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. Haemophilus influenzae
4. Legionella
5. Aspiration
6. Influenza A and B, adenovirus, respiratory syncytial virus, parainfluenza
7. 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: ❑ Fever ❑ Cough ❑ Sputum production ❑ Dyspnea ❑ Pleuritic chest pain ❑ Confusion most prominently in the elderly ❑ Shaking chills

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 and imaging: ❑ 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 ❑ Check Blood urea nitrogen (BUN) Uremia (BUN >20 mg/dL) is one of the minor criteria of severity ❑ Chest X-ray The presence of the infiltrates is confirmatory for the diagnosis

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 ❑ Expectorated sputum gram stain and culture ❑ Endotracheal aspirate gram stain and culture (if patient is intubated) ❑ Urine legionella antigen ❑ Urine streptococcal antigen ❑ Influenza testing during influenza season

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

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

• Obtain a sputum gram stain, sputum culture and blood cultures before initiating antibiotic therapy.
• Provide coverage for Streptococcus pneumoniae and atypical bacteria like (Mycoplasma, Chlamydophila, Legionella ).
• Consider acute and convalescent serologic testing to identify atypical pathogens like C.pneumoniae, Q fever and Hantavirus.
• Perform aggressive fluid resuscitation, prompt antibiotic initiation, measure arterial blood gas in all patients who have borderline hypoxemia or lactate.
• Treat co-existing illness like asthma and COPD with bronchodilators.
• Start empirical therapy with coverage for Pseudomonas aeruginosa and MRSA if patient is hospitalized for more than 2 days.
• Give high priority to patients with elevated blood urea nitrogen (BUN), confusion and high respiratory rate.
• First antibiotic dose should be administered within 6 hours of admission into the emergency room.
• Shock is an exception where antibiotic should be started within an hour of hypotension. A decrease in 8% of survival rate for each hour of delay is noted.
• Treat with antibiotics for atleast 5-7 days.
• Narrow down antibiotic therapy as soon as a specific microbiological etiology is identified.
• Chest X-ray should be performed and checked for signs of consolidation, cavitation or interstitial infiltrates.
• Use fibre-optic bronchoscopy in immunocompromised individuals to detect less common organisms, do a tissue biopsy and identify anatomic lesions if any.

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.
• Don't discontinue antibiotics till the patient is afebrile for 48 to 72 hours and has signs of clinical improvement.