Pleural effusion, Light's Criteria

Light's Criteria:

Exudates will have at least one of the following:

    • Pleural/Serum protein ratio >0.5.

    • Pleural/Serum LDH ratio >0.6

    • Pleural LDH >200 U/L (>2/3 upper limit of normal for a simultaneously taken Sr LDH.)

Thoracentesis can be performed safely in the absence of d/o of hemostasis, on effusions that extend >10 mm from the inner chest wall on a lateral decubitus film.

Pleural effusion - causes:

    • Transudates: Usually bilateral on CXR

      • CHF

      • Cirrhosis with ascites

      • Nephrotic syndrome, renal failure

    • Exudates: Usually unilateral on CXR

      • Pneumonia

      • Parapneumonic effusion

      • Malignancy

      • PE: the only effusion which may be either exudative or transudative.

      • Collagen vascular disease

      • Pancreatitis

      • TB

      • Post-cardiac injury syndrome, chylothorax

      • Uremia

      • Esophageal perforation

      • Mesothelioma

      • Viral infection

      • sarcoidosis

      • yellow-nail syndrome

      • myxedema

      • urinothorax.

Orders: 4 tubes.

Tube 1: LDH, Protein, Glucose, Amylase, TG

Tube 2: GS, C&S, Fungal C&S, AFB

Tube 3: Cell count, diff

Tube 4: Cytology, pH, Adenosine deaminase (TB)

Transudate:

  • WBC <100/mm3; and RBC <10,000/mm3

  • Pleural fluid pH is > than Sr. pH

  • Pleural fluid glucose = serum glucose

Exudate:

  • Sr. albumin - Pleural albumin. If it is <1.2 mg/dL, then effusion is exudates.

  • Bloody pleural fluid = malignancy, PE, or trauma

  • Hemothorax: pleural fluid Hct : Serum Hct ratio >0.5 (50%). Insert Chest tube.

  • Eosinophilia >10% suggest air or blood in pleural space; fungal, parasitic inf; drug induced; PE; asbestos related; or Churg-Strauss syndrome.

  • Lymphocytes >50% = TB or malignancy.

  • Plasma cells = multiple myeloma

  • Mesothelial cells = not likely to be TB, likely mesothelioma.

  • LDH is indicator of pleural inflammation

  • Glucose <60 mg/dL - TB, cancer, RA, parapneumonic effusion

    • If glu <40 - insert CT.

  • pH <7.3 - Empyema, TB, cancer, collagen vascular dz, esophageal rupture

    • Empyema needs drainage (CT or VATS).

  • Amylase (salivary) - pancreatic dz, cancer, esophageal rupture.

  • Chylothx: TG >110 mg/dL, turbid. Also in lymphoma.

  • When the pt has lymphocytic pleocytosis in pleural fluid, suspect TB even if there are negative sputum stains for AFB.

  • Cytology +ve in 60% of malignant pleural effusions. Collect in fluid collection bag that is primed with Heparin, 1000 IU.