Hospital-Acquired Pneumonia (HAP)

When beginning to consider whether the patient might have HAP, roughly four pieces of information should be considered:

(#1/4) evidence of inflammation

• Leukocytosis.
• Bandemia, left-shift, and neutrophil/lymphocyte ratio.
• Fever or hypothermia.
• Septic shock.

(#2/4) evidence of pulmonary dysfunction

symptoms suggestive of pneumonia

• ? Cough.
• ? Production of purulent sputum.

general symptoms of respiratory failure

• Worsening oxygenation (requirement for increased FiO2).
• Tachypnea, respiratory distress.

(#3/4) radiographic evidence

chest radiograph

• Chest radiography has poor performance in HAP.
• Sensitivity may be as low as 44%. (30028740) Imperfect sensitivity is due partially to portable films that often miss infiltrates hiding behind the heart or diaphragm. Among patients with pre-existing radiographic abnormalities, detecting a new infiltrate is even harder.
• Specificity is a major problem as well. For example, opacities may also represent atelectasis, aspiration pneumonitis, pulmonary infarction, chronic pulmonary fibrosis, or cardiogenic pulmonary edema.
• Repeat chest radiograph may sometimes help clarify the diagnosis. A true pneumonia will resolve very slowly, whereas atelectasis or aspiration can often resolve within 1-2 days.

lung ultrasonography

• Ultrasonography is less useful for HAP than for community-acquired pneumonia, because many patients in the ICU will have dependent consolidation and B-lines due to atelectasis.
• However, ultrasonography may remain useful (e.g., to distinguish pleural effusion vs. consolidation at the lung bases).

(#4/4) alternative diagnostic considerations

• It's important to avoid falling into the trap of anchoring on a binary diagnostic approach (does the patient have HAP – yes or no?). A better approach is to consider all possibilities (e.g. what process does the patient have?). If an alternative diagnosis is established (e.g., empyema), this makes HAP unlikely.
• Some common alternative diagnoses to consider include the following:
  • Pulmonary embolism with infarction (which may produce infiltrates).
  • The combination of two processes:
    • #1 = Pulmonary process that doesn't cause inflammation: Atelectasis, asymmetric pulmonary edema, transudative pleural effusion.
    • #2 = Extrapulmonary inflammatory process: Infection elsewhere (e.g., line infection, Clostridioides difficile) or noninfectious fever (e.g., drug fever).

    2) consider CT scan

    

    CT scan for HAP

    • CT scan is the gold-standard imaging study for thoracic infection. Chest radiograph has been shown to have poor sensitivity and specificity as compared to CT scan. (30697596) The main drawback of CT scanning is the logistic challenge of transporting the patient to the CT scanner.
    • CT scan may be extremely helpful when it reveals an alternative diagnosis, for example:
      • Aspiration pneumonitis.
      • Atelectasis.
      • Heart failure.
      • Pleural effusions.
      • Pulmonary embolism.
      • Large airway obstruction.

      how to protocol the CT scan

      • CT angiography is preferred if pulmonary embolism is possible.
      • If pulmonary embolism has been excluded, contrasted CT scan may still be helpful (for diagnosis of abscess, necrotizing pneumonia, atelectasis, and/or empyema).

