Indian Pediatrics 2002; 39:145-157  

Management of Empyema Thoracic in Children

Meenu Singh
Saroj Kumar Singh*
Sujit Kumar Chowdhary+

From the Departments of Pediatrics and +Pediatric Surgery, Postgraduate Institute of Medical Education and Research, Chandigarh 160 072, India and *Department of Pediatrics, Division of Pulmono-logy, St. Stephen’s Hospital, Tis Hazari, Delhi, India.

Correspondence to: Dr. Saroj Kumar Singh, Specialist, Department of Pediatrics, Division of Pulmonology, St. Stephen’s Hospital, Tis Hazari, Delhi, India.

E-mail: [email protected]

Pneumonias are often associated with pleural effusions and a small proportion of them progress to empyema. Due to poor facilities for culture, delay in seeking medical opinion and indiscriminate use of antibiotics, it is very difficult to isolate microorganisms in Indian conditions. Only one study from India is reported in pediatric medical literature(1). There are no universally accepted guidelines for management of empyema thoracic. This article will discuss the diagnosis and management of empyema based on current evidence in medical literature.

Empyema thoracic is characterized by presence of pus or microorganism in the pleural fluid. Microorganisms may be seen on smear examination or on culture. In the absence of microorganism, the diagnosis is made if the following criteria are met: (a) The pH of pleural fluid is less than 7.0; (b) Lactic dehydrogenase (LDH) is more than 1000 IU/L, glucose is less than 40 mg/dl or lactate is more than 5 mol/L or 45 mg/ml(2-4).

Half of the patients with empyema develop it as a complication of pneumonia(5). Factors that predispose a patient to pulmonary infec-tion and empyema are poor orodental hygiene, periodontal disease, mental retardation, cardiac failure, sedative drug use, cortico-steroid or immuno suppressive therapy and aspiration syndromes(6-9). Other factors which can predispose to empyema are IV drug abuse, sub diaphragmatic infection, lung abscess, retropharyngeal abscess, abscessed mediastinal lymph nodes, paravertebral abscess, introduction of organism related to upper abdominal surgery, trauma, thoracic surgery or thorcocentesis(7-10). Neglected foreign body can cause bronchiectasis and predispose to empyema(11). Predisposing conditions unique to children include cerebral palsy, immunosuppression, congenital heart disease and prematurity(12-14). Cerebral palsy and congenital heart disease predispose to empyema due to aspiration and poor nutritional status respectively. Some cases of empyema occur without a predisposing factor(9,15).

Table I__Common Bacterial Pathogens Leading to Empyema Thoracic in Children

Common aerobic and anerobic bacteria leading to empyema are summarized in Table I(2,5,7,12,14-22). Staphylococcus aureus, Streptococcus pneumoniae and Streptococcus pyogenes are the organisms most commonly implicated in empyema thoracic(14,15). S. aureus is the most common pathogen(1,16). Although Pneumococcal pneumonia presents with effusion in 40% patients, empyema occurs only in 5%(14). Group A Streptococcus is less common but it produces large pleural effusions that progress rapidly to produce empyema and sepsis (15,17). Haemophilus influenzae pneumonia with empyema was common in children below 8 years of age in developed countries but its incidence has decreased following vaccina-tion(18). In an Indian series, S. aureus was most common organism followed by S. pneumoniae, Klebsiella aerogenes, S. faecalis while Escherichia coli, Erysipelothrix rhusio-pathiae were seen in one cases each(1). Pseudomonas aeruginosa was found to be the second most common pathogen in one series(19). Frank tuberculous empyema is rare, occurring in only about 2% cases of tuberculous pleurisy(16). It represents a chronic active infection of the pleural space that contains large number of tubercle bacilli(20).

Anaerobes and enterobacter are common in mixed infections. Anaerobes are more common after 6 years of age. For anaerobes, aspiration pneumonia is the most common cause followed by lung abscess, sub diaphrag-matic abscess and spreading infection from adjacent sites, e.g. periodontal, retropharyn-geal, peritonsillar and neck abscesses. Aspergillus fumigatus and Candida albicans are fungi which can cause empyema(22). Entamoeba histolytica may cause empyema if a subdiaphragmatic abscess bursts in pleural cavity(5).

