PNEUMONIADefinition:An acute respiratory illness associated with recentlydeveloped radiological pulmonary shadowing inconstellation with signs and symptoms(fever, chills, cough, pleuritic chest pain, sputumproduction, hyper- or hypothermia, increased respiratoryrate, dullness to percussion, bronchialbreathing, egophony, crackles, wheezes, pleural frictionrub)Classification: Community-acquired pneumonia Hospital-acquired pneumonia (nosocomial) Pneumonia occurring in immunocompromised hosts orpatients with underlying damaged lung (includingsuppurative and aspiration pneumonias)
FACTORS THAT PREDISPOSE TO PNEUMONIA Cigarette smoking Upper respiratory tract infections Alcohol Corticosteroid therapy Old age Recent influenza infection Pre-existing lung diseasePATHOLOGYThe pathology of pneumonia manifests as fourgeneral patterns: lobarpneumonia, bronchopneumonia, interstitialpneumonia, and miliary pneumonia.
LOBAR PNEUMONIAA radiological pathological term referring to homogenousconsolidation of one or more lung lobes, often with associatedpleural inflammation. Four stages of lobar pneumonia may exist:I.Congestion: Occurs during the 1st 24 hours; affected lobe isheavy, red and boggy; vascular congestion can be seen, withproteinaceous fluid, scattered neutrophils, and many bacteria inthe alveoli.II.Red Hepatization: The lung lobe has a liver-like consistency;alveolar spaces are filled with neutrophils, red cells, and fibrin; thepleura usually demonstrates a fibrinous or fibrinopurulent exudates.III.Grey Hepatization: The lung is dry, friable, and gray-brown toyellow as a consequence of a persistent fibrinopurulentexudates, progressive destruction of red blood cells, and thevariable presence of hemosiderin. The 2nd and 3rd stage last for 2-3days each, with a 2-6 day duration for maximal consolidationIV.Resolution: Characterized by enzymatic digestion of the alveolarexudates; resorption, phagocytosis, or coughing up of the residualdebris; and restoration of the pulmonary architecture. The pleuralreaction may similarly resolve or undergo organization, leavingfibrous thickening or pleural adhesions, causing a rub heard byauscultation
BronchopneumoniaRefers to patchy alveolar consolidation associated with bronchialor bronchiolar inflammation involving one or several lobes, usuallyinvolves the dependent lower and posterior portions of the lung(often bilaterally)—a pattern results in respect to the distribution ofaspirated oropharyngeal contents by gravity.Interstitial PneumoniaDefined by histopathologic identification of an inflammatoryprocess predominantly involving the interstitium, including thealveolar walls and the connective tissue around thebronchovascular tree. The inflammation may be patchy or diffuse.Miliary PneumoniaRefers to numerous discrete lesions resulting from the spread of thepathogen to the lungs via the bloodstream (occurs when organismsdrain through lymphatics into the lymphatic ducts, which emptyinto the venous return to the right side of the heart and thence intothe pulmonary arteries). Individual lesions are either microscopic orsmall, visible foci (2-mm) of yellowish-white consolidation arescattered through the lung parenchyma.
PULMONARY COMPLICATIONS OFPNEUMONIA Uncontrolled infection by particular agents may leadto necrotizing pneumonia, formation ofabscesses, vascular invasion withinfarction, cavitation, and extension to the pleura withempyema or bronchopleural fistula. Complications of mechanical ventilation andsupplemental oxygen administration include interstitialemphysema, pneumothorax, and ARDS. In patients with severe damage, tissue repair may leadto fibrosis with various anatomical distributions, such asorganizing pneumonia, bronchiolitis obliterans, andpleural adhesions.
COMMUNITY ACQUIRED PNEUMONIAo Indicates pneumonia in person occuring outside of hospitalor extended-care facilityo The overall rate of pneumonia ranges from 8-15 per 1000 personsper year, with the highest rates at the extremes of age andduring the winter months. Rates of pneumonia are higher for menthan for women and for black than for white population.o CAP is usually spread by droplet infection and most cases occurin previously healthy individuals.o Most patients may be safely managed as out-patient, buthospital admission is necessary in 20-40% of patients (5-10% ofwhom may require intensive care).o Mortality rate of adult patients managed as:Out-patients------is very low <1%In-patients---------is between 5 to10% and may be as high as 50%in severe illness.
Risk factors for CAP include: Current tobacco smoking or passive exposure to tobacco smoke. Alcoholism Immunosuppression Age >70 years Asthma COPD Congestive heart failureEtiologyCommon organisms causing CAP are:BACTERIAL•Streptococcus pneumoniae•Mycoplasma pneumoniae•Haemophilus influenzae•Chlamydia pneumoniae•Legionella pneumophilia•Oral anaerobes•Moraxella catarrhalis•Staphylococcus aureus•Mycobacterium tuberculosis•Chlamydia psittaciVIRAL•Influenza virus•Cytomegalovirus• Respiratory syncytial virus•Measles virus•Varicella-zoster virusFUNGAL•Histoplasma•Coccidiodies•Blastomyces spp.
