PNEUMONIA - An approach to Pneumonia updates
Pneumonia: Inflammation of one or both lungs, with dense areas of lung inflammation. PNEUMONIA is frequently but not always due to infection. The infection may be bacterial, viral, fungal, or parasitic. Symptoms may include FEVER , chills, cough with sputum production, CHEST PAIN and shortness of breath. Pneumonia is suggested by the symptoms and confirmed by CHEST X-ray testing. Treatment includes antibiotics.
Community Acquired Pneumonia (CAP) = patients without significant healthcare contact
Healthcare-Associated Pneumonia (HCAP) = patients with exposure to healthcare (e.g. chronic dialysis, recent hospitalization)
Diagnosing pneumonia :
Diagnosis is generally based on three lines of evidence:Imaging evidence of a chest infiltrate (e.g., CXR, CT, ultrasound)
Inflammation (e.g., fever/hypothermia, rigors, night sweats, leukocytosis, left-shift, procalcitonin)
Pulmonary symptoms (e.g., dyspnea, cough, sputum production, pleuritic chest pain) and signs (tachypnea, hypoxemia).
Patients often present to the hospital with septic shock plus pulmonary infiltrates on chest X-ray. Two possibilities are:
- Chest infiltrates due to atelectasis/aspiration plus occult focus of sepsis elsewhere (e.g. abdominal sepsis)
A common error is to assume that the septic shock must be due to pneumonia, when in fact the chest infiltrates are a red herring. When in doubt, err on the side of investigating further to exclude an alternative source of sepsis.
CT SCAN TO ASSIST THE DIAGNOSIS OF PNEUMONIA
- Some patients with pneumonia will have a negative chest X-ray with a positive CT scan (due to subtle infiltrates). However, among patients who are critically ill due to pneumonia, there really ought to be some abnormality seen on chest X-ray.
- The main use for CT scan is differentiation from pneumonia mimics. As shown in the table above, a CT scan is probably the single most versatile test to differentiate pneumonia from a mimic.
- CT scan can be helpful to detect pneumonia in patients with chronic lung disease and chronically abnormal chest X-ray.
Occasionally useful to exclude a pneumonia mimic (e.g. diffuse alveolar hemorrhage, eosinophilic pneumonia).
- Elderly patients may present with non-pulmonary complaints (e.g. falling, delirium, sepsis).
- When in doubt, it is reasonable to get cultures and start antibiotics for pneumonia. Within the next 24-48 hours, the diagnosis may be re-considered and antibiotics discontinued as appropriate.
- More common pneumonia mimics are listed below. These can be devilishly hard to find, because you’re searching for a needle in a haystack.
TESTS TO OBTAIN AFTER DIAGNOSING PNEUMONIA
Blood culturesRecommended for severe pneumonia, although yield is low (~10%).
If patient already had blood cultures at another hospital, don’t repeat them (follow up on results from the outside hospital lab).
Sputum for gram stain & cultureIntubated patient: tracheal aspirate is very useful.
Non-intubated patient: expectorated sputum (low yield, but very helpful when high-quality sputum reveals single type of organism).3
Urine legionella antigenSensitivity 80% and specificity of ~95%.3
Negative result doesn’t exclude legionella, but positive result may allow focusing antibiotic therapy on legionella.
Urine pneumococcal antigen Sensitivity 70% and specificity 95% (may have false-positive due to pneumonia within past several weeks).3 4
Nares PCR for MRSA
Winter: PCR for influenza & respiratory virusesIf nasopharyngeal influenza PCR is negative and high suspicion remains, a lower respiratory tract PCR may be positive.5
Be careful: patients may be co-infected with viral and bacterial pathogens. Just because the viral PCR is positive doesn’t mean that you should stop antibacterial therapy.3
ProcalcitoninProcalcitonin <0.5 ng/mL argues against typical bacterial pneumonia (but this may still be seen with atypical infections).
Procalcitonin is unreliable in immunocompromised patients (e.g. neutropenia).
Daily procalcitonin may help determine timing of antibiotic discontinuation
Epidemiological history .
Review of radiograph
(1) Triage solely based on the amount of oxygen the patient requiresA common myth is that if the patient can saturate adequately on nasal cannula then it’s OK for them to go to the ward. This is completely and utterly wrong.
(2) Triage based on CURB65 and PORT scoresThese are validated as mortality prediction tools, they aren’t designed to determine disposition.