Empyema is more common in the poor socioeconomic group. The incidence peaks between 0-3 years of age(19). Clinical signs vary depending on the type of organism iso-lated, age of the patient, stage of the effusion and type of prior antibiotic therapy(12). A high index of suspicion and appreciation of factors that predispose to development of empyema facilitates its recognition. Common symptoms are chills, fever, dyspnea, chest pain or referred pain, night sweat, malaise, cough and increased sputum produc-tion(2,5,12,21,23). Fever may not be present in immunocompromised or debilitated patients(22,24). When pneumonia results in empyema with aerobes, there is a symptom free period at the end of the episode of pneumonia during which the bacteria are multiplying in the pleural space(12,23).

On physical examination, diminished breath sounds, dullness to percussion, pleural friction rub, bronchophony or aegophony above pleural effusion and mediastinal shift are common signs. Focal chest wall heat, erythema, swelling, splinting of the chest or a preference to lie on the affected side may be noticed(5).

Pleural effusions are nutritionally rich culture media with poor white blood corpuscles (WBC) defenses. The pleural space is normally sterile but readily colonized once pleural fluid is accumulated(5). Para-pneumonic effusions that occur in first 48-72 hours are small, sterile polymorphonuclear leucocytes (PMNS) predominant exudate with pleural fluid pH more than 7.30, glucose more than 60 mg/dl and LDH less than 500 IU/L (25-28). If pneumonia remains untreated, the amount of pleural fluid increases with time due to endothelial injury, increased localized permeability and edema. Bacteria invade pleural space and become persistent(29). Then comes fibrinopurulent phase characterized by an increased number of PMNS, a fall in pleural fluid pH and glucose with an increase in the pleural fluid LDH. The pleural fluid/serum glucose ratio decreases to less than 0.5 and the absolute concentration of glucose is usually less than 40 mg/dl because of increased glycolysis due to PMNS phago-cytosis and bacterial metabolism(30). As the end products of glucose metabolism, lactic acid and CO2 accumulate in the pleural space, the pH falls below 7.10 and the level of LDH increases above 1000 IU/L due to cell lysis. During this phase, pleural fluid becomes clottable with a large concentration of plasma proteins in the pleural space and reduced fibrinolytic activity due to inflammatory injury(31). These processes result in deposition of a dense layer of fibrin on both pleural surfaces. Fibroblasts move into the pleural space and produce septa leading to loculations. Later on fibroblasts grow in the exudate and lead to formation of the peel(32). A patient has simple empyema if the pleural fluid is frank pus, free flowing with single locule. A patient is said to have a complex empyema if the pleural fluid is frank pus and multi loculated.

In empyema, pathological response may be divided in three phases that are not sharply distinct but gradually one phase merges into another with progression depending largely on the infecting organism(12,32,33).

(a) Exudative stage (1-3 days): This is the immediate response with outpouring of the fluid. The cellular content of the exudates is relatively low. During this stage the fluid is thin and lungs are readily re-expandable. At this point fluid is considered a simple parapneumonic effusion with normal pH and glucose levels. Pleural fluid analysis shows pH more than 7.30, glucose more than 60 mg/dl, pleural fluid/serum glucose ratio more than 0.5, LDH less than 1000 IU/L while Gram stain and culture is negative for micro-organism.

(b) Fibrino purulent stage (4 to 14 days): In this stage a large number of poly-morphonuclear leukocytes and fibrin accumulate in the effusion. Pleural fluid pH and glucose level fall while LDH rises. With continued accumulation of neutro-phils and fibrin, effusion becomes purulent and viscous leading to development of empyema. There is progressive tendency towards loculations and formation of a limiting membranes. Pleural fluid analysis shows purulent fluid or pH less than 7.10, glucose less than 40 mg/dl and LDH more than 1000 IU/L. Gram stain and culture reports show microorganism.

(c) Organizing stage (after 14 days): Fibro-blasts grow into exudates on both the visceral and parietal pleural surfaces, producing an inelastic membrane "the peel". Thickened pleural peel may prevent the entry of anti-microbial drugs in the pleural space and in some cases can lead to drug resistance. It is most common in S. aureus infection. A thickened pleural peel can restrict lung movement and it is commonly termed as trapped lung.

There can be leukocytosis with poly-morphonuclear cells predominance(13). Rarely leukopenia has been observed in severely ill patients having organ trans-plant(23). Patients with lower hemoglobin, low serum albumin and abnormal liver func-tion test such as increased serum bilirubin, abnormally raised aspartate aminotransferase (AST), increased alkaline phosphatase are more severely ill(2,13).

Chest radiography is the primary investigation for patients with pleural disease(34). Large pleural effusion can be diagnosed in posteroanterior view(14). Lateral decubitus view with affected side inferior facilitates recognition of smaller volumes of fluid. X-ray in different positions helps to recognize the extent of parenchymal infection and may reveal loculated fluid(16).

