Community acquired pneumonia resident survival guide

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Chetan Lokhande, M.B.B.S [2]

Overview

A lower respiratory tract infection in a previously normal individual acquired through normal social contact rather than contracting it in a hospital. Community-acquired pneumonia (CAP) is a disease in which individuals who have not recently been hospitalized develop an infection of the lungs. CAP is a common illness and can affect people of all ages. It often causes problems like dyspnea, fever, chest pain, and cough. CAP causes fluid accumulation in the alveoli leading to poor gas exchange. CAP is common worldwide and is a leading cause of illness and death. Causes of CAP include bacteria, viruses, fungi, and parasites. CAP can be diagnosed by history and a physical examination alone, though x-rays, sputum examinations, and other diagnostic tests are often used. As CAP is often bacterial, the primary empiric treatment consists of wide-spectrum antibiotics. Some forms of CAP, such as pneumococcal pneumonia may be prevented by vaccination.

Causes

Life Threatening Causes

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated. Complications of community acquired pneumonia, such as pleural effusion, lung abscess, bacteremia and septicemia are life-threatening conditions and must be treated as such irrespective of the causes.

Common Causes

Following are the causes listed according to the microbiological etiology

• Typical Bacteria

1. Streptococcus pneumoniae
2. Haemophilus influenzae
3. Escherichia coli
4. Klebsiella pneumoniae
5. Pseudomonas aeruginosa

• Atypical Bacteria

1. Mycoplasma pneumoniae
2. Chlamydophila pneumoniae
3. Legionella pneumophila

• Viruses

1. Influenza
2. Parainfluenza
3. Respiratory syncytial virus (RSV)
4. Metapneumovirus
5. Adenovirus

Following are the causes listed according to the the location of the patient

• Outpatient

1. Streptococcus pneumoniae
2. Mycoplasma pneumoniae
3. Haemophilus influenzae
4. Chlamydophila pneumoniae
5. Influenza A and B, adenovirus, respiratory syncytial virus, parainfluenza

• Inpatient (non-ICU)

1. Streptococcus pneumoniae
2. Mycoplasma pneumoniae
3. Chlamydophila pneumoniae
4. Haemophilus influenzae
5. Legionella
6. Aspiration
7. Influenza A and B, adenovirus, respiratory syncytial virus, parainfluenza
8. Yersinia enterocolitica

• Inpatient (ICU)

1. Streptococcus pneumoniae
2. Staphylococcus aureus
3. Legionella
4. Gram-negative bacilli
5. Haemophilus influenzae
6. Acinetobacter baumannii

Management

Shown below is an algorithm depicting the management of community acquired pneumonia according to the Infectious Diseases Society of America (IDSA) and Thoracic Society Consensus Guidelines on the Management of Community Acquired Pneumonia in Adults.

Characterize the symptoms: Typical (acute onset) ❑ Fever ❑ Cough ❑ Sputum production ❑ Dyspnea ❑ Pleuritic chest pain ❑ Confusion most prominently in the elderly ❑ Shaking chills Atypical (insidious onset) ❑ Dry cough ❑ Sore throat ❑ Headache ❑ Myalgia ❑ Diarrhea