Not great at sorting out who needs the ward vs. ICU.
better approaches to triage
Patients with significant work of breathing or tachypnea (e.g. respiratory rate >30) should be considered for ICU admission and high-flow nasal cannula.
The IDSA/ATS criteria have been validated for use in ICU triage. Patients with three or more criteria may benefit from ICU admission: Respiratory rate >29 breaths/min10
Hypotension requiring volume resuscitation
PaO2/FiO2 < 250 (patients requiring >3 liters oxygen) Temperature < 36C
BUN >20 mg/dL
An updated clinical guideline on pneumonia emphasizes antimicrobial stewardship with recommendations for increased microscopic studies of respiratory tract specimens in certain patients and revised recommendations for empiric treatment strategies.
The American Thoracic Society (ATS)/Infectious Diseases Society of America (IDSA) ad hoc committee on community-acquired pneumonia (CAP) in adults published the guideline online October 1 in the American Journal of Respiratory and Critical Care Medicine. The recommendations update 2007 guidance and are primarily focused on adults who are not immunocompromised.
“CAP remains one of the leading causes of deaths in the world,” Grant Waterer, MBBS, PhD, co-chair of the guideline committee and a professor of medicine at the University of Western Australia in Perth, said in a news release. “Not only has there been new data in the past decade, but there is now a strong national and international focus on antibiotic stewardship. It was time to update the guideline so that clinicians could be certain they were still practicing evidence-based care.”
“[T]he resistance patterns have changed some of our recommendations, but the first-line agents are fairly similar as the last time around,” co-committee chair Joshua P. Metlay, MD, PhD, from Massachusetts General Hospital and Harvard Medical School in Boston, told Medscape Medical News.
“We are suggesting that physicians and health centers continue to do diagnostic tests so we can learn more about the epidemiology of what’s going on here in the hope that we’ll have better-targeted therapy,” Metlay said.
The authors identified a list of 16 core clinical questions identified by the committee as high priority and made recommendations in response to those questions.
NO HOSPITAL- VS COMMUNITY-ACQUIRED DISTINCTION
In the updated guideline, the authors recommend sputum and blood culture for severely ill patients and for all inpatients who have received empiric treatment for Methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa. (The 2007 guideline recommended sputum and blood culture for severely ill patients.)
Macrolide monotherapy is now conditionally recommended for outpatients on the basis of resistance levels; in the 2007 guideline, macrolide monotherapy was strongly recommended for outpatients.
The authors recommend against the use of serum procalcitonin for distinguishing between bacterial and viral infection and whether or not a patient requires antibacterial therapy. “Although low levels of biomarkers such as procalcitonin decrease the likelihood that patients have bacterial infections, these biomarkers do not completely rule out bacterial pneumonia in an individual patient with sufficient accuracy to justify initially withholding antibiotic therapy, especially among patients with severe CAP,” the authors write.
The committee also recommends against the use of corticosteroids in patients with community-acquired pneumonia, but say clinicians may consider using them for patients with refractory septic shock. Although the previous guidelines did not address corticosteroids, there has been a great deal of literature on the use of corticosteroids in patients with pneumonia, Metlay said. “On the final analysis, it’s probably not a preferred therapy for most patients with pneumonia as an adjunct therapy,” he added.
Notably, the updated guideline recommends abandoning the use of the healthcare-associated pneumonia category. Rather, the focus is on using local epidemiology data and validated risk factors to determine whether the patient needs coverage for MRSA or P aeruginosa and an increased emphasis on deescalating treatment if culture results are negative.
“The category itself poorly predicts situations where patients have drug-resistant pathogens, and it has also been overused as a category such that there’s a lot of empiric therapy of patients with pneumonia with very broad-spectrum antibiotics that are probably causing more harm than good,” Metlay explained.
“There’s really growing evidence that the implementation of that category has led to excess overuse of broad-spectrum antibiotics and not improved outcomes — and actually may have worsened outcomes. So it was time to come up with a better strategy to deal with the small but real risk that, in some patients, there are causative agents that are not covered by the usual antibiotics that we prescribe,” he added.
The updated clinical guideline recommends both β-Lactam/macrolide and β-lactam/fluoroquinolone combinations for treatment but says there is stronger evidence favoring a β-lactam/macrolide combination.
In addition, the routine use of follow-up chest imaging is not recommended, but the committee notes that patients who are eligible for lung cancer screening should undergo chest imaging as clinically indicated.