AUTHOR INFORMATION

Section 1 of 11

Authored by Mark Zwanger, MD, MBA, Assistant Professor, Department of Emergency Medicine, Thomas Jefferson University

Coauthored by Patti Purpura, MD, Consulting Staff, Department of Emergency Medicine, Virginia Mason Hospital

Mark Zwanger, MD, MBA, is a member of the following medical societies: American College of Emergency Physicians

Edited by Mark S Slabinski, MD, Director, Emergency Services, Southeastern Ohio Regional Medical Center; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Paul Blackburn, DO, Program Director, Department of Emergency Medicine, Maricopa Medical Center; Assistant Professor, Department of Surgery, University of Arizona; John Halamka, MD, Chief Information Officer, CareGroup Healthcare System, Assistant Professor of Medicine, Department of Emergency Medicine, Beth Israel Deaconess Medical Center; Assistant Professor of Medicine, Harvard Medical School; and Robert E O'Connor, MD, MPH, Director of Education and Research, Department of Emergency Medicine, Christiana Care Health System; Professor of Emergency Medicine, Thomas Jefferson University

Author's Email:	Mark Zwanger, MD, MBA
Editor's Email:	Mark S Slabinski, MD

eMedicine Journal, March 21 2005, VOLUME 6, Number 3

INTRODUCTION

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Background: A lung abscess is a subacute infection in which an area of necrosis forms in the lung parenchyma. It usually is in a dependent section of the lung, more often involves the right lung than the left, and is most commonly seen after aspiration of oropharyngeal secretions. Lung abscesses have a slow, insidious presentation and usually develop 1-2 weeks after the initial aspiration event.

Empyema is defined as pus in the pleural space. It typically is a complication of pneumonia. However, it can also arise from penetrating chest trauma, esophageal rupture, or inoculation of the pleural cavity after thoracentesis or chest tube placement. An empyema can also occur from extension of a subdiaphragmatic or paravertebral abscess.

Pathophysiology: Lung abscesses involve the lung parenchyma, while empyema involves the pleural space.

Mortality/Morbidity: The mortality rate for lung abscesses is approximately 4-7% but varies with the type of material aspirated. Aspiration of fluids with mixed gram-negative flora has a mortality rate approaching 20%, while aspiration of acidic materials has an even higher rate.

Age: These conditions occur more commonly in the elderly.

CLINICAL

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History: The patient's history may reveal the following findings:

• Recent diagnosis and treatment for pneumonia

• Recent history of penetrating chest trauma (should raise clinical suspicion for empyema)

• Cough productive of bloody sputum that frequently has a fetid odor or offensive appearance

• Fever

• Shortness of breath

• Anorexia, weight loss

• Night sweats

• Pleuritic chest pain

Physical: The physical examination may reveal the following findings:

• Temperature frequently elevated but usually not greater than 102°F

• Tachypnea

• Rales

• Rhonchi

• Egophony

• Tubular breath sounds

• Decreased breath sounds

• Dullness to percussion

Causes:

• The most common cause of lung abscess or empyema is aspiration. Patients at the highest risk are those who have the following:

• Poor dentition

• Seizure disorder

• Alcohol abuse

• Inability to protect their airway because of an absent gag reflex (eg, patients who are comatose, have a change in mentation, or who might be undergoing general anesthesia)

• Primary lung disorders, such as septic emboli, vasculitic disorders, cavitating lung malignancies, or pulmonary cystic disease

• A cause of lung abscess or empyema includes penetrating chest trauma.

• Empyema secondary to chest penetration is caused by primary contamination of the trauma wound or inadequate skin preparation before needle decompression, chest tube placement, or thoracentesis.

• The microbiologic organisms involved in lung abscesses and empyema typically are polymicrobial oral flora, including Bacteroides, Fusobacterium, and Peptostreptococcus species.

• Pseudomonas species, Klebsiella species, Staphylococcus aureus, Streptococcus pneumoniae, Nocardia species, and fungal species are less commonly seen. Increasingly in the pediatric population, S aureus has become the predominant organism associated with empyemas because of the widespread use of the pneumococcal conjugate vaccine. One should always consider methicillin-resistant Staphylococcus aureus (MRSA) and Mycobacterium tuberculosis potential pathogens.

• The microbiologic organisms involved in empyema caused by chest penetration typically are skin flora, such as S aureus or Staphylococcus epidermis.

DIFFERENTIALS

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Pleural Effusion
Pneumonia, Aspiration
Pneumonia, Bacterial
Pneumonia, Immunocompromised
Pneumonia, Mycoplasma
Pneumonia, Viral
Tuberculosis

Other Problems to be Considered:

Sarcoidosis

WORKUP

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Lab Studies:

• A CBC with differential may reveal a leukocytosis and a left shift.

• Collect sputum for Gram staining, culturing, and sensitivity testing.

• If tuberculosis is suspected, acid-fast bacilli testing should be obtained.

• Blood culturing is also appropriate.

Imaging Studies:

• Perform chest radiography to diagnose and differentiate pneumonia, pulmonary abscess, and empyema. Distinction of these conditions is important because lung abscesses and pneumonia require medical treatment, while empyema frequently requires definitive surgical therapy.

• On the chest radiograph, a lung abscess appears as a solitary cavitary area with an air-fluid level, which typically is present in a dependent portion of the lung.

• A surrounding patchy area of infiltrate aids in differentiating a pulmonary abscess from a cavitary lung cancer.

• On the chest radiograph, findings that suggest empyema, as opposed to lung abscess, include extension of the air-fluid level to the chest wall, extension of the air-fluid level across fissure lines, and a tapering border of the air-fluid collection.

• The costophrenic angle should be closely inspected on the chest radiograph to assess the presence of fluid that suggests effusion or empyema.

• On the chest radiograph obtained of the patient in an upright position, blunting of the costophrenic angle occurs when approximately 175 mL of fluid accumulates.

• A lateral chest decubitus radiograph, obtained with the patient on his or her side, reveals whether the pleural fluid is mobile and forms layers or whether it is loculated.

• If the chest radiograph does not adequately distinguish between lung abscess and empyema (versus mass or tumor), CT of the chest or ultrasonography is required.

Other Tests:

• Pulse oximetry - To assess oxygenation

• ABG analysis - To assess respiratory adequacy

• Transtracheal aspiration for culturing - If sputum findings are nondiagnostic

Procedures:

• If a pleural effusion is present, a diagnostic thoracentesis should be performed, and the fluid should be analyzed for pH, lactate dehydrogenase, and glucose levels; specific gravity; and cell count with differential.

• Gram staining, cultures, and acid-fast bacillus and sensitivity tests should also be obtained.

• The fluid should be sent for cytology if cancer is suspected.

• The following findings are suggestive of an empyema or a parapneumonic effusion, which resolves only with a chest tube:

• Grossly purulent pleural fluid

• pH level less than 7.2

• WBC count greater than 50,000 cells/mL (or polymorphonuclear leukocyte count of 1,000 IU/dL)

• Glucose level less than 60 mg/dL

• Lactate dehydrogenase level greater than 1,000 IU/mL

• A pleural fluid marker currently being studied is tumor necrosis factor (TNF)–alpha. In patients who have pleural effusions, a TNF-alpha level >80 pg/mL is suggestive of an empyema or complicated parapneumonic effusion.

TREATMENT

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Prehospital Care:

• Supplemental oxygen should be given and an intravenous line started.

• Appropriate airway management, including intubation, should be performed depending on the patient's clinical condition.

Emergency Department Care:

• All patients should undergo pulse oximetry and evaluation of their respiratory status.

• If respiratory failure is found or likely to occur, intubation and mechanical ventilation is necessary.

• Supplemental oxygen should be started for any patient who is acutely short of breath or who is hypoxic based on pulse oximetric findings.

• Once the diagnosis of a lung abscess is made, parenteral antibiotics should be started. Ideally, sputum and blood culture findings should be obtained prior to the initiation of antibiotics.

• After the diagnosis of empyema is made, prompt drainage by means of tube thoracostomy with use of parenteral antibiotics should be initiated.

Consultations: Treatment of lung abscesses or empyema is performed in-hospital, with consultations involving internists and/or thoracic surgeons. Many now advocate administering intrapleural fibrinolytics in patients with empyemas to assist in the breakdown of fibrin bands that can cause loculation of the empyema and to allow for better chest tube drainage of the infected material. If chest tube drainage and fibrinolytic treatment are unsuccessful, many authors recommend video-assisted thoracoscopic surgery (VATS) rather than the more traditional open thoracotomy. VATS is less invasive and well tolerated, and outcomes compare favorably with open thoracotomy.

MEDICATION

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Lung abscesses are treated with a prolonged course of parenteral antibiotics that target organisms found in aspiration pneumonia. The initial choice of antibiotics frequently is empiric, beginning with clindamycin, cefoxitin, ticarcillin, or piperacillin/tazobactam, although penicillin has been very effective when the organism is sensitive. Subsequent therapy should be based on sputum or blood culture results.

An empyema is treated with prompt chest tube drainage with the use of parenteral antibiotics. Empiric therapy for an empyema is frequently with imipenem or piperacillin/tazobactam until a definitive organism is identified on pleural fluid cultures and sensitivities are obtained. For an empyema secondary to aspiration pneumonia or a parapneumonic process, choose antibiotics that are active against mouth flora, S aureus and Streptococcus species. For an empyema secondary to penetrating chest trauma, administer antibiotics that have coverage for skin flora. If MRSA is suspected, include vancomycin in the treatment plan. Pleural fluids or sputum specimens that are obtained should be cultured for M tuberculosis as well.

Drug Category: Antibiotics -- Empiric antimicrobial therapy must be comprehensive and should cover all likely pathogens in the context of the clinical setting

Drug Name	Clindamycin (Cleocin) -- Lincosamide for the treatment of serious skin and soft-tissue staphylococcal infections. Also effective against aerobic and anaerobic streptococci (except enterococci). Inhibits bacterial growth, possibly by blocking dissociation of peptidyl t-RNA from ribosomes causing RNA-dependent protein synthesis to arrest.
Adult Dose	600 mg IV q6-8h
Pediatric Dose	25-40 mg/kg/d IV divided tid/qid
Contraindications	Documented hypersensitivity; regional enteritis; ulcerative colitis; hepatic impairment; antibiotic-associated colitis
Interactions	Increases duration of neuromuscular blockade, induced by tubocurarine and pancuronium; erythromycin may antagonize effects; antidiarrheals may delay absorption
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Adjust dose in severe hepatic dysfunction; no adjustment necessary in renal insufficiency; associated with severe and possibly fatal colitis

Drug Name	Cefoxitin (Mefoxin) -- Second-generation cephalosporin indicated for infections with gram-positive cocci and gram-negative rod. Infections caused by cephalosporin- or penicillin-resistant gram-negative bacteria may respond.
Adult Dose	2 g IV q6-8h
Pediatric Dose	80-160 mg/kg/d IV divided q4-6h
Contraindications	Documented hypersensitivity
Interactions	Probenecid may increase effects; coadministration with aminoglycosides or furosemide may increase nephrotoxicity (closely monitor renal function)
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Bacterial or fungal overgrowth of nonsusceptible organisms may occur with prolonged use or repeated treatment; caution in patients with previously diagnosed colitis

Drug Name	Penicillin G (Pfizerpen) -- Interferes with synthesis of cell wall mucopeptide during active multiplication, resulting in bactericidal activity against susceptible microorganisms; traditional drug for the treatment of lung abscess, but its spectrum of activity is narrow.
Adult Dose	2 million U IV q4h
Pediatric Dose	150,000 U/kg/d IV divided q4h
Contraindications	Documented hypersensitivity
Interactions	Probenecid can increase effects; coadministration of tetracyclines can decrease effects
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Caution in impaired renal function

Drug Name	Ticarcillin/clavulanate (Timentin) -- Inhibits biosynthesis of cell wall mucopeptide and is effective during active growth stage. Antipseudomonal penicillin plus beta-lactamase inhibitor that provides coverage against most gram-positive bacteria, most gram-negative bacteria, and most anaerobes.
Adult Dose	3.1 g IV q4-6h
Pediatric Dose	75 mg/kg IV q6h
Contraindications	Documented hypersensitivity; severe pneumonia, bacteremia, pericarditis, emphysema, meningitis, and purulent or septic arthritis should not be treated with oral penicillin during acute stage
Interactions	Tetracyclines may decrease effects of ticarcillin; high concentrations of ticarcillin may physically inactivate aminoglycosides if administered in same IV line; synergistic effects when administered concurrently with aminoglycosides; probenecid may increase penicillin levels
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Perform CBC prior to initiation of therapy and at least weekly during therapy; monitor for liver function abnormalities by measuring AST and ALT levels during therapy; caution in patients with hepatic insufficiencies; perform urinalysis and BUN and creatinine determinations during therapy, and adjust dose if values become elevated; monitor blood levels to avoid possible neurotoxic reactions

Drug Name	Piperacillin/tazobactam (Zosyn) -- Antipseudomonal penicillin plus beta-lactamase inhibitor. Inhibits biosynthesis of cell wall mucopeptide and is effective during stage of active multiplication.
Adult Dose	3.375 g IV q6h
Pediatric Dose	<12 years: Not established >12 years: Administer as in adults
Contraindications	Documented hypersensitivity; severe pneumonia, bacteremia, pericarditis, emphysema, meningitis, and purulent or septic arthritis should not be treated with an oral penicillin during the acute stage
Interactions	Tetracyclines may decrease effects of piperacillin; high concentrations of piperacillin may physically inactivate aminoglycosides if administered in same IV line; synergistic effects when administered concurrently with aminoglycosides; probenecid may increase penicillin levels; high-dose parenteral penicillins may result in increased risk of bleeding
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Perform CBC prior to initiation of therapy and at least weekly during therapy; monitor for liver function abnormalities by measuring AST and ALT levels during therapy; caution in patients with hepatic insufficiencies; perform urinalysis and BUN and creatinine determinations during therapy, and adjust dose if values become elevated; monitor blood levels to avoid possible neurotoxic reactions

Drug Name	Imipenem and cilastatin (Primaxin) -- For treatment of multiple organism infections in which other agents do not have wide-spectrum coverage or are contraindicated because of potential for toxicity.
Adult Dose	Base initial dose on severity of infection and administer in equally divided doses; dose may range from 250-500 mg IV q6h for a maximum of 3-4 g/d Alternatively, 500-750 mg IM q12h or intra-abdominally
Pediatric Dose	<12 years: Not established; 15-25 mg/kg/dose IV q6h suggested for > 3 months Fully susceptible organisms: Not to exceed 2 g/d Infections with moderately susceptible organisms: Not to exceed 4 g/d >12 years: Administer as in adults
Contraindications	Documented hypersensitivity
Interactions	Coadministration with cyclosporine may increase CNS side effects of both agents; coadministration with ganciclovir may result in generalized seizures
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Adjust dose in renal insufficiency; avoid use in children <12 years

Drug Name	Vancomycin (Vancoled, Vancocin, Lyphocin) -- Potent antibiotic directed against gram-positive organisms and active against Enterococcus species. Useful in the treatment of septicemia and skin structure infections. Indicated for patients who cannot receive or whose conditions are unresponsive to penicillins and cephalosporins or have infections with resistant staphylococci. For abdominal-penetrating injuries, it is combined with an agent active against enteric flora and/or anaerobes. To avoid toxicity, current recommendation is to assay vancomycin trough levels after third dose drawn 0.5 h prior to next dosing. Use CrCl to adjust dose in patients with renal impairment.
Adult Dose	500 mg to 2 g/d IV divided tid/qid
Pediatric Dose	40 mg/kg/d IV divided tid/qid
Contraindications	Documented hypersensitivity
Interactions	Erythema, histaminelike flushing, and anaphylactic reactions may occur when administered with anesthetic agents; taken concurrently with aminoglycosides, risk of nephrotoxicity may increase above that associated with aminoglycoside monotherapy; effects in neuromuscular blockade may be enhanced when coadministered with nondepolarizing muscle relaxants
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Caution in renal failure and neutropenia; red man syndrome is caused by too rapid IV infusion (dose given over a few min) but rarely happens when dose given IV over 2 h or as PO or IP administration; red man syndrome is not an allergic reaction

FOLLOW-UP

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Further Inpatient Care:

• Inpatient care is mandatory for the management and assistance of the patient's respiratory status, continuation of intravenous antibiotics, and drainage of the abscess or empyema as needed.

In/Out Patient Meds:

• Outpatient therapy for these conditions is not indicated or advised; inpatient care is mandatory.

• Antimicrobial therapy should be continued empirically until therapy can be guided with culture results.

Transfer:

• Transfer of these patients usually is not indicated unless advanced respiratory management or surgical drainage is not available without transfer.

• Patients should be transferred only after stabilization of their respiratory status and administration of intravenous antibiotics.

Deterrence/Prevention:

• Prevention of aspiration is important to minimize the subsequent risk of lung abscess.

• Early intubation should be performed in patients who do not have a gag reflex.

• Position the patient in a manner that minimizes the risk of aspiration. For example, a patient who is vomiting should be placed on his or her side.

• Immediately suction the patient's orotracheal area if he or she aspirates in the ED.

Complications:

• Complications of pulmonary abscess include pleural fibrosis, trapped lung, restrictive ventilatory defect, bronchopleural fistula, and pleurocutaneous fistula.

Prognosis:

• The prognosis for both lung abscess and empyema generally is good. Ninety percent of lung abscesses are cured with medical management alone.

Patient Education:

• For excellent patient education resources, visit eMedicine's Infections Center, Lung and Airway Center, and Pneumonia Center. Also, see eMedicine's patient education articles Bacterial Pneumonia, Abscess, and Antibiotics.

MISCELLANEOUS

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Medical/Legal Pitfalls:

• Failure to suspect the diagnosis

• Failure to perform thoracentesis for a pleural effusion: The fluid results assist in the treatment of the patient by allowing differentiation of an empyema and parapneumonic effusion. Empyema requires chest tube placement. On the contrary, an effusion can be treated with intravenous antibiotics alone.

TEST QUESTIONS

Section 10 of 11

CME Question 1: Which of the following organisms is least likely to cause a pulmonary abscess?

A: Bacteroides species
B: Fusobacterium species
C: Peptostreptococcus species
D: Streptococcus pneumoniae
E: None of the above

The correct answer is D: Lung abscesses are usually polymicrobial and result from aspiration of oral flora. The most common organisms are Bacteroides, Fusobacterium, and Peptostreptococcus species.

CME Question 2: Which of the following is not an indication for a chest tube in empyema?

A: pH level of 7.3
B: Glucose level of 55 mg/dL
C: WBC count of 70,000 cells/mL
D: Lactate dehydrogenase level of 1,200 IU/mL
E: Polymorphonuclear leukocyte count greater than 5,000 IU/dL

The correct answer is A: All options except A are indications of an empyema that requires treatment with tube thoracostomy. Grossly purulent pleural fluid is another indication of empyema that requires chest tube placement.

Pearl Question 1 (T/F): Empyema from penetrating trauma is most often caused by skin flora.

The correct answer is True: Typically, Staphylococcus aureus or Staphylococcus epidermis is the cause.

Pearl Question 2 (T/F): The prognosis for patients with empyema typically is poor.

The correct answer is False: The prognosis for patients with empyema generally is good with appropriate respiratory support, antibiotics, and drainage.

Pearl Question 3 (T/F): Patients who are edentulous are less likely to develop a pulmonary abscess.

The correct answer is True: They are less likely since they do not have poor dentition, which is a risk factor for aspiration and subsequent development of a pulmonary abscess.

Pearl Question 4 (T/F): Aspiration is the most common cause of lung abscess.

The correct answer is True: The microbiologic organisms involved in lung abscesses and empyema typically are polymicrobial oral flora, including Bacteroides, Fusobacterium, and Peptostreptococcus species.

BIBLIOGRAPHY

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