin/tazobactam: 3.375 g IV every 6 hours
cefoxitin 2 g IV every 8 hours
cefotetan 2 g IV every 12 hours
ciprofloxin 400 mg IV every 12 hours and metronidazole 500 mg IV every 6 hours

Adding an aminoglycoside (eg, tobramycin) to any of the above is a consideration,⁵ although all of the above do act against gram-negative aerobes.

The aminogycosides have serious side effects and morbidity; proper dosing may decrease these risks. These agents may be dosed once daily or by multiple daily dosing. After the loading dose, all subsequent doses are calculated according to renal function and peak/trough serum levels. This information is available from your pharmacy, in many reference texts, or on the web.

Tobramycin:

once daily: 5.1 mg/kg IV (increase to 7 mg/kg if critically ill) every 24 hours
multiple dose daily: 2 mg/kg IV load, then 1.7 mg/kg every 8 hours

References

Diagnosis, treatment and prevention of spontaneous bacterial peritonitis. Baillieres Best Prac Res Clin Gastroenterol. 2000 Dec;14(6):975-990.
Rozycki GS, et al. Three hundred consecutive emergent celiotomies in general surgery patients: influence of advanced diagnostic imaging techniques and procedures on diagnosis. Ann Surg. 2002 May;235(5):681-689.
Sort P, Navasa M, Arroyo V, et al. Effect of intravenous albumin on renal impairment and mortality in patients with cirrhosis and spontaneous bacterial peritonitis. N Engl J Med. 1999;341:403-409.
Gilbert D, Moellering R, Sande M. The Sanford Guide to Antimicrobial Therapy, 32nd Ed. 2002.
The Medical Letter on Drugs and Therapeutics. The Choice of Antibacterial Drugs. 2001: Vol 43 (Issue 1111-1112); 69-70.
Perit Dialysis Int. 13:14, 1993.

Infection 4: Abdominal Sepsis Portal

References

Edition 13-October 2011