Examine the patient: Vital signs ❑ Temperature Fever is usually present in pneumonia Hypothermia is one of the minor criteria of severity ❑ Respiratory rate (tachypnea may be present) ❑ Heart rate (tachycardia may be present) ❑ Blood pressure (Hypotension requiring fluid rescusitation is one of the minor criteria of severity) ❑ Pulse oximetry (Hypoxia might be present) Respiratory examination: ❑ Decreased expansion of the thorax on inspiration on the affected side ❑ Dull percussion on affected side ❑ Bronchial breath sounds ❑ Rales ❑ Increased vocal fremitus ❑ Pleural friction rub Signs of increased severity: ❑ Cyanosis ❑ Dehydration ❑ Convulsions ❑ Persistent vomiting ❑ Fluctuating temperatures ❑ Decreased level of consciousness Look for signs suggestive of the infectious agent: ❑ Abdominal pain, diarrhea, or confusion suggestive of Legionella ❑ Rusty colored sputum suggestive of Streptococcus pneumoniae ❑ Bloody sputum often described as "currant jelly" suggestive of pneumonia caused by Klebsiella ❑ Hemoptysis suggestive of tuberculosis ❑ Lymph node swelling and middle ear infection suggestive of Mycoplasma pneumonia Inquire about history clues suggestive of the infectious agent: ❑ Recent travel ❑ Endemic exposure Consider alternate diagnosis: ❑ Acute bronchitis ❑ Asthma ❑ Congestive heart failure ❑ Chronic obstructive pulmonary disease ❑ Gastroesophageal reflux disease ❑ Upper respiratory tract infection ❑ Vasculitis ❑ Bronchiolitis obliterans with organizing pneumonia ❑ Pulmonary edema

Order laboratory tests: ❑ Complete blood count (CBC) Leukocytosis is usually present Leukopenia (WBC <4000 cells/mm3) is one of the minor criteria of severity Thrombocytopenia (platelets < 100,000 cells/mm3) is one of the minor criteria of severity ❑ Blood urea nitrogen (BUN) Uremia (BUN >20 mg/dL) is one of the minor criteria of severity ❑ Transaminases Elevated transaminases are suggestive of atypical pneumonia ❑ Electrolytes Hyponatremia is suggestive of Legionella infection Order imaging studies: ❑ Chest X-ray PA and lateral Consolidation (suggestive of typical pneumonia) Patchy interstitial infiltrates (suggestive of atypical pneumonia) Tap if pleural effusion > 5 cm

Does the patient have any of the following conditions that warranty additional testing? ❑ Admission to ICU due to severe pneumonia ❑ Failure of outpatient antibiotic therapy ❑ Cavitary infiltrates ❑ Leukopenia ❑ Alcohol abuse ❑ Chronic severe liver disease ❑ Severe obstructive or structural lung disease ❑ Recent travel (within the last 2 weeks) ❑ Pleural effusion ❑ Asplenia ❑ Positive Legionella urine analysis test ❑ Positive pneumococcal urine analysis test

Yes Additional lab tests are recommended

Additional lab tests are optional

Order additional testing: ❑ Blood gram stain and culture Should be obtained before initiation of antibiotics ❑ Expectorated sputum gram stain and culture Good sample should have <10 squamous cells/lpf, and >25 PMN/lpf if purulent sample Sample should be transported to lab within 1-2 hours Consider virus PCR or DFA for viruses ❑ Endotracheal aspirate gram stain and culture (if patient is intubated) ❑ Arterial blood gas ❑ Urine legionella antigen ❑ Urine streptococcal antigen ❑ Influenza testing during influenza season ❑ Mycoplasma PCR for sputum or throat ❑ Acid fast bacillus stain on induced sputum for tuberculosis ❑ PCP in induced sputum if immunocompromised ❑ Consider HIV test among adults (15-60 years) if severe pneumonia ❑ Bronchoscopy if: ❑ Immunosuppression ❑ Failure to response ❑ Critical illness ❑ Chronic symptoms ❑ Suspected PCP but induced sputum test negative or inadequate ❑ Suspected tuberculosis but induced sputum is inadequate

Does the patient meet any of the following criteria for hospital admission? ❑ CURB-65 score ≥ 2, OR ❑ High The Pneumonia severity index (PSI)