      argument for broader use of CT angiography in evaluation for possible HAP

      • (1) Safety of CT scan:
        • New evidence shows that CT angiography doesn't cause kidney injury. 📖
        • Risk of secondary malignancy from radiation exposure is minimal, especially above ~30 years old (which describes most hospitalized patients).
        • Hospital-associated pneumonia is associated with a mortality of ~30% or higher (far greater than, for example, STEMI).
        • HAP should be treated with respect, which includes securing a prompt and definitive diagnosis.
        • For patients who do have HAP, CT scan remains helpful in some cases:
        • (a) Cavitation, nodular lesions, lung abscess, or atypical radiographic patterns may help direct attention to specific pathogens.
        • (b) Early identification of parapneumonic effusions may facilitate appropriate monitoring and prompt intervention.
        • Many cases of “possible HAP” are not in fact pneumonia. Misdiagnosis of HAP frequently leads to a week-long course of broad-spectrum antibiotics (while another cause of respiratory failure is being ignored).
        • CT scan may often immediately disprove a diagnosis of HAP, thereby avoiding unnecessary antimicrobial exposure (while shifting focus to the true etiology of respiratory failure – such as atelectasis).
        • Among hospitalized patients with new-onset respiratory failure, the pre-test probability of pulmonary embolism will generally be >>2% (e.g., studies on critically ill patients commonly reveal a PE rate of ~15% among all patients!). (26283414) This risk is above the test threshold for pulmonary embolism, which makes further investigation for pulmonary embolism reasonable.
        • Although the diagnostic yield for pulmonary embolism for patients with suspected HAP will be low (perhaps in the 10% range), PE is a life-threatening diagnosis with important treatment implications.

        3) diagnosis & treatment for probable HAP

        

        additional diagnostic studies for a patient with probable HAP

        • Blood cultures (two peripheral cultures, plus cultures of any central line in place >72 hours).
        • Sputum for Gram stain & culture (If possible. Unfortunately, hospitalized patients are often incapable of expectorating sputum.)
        • Nasal PCR for MRSA (repeat this if it wasn't recently performed).
        • Nasal PCR for respiratory viruses
          • Unfortunately, respiratory viruses can be nosocomially acquired.
          • One study found that 24% of patients with HAP were positive for a respiratory virus. (30028739)
          • Streptococcus pneumoniae is one of the most common pathogens among patients with HAP (which is unlike ventilator-associated pneumonia). (30028739)
          • Legionella is an uncommon HAP pathogen, but may occasionally contaminate hospital water supplies. Additionally, it's notable that patients with early-onset HAP (within
          • Procalcitonin levels may be useful (in the absence of severe immune compromise).
          • C-reactive protein is an alternative (if procalcitonin is unavailable, or in severe renal failure).
          • If infiltrates rapidly disappear (within
          • Stable or worsening infiltrates may support a pneumonia diagnosis.
          • Repeat chest radiograph is especially useful if a CT scan could not be obtained initially.

          empiric antibiotic therapy for HAP

          If the patient is considered to have probable HAP, then initiation of antibiotics is appropriate. There are no precise criteria for exactly when to start antibiotics, so clinical judgement is required.

          Pathogens involved in HAP are difficult to determine, as most patients are unable to provide high-quality sputum samples. The risk of drug-resistant organisms appears to lie in between the risk for CAP (lowest) and VAP (highest). Optimal antibiotic therapy is not well defined – and likely varies among different contexts, depending on local antibiograms.

          occasionally, a treatment regimen for community-acquired pneumonia (CAP) is appropriate:

          • CAP coverage is appropriate if all of the criteria listed below are met: (32157357)
            • (a) Patient admitted within
            • (b) Not recently admitted to the hospital or treated with IV antibiotics (within 90 days).
            • (c) Not immunosuppressed.
            • (d) Structurally normal lungs (e.g., no bronchiectasis or severe COPD).
            • (e) Not in septic shock.
            • (f) No ARDS or acute dialysis prior to HAP onset.
            • (g) No prior colonization with multidrug-resistant bacteria.

            Most patients will require an antibiotic regimen for HAP, which will involve:

            backbone agent: Antipseudomonal beta-lactam

            • A broad-spectrum antipseudomonal agent is the backbone of therapy.
            • This is generally cefepime or piperacillin/tazobactam (more on comparison of these antibiotics here: 📖). Meropenem may occasionally be considered, if there is concern for an extended-spectrum beta-lactamase resistance organism (ESBLs).
            • Factors to consider:
              • Recent antibiotic exposure (an agent which they weren't exposed to might be preferable).
              • Prior infection or colonization with drug-resistant organisms.

