What changes should I consider in my diagnostic approach to hospitalized patients with community-acquired pneumonia (CAP) in light of the 2019 guidelines of the American Thoracic Society (ATS) and Infectious Diseases Society of America (IDSA)?

Compared to 2007,1 the 2019 ATS/IDSA guidelines2 have 2 major “Do’s” and 2 major “Dont’s” in the diagnostic approach to CAP in hospitalized patients:

  • DO order sputum and blood cultures in patients empirically treated for methicillin-resistant Staphylococcus aureus (MRSA) or Pseudomonas aeruginosa—in addition to those with severe CAP as in 2007.  
  • DO order rapid influenza molecular assay—in preference to antigen test— when influenza viruses are circulating in community, irrespective of pneumonia severity
  • DON’T routinely order urine antigens for pneumococcal or Legionella antigens, except in severe CAP or in the presence of suggestive epidemiological factors (eg. Legionella outbreak, recent travel)
  • DON’t routinely order serum procalcitonin to determine need for initial antibacterial therapy

Patients at risk of MRSA or P. aeruginosa include those with prior infection with the same pathogens as well as those with hospitalization and treated with parenteral antibiotics—in or out of the hospital— in the last 90 days; HCAP is no longer recognized as an entity.

The definition of severe CAP is unchanged: 1 of 2 major criteria (septic shock or respiratory failure requiring mechanical ventilation) or 3 or more of the following minor criteria or findings listed below:

  • Clinical
    • Respiratory rate ≥30 breath/min
    • Hypotension requiring aggressive fluid resuscitation
    • Hypothermia (core temperature <36 ᵒC, 96.8 ᵒF)
    • Confusion/disorientation
  • Radiographic 
    • Multilobar infiltrates
  • Laboratory 
    • Leukopenia (WBC <4,000/ul)
    • Thrombocytopenia (platelets <100,000/ul)
    • BUN ≥20 mg/dl
    • Pa02/FI02 ratio ≤250

Keep in mind that these guidelines focus on adults who are not immunocompromised or had recent foreign travel and are often based on expert opinion but low or very low quality evidence due to the dearth of properly designed studies.

Bonus Pearl: Did you know that the urine Legionella antigen only tests for L. pneumophila type I, with an overall sensitivity ranging from 45% to 100%!3,4

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References

  1. Mandell LA, Wunderink RG, Anzueto A. Infectious Disease Society of America/American Thoracic Society Consensus Guidelines on the Management guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis 2007;44:S27-72. https://www.ncbi.nlm.nih.gov/pubmed/17278083
  2. Metlay JP, Waterer GW, Long AC, et al. Diagnosis and treatment of adults with community-acquired pneumonia. Am J Respir Crit Care Med 2019;200:e45-e67. https://www.ncbi.nlm.nih.gov/pubmed/31573350
  3. Blazquez RM, Espinosa FJ, Martinez-Toldos CM, et al. Sensitivity of urinary antigen test in relation to clinical severity in a large outbreak of Legionella pneumonia in Spain. Eur J Clin Microbiol Infect Dis 2005;24:488-91. https://www.ncbi.nlm.nih.gov/pubmed/15997369
  4. Marlow E, Whelan C. Legionella pneumonia and use of the Legionella urinary antigen test. J Hosp Med 2009;4:E1-E2. https://www.ncbi.nlm.nih.gov/pubmed/19301376

 

 

What changes should I consider in my diagnostic approach to hospitalized patients with community-acquired pneumonia (CAP) in light of the 2019 guidelines of the American Thoracic Society (ATS) and Infectious Diseases Society of America (IDSA)?

Why is my hospitalized patient with alcohol withdrawal syndrome so thrombocytopenic?

Although thrombocytopenia associated with chronic alcoholism may be related to complications of cirrhosis (eg, platelet sequestration in spleen due to portal hypertension, poor platelet production, and increased platelet destruction) (1), it may also occur in the absence of cirrhosis due to the direct toxic effect of alcohol on platelet production and survival (2).

 
In a prospective study of patients ingesting the equivalent of a fifth or more daily of 86 proof whiskey admitted for treatment of alcohol withdrawal—without evidence of severe liver disease, infection or sepsis— 81% had initial platelet counts below 150,000/µl, with about one-third having platelet counts below 100,000 µl (as low as 24,000/ul) (3).
In most patients, 2-3 days elapsed before the platelet count began to rise significantly, peaking 5-18 days after admission. Others have also reported that platelet counts rise within 5-7 days and normalize in a few weeks after alcohol withdrawal (1); bleeding complications have been uncommon in this setting.
Perhaps even more intriguing is the report of the association between thrombocytopenia in early alcohol withdrawal and the development of delirium tremens or seizures (sensitivity and specificity ~ 70%, positive predictive value less than 10% but with a negative predictive value of 99%) (4)! In fact, the authors suggested that, if their findings are corroborated, a normal platelet count could potentially be used to identify patients at low risk of alcohol withdrawal syndrome and therefore outpatient therapy. 

References
1. Mitchell O, Feldman D, Diakow M, et al. The pathophysiology of thrombocytopenia in chronic liver disease. Hepatic Medicine: Evidence and Research 2016;8 39-50. https://www.dovepress.com/the-pathophysiology-of-thrombocytopenia-in-chronic-liver-disease-peer-reviewed-article-HMER

2. Cowan DH. Effect of alcoholism on hemostasis. Semin Hematol 1980;17:137-47. https://www.ncbi.nlm.nih.gov/pubmed/6990498

3. Cowan DH, Hines JD. Thrombocytopenia of severe alcoholism. Ann Intern Med 1971;74:37-43. http://annals.org/aim/article-abstract/685069/thrombocytopenia-severe-alcoholism.

4. Berggren U, Falke C, Berglund KJ, et al. Thrombocytopenia in early alcohol withdrawal is associated with development of delirium tremens or seizures. Alcohol & Alcoholism 2009;44:382-86. https://www.ncbi.nlm.nih.gov/pubmed/19293148

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Why is my hospitalized patient with alcohol withdrawal syndrome so thrombocytopenic?

Should I use a hemoglobin level of 7 or 8 g/dL as a threshold for blood transfusion in my hospitalized patient?

Unlike its previous 2012 guidelines that recommended overlapping hemoglobin level triggers of 7 g/dL to 8 g/dL for most inpatients, the 2016 guidelines from AABB (formerly known as the American Association of Blood Banks) assigns 2 distinct tiers of hemoglobin transfusion triggers: 7 g/DL for hemodynamically stable adults, including those in intensive care units, and 8 g/dL for patients undergoing cardiac or orthopedic surgery or with preexisting cardiovascular disease1 , often defined as history of coronary artery disease, angina, myocardial infarction, stroke, congestive heart failure, or peripheral vascular disease2,3.  

These recommendations are based on an analysis of over 30 randomized trials, taking into account the potential risks of withholding transfusions, including 30-day mortality, and myocardial infarction. The new 2-tier recommendation specifically excludes those with acute coronary syndrome, severe thrombocytopenia (patients treated for hematological or oncological reasons who are at risk of bleeding), and chronic transfusion-dependent anemia.

The guidelines also emphasize that good clinical practice dictates considering not only the hemoglobin level but the overall clinical context when considering blood transfusion in patients. These factors include alternative therapies to transfusion, rate of decline in hemoglobin level, intravascular volume status, dyspnea, exercise tolerance, light-headedness, chest pain considered of cardiac origin, hypotension, tachycardia unresponsive to fluid challenge, and patient preferences.

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References

  1. Carson JL, Guyatt G, Heddle NW. Clinical practice guidelines from the AABB red blood cell transfusion thresholds and storage. JAMA. Doi:10.1001/jama.2016.9185. Published online October 12, 2016. https://www.ncbi.nlm.nih.gov/pubmed/27732721
  2. Carson JL, Duff A, Poses RM, et al. Effect of anemia and cardiovascular disease on surgical mortality and morbidity. Lancet 1996;348:1055-60. https://www.ncbi.nlm.nih.gov/pubmed/8874456
  3. Carson JL, Siever F, Cook DR, et al. Liberal versus restrictive blood transfusion strategy: 3-year survial and cause of death results from the FOCUS randomized controlled trial. Lancet 2015;385:1183-1189. https://www.ncbi.nlm.nih.gov/pubmed/25499165
Should I use a hemoglobin level of 7 or 8 g/dL as a threshold for blood transfusion in my hospitalized patient?