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R22 Respirology
Diseases of the Mediastinum and Pleura Toronto Notes 2019
Mediastinitis
• mostcommoncauses:post-operativecomplicationsofcardiovascularorthoracicsurgicalprocedures
Acute
• etiology
■ complication of endoscopy (e.g. esophageal perforation providing entry point for infection) ■ esophageal or cardiac surgery
■ tumour necrosis
• signsandsymptoms
■ fever, substernal pain
■ pneumomediastinum, mediastinal compression
■ Hamman’s sign (auscultatory “crunch” during cardiac systole)
• treatment
■ antibiotics (IV vancomycin + 3rd gen cephalosporin), drainage, ± surgical closure of perforation
Chronic
• usuallygranulomatousprocessorfibrosisrelatedtopreviousinfection(e.g.histoplasmosis,TB, sarcoidosis, syphilis)
Pleural Effusions
Definition
• excessamountoffluidinthepleuralspace(upto25mLnormalamount)
Etiology
• disruptionofnormalequilibriumbetweenpleuralfluidformation/entryand/orpleuralfluid absorption/exit
• pleuraleffusionsareclassifiedastransudativeorexudative
■ distinguish clinically using Light’s Criteria (98% sensitivity and 83% specificity for identifying
exudative pleural effusions)
Table 24. Laboratory Values in Exudative Pleural Effusion
All criteria for transudate must be fulfilled to be considered a transudative effusion. If any one of the criteria for exudates is met – it is an exudate
Transudative effusions are usually bilateral, notunilateral
Exudative effusions can be bilateral or unilateral
Protein – Pleural/Serum LDH – Pleural/Serum Pleural LDH
Exudate = any one criterion
Light’s Criteria
>0.5
>0.6
>2/3 upper limit of N serum LDH
Modified Light’s Criteria
>0.5
>0.6
>0.45 upper limit of N serum LDH
Ann Intern Med 1979;77:507-513 Chest 1997;111:970-980
Transudative Pleural Effusions
• pathophysiology:alterationofsystemicfactorsthataffecttheformationandabsorptionofpleuralfluid (e.g. increased capillary hydrostatic pressure, decreased plasma oncotic pressure)
• etiology
■ CHF:usuallyright-sidedorbilateral
■ cirrhosis leading to hepatic hydrothorax
■ nephrotic syndrome, protein losing enteropathy, cirrhosis
■ pulmonary embolism (may cause transudative but more often causes exudative effusion) ■ peritoneal dialysis, hypothyroidism, CF, urinothorax
Exudative Pleural Effusions
• pathophysiology:increasedpermeabilityofpleuralcapillariesorlymphaticdysfunction • etiology(seeTable25)