              MRSA coverage?

              • Not all patients with HAP require MRSA coverage:
                • Roughly half of patients with probable HAP won't be found to have an actual pneumonia. The overall risk of MRSA pneumonia will depend on MRSA prevalence within any individual hospital unit, but it's often quite low.
                • Patients with a recent nares PCR that was negative for MRSA don't require MRSA coverage. (Murray 2022; 29340593)
                • Receipt of intravenous antibiotics within the last 90 days.
                • Hospitalization in a unit where MRSA is common (e.g., >20% of Staph. aureus isolates are MRSA).
                • Patients at high risk of mortality (e.g., septic shock, more severe pneumonia).
                • Known colonization with MRSA.

                4) review data & course over 24-72 hours

                

                Many patients who are started on empiric antibiotics won't ultimately be diagnosed with pneumonia. Therefore, it's essential to reconsider the diagnosis as additional information becomes available. If emerging evidence is inconsistent with a diagnosis of pneumonia, antibiotics should be discontinued and the diagnosis should be discarded.

                (1) Consider data that may question the diagnosis of HAP, for example:

                • Procalcitonin :
                  • Procalcitonin may be helpful among patients who are not immunosuppressed.
                  • A procalcitonin value of
                  • Blood cultures are only occasionally positive in HAP (perhaps roughly 10% of the time).
                  • If blood cultures are positive, be thoughtful about looking for a nonpulmonary focus of infection – especially if blood cultures reveal an organism which doesn't usually cause pneumonia (e.g., Candida,Enterococcus). (33004324)

                  (2) Discontinue MRSA coverage within 48 hours unless there is objective data of MRSA

                  • MRSA coverage should be discontinued within
                  • If a recent MRSA nares PCR is negative, this is generally sufficient evidence to discontinue anti-MRSA therapy. (Murray 2022; 29340593)

                  5) ongoing management of HAP

                  

                  If HAP remains the leading diagnosis, then antibiotics should be continued to complete a course.

                  duration of antibiotic therapy

                  • The IDSA/ATS guidelines generally recommend a seven-day course of antibiotics (even for Pseudomonas). (27418577)
                  • Potential indications for prolonged therapy: (32157357, 30601179)
                    • Empyema.
                    • Lung abscess or necrotizing pneumonia.
                    • Bacteremia with certain gram-positive organisms (e.g., Staph. aureus).
                    • Severe immunodeficiency.
                    • Cystic fibrosis.
                    • Procalcitonin levels falling below 20% of the initial value or
                    • Procalcitonin should be used only as an antibiotic-stopping tool. Therefore, a low procalcitonin may support discontinuation of antibiotics before seven days. Antibiotics should generally be discontinued after a seven-day course, regardless of the procalcitonin level.

                    approach to treatment failure

                    • The diagnosis of HAP is rarely entirely secure (due to difficulty in obtaining high-quality sputum for analysis).
                    • If patients aren't responding to therapy, it's important to reconsider the diagnosis. Unfortunately, it may also be possible that the patient is infected with a drug-resistant organism which is not being covered by current antibiotics.
                    • The approach to treatment failure is similar to that for community-acquired pneumonia, discussed here: 📖

                    bronchoscopy in HAP

                    bronchoscopy is generally not utilized in HAP

                    • Among patients who aren't intubated, the risk of sedation and bronchoscopy is increased.
                    • Available evidence hasn't found an improvement in patient outcomes following bronchoscopy (as compared to empiric antibiotic therapy). (19154492, 30028739)

                    potential indications for bronchoscopy

                    • Severe immunosuppression creates a very broad differential diagnosis for the potential infection (e.g., organ transplantation patients).
                    • CT scan reveals nodular or cavitary lesions which increase the likelihood of unusual pathogens (such as fungi).
                    • Failure to respond to empiric antimicrobial therapy.
                    • Suspected alternative diagnosis that requires bronchoscopy for diagnosis (e.g., possible eosinophilic pneumonia, or possible diffuse alveolar hemorrhage).

                    questions & discussion

                    To keep this page small and fast, questions & discussion about this post can be found on another page here.

