Pleural Fluid Analysis

Synonym/Acronym

Thoracentesis fluid analysis.

Rationale

To assess and categorize fluid obtained from within the pleural space for infection, cancer, and blood as well as identify the cause of its accumulation.

Patient Preparation

There are no food, fluid, or activity restrictions unless by medical direction. Regarding the patient’s risk for bleeding, the patient should be instructed to avoid taking natural products and medications with known anticoagulant, antiplatelet, or thrombolytic properties or to reduce dosage, as ordered, prior to the procedure. Number of days to withhold medication is dependent on the type of anticoagulant. Note the last time and dose of medication taken.

Normal Findings

Method: Spectrophotometry for amylase, cholesterol, glucose, lactate dehydrogenase (LDH), protein, and triglycerides; ion-selective electrode for pH; automated or manual cell count; macroscopic and microscopic examination of cultured microorganisms; microscopic examination of specimen for microbiology and cytology.

Appearance		Clear
Color		Pale yellow
Amylase		Parallels serum values
Cholesterol		Parallels serum values
CEA		Parallels serum values
Glucose		Parallels serum values
Protein		3 g/dL
Fluid protein–to–serum protein ratio		0.5 or less
Triglycerides		Parallel serum values
pH		7.37–7.43
RBC count		None seen
WBC count		Less than 1,000 cells/microL
Culture		No growth
Gram stain		No organisms seen
Cytology		No abnormal cells seen

CEA = carcinoembryonic antigen; LDH = lactate dehydrogenase; RBC = red blood cell; WBC = white blood cell.

Critical Findings and Potential Interventions ⬆ ⬇

Positive culture findings in any sterile body fluid.
Timely notification to the requesting health-care provider (HCP) of any critical findings and related symptoms is a role expectation of the professional nurse. A listing of these findings varies among facilities.

Overview ⬆ ⬇

Study type: Pleural fluid collected in a green-top [heparin] tube for amylase, cholesterol, glucose, LDH, pH, protein, and triglycerides; lavender-top [EDTA] tube for cell count; sterile containers for microbiology specimens; 200–500 mL of fluid in a clear container with anticoagulant for cytology. Ensure that there is an equal amount of fixative and fluid in the container for cytology; related body system: Immune and Respiratory systems.

The pleural cavity and organs within it are lined with a protective membrane. The fluid between the membranes is called serous fluid. Normally, only a small amount of fluid is present because the rates of fluid production and absorption are about the same. Many abnormal conditions can result in the buildup of fluid within the pleural cavity. Specific tests are usually ordered in addition to a common battery of tests used to distinguish a transudate from an exudate. Transudates are effusions that form as a result of a systemic disorder that disrupts the regulation of fluid balance, such as a suspected perforation. Exudates are caused by conditions involving the tissue of the membrane itself, such as an infection or malignancy. Fluid is withdrawn from the pleural cavity by needle aspiration (thoracentesis) and tested as listed in the previous and following tables. A significant number of pleural effusion cases remain undiagnosed after pleural fluid analysis.

Further investigation, by pleural biopsy, is indicated in circumstances such as undiagnosed recurrent pleural effusion, identification or exclusion of conditions such as tuberculosis or tumor (e.g., malignant mesothelioma), or pleural thickening in the absence of abnormal accumulations of pleural fluid. Various biopsy techniques include closed needle biopsy, image-guided biopsy, and thoracoscopic biopsy. Closed needle biopsy carries increased risk for pneumothorax, is mainly used in the presence of large effusions, requires multiple samples to provide sufficient specimen yield, and has largely been replaced by ultrasound or computed tomography image-guided and thoracoscopic biopsy in combination with immunohistochemistry. The newer techniques provide a higher quality specimen yield with more sensitive and accurate findings. Pleuroscopy or thoracoscopic biopsy is a technique that allows direct, minimally invasive visualization of the pleural space. It is usually performed by a pulmonologist in an endoscopy suite or operating room under conscious sedation with local anesthesia.

Characteristic	Transudate	Exudate
Appearance	Clear to pale yellow	Cloudy, bloody, or turbid
Specific gravity	Less than 1.015	Greater than 1.015
Total protein	Less than 2.5 g/dL	Greater than 3 g/dL
Fluid protein–to–serum protein ratio	Less than 0.5	Greater than 0.5
Fluid cholesterol	Less than 55 mg/dL	Greater than 55 mg/dL
WBC count	Less than 100 cells/microL	Greater than 1,000 cells/microL

Indications ⬆ ⬇

Differentiate transudates from exudates.
Evaluate effusion of unknown cause.
Investigate suspected rupture, immune disease, malignancy, or infection.

Interfering Factors ⬆ ⬇

Contraindications

Abnormal bleeding tendencies or diagnosed bleeding conditions.

Factors That May Alter the Results of the Study

Bloody fluids may be the result of a traumatic tap.
Unknown hyperglycemia or hypoglycemia may be misleading in the comparison of fluid and serum glucose levels. Therefore, it is advisable to collect comparative serum samples a few hours before performing thoracentesis.

Potential Medical Diagnosis: Clinical Significance of Results ⬆ ⬇

Bacterial or Tuberculous Empyema: Elevated WBC count with a predominance of neutrophils, increased fluid protein–to–serum protein ratio, increased fluid LDH–to–serum LDH ratio, decreased glucose, pH less than 7.3
Chylous Pleural Effusion: Marked increase in both triglycerides (two to three times serum level) and chylomicrons
Effusion Caused by Pneumonia: Elevated WBC count with a predominance of neutrophils and some eosinophils, increased fluid protein–to–serum protein ratio, increased fluid LDH–to–serum LDH ratio, pH less than 7.4 (and decreased glucose if bacterial pneumonia)
Esophageal Rupture: Significantly decreased pH (6) and elevated amylase
Hemothorax: Bloody appearance, increased RBC count, elevated hematocrit
Malignancy: Elevated WBC count with a predominance of lymphocytes, possible elevated RBC count, abnormal cytology, increased fluid protein–to–serum protein ratio, increased fluid LDH–to–serum LDH ratio, decreased glucose, pH less than 7.3
Pancreatitis: Elevated WBC count with a predominance of neutrophils, elevated RBC count, pH greater than 7.3, increased fluid protein–to–serum protein ratio, increased fluid LDH–to–serum LDH ratio, increased amylase
Pulmonary Infarction: Elevated RBC count, elevated WBC count with a predominance of neutrophils, pH greater than 7.3, normal glucose, increased fluid protein–to–serum protein ratio, and increased fluid LDH–to–serum LDH ratio
Pulmonary Tuberculosis: Elevated WBC count with a predominance of lymphocytes, positive acid-fast bacillus stain and culture, increased protein, decreased glucose, pH less than 7.3
Rheumatoid Disease: Elevated WBC count with a predominance of either lymphocytes or neutrophils, pH less than 7.3, decreased glucose, increased fluid protein–to–serum protein ratio, increased fluid