Equipment
The necessary equipment for a thoracentesis is
usually available as a packaged, sterilized set.
Antiseptic—povidone-iodine
Local anesthetic—lidocaine hydrochloride
Sterile syringes and plungers—a 10-ml syringe is
used to administer the anesthetic. A 30 or 50-ml
syringe is used to collect the specimen
Disposable needles—25- and 20-gauge needles are
usually used when administering the anesthetic
Intravenous catheter—a 16- or 14-gauge catheter
with trocar is preferred
Three-way stopcock
Sterile tubing—two 30-50 cm lengths of tubing may
be needed
Specimen containers
Sterile adhesive bandage
Procedure
1. Place the patient in the sitting position, prefera-
bly with his or her legs over the side of the
procedure table. Support the patient's feet and
rest his or her arms on a pillow on a bedside
stand.
2. Identify the puncture site - the intercostal space
at the location of maximum dullness to percus-
sion, usually in its posterolateral aspect. Poste-
riorly the site should be above the ninth rib, and
laterally, above the seventh rib.
3. Cleanse the skin over the puncture site using the
antiseptic. Allow it to air dry. An area incorpo-
rating three interspaces should be cleansed. The
remainder of the procedure is performed with
sterilized equipment and sterile technique.
4. Infiltrate the skin and soft tissue at the puncture
site with 5 ml of the anesthetic. Use the
25-gauge needle for the skin and the 20-gauge
needle for the soft tissues. Always advance the
needle perpendicular to the chest surface and
above the lower rib. The intercostal nerve and
blood vessels located at the lower margin of the
upper rib are thereby avoided. Advance the
needle in 1-2 mm increments injecting a small
portion of the anesthetic at each step. Negative
pressure is applied to the syringe prior to each
injection to assure that the anesthetic is not
injected into a blood vessel. The patient will
usually complain of pain when the parietal
pleura is reached. Inject a generous amount of
anesthetic there. Continue to advance the needle
in steps until pleural fluid is aspirated. If the
needle is inserted all the way to its hub without
obtaining fluid, withdraw it slowly while apply-
ing constant negative pressure. Puncture at a
site one interspace inferior or superior to the
original site may then be considered.
5. When pleural fluid is aspirated, withdraw the
needle, insert the trocar with catheter into the
prepared site, and advance it on through the
parietal pleura, always staying just above the
lower rib. When fluid appears in the catheter
tubing remove the trocar while keeping the
catheter in place. Attach a length of tubing to
the catheter hub and the large syringe to the free
end of the tubing.
6. Withdraw an adequate amount of fluid.
7. If a large volume of fluid is to be removed, insert
the stopcock into the free end of the tubing.
Attach the large syringe and the other length of
tubing to the stopcock. Aspirate fluid into the
syringe then expel it through the open tubing.
8. Remove the catheter. Apply direct pressure to
the puncture site to seal the puncture track and
prevent aspiration of air.
9. Apply a sterile adhesive bandage.
10. Monitor the patient's respiratory status.
Sources of Variability
1. Incision of a vessel can lead to contamination of
the pleural fluid specimen with blood. The
volume of fluid is usually so large that such
contamination has little effect upon the labora-
tory studies. However, this possibility must be
kept in mind if the study results are at variance
with the clinical impression.
Medical Considerations
1. The most common complication of thoracentesis
is pneumothorax due to puncture of the visceral
Specimen Collection Procedures A-12
PLEURAL FLUID