Yes Treat as inpatient

No Treat as outpatient

Does the patient have any of the following criteria for ICU admission? ❑ Invasive mechanical ventilation (major criteria), OR ❑ Septic shock with need for vasopressors (major criteria), OR ❑ At least 3 of the following minor criteria: ❑ Respiratory rate >30 breaths/min ❑ PaO2/FiO2 ratio <250 ❑ Multilobar infiltrates ❑ Confusion/disorientation ❑ Uremia (BUN >20 mg/dL) ❑ Leukopenia (WBC <4000 cells/mm3) ❑ Thrombocytopenia (platelets <100,000 cells/mm3) ❑ Hypothermia (temperature <36 degrees C) ❑ Hypotension that requires aggressive fluid resuscitation

Yes Admit to ICU

No Admit to general medical floor

❑ Begin empiric antibiotic treatment

❑ Follow up with cultures (if ordered) and change antibiotics according to the resistance profile ❑ Manage complications

Empiric Antibiotics

Scenario	Empiric Antibiotics
Outpatient
Previously healthy and no use of antimicrobials within the previous 3 months	A macrolide Doxycyline
Presence of comorbidities such as chronic heart, lung, liver or renal disease; diabetes mellitus; alcoholism; malignancies; asplenia; immunosuppressing conditions or use of immunosuppressing drugs	A fluoroquinolone (moxifloxacin, gemifloxacin, or levofloxacin [750 mg]) A b-lactam plus a macrolide
Use of antimicrobials within the last 3 months	An alternative from a different class should be selected: A fluoroquinolone (moxifloxacin, gemifloxacin, or levofloxacin [750 mg]) (strong recommendation; level I evidence) A b-lactam plus a macrolide (strong recommendation; level I evidence)
In regions with a high rate (125%) of infection with high-level (MIC 16 mg/mL) macrolide-resistant Streptococcus pneumoniae	A fluoroquinolone (moxifloxacin, gemifloxacin, or levofloxacin [750 mg]) A b-lactam plus a macrolide
Inpatient
General medical ward admission	A respiratory fluoroquinolone A b-lactam plus a macrolide
ICU admission	A b-lactam (cefotaxime, ceftriaxone, or ampicillin-sulbactam) plus azithromycin A b-lactam (cefotaxime, ceftriaxone, or ampicillin-sulbactam) plus a fluoroquinolone For penicillin-allergic patients: a respiratory fluoroquinolone and aztreonam
Concern about pseudomonas	An antipneumococcal, antipseudomonal b-lactam (piperacillintazobactam, cefepime, imipenem, or meropenem) plus either ciprofloxacin or levofloxacin (750 mg) B-lactam plus an aminoglycoside and azithromycin B-lactam plus an aminoglycoside and an antipneumococcal fluoroquinolone For penicillin-allergic patients, substitute aztreonam for above b-lactam
Concern about community acquired MRSA	Add vancomycin or linezolid

Empiric Antiviral

Scenario	Empiric Antiviral
Symptoms suggestive of influenza and exposure to poultry in areas with previous H5N1 infection	Test for H5N1 Initiate droplet precautions Initiate routine infection control measures Treat influenza with oseltamivir Antibiotic coverage for S. pneumonia and S. aureus

Considerations in Severe Cases

CAP + persistent septic shock	Administer drotrecogin alpha
CAP + hypotension requiring resuscitation	Screen for occult adrenal insufficiency
Hypoxemia	Trial of noninvasive ventilation
Severe hypoxemia (PaO2/FiO2 < 150) + bilateral alveolar infiltrates	Immediate intubation
ARDS or diffuse bilateral pneumonia on ventilation	Low tidal volume ventilation (6 cm3/kg of ideal body weight)

Assessment of Response to Treatment

Criteria for Clinical Stability

• Temperature ≤ 37.8 c
• Respiratory rate ≤ 24 breaths/min
• Heart rate ≤ 100 beats/min
• Systolic blood pressure ≥ 90 mmHg
• Normal mental status
• Ability to tolerate oral intake
• Arterial oxygen saturation ≥ 90% or pO2 ≥ 60 mmHg on room air

Failure to Response

Potential causes of failure to response:

• The causative agent is not covered by antibiotics
• Resistant organism
• Parapneumonic effusion
• Parapneumonic empyema
• Nosocomial superinfection
• Alternate diagnoses (for example PE, MI
• Drug fever
• Exacerbation of an existing comorbidity

The PSI Algorithm

The PSI Algorithm is detailed below. An online, automated PSI calculator is available on the US AHRQ website.

Step 1: Stratify to Risk Class I vs. Risk Classes II-V
	Presence of:
		Over 50 years of age	Yes/No
		Altered mental status	Yes/No
		Pulse ≥125/minute	Yes/No
		Respiratory rate >30/minute	Yes/No
		Systolic blood pressure ≥90 mm Hg	Yes/No
		Temperature <35°C or ≥40°C	Yes/No
	History of:
		Neoplastic disease	Yes/No
		Congestive heart failure	Yes/No
		Cerebrovascular disease	Yes/No
		Renal disease	Yes/No
		Liver disease	Yes/No
		If any "Yes", then proceed to Step 2
		If all "No" then assign to Risk Class I
Step 2: Stratify to Risk Class II vs III vs IV vs V
	Demographics		Points Assigned
		If Male	+Age (yr)
		If Female	+Age (yr) - 10
		Nursing home resident	+10
	Comorbidity
		Neoplastic disease	+30
		Liver disease	+20
		Congestive heart failure	+10
		Cerebrovascular disease	+10
		Renal disease	+10
	Physical Exam Findings
		Altered mental status	+20
		Pulse ≥125/minute	+20
		Respiratory rate >30/minute	+20
		Systolic blood pressure ≥90 mm Hg	+15
		Temperature <35°C or ≥40°C	+10
	Lab and Radiolographic Findings
		Arterial pH <7.35	+30
		Blood urea nitrogen ≥30 mg/dl (9 mmol/liter)	+20
		Sodium <90 mmol/liter	+20
		Glucose ≥250 mg/dl (14 mmol/liter)	+10
		Hematocrit <30%	+10
		Partial pressure of arterial O2 <60mmHg	+10
		Pleural effusion	+10
		∑ <70 = Risk Class II
		∑ 71-90 = Risk Class III
		∑ 91-130 = Risk Class IV
		∑ >130 = Risk Class V

CURB-65

CURB-65 is a clinical prediction rule that has been validated for predicting mortality in community-acquired pneumonia and infection of any site. The CURB-65 is based on the earlier CURB score and is recommended by the British Thoracic Society for the assessment of severity of pneumonia.

The score is an acronym for each of the risk factors measured. Each risk factor scores one point, for a maximum score of 5:

• Confusion (defined as an AMT of 8 or less)
• Urea greater than 7 mmol/l (Blood Urea Nitrogen > 20)
• Respiratory rate of 30 breaths per minute or greater
• Blood pressure less than 90 systolic or diastolic blood pressure 60 or less
• Age 65 or older

Do's

• If the patient presented to the emergency department, administer the fist dose of antibitoic therapy as soon as possible, preferably within 6 hours of presentation.

• Among patients admitted to the hospital, switch from IV to PO antibiotics as soon as the patient is hemodynamically stable with clinical improvement and ability to tolerate oral intake. When the patient is switched to PO antibiotics, the patient can be discharged on PO home medications.

• The duration of antibiotics is at least 5 days; antibiotic treatment are not discontinued until the patient is afebrile for 48-72 hours and with not more than one sign of instability.

• Use fibre-optic bronchoscopy in immunocompromised individuals to detect less common organisms, obtain a tissue biopsy, and identify anatomic lesions if any.

• Treat influenza A with oseltamivir or zonamivir only if time from onset of symptoms < 48 hours.

Dont's

• Inadvertently use of antibiotic for patients without community-acquired pneumonia who require treatment within 4 hours may increase the risk of Clostridium difficile colitis. Hence, use antibiotics judiciously.