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Home , Abdominal guarding, Nausea

INTRA-ABDOMINAL INFECTIONS

Learning Objectives: 1. Describe patient risk factors, that may indicate an intra-abdominal infection 2. Identify tests and significant laboratory values used to diagnose intra-abdominal infections and differentiate among the various types of intra-abdominal infections 3. List common causative organisms for intra-abdominal infections 4. Distinguish between antimicrobial treatment options for intra-abdominal infections based on causative organisms 5. Describe supportive care and monitoring that may be needed for intra-abdominal infections

Patient Case:

Chief Complaint: “My belly hurts so bad I can barely move.”

HPI: John Chavez is a 47-year-old Hispanic man who was brought to the ED by his wife. She stated that he has been from , , and severe abdominal for the last 2–3 days. His intake of food and fluids has been minimal over the past several days.

Meds: 100 mg PO once daily, Omeprazole 20 mg PO once daily, 30 mL PO QID PRN

PMH: , diagnosed 2014 with onset of , GERD, Cholecystectomy 15 years ago, Chronic C virus infection diagnosed 2014.

FH: Mother was alcoholic; died 10 years ago in car accident. Father’s history unknown.

SH: Retired construction worker; EtOH abuse with 10–12 cans of beer per day × 25 years, sober for 6 months; however, recently did binge drink after an argument with his wife; denies use of tobacco or illicit drugs; poor adherence to medications and dietary restrictions

Background ● Contained within the or retroperitoneal space. Two general types: and ● Peritonitis- acute, inflammatory response of peritoneal lining to microorganisms, chemicals, irradiation, or foreign body injury ○ Primary - intra-abdominal focus of disease may not be evident ○ Secondary- a focal disease process is evident within the ● Abscess-purulent collection of fluid separated from surrounding tissue by a wall consisting of inflammatory cells and adjacent organs ○ Usually contains necrotic debris, , and inflammatory cells.

Pathophysiology ● Causes ○ is MOST common ○ Entry into host . From bacterial collections within intra-abdominal organs, peritoneal dialysis (skin surface flora introduced via the peritoneal catheter) . In primary peritonitis → enter abdomen via bloodstream or lymphatic system, transmigration through the bowel wall, through an indwelling peritoneal dialysis catheter, or fallopian tubes in female patients . In secondary peritonitis → enter peritoneum or retroperitoneum as a result of disruption of the integrity of the GI tract caused by diseases or traumatic injuries . Fluid and protein shift into abdomen (called “third spacing”) may decrease circulating blood volume and cause hypotension, shock & death . An abscess begins by the combined action of inflammatory cells, bacteria, fibrin, and other inflammatory component; O2 is low → anaerobic bacteria! Signs/Symptoms ● Primary ○ Loss of appetite ○ ○ Nausea/ Vomiting (sometimes with ) ○ Abdominal tenderness ○ Fever - may be only mildly elevated or not elevated in patients undergoing peritoneal dialysis ○ Bowel sounds are hypoactive ○ Cirrhotic patients may have worsening encephalopathy ○ Culture of peritoneal dialysate or ascitic fluid should be positive, particularly if collected prior to initiation of ○ Procalcitonin in conjunction with clinical findings is a sensitive test for bacterial peritonitis ● Secondary ○ Generalized ○ Tachypnea ○ Tachycardia ○ Nausea/Vomiting ○ Fever - normal initially, then increases to 37.8–38.9°C (100–102°F) within the first few hours and may continue to rise for the next several hours ○ Hypotension, hypoperfusion, and shock if volume is not restored ○ Decreased urine output due to vascular volume depletion ○ Voluntary changing to involuntary guarding and a “board-like abdomen” ○ Abdominal tenderness and distension ○ Faint bowel sounds that cease over time

Back to our case: What are the signs/symptoms of an intra-abdominal infection in this patient? Which type is most likely?

Gen: Thin man who appears older than his stated age, disoriented, and in severe pain

VS: BP 154/82, P 102, RR 32, T 38.2°C; current Wt 92 kg, (IBW 68 kg)

Skin: Jaundiced, warm, coarse, and very dry. Spider angiomata present on chest, back and arms.

HEENT: Yellow sclera; PERRLA; Oropharynges show poor dentition but are otherwise unremarkable

Neck/Lymph Nodes: Supple; normal size thyroid; no JVD or palpable lymph nodes

Chest: Lungs are CTA; shallow and frequent breathing

CV: Tachycardia, normal S1 and S2 with no S3 or S4 Abd: Distended; pain on pressure or movements; pain is sharp and diffuse throughout abdomen; (+) guarding. (+) HSM. Decreased bowel sounds.