                    Guide to emoji hyperlinks

                    • = Link to online calculator.
                    • = Link to Medscape monograph about a drug.
                    • = Link to IBCC section about a drug.
                    • = Link to IBCC section covering that topic.
                    • = Link to FOAMed site with related information.
                    • 📄 = Link to open-access journal article.
                    • = Link to supplemental media.

                    References

                    • 27418577 Kalil AC, Metersky ML, Klompas M, Muscedere J, Sweeney DA, Palmer LB, Napolitano LM, O'Grady NP, Bartlett JG, Carratalà J, El Solh AA, Ewig S, Fey PD, File TM Jr, Restrepo MI, Roberts JA, Waterer GW, Cruse P, Knight SL, Brozek JL. Management of Adults With Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society. Clin Infect Dis. 2016 Sep 1;63(5):e61-e111. doi: 10.1093/cid/ciw353 [PubMed]
                    • 30028739 Niederman MS. Antibiotic treatment of hospital-acquired pneumonia: is it different from ventilator-associated pneumonia? Curr Opin Crit Care. 2018 Oct;24(5):353-360. doi: 10.1097/MCC.0000000000000531 [PubMed]
                    • 30028740 Ranzani OT, De Pascale G, Park M. Diagnosis of nonventilated hospital-acquired pneumonia: how much do we know? Curr Opin Crit Care. 2018 Oct;24(5):339-346. doi: 10.1097/MCC.0000000000000525 [PubMed]
                    • 30601179 Kelly DN, Martin-Loeches I. Comparing current US and European guidelines for nosocomial pneumonia. Curr Opin Pulm Med. 2019 May;25(3):263-270. doi: 10.1097/MCP.0000000000000559 [PubMed]
                    • 32157357 Papazian L, Klompas M, Luyt CE. Ventilator-associated pneumonia in adults: a narrative review. Intensive Care Med. 2020 May;46(5):888-906. doi: 10.1007/s00134-020-05980-0 [PubMed]
                    • 32331563 Sposato KA. Non-ventilator health care-associated pneumonia (NV-HAP): The infection preventionist's role in identifying NV-HAP. Am J Infect Control. 2020 May;48(5S):A3-A6. doi: 10.1016/j.ajic.2020.03.001 [PubMed]

                    Books:

                    • Shah , P. L., Herth, F. J., Lee, G., & Criner, G. J. (2018). Essentials of Clinical pulmonology. In CRC Press eBooks. https://doi.org/10.1201/9781315113807
                    • Shepard, JO . (2019). Thoracic Imaging The Requisites (Requisites in Radiology) (3rd ed.). Elsevier.
                    • Walker C & Chung JH (2019). Muller’s Imaging of the Chest: Expert Radiology Series. Elsevier.
                    • Palange, P., & Rohde, G. (2019). ERS Handbook of Respiratory Medicine. European Respiratory Society.
                    • Rosado-De-Christenson , M. L., Facr, M. L. R. M., & Martínez-Jiménez, S. (2021). Diagnostic imaging: chest. Elsevier.
                    • Murray & Nadel : Broaddus, V. C., Ernst, J. D., MD, King, T. E., Jr, Lazarus, S. C., Sarmiento, K. F., Schnapp, L. M., Stapleton, R. D., & Gotway, M. B. (2021). Murray & Nadel’s Textbook of Respiratory Medicine, 2-Volume set. Elsevier.
                    • Fishman's : Grippi, M., Antin-Ozerkis, D. E., Cruz, C. D. S., Kotloff, R., Kotton, C. N., & Pack, A. (2023). Fishman’s Pulmonary Diseases and Disorders, Sixth Edition (6th ed.). McGraw Hill / Medical.