There are two types of plural effusions, transudative and exudative.
A transudate is defined as pleural fluid to serum total protein ratio < 0.5, pleural fluid to serum LDH ratio < 0.6, and absolute pleural fluid LDH < 200 IU or < 2/3 of the normal serum. All other effusions are exudative. An exudate usually indicates inflammation or malignancy, while a transudate may indicate Congestive heart failure, Nephrotic Syndrome or Cirrhosis.
The most common causes of pleural effusions are cancer, congestive heart failure, pneumonia, recent surgery and tuberculosis, in countries where it is common.
Further evaluation of plural fluid may also aid diagnosis. A pleural fluid glucose value less than 50% of the normal serum value or a pH below 7.30 with normal arterial blood pH may indicate malignancy, autoimmune disorders or infections. An amylase level > 160 Somogy units is indicative of pancreatitis. A triglyceride level > 110 mg/dl and the presence of chylomicrons in the plural fluid, indicates a chylous effusion most commonly due to traumatic rupture of the thoracic duct. CBC, microbiological culture and cytology of the plural fluid may further narrow the differential diagnosis.
Before the procedure, erect & lateral decubiti chest x rays (CXR) should be preformed to assess the size, location of the effusion and if it is loculated or free flowing.
For free flowing effusions the patient is seated upright & leaning forward. The patient is asked to hold his breath & the thorax is entered posteriorly 5cm lateral to the spinal column and 2 interspaces bellow the cessation of the tectile fremitus / where the percussion is dull.
Loculated effusions are localized by US and the site for thoracocentesis is marked on the skin.
Prep the skin with Iodine and infiltrate 1% lidocane into the subcutaneous tissue over the rib bellow the interspace to be entered & then deeper into the rib's periosteum. Now place a negative pressure on the needle and advance it over the top of the rib, to avoid injury to the neurovascular bundle, until plural fluid is returned, then inject lidocaine to the pleura and as you come out into the intercostal muscles too.
Thoracocentesis kits have a 14 gauge needle inside a plastic catheter with an attached syringe and stopcock.
Once the plural cavity is entered, advance the catheter over the needle, and connect a drainage bag to the stopcock for plural fluid removal.
The amount of fluid removed depends on the indication for thoracocentesis. A diagnostic thoracocentesis requires 20-30 mL, while a therapeutic thoracocentesis requires removal of 1-1.5L of fluid. The aspiration should not exceed 1.5L, as there is a risk of re- expansion pulmonary edema.
A CXR is done after the procedure to evaluate for pneumothorax (PTX) and resolution of the effusion.
The most common complication is PTX. If it is small and the patient is hemodynamically stable, repeat the CXR in 6 hours. A large or unresolved PTX is treated with tube thoracostomy & negative suction until the air leak seals. Other complications include re-expansion pulmonary edema when large amounts of fluid are removed, hematoma and injury to the neurovascular bundle.
When the patient's cardiopulmonary status is compromised which may be seen in a large PTX, effusion or hematoma, this procedure is usually replaced with tube thoracostomy.
Tube thoracostomy
http://www.medicalvideos.us/videos-186-Chest-Tube-Insertion
A flexible plastic tube that is inserted through the side of the chest into the pleural space is indicated for a large PTX, hemothorax, recurrent pleural effusion, cylothorax and empyema.
A "safe triangle" (shown below) is the preferred site of insertion. The triangle is bordered by the anterior border of the latissimus dorsi, the lateral border of the pectoralis major muscle, a line superior to the horizontal level of the nipple, and an apex below the axilla
The tube should not be inserted lower than the 6th intercostal space, to avoid injury to the diaphragm which can rise up to the fourth intercostal space. The tube should also be passed over the top of the rib to avoid the neurovascular bundle found on the inferior aspect of the rib.
The size of the thoracostomy tube depends on the material needed to be drained. Usually a 32- 36 French tube is used for hemothorax or pleural effusion while a 24-28 French is used for pneumothorax.
Coagulopathy is a relative contraindication for insertion.
Place the patient in a lateral position with the unaffected side down.and the head of the bed inclined to 15 degrees. Extend the patient's arm on the affected side is forward or above the head. Prep the skin with iodine & using a 25 gauge needle, infiltrate 1% lidocaine over the 5th or 6th rib in the middle or anterior axillary line and into the subcutaneous tissue, periosteum, intercostal muscles & the pleura. Return of air, blood or pus into the syringe confirms that the needle entered the pleural cavity.
Using a No. 10 /11 blade make a 2cm transverse incision through the skin & subcutaneous tissue.
Use a curved Kelly clamp to bluntly dissect a tract to the rib.
Advance the closed & locked clamp over the top of the rib and puncture the parietal pleura. Once the pleura is punctured an efflux of air or fluid is usually seen. The clamps jaws can then be opened to enlarge the tract & removed.
Insert a finger into the tract, to lyse any adhesions.
Insert the fenestrated chest tube using the clamp as a guide. The tube should be directed basally for a dependent effusion or apically for a PTX. Advance the tube till the last fenestrated hole in the tube is inserted. Place a clamp at the free edge of the chest tube until you connect it to a closed suction or a water seal system, below the level of the chest. The appearance of bubbles in the water chamber is a sign that the chest tube drainage device is functioning properly.
When the tube is functioning properly, secure it to the skin using 0 or 1-0 silk or nylon sutures. Two separate through-and-through, simple, interrupted stitches on each side of the chest tube are recommended to prevent routine patient movements from dislodging the chest tube. Each stitch should be tightly tied to the skin, then wrapped tightly around the chest tube several times to cause slight indentation, and then tied again. A U stitch is put around the tube & is used as a purse string to close the tract once the tube is removed. Place petrolatum gauze over the skin incision and then an occlusive dressing over the chest tube.
A CXR is done after the procedure to assess for re-expansion & tube position.
Complications include injury to the diaphragm & neighboring viscera, subcutaneous emphysema, phrenic nerve injury & Re-expansion pulmonary edema. Tube clogging can also be a major complication and may lead to pericardial tamponade, tension pneumothorax, or in the setting of infection, an empyema. To minimize potential for clogging, larger diameter tubes may be used although they are associated with chest tube related pain.
