Community acquired pneumonia Flashcards
what is the definition of CAP?
Community-acquired pneumonia (CAP) is defined as pneumonia acquired outside hospital or healthcare facilities. Clinical diagnosis is based on a group of signs and symptoms related to lower respiratory tract infection with presence of fever >38ºC (>100ºF), cough, mucopurulent sputum, pleuritic chest pain, dyspnoea, and new focal chest signs on examination such as crackles or bronchial breathing. Older patients present more frequently with confusion or worsening of pre-existing conditions, and without chest signs or fever.
what is the epidemiology of CAP?
Higher incidence in men
5 leading cause of mortality in europe
what is the aetiology of CAP?
Streptococcus pneumoniae (the pneumococcus) is the most common causative pathogen of CAP across a range of severities and patient ages. However, other studies have found that influenza virus is the most common cause of CAP in adults. In Europe and the US, S pneumoniae accounts for about 30% to 35% of cases. Other bacterial causes include Haemophilus influenzae, Staphylococcus aureus (including MRSA), group A streptococci, and Moxarella catarrhalis Vaccine given for >65 years, splenic dysfunction, immunocompromised, chronic medical condition
what are the risk factors for CAP?
Aged >65 Residency in healthcare setting COPD Exposure to cigarette smoke Alcohol abuse Poor oral hygiene Use of acid reduced drugs Contact with children
what is the pathophysiology of CAP?
Pneumonia develops subsequent to the invasion and overgrowth of a pathogenic micro-organism in the lung parenchyma, which overwhelms host defences and produces intra-alveolar exudates.
Pathogens can reach the lower respiratory tract by 4 mechanisms:
Inhalation, a common route of entry for viral and atypical pneumonia in younger healthy patients. Infectious aerosols are inhaled into the respiratory tract of a susceptible person to initiate infection
Aspiration of oropharyngeal secretions into the trachea, the primary route through which pathogens enter the lower airways
Haematogenous spread from a localised infected site (e.g., right-sided endocarditis)[34]
Direct extension from adjacent infected foci (e.g., tuberculosis can spread contiguously from the lymph nodes to the pericardium or the lung, albeit rarely).
what are the key presentations of CAP?
Cough with increasing sputum production Dyspnoea Pleuritic chest pain Rigours and night sweats Fever Abnormal auscultatory findings Confusion Presence of risk factors Raised heart rate Raised resp rate Low blood pressure Dehydration
what are the first line and gold standard investigations for CAP?
Chest x-ray - new shadowing (consolidation)
Pulse oximetry - may reveal low arterial oxygen saturation
oxygen saturation <94% in a patient with CAP is an adverse prognostic factor and may be an indication for oxygen therapy and/or urgent referral to hospital
Arterial blood gas - may reveal low arterial oxygen saturation
Urea and electrolytes - usually normal; elevated in patients with severe CAP
urea >7 mmol/L (>19.6 mg/dL) counts for 1 point in the 6-point CURB-65 score to assess severity
FBC - leukocytosis
WBC count > 15 x109/L indicates a bacterial aetiology (particularly pneumococcal,) although lower counts do not exclude a bacterial cause
CRP - elevated, a level >100 mg/L makes pneumonia likely, a level <20 mg/L with symptoms for more than 24 hours makes the presence of pneumonia highly unlikely
LFT - usually normal; abnormal in patients with underlying liver disease or legionella infection
HIV test, hep B and C
Legionella urine test
Sputum culture and sensitivities
Blood cultures
Serology
Urinary antigen
PCR
Acid fast bacilli stain (TB)
what are the differential diagnoses for CAP?
COVID 19
Acute bronchitis
Congestive heart failure
how is CAP managed?
Suspected:
Empirical antibiotic therapy
Confirmed:
High severity - IV empirical antibiotics, saline rehydration, oxygen, analgesics >5 days (may need 14-21 days for S.aureus, gram negs and legionella
Moderate - IV or oral empircal antibiotics
CURB65 0-1 - amoxicillin
CURB65 2 - amoxicillin clarithromycin (c.diff risk)
CURB65 3-5 - IV co-amoxiclav and clarithromycin
how is CAP monitored?
Consider repeat CXR or referral to respiratory physician
what are the complications of CAP?
Septic shock
ARDS
Antibiotic related clostridium difficile colitis
Heart failure
Parapneumonic effusion leading to empyema (failure to improve)
what is the prognosis of CAP?
For patients admitted to hospital, mortality rate ranges from 5% to 15%, but increases to 20% to 50% in patients requiring admission to the intensive care unit (ICU)
what is the most common causative agent of CAP?
Streptococcus pneumoniae (pneumococcus)Accounts for 80% of cases Particularly associated with high fever, rapid onset and herpes labialis A vaccine to pneumococcus is available - treat with amoxicillin, cefuroxime, cefotaxime or macrolides (clarithromycin, fluoroquinolones, ciprofloxacin)
what is the causative agent in a patient with CAP and COPD?
Haemophilus influenzae, treat with co-amoxiclav
what is the causative agent in CAP often occuring in patient following influenza infection
staph aureas treat with flucoxacillin, caefuroxime, vanomycin in MRSA