Classification:Features Typical Pneumonia Atypical PneumoniaOnset Rapid SlowOrganisms • Strep. pneumoniae (mostcommon cause of pneumonia)•H. infulenza•Mycoplasma pneumoniae•Legionella pneumoniae•Chlamydia pneumoniae•Strep. pneumoniae•Viral pneumoniaC/F Fever a/w chills, andpredominant pulmonary featuressuch as productive cough withmucopurulent sputum, pleuriticchest pain ; signs of consolidationsuch as decreased chestmovement, dullness, increasedvocal fremitus, egophony,bronchial breath sounds andcrepitations.Non-pulmonary features arepredominant such as gradualonset of fever and dry cough;myalgia, arthralgia, headache,sore throat, nausea, vomiting anddiarrhea.Respiratory signs like chest painand productive cough, are lessprominent.Labs Leucocytosis WBC count may be WNL ormarginally raisedChest X-ray Patchy or lobar infiltrates(opacity)Patchy non-lobar infiltrates presentbilaterally
Physical Examination:General :Patient appears ill with rapid pulse and rapid respiration, high fever,flushed dry skin.Pulmonary Signs:Within 24 hours—Decreased respiratory movementsSlight impairment of percussion notesPleural rub on affected sitesOn 2nd and 3rd day–signs of consolidation appearDecreased chest movement on affected siteIncreased vocal fremitusDull note over consolidated areaBronchial or absent breath soundsFine crepitationsResolution phase—Most signs disappear by the end of second week. When resolutionbegins numerous coarse crepitations are heard, which indicateliquefaction of alveolar exudates.
Investigations:Radiological Examinations—Chest X-rayCT scanRadiological examination is also helpful if complications such asparapneumonic effusion, intrapulmonary abscess formation, or empyema aresuspected.Microbiological Investigations–A full range of microbiological tests should be performed on patients withsevere CAP. In patients who donot respond to initial therapy, microbiologicalinvestigations may lead to the appropriate modification of therapy. It includes:All patients: Sputum---- Gram and Zeihl-Neelsen stain; culture and antimicrobialsenstivity testing Blood culture Serology--- acute and convalescent titres to diagnoseMycoplasma, Chlamydia, Legionella and viral infections. Pneumococcalantigen detection in serum.Severe CAP:Above tests plus Tracheal aspirate, induced sputum, bronchoalveolar lavage, protectedbrush specimen or percutaneous needle aspiration. Serology--- Legionella antigen in urine; Pneumococcal antigen in sputumand blood, immediate IgM for Mycoplasma. Cold agglutinins--- positive in 50% patients with mycoplasma
Selected patients: Throat/nasopharyngeal swabs Pleural fluid analysisGeneral blood tests: WBC--- >20,000/mm3 or <4,000/mm3 may be seen in severe pneumonia.Neutophilic leucocytoses of >15,000/mm3 favours a bacterial aetiology. Urea and electrolytes Liver function tests C-reactive protein(CRP)--- is typically elevated.Assessment of Gas Exchange: Pulse oximetry--- non-invasive method to measure arterial oxygensaturation (SaO2), and assists in monitoring response to oxygen therapy. Arterial blood gas: should be sampled if Sao2 <92% or presence offeatures of severe pneumonia to assess whether the patient hasevidence of ventilatory failure or acidosis.NB: an expectorated sample is often inadequate due to contaminationfrom oral flora. Therefore a specimen may be considered adequate ifthe gram stain shows >25 neutrophils and <10 squamous epithelial cellsper low-power field.
ManagementApproach to the Patient with Community-AcquiredPneumonia1. Assess pneumonia severity. Pay attention to vital signs, includingoxygen saturation. Always count the respiratory rate yourself for 1min.2. Ensure adequate oxygenation and support of circulation.3. Perform etiologic workup (dictated by pneumonia severity).4. Determine site of treatment: home, hospital (ward or intensive careunit), or long-term-care facility.5. Institute empirical antibiotic therapy.6. Rule out empyema in all patients with a pleural effusion of 1 cm onlateral decubitus chest radiography.7. Never forget tuberculosis and Pneumocystis infection as possibleetiologies.8. Consider pulmonary embolus in all patients with pleuritic chest pain.
9. Consider end-of-life decision-making.10. Monitor and treat comorbid illnesses.11. Monitor for achievement of stability of selected physiologicparameters.12. Assess ability to perform activities of daily living.13. Assess mental status.14. Consider preventive measures:a. Smoking cessation counseling (if appropriate)b. Assessment of pneumococcal and influenza vaccinationstatus, with vaccine administration as necessaryc. Assessment of risk of aspiration and institution of preventivemeasures15. Follow up to ensure radiographic clearance of pneumonia. All patients40 years old and all tobacco smokers should have a follow-up chestradiograph to document pneumonia resolution.
