Pneumonia Flashcards
What are signs of a severe respiratory infection?
- High fever
- Low blood pressure
- High respiratory rate
- Confusion
What is the definition of community-acquired pneumonia?
Signs of lower respiratory chest infection (fever/cough/phelgm/crackles or bronchial breathing) + changes on chest x-ray
What parameters are used in calculating a NEWS2 (National Early Warning Score 2) score?
- respiration rate
- oxygen saturation
- systolic blood pressure
- pulse rate
- level of consciousness or new confusion*
- temperature
Discuss why the ST4 may have decided to commence intravenous broad spectrum antibiotic such as PipTaz at this stage. Why was Clatrithromycin also prescribed? Why despite having correct therapy, Mr Harper deteriorated? Why was the prescription changed to penicillin by the microbiologists?
- The ST4 changed antibiotic therapy to broad spectrum Tazocin due to clinical deterioration to make sure a broader spectrum of bacteria are covered by the antibiotic.
- Clarithromycin was needed to cover for the atypical, intracellular causes of pneumonia.
It is likely that he was vomiting due to clarithromycin which meant he may not be absorbing his co-amoxiclav as well, so we should endeavor to give therapy by appropriate route based on clinical grounds. Also in retrospect he should have continued with IV therapy for a longer period as he had ‘severe’ pneumonia and changeover of IV to oral therapy should be based on clinical improvement rather than time. - The Tazocin was changed to penicillin as it is a narrow spectrum antibiotic and the Streptococcus pneumoniae were sensitive to it. We should avoid using broad spectrum antibiotic to decrease the risk of developing resistance.
What are the typical findings of someone with CAP pneumonia?
- Fever (38.5-40+)
- Tachypnea
- Dull percussion
- Bronchial breathing
- Focal crackles
- Mental confusion
What investigations are used for CAP?
- Chest xray
- Inflammatory markers (PCT, CRP, WBC)
- SpO2
- ABGs
- Sputum culture + stain
- Blood culture (for resistance patterns for antibiotics)
- Throat swabs
- Urine pneumococcus + legionella antigen
What is CURB-65?
Confusion Urea > 7mmol/L Respiratory rate ≥ 30 breaths/min BP (SBP < 90 or DBP < 60mmHg) ≥ 65y
What antibiotics are used in CAP?
Mild pneumonia: PO Amoxicillin (or doxycycline, clarithromycin)
Moderate pneumonia:
Amoxicillin + macrolide PO
Severe pneumonia:
Broad spectrum B-lactalase (i.e. amoxicillin + co-amoxiclav + macrolide)
What are some complications of pneumonia?
- parapneumonic effusion
- infectious complications (empyema, abscess, metastatic infection)
- venous thromboembolism
- worsening of comorbidities (AF, heart failure, kidney failure, respiratory failure - COPD)
- side effects to antibiotics (C. diff infection, antimicrobial resistance)
What are the common clinical signs of pneumonia?
- Cough: may be dry or productive of sputum. Sputum in pneumococcal pneumonia is characteristically rust/red coloured. Haemoptysis can also occur.
- Breathlessness: alveoli become filled with pus which impairs gas exchange, the patient will complain of feeling breathless, not able to lie down, reduction in oxygen saturations.
- Fever: this can be very high up to 39.5°C to 40°C.
- Chest Pains: commonly pleuritic in nature and worse when coughing.
What blood tests are useful in pneumonia?
FBC, U+E, LFTs, CRP, Lactate
What in particular do we want to look at in the FBC for pneumonia?
- White cell count: total white cell count increases in acute infection, neutrophilia tends to indicate bacterial infection, neutropenia can indicate viral infections. Lymphopenia can indicate severe infection.
- Haemoglobin: anaemia can complicate pneumonia
- Platelets: high or low platelets can be indicative of an inflammatory process which would be in keeping with a diagnosis of infection.
Why are U+E, LFTs, CRP, and Lactate important to measure in pneumonia?
- U&Es especially urea and creatinine show acute kidney injury (to be discussed in case 13)
- LFTs if deranged can be a reflection of reduction in liver perfusion associated with sepsis.
- CRP (C reactive protein) is an acute phase protein produced by the liver in response to infection or trauma. CRP typically rises with any inflammation but to a much higher degree in patients with severe bacterial infections. CRP has been described as a test for pneumococcal pneumonia and was named after its ability to precipitate the C-polysaccharide of Strep. pneumoniae. Very high levels (>100) are more indicative of infection whereas lower levels are seen in inflammatory conditions and malignancies.
- Lactate is produced as a product of anaerobic respiration and increases in sepsis and shock. It is a general marker of illness severity and is used in sepsis scoring systems
Clinical findings can be less obvious in immunocompromised patients
How is bacterial pneumonia characterized microscopically?
- Extensive infiltration of the interstitium with neutrophils
- Alveolar septa are thickened due to the presence of inflammatory exudate
- Loss of alveolar spaces
What are the main mechanisms of antibiotic resistance?
- Chemically modify the antibiotic
- Render it inactive through physical removal from the cell
- Modify target site so that it’s not recognized by the antibiotic
Name the 4 typical bacterial causes of CAP and if they’re gram + or -
- Strep. pneumoniae (gram + coccus)
- H. influenzae (gram - bacillus) -> children
- Klebsiella pneumoniae (gram - bacillus) -> elderly
- Staph aureus (gram + coccus) -> IVDU
Name 4 atypical causes of CAP and some features of them
- Mycoplasma pneumoniae
- Tend to affect younger patients
- Chest X-ray with patchy consolidation, dry cough
- Diagnosis by PCR, serology
- Treat with macrolides - Legionella pneumophilia
- Associated with AC systems (think travel)
- Affects males and smokers
- Prodromal symptoms of high fever before dry cough
- Diagnosed with urine antigen
- Treat with macrolide - Chlamydia pneumoniae
- Extremes of age are vulnerable
- Treat with macrolide or doxycycline - Chlamydia psitacci
- Classically associated with contact with birds
- Can cause hepatosplenomegaly
- Treat with macrolide or doxycycline
What is meant by typical and atypical organisms?
Pneumonia is classically divided into typical and atypical organisms based on historical laboratory techniques: typical organisms can be cultured in the laboratory whereas atypical organisms are intracellular pathogens and cannot be cultured using standard methods and alternative diagnostic tools are needed.
This division is clinically relevant as atypical organisms need to be treated with antibiotics which get into intracellular space (e.g. macrolides). Also, atypical organisms do not possess a cell wall on which penicillins or cephalosporins can act.
What are the commonest viruses to cause pneumonia?
Influenza A + B
Adenovirus
Parainfluenza virus
Respiratory syncytial virus