Ultrasonography (USG) chest is a very useful tool for diagnosis, guidance of thoraco-centesis, or pleural catheter placement. Sonographic appearance of pleural fluid is quite variable ranging from an anechoic (completely echofree or sonolucent) to very echogenic. Transudates are usually anechoic, whereas exudates can be echoic or anechoic(35). Sonography can distinugish solid from liquid pleural abnormalities with 92% accuracy compared to 68% accuracy with chest X-ray. When both are combined, accuracy rises to 98%(36). USG shows limiting membranes suggesting the presence of loculated collections even when they are invisible by CT scan. In one series, sono-graphy was used to determine nature of effusion. In addition to being anechoic, complex non-septated and complex septated, a pleural effusion can be homogenously echogenic.

Empyema appears well defined, smooth, round or elliptical on computed tomography (CT Scan). The margins are composed of inflamed visceral and parietal pleura that often have a markedly thickened appearance and enhance after administration of contrast material. The parietal and visceral layers are separated by interposed empyema fluid, giving rise to "split pleura sign" of empyema(37). CT scan can differentiate extra pleural and subcostal fat external to thickened pleura by its much lower CT attenuation. CT chest usually differentiates empyema from consolidation and lung abscess. The optimal evaluation of pleuropulmonary disease necessitates the use of intravenous contrast, which causes enhancement of pleural membrane(37). In tuberculous empyema, CT scan show a thick calcific ring and rib thickening surrounding loculated pleural fluid(20).

In all patients with pneumonia, a careful search should be made for a pleural effusion including a decubitus view X-ray. If effusion is free flowing and greater than one centimeter from inside of the chest wall to the pleural fluid line on the lateral decubitus view, immediate diagnostic thoracocentesis should be done(38). If loculated, thoracocentesis should be done under ultrasound guidance. The site for thoracocentesis is 1 cm below upper level of dullness because inflammed pleura may lead to upward displacement of solid organs lying below diaphragm(16). The characteristic of the fluid including odor must be noted. Gram stain, culture, pH, glucose, LDH and WBC count are performed on the aspirate. Pleural fluid for pH must be handled meticulously like arterial blood for pH and drawn anaerobically into a syringe with 0.2% of 1:1000 heparin and placed on an ice until analyzed. In the tube for glucose estimation, antiglycolytic substance fluoride oxalate 0.1 ml (containing 2 mg of sodium fluoride and 6 mg of potassium oxalate) must be added per 2 ml of pleural fluid to prevent in vitro glycolysis due to the polymorphs present(39). Uncomplicated parapneumonic effusion show pH more than 7.30, glucose more than 60 mg/dl and LDH less than 1000 IU/L (mostly less than 500 IU/L). Complicated parapneumonic effusion is characterized by pH less than 7.10, glucose less than 40 mg/dl and LDH more than 1000 IU/L. When acidemia is present, pleural fluid acidosis is defined as pH at least 0.15 unit below blood pH. Pleural fluid pH value 0.3 unit less than serum pH value may need chest tube insertion(39). Two third of the cases of anaerobic infection have malodorous empyema(40,41). Protein level and specific gravity is rarely helpful in differentiating stages of empyema(5). Microbes can be seen on Gram stain but empyema fluid can be sterile in culture. In some cases with frank pus, organisms are neither seen on Gram stain nor grown in culture. Such cases must raise a suspicion of chylous effusion which should be excluded by testing the fluid for neutral fat, pH and sedimentation values after centrifugation at 5000 g. Purulent empyema has acid pH and cell fragments will sediment where a chylous effusion will have a neutral pH and remain opaque after centrifugation(5). Tuberculous empyema can be confirmed by stains for acid fast bacilli in fewer than 25% cases but pleural biopsy and culture can diagnose more than 90% cases(42). Demonstration of pleural fluid adenosine deaminase levels more than 70 U/L supports the diagnosis of tuberculous pleural empyema. Diagnostic utility of polymerase chain reaction (PCR) for detection of mycobacterial antigen in pleural fluid is still under investigation(5).

Effective therapy requires control of infection, drainage of pus and expansion of lungs. Fig. 1 depicts a suggested treatment plan which is based on stage of empyema, quantity of fluid present, the result of Gram stain and cultures, the biochemical character-isitics, the presence or absence of loculations and the gross characteristics of pleural fluid(12,39,43).

Antibiotic coverage should be given in all cases of empyema depending on suspected etiological agent. Antibiotics should be changed later on the basis of culture and sensitivity report. Antibiotics used against common pathogens leading to empyema are given in Table II(16).

Bearing in mind the pathogens involved, Injection Cloxacillin alongwith Injection Cefotaxime or Injection Ceftriaxone can be used for initial therapy. If anaerobic infection is strongly suspected, Injection Clindamycin should be added. Aminoglycosides can be added in suspected S. aureus case for synergy(43). Monotherapy with aminoglyco-sides is contraindicated because they have poor activity in the pus. Ciprofloxacin can be substituted for aminoglycosides(5). Amoxi-cillin combined with b-lactamase inhibitor such as clavalunic acid at a dose based on amoxycillin component of 40-80 mg/kg can be effective in S. aureus and H. influenzae infection(43,44). Clindamicin, Cefazolin, Nafcillin, first generation cephalosporins such as Cephalexin, trimethoprim-sulphamethaxa-zole and imipenem are effective against S.aureus infection(43). In methicillin resistant S. aureus intravenous Vancomycin 60 mg/kg/day in four divided dosage is the drug of choice. Lower range of dose regime is used in neonates. S. pneumoniae and H. influenzae respond to parenteral Cefuroxime or Chloramphenicol(45). Resistance to extended spectrum cephalosporins such as cefotaxime or ceftriaxone is not reported in H. influenzae infection (44). Penicillin G is drug of choice for penicillin susceptible pneumococci. Cephalosporin susceptible pneumococci with intermediate susceptibility to penicillin should be treated with cefotaxime or ceftriaxone. S. pneumoniae with high level of resistance to pencillin (MIC >2 µg/ml) and to ceftriaxone or cefotaxime (MIC >4mg/ml) should be treated with Vancomycin(5). All these antibiotics attain many fold higher concentration in pleural fluid than minimum inhibitory concentration needed. In case of S. pneumoniae and H. influenzae infection children can remain febrile for 7 or more days after adequate antibiotic therapy has been instituted while children having S. aureus infection can remain febrile for 10-14 days despite appropriate management(45). Paren-teral therapy should be continued for 48-72 hours after abatement of fever and then oral therapy can be used to complete the course(45). Antibiotic should be continued until patient is afebrile, WBC count is normal, tube thoracostomy yield is less than 50 ml of fluid per day and radiograph show consider-able clearing(46). Normally, H. influenzae and S.pneumoniae need 7-14 days course of antibiotics while S. aureus needs 3-4 weeks. Duration of therapy for anaerobic empyema is variable depending on whether lung lesions go on to cavitate. Often 6-12 weeks are required before the lung lesions clear or only a small stable residual disease is left(16).

In suspected cases of multidrug resistant tuberculous empyema, treatment should be started with five drug combination of Iso-niazid (H), Rifampicin (R), I. Pyrazinamide (Z), Ethambutol (E), Streptomycin (S) {sometimes added Thiacetazone} for first 2 months followed by another month of four drug therapy (HRZE). This is followed by three drug therapy (HRE) for 5-6 months. If the patient is sputum positive at the end of four months and can afford the treatment cost, he is considered for second line drug therapy(47). Once culture report is available, indivi-dualized regimes based on antimicrobial susceptibility with two or more effective drugs should be given(5). Tuberculous empyema presents a special situation. Like all tuberculous effusions steroids may help to reduce effusion and its sequelae, however our institutional practice is not to use cortico-steroids because of the large number of mycobacteria present in the empyema fluid.

*Lower dose in dose range and less frequent intervals of administration are recommended for neonates. IV–intravenously.

Empyema drainage is a major component of empyema treatment. Patients with loculated fluid, or frank pus, or smear positive fluid, or fluid with pH less than 7.10, glucose less than 40 mg/dl and LDH more than 1000 IU/L, require chest tube drainage(16). Repeated thoracocentesis is rarely successful in such cases. Small-bore percutaneous catheters can be used if the fluid is thin. A chest tube with an under water seal should be placed. Drainage under direct CT guidance is most convenient if empyema collection is small(48). Chest tube drainage is advised for drainage of tuberculous empyema. Chest tube must be kept inside till drainage is less than 30-50 ml per day and cavity size is less than 50 ml in size(16,29).

This is useful in multiloculated empyema. Streptokinase (SK) and Urokinase (UK) are used as thrombolytics. SK is a nonenzymatic streptococcal exotoxin. It becomes plasmin activator after combining with plasminogen. When inactive plasminogen is cleaved, plasmin is generated. Plasmin hydrolyse fibrin leading to hydrolysis of fibrin coagulum. UK is a direct plasminogen activator. For one molecule of UK, one molecule of plasmin is produced and thus making it more effective(49).

Multiloculation of empyema was defined on the basis of USG/CT finding showing presence of two or more loculations that were separated and without communication(49). Loculations were defined by one or more of the following criteria-failure of effusion to layer on decubitus film, fixed fluid in abnormal locations, septations seen on USG or CT scan (present prior to instrumentation). Patients with loculated empyema fared badly(49). SK 2,50,000 unit or UK 1,00,000 unit in 100 ml normal saline was instilled through chest tube in randomly assigned two groups and tube was clamped for 3 hours. Number of instillation in SK and UK were 6 ± 2.16 and 5.92 ± 2.05, respectively and increase in total net volume of fluid drained was comparable in both groups. In both groups two patients out of 25 patients failed to respond completely(7). Transient increase of body temperature was noted in 28% cases of SK while no complication was noted with UK. UK as little as 50,000 unit per instillation was found to be successful in 95% cases in one series. No changes in coagulation profile were noted in that series. The cost of therapy with 50,000 unit UK was equal to 2,50,000 unit of SK(8).

(a) Videoassisted Thoracoscopic Surgery (VATS): It is quite effective in lysis of adhesions in multiloculated effusions and removal of fibrinous material from pleural cavity. When necessary, a limited decortication of fibrinous material can be done using a standard or endosurgical instruments(50,51). If significant fibrosis or entrapment is identified at VATS exploration, thoracostomy is performed. The VATS instrument helps in identifying most appropriate site for thoracostomy incision, helps in visualization and breakdown of deeper pockets and putting drainage catheter at appropriate site(50). VATS is often not as useful in organizing stage.

(b) Thoracoscopic Debridement and Irrigation: It is quite effective in cases with multiloculated empyema. Success rate is as high as 69% to 89%(52,53). This is as effective as enzymatic treatment using SK or UK. It helps by breaking adhesions and converting the multi-loculated cavity into a single cavity. Formal decortication is reserved for cases with fibrotic visceral peel that restricts the expansion of underlying lung(54).

(c) Decortication: It is advised for the cases not helped by above procedures. Some studies advocate early decortication to avoid permanent surgical impair-ment(2,13,21). If patient is too debilitated to tolerate thoracostomy, then open drainage is preferable(29).

Spontaneous healing of bronchopleural fistula is extremely rare. Very few cases may heal after closed tube drainage of thoracic cavity. If this fails to happen in 2-3 weeks time, decortication with excision of the fibrous encasement of the lung and resultant expansion of lung with closure of obvious fistula will succeed in a few. Persistence of bronchopleural fistula because of inability to suture, or sutures giving way is treated with long-term external drainage after two weeks of surgery with gradual withdrawl of the chest tube. This may allow the fistula to close over a period of upto one-year. If all these interventions fail, then one is left with the option of thoracoplasty or resectional surgery of the lung parenchyma (lobar resection). These are formidable procedures in children and should not be undertaken without adequate conservative management and experience. The response to all these attempts depends on the size of fistula, state of underlying lung and contralateral lung, presence or absence of systemic illness, nutritional rehabilitation and medical measures(55).

In most of the cases, pulmonary function is found to be normal(56). Few cases show complications such as scoliosis, mild pleural thickening and mild restrictive defect(54). Mild obstruction has been documented on pulmonary function testing. This complication was similar in cases who underwent chest tube drainage and those who did not(57). A positive correlation between age and recovery period has been reported. Younger children fared less well(19).

Empyema thoracic is a common complication of pneumonia. Children of poor socio-economic status and below 3 years of age are most commonly affected. Staphylo-coccus aureus is the most common causative organism. A high index of suspicion helps in diagnosis. X-ray chest, USG chest and CT scan are most useful modalities for diagnosis and follow-up. Thoracocentesis and pleural fluid analysis help in deciding therapy. Proper antibiotic coverage and drainage by chest tube is needed, if empyema is not loculated. Streptokinase and Urokinase can be used in multiloculated empyema. Video assisted thoracoscopic surgery or thoracoscopy with debridement are equally effective for multi-loculated empyema. Cases not responding to above measures need decortication. Long term follow up shows normal pulmonary function test in majority of the cases.

Contibutors: SKS reviewed literature and drafted the manuscript while MS critically analyzed the paper. SKC reviewed surgical aspect especially broncho-pleural fistula. SKS will act as the guarantor for the manuscript.

Funding: None.

Competing interests: None stated.

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