SITE OF CARECan be decided on the basis of pneumonia severity index, that canassessed by following methods:PORT Study
The PORT score (based on a pneumonia-specific severity-of-illnessscoring system)has been advocated as a tool to guide the decisionregarding the site of care (home vs. hospital). Because of the low mortality rates in risk classes I and II, it isrecommended that these patients be treated at home.Patients in risk classes IV and V require hospital admission.Patients in class III may benefit from a period of observation in theemergency room before a decision is made regarding the site ofcare.American Thoracic Society Definition of Severe PneumoniaCategory CriteriaMajor Need for mechanical ventilationRequirement for vasopressors: > 4 hMinor Systolic blood pressure: 90 mmHgPaO /FIO : 250 2 2Multilobar involvement
BRITISH THORACIC SOCIETY RULE FOR DEFINITTION OFSEVERE CAP (CURB-65)Any of:ConfusionUrea >7 mmol/lRespiratory rate 30/minBlood pressure (systolic <90mmHg or diastolic <60 mmHgAge 65 yearsScore 1 point for each feature presentLikely to be suitablefor home treatmentConsider hospitalsupervised treatmentOptions may include:Short-stay inpatientHospital-supervisedinpatientManage in hospital assevere pneumoniaAssess for ICUadmission if CURB-65score = 4or 5Score 0 or 1 Score 2 Score 3 or more
Oxygenation:Administered to all patients with tachypnea, hypoxaemia, hypotension oracidosis, with the aim of maintaining PaO2 > 8 kPa (60 mmHg) or SaO2 > 92%Fluid balance:An adequate oral intake of fuids should be encouraged but I.V. fluids should beconsidered in those with severe illness, elderly patients and those whosesystemic features include vomiting. Inotropic support may be required inpatient with shock.Antibiotic treatment: Outpatient; no cardiopulmonary disease, no risk factors for DRSP infectionMacrolide (e.g., clarithromycin 500 mg bid PO10 days; or azithromycin 500mg PO once, then 250 mg/d 4 days) orDoxycycline 100 mg bid PO 10 days Outpatient; cardiopulmonary disease and/or risk factors for DRSP infection orhigh DRSP prevalence in communityQuinolone with enhanced activity against Streptococcus pneumoniae—e.g., levofloxacin 500 mg/d PO, moxifloxacin 400 mg/d PO, or gatifloxacin400 mg/d PO orB-Lactam (cefpodoxime 200 mg bid, cefuroxime axetil 750 mg tid, oramoxicillin 1000 mg tid, PO; amoxicillin/clavulanic acid 875/175 mg tid)plusmacrolide ordoxycycline orTelithromycin 800 mg q24h 10 days(DRSP—drug resistant Streptococcus pneumoniae)
Hospital ward Cefuroxime 750 mg q8h IV or ceftriaxone 1 g/d IV or cefotaxime 2 g q6hIV or ampicillin/sulbactam 1.5–3 g q6h IV plus Azithromycin 1 g/d IV followed by 500 mg/d IV or Quinolone with enhanced activity against S. pneumoniae (see above) Intensive care unitno risk factors for Pseudomonas aeruginosa infection--- Azithromycin 1 g IV, then start 500 mg IV 24 h later plus Ceftriaxone 1 g q12h IV or Cefotaxime 2 g q6h IV or Quinolone IVrisk factors for P. aeruginosa--- Imipenem (or meropenem)500 mg q6h IV or Piperacillin/tazobactam 3.375 g q6h IV plus Ciprofloxacin 750 mg q8h IV
Nursing home Amoxicillin/clavulanic acid 875/125 mg tid PO plusMacrolide PO (see above) orQuinolone PO with enhanced activity against S.pneumoniae (see above) orCeftriaxone 500–1000 mg/d IM or cefotaxime 500mg IM q12h plus Macrolide (see above)
Treatment of pleural pain:Mild analgesics such as Paracetamol are rarely adequate;however, opiates must be used with extreme caution in patient with poorrespiratory functionDischarge and follow up:Discharge from hospital should be contemplated when patients areclinically stable with no more than one of following clinical signs: Temp. >38*C HR >100/MIN Resp. rate > 24/min Systolic BP <90 mmHg SaO2 <90% Inability to maintain oral intake Abnormal mental statusChest X-ray may often take several weeks to months to resolve.Follow-up--- arranged at around 6 weeks and a cxr obtained if there arepersistent symptoms.
PreventionInfluenza vaccination:Recommended to those at high risk of mortality (elderly people) frominfluenza or pneumonia.Pneumococcal vaccination: Polysaccharide pneumococcal vaccine do not appear to reducethe incidence of pneumonia or death but may reduce the incidenceof invasive pneumococcal disease. Protects against 23 serotypes of Strep. Pneumoniae (90% of invasivepneumonia infections) Can be given to anyone over age 65 and/or accompanied withchronic medical problem such as cancer, diabetes, heartdisease, lung disease, alcoholism, cirrhosis, sickle cell disease, kidneyfailure, HIV, damaged spleen or no spleen, CSF leaks Anyone receiving cancer therapy, radiation, steroids Can be given after 5 years from first dose.