"When an empyema is treated either by the cautery or incision, if pure pus flows from the wound, the patients recover; but if mixed with blood, slimy and fetid, they die" Hippocrates
still true today!
Anatomy of the Pleura
Serous membrane that covers the lung parenchyma, the mediastinum, the diaphragm and the rib cage.
Divided into the visceral pleura and the parietal pleura. The parietal pleura lines the inner portion of each hemithorax, while the visceral pleura covers the lung parenchyma.
While the visceral and parietal portions of the pleura are continuous with one another at the lung root, they are histologically and functionally quite different.
At end expiration there is a fair amount of space between the visceral and parietal pleuras. The pleural space contains a small amount of pleural fluid (acts to lubricate the pleural surfaces), allowing them to slide over one another during each respiratory cycle.
Formation of pleural fluid is regulated by the differential hydrostatic and oncotic pressures between the capillaries in the parietal (supplied by systemic vessels) and visceral (supplied most likely by bronchial arteries) pleura and the pleural space. Pleural fluid is removed from the pleural space by stomata in the parietal pleura, then cleared by pleural lymphatic vessels (maximum capacity of approximately 500 cc/pleural space/day), which drain into the mediastinal lymph nodes. Summary: Both production and drainage of pleural fluid happens in parietal pleura.
Pleural Effusion: Findings on PE and CXR
PE
: Change in size of the thoracic cavity, bulging of the intercostal spaces, ß breath sounds and fremitus, dullness to percussion, pleural rub. Decreased fremitus is the most sensitive of these findings. (Ý fremitus = consolidation)
CXR
: ß ability to see diaphragm. meniscus sign (rounded out edges of lung)=~ 500 cc of pleural fluid!! Put patient decubitus and xray to see if fluid layers out between lung and chest wall.
Look at trachea: contralateral shift=mass or moving fluid, Ipsilateral shift=collapsed lung
Transudative vs. Exudative Pleural Effusions
(1) Transudative Effusions
are caused by:
(1) Ý systemic capillary pressure
(2) Ý pulmonary capillary pressure
(3) ß oncotic pressure
Etiologies
:
CHF
most common form of transudate, forms acutely with PCWP>24, can become exudative with diuresis.
Nephrotic Syndrome
usually small subpulmonic effusions, Ý incidence of pulmonary emboli
Cirrhosis
6% of clinical ascites, negative pleural pressure helps movement of fluid into the pleural space (large effusion usually right sided), pleural and peritoneal fluid is identical
Hypothyroidism
Peritoneal Dialysis
small bilateral effusion due to Ý lymphatic drainage, large right effusion due to diaphragmatic defect
Urinothorax
due to obstructive uropathy; P/S creat.>1, only cause of low pH transudate
Pulmonary Embolism
- (can either be transudative or exudative!!!)
(2) Exudative effusions
are caused by:
(1) alteration of pleural permeability most common
(2) ß lymphatic flow from the pleural space
(3) Ý in negative pleural pressure
Etiologies
:
Malignancy
metastatic lung Ca, mesothelioma
Infection
(parapneumonic vs empyema) pneumonia, pancreatice abscess, mediastinal or pericardial infection
thoracic duct crosses at T6 across vertebrae. Any rupture below this level will cause effusions into Right side! Above this get effusions on the left. Causes: lymphoma, trauma
= a long-standing pleural effusion. Thought to form from the slow transfer of cholesterol and lipids out of the pleural space. The origin of the cholesterol and lipids is not known, but may result from degenerated red and white blood cells in the pleural space. Hence, contrary to a finding of a chylothorax, a pseudochylothorax is of no immediate concern.
Diagnostic Thoracentesis
Indications for Diagnostic Thoracentesis
Should be performed on patients with any one of the following conditions:
(1) effusion are not bilateral and comparably sized
(2) patient has pleuritic chest
(3) patient is febrile
Contraindications for Performing thoracentesis
no absolute contraindications
relative contraindications include:
(1) less than 10 mm of fluid on lateral decubitus film
(2) uncorrected bleeding diathesis
(3) administration of anticoagulants or thrombolytics
(4) mechanical ventilation/PEEP
(5) uncooperative patient
How to do a Thoracentesis
Put needle above the rib, because intercostal artery is located below!
Put lidocaine along periosteum that lines rib thats what hurts!
Gold standard Criteria for exudative pleural effusion: need 2 out of 3 of these to determine an exudate, if doesnt meet it is a transudate
(1) Pleural fluid/serum protein ratio of > 0.50 Þ exudate
(2) Plerual fluid/serum LDH ratio of > 0.60 Þ exudate
(3) Pleural fluid LDH greater than 2/3 the upper limits of normal serum LDH Þ exudate
If it is exudate need additional things:
pH = <7.20 can indicate infection (complicated parapneumonic effusion, tuberculous pleuritis), malignancy, rheumatoid and lupus pleuritis
amylase - Ý in pancreatitis, esophageal rupture, malignancy
gram stain and cultures
cytology
Cell count and differential:
most transudates have a WBC < 1000
most exudates have a WBC > 1000
Ý
PMNs indicates acute inflammation
Triglycerides, creatinine, ANA, LE cells
Therapeutic Thoracentesis
40-50% of patients with pneumonia develop pleural effusions. Which need drainage?
Chest tube placement should be considered in all patients with empyemas (pus in the pleural space)
Indications for placement of a chest tube include
:
(1)Complicated Parapneumonic Effusion - pus in the pleural space, or nonpyogenic fluid with a positive Gram stain or culture. pH < 7.10, glucose < 40 mg/dL and the LDH is greater than 1000 U/L. pH<7.00 always needs drainage.