Genitorectal: Prostate normal size; guaiac (–) stool

Extremities: No clubbing or cyanosis; bilateral pitting pedal edema 1+

Neuro: Oriented to place; lethargic and apathetic, slumped posture, slowed movements

Testing/Diagnosis ● Primary ○ Cloudy dialysate fluid with peritoneal dialysis ○ WBC count may be only mildly elevated ○ Ascitic fluid usually contains greater than 250 leukocytes/mm3 (0.25 × 109/L), and bacteria may be evident on Gram stain of a centrifuged specimen ○ In 60%–80% of patients with cirrhotic ascites, the Gram stain is negative ● Secondary ○ Leukocytosis (15,000–20,000 WBC/mm3 [15 × 109 to 20 × 109/L]), with neutrophils predominating and an elevated percentage of immature neutrophils (bands) ○ Elevated hematocrit and blood urea nitrogen because of ○ Patient progresses from early alkalosis because of hyperventilation and vomiting to ○ Abdominal radiographs may be useful because free air in the abdomen (indicating intestinal perforation) or distension of the small or large bowel is often evident

Back to our case: What lab values indicate an intra-abdominal infection?

Abdominal US: Nodular consistent with cirrhosis; ascites;

Paracentesis: Ascitic fluid: leukocytes 720/mm3, protein 2.8 g/dL, albumin 1.1 g/dL, pH 7.28, lactate 30 mg/dL

Causal Organisms ● Primary bacterial peritonitis: ○ Usually a single organism ○ Children . Group A Streptococcus, Escherichia coli, Streptococcus pneumoniae, or Bacteroides species ○ When peritonitis occurs in association with cirrhotic ascites, E. coli is isolated most frequently ● Peritonitis in patients undergoing peritoneal dialysis: ○ Common skin organisms . Coagulase negative staphylococci, Staphylococcus aureus, streptococci and enterococci ○ Gram-negative bacteria . E. coli, Klebsiella, and Pseudomonas ● Secondary intra-abdominal infections: ○ Usually polymicrobial - gram positive and gram negative ○ Combination of aerobic & anaerobic organisms appears to greatly affect the severity of infection . Aerobic bacteria: ● E. coli - responsible for the early mortality from peritonitis . Anaerobic bacteria ● Bacteroides fragilis (think )

Back to our case: What do you think is the most common causative organism for this patient? Blood Cultures: Pending × 2

Paracentesis: Gram stain: numerous PMNs, no organisms.

Treatment Options ● 3 Major Modalities ○ Prompt surgical drainage of the infected site . Secondary treated surgically - “source control”!! ● Physical measures to eradicate the focus of infection ● Abdominal laparotomy may be used to correct the cause ○ Hemodynamic resuscitation and support of vital functions . To ensure intravascular volume, CO, tissue perfusion, correct acidosis . The Surviving Sepsis Campaign: International Guidelines for Management of Severe Sepsis and Septic Shock recommend treatment goals during the first 6 hours or resuscitation: ● CVP 8-12 mm Hg ● MAP more than or equal to 65 mm Hg ● UO more than or equal to 0.5 mL/kg/h . In 1st hour- 30 mL/kg bolus of IV fluids (lactated ringers or normal saline) may be needed for intravascular volume, followed by up to 1 L/hr . Significant blood loss (hematocrit ≤25%) → PRBC ○ Early administration of appropriate antimicrobial therapy to treat infection not removed by surgery . Empiric regimens (before organism is known)

○ For continuous ambulatory peritoneal dialysis–associated peritonitis: . cefazolin (loading dose 500 mg/L; maintenance dose 125 mg/L) . vancomycin (LD 1000 mg/L; MD 25 mg/L) in cases of high prevalence of methicillin-resistant Staphylococcus aureus (MRSA) or β-lactam allergy, may be utilized for Gram-positive coverage . One of these Gram-positive agents should be combined with a Gram- negative agent such as: ● ceftazidime (LD 500 mg/L; MD 125 mg/L) ● cefepime (LD 500 mg/L; MD 125 mg/L) ● aminoglycoside (gentamicin or tobramycin LD 8 mg/L; MD 4 mg/L) ○ Check peak and trough levels! ● Definitive therapy (once organism is identified) ○ At 24-48 hours, aerobic cultures should return . If pathogen not sensitive to empiric regimen → change . If sensitive and susceptible, improving → can de-escalate therapy . Anaerobic cultures at 4-7 days

Duration of therapy ● Patients should start improving in 2-3 days ● Established infections → 4 to 7 days ● At least 1 week after the dialysate fluid is clear and for a total of at least 14 days ○ Treatment failure if re-operation needed, or do not improve until 1-2 weeks ● Adjunctive Therapy ○ Enteral or parenteral nutrition to improve immune function and wound healing to ensure recovery

Other considerations ● Superinfection ○ Due to candida usually - treat with an azole antifungal ○ Enterococci, opportunistic gram-negative bacilli (pseudomonas, serratia) may be involved Monitoring ● MAP, CVP ● Urine output, renal function tests ● Weight to ensure proper nutrition ● Wound healing ● Aminoglycoside peaks/troughs (if applicable) ○ See “General ID Knowledge Sheet”

References: - Link to Dipiro Textbook - Chapter 114 - https://accesspharmacy.mhmedical.com/content.aspx?bookid=1861§ionid=1 46072317 - Link to Dipiro Handbook - Chapter 42 - https://accesspharmacy.mhmedical.com/content.aspx?bookid=2177§ionid=1 65473051