Question 9

Created on Tue, 06/02/2015 - 15:58
Last updated on Thu, 08/27/2015 - 18:33
Pass rate: 58%
Highest mark: ?

Other SAQs in this paper

Other SAQs on this topic

List the potential  causes of diffuse pulmonary infiltrates in a patient  with AIDS, and outline how they would influence your management.

[Click here to toggle visibility of the answers]

College Answer

Many potential causes should be considered.  High pressure pulmonary oedema (fluid overload: CPAP/PEEP, diurese, fluid restrict, remove blood; cardiac failure: diurese, vasodilate ± inotropes; acute ischaemia: nitrates, morphine ± betablockers, anticaogulants).  Low pressure pulmonary oedema/ARDS  (CPAP/PEEP, fluid restrict, diurese, treat underlyimg cause eg. sepsis).   Diffuse pneumonia (diffuse typical or atypical: CPAP/PEEP, likely to need invasive investigation [eg. lavage], diurese and fluid restrict, specific treatment [anti-agent therapy] according to underlying cause: bacteria [eg. strep or TB], viral [eg. CMV/influenza/SARS], protozoal [eg. pneumocystis], fungal [eg. cryptococcus]). Others: could uncommonly also be malignant (eg. Karposi’s sarcoma), pulmonary haemorrhage (eg. if low platelets: consider platelet transfusion) or auto- immune/vasculitic (consider steroids, immunosuppression).

Discussion

A good free full-text article is available to cover this terrain. In it, there is an excellent table, "Aetiology of pulmonary infections in HIV-infected patients". It also presents the incidence of the aetiology. Turns out, in 97% of cases the pulmonary infiltrates are infectious in nature. The bacterial pathogens are surprisingly mundane- its S.pneumoniaeH.influenzae and Legionella. Together they cover something like 60% of pulmonary infections. Pneumocystis accounts for another 20%, and viruses for 5%. Other fungal infections are surprisingly rare - 2% - and protozoal parasites represent only 0.5%.

Causes of diffuse pulmonary infiltrates in the AIDS patient, and a brief note on their specific treatment

Non-infectious:

  • Pulmonary oedema - PEEP and preload reduction
  • Diffuse alveolar haemorrhage - correction of coagulopathy
  • Malignant (eg. lymphangitis carcinomatosis) - dexamethasone
  • Autoimmune (vasculitis) - high dose steroids
  • Inflammatory - ARDS - lung-protective ventilation

Infectious:

  • Bacterial:
    • Streptococcus pneumoniae - ceftriaxone
    • Mycobacterium tuberculosis - standard cocktail
    • Mycoplasma pneumonia - azithromycin
    • Generally speaking, broad spectrum antibiotics which are narrowed when the pathogen is isolated
  • Viral
    • CMV - ganciclovir or foscarnet
    • VZV - acyclovir
    • HSV - acyclovir
    • Influenza - possibly oseltamivir
    • Human metapneumovirus - supportive management
  • Fungal:
    • Pneumocystis jirovecii - cotrimoxazole
      • This is the second most common cause of pneumonia, behind S.pneumoniae
    • Cryptococcus - fluconazole or amphotericin
  • Protozoal:
    • Toxoplasma gondii - pyrimethamine plus cotrimoxazole or sulfadiazine

References

Segal, Leopoldo N., et al. "HIV-1 and bacterial pneumonia in the era of antiretroviral therapy." Proceedings of the American Thoracic Society 8.3 (2011): 282-287.

Feldman, Charles. "Pneumonia associated with HIV infection." Current opinion in infectious diseases 18.2 (2005): 165-170.

Arora, V. K., and S. V. Kumar. "Pattern of opportunistic pulmonary infections in HIV sero-positive subjects: observations from Pondicherry, India." The Indian journal of chest diseases & allied sciences 41.3 (1998): 135-144.

Benito, Natividad, et al. "Pulmonary infections in HIV-infected patients: an update in the 21st century." European Respiratory Journal 39.3 (2012): 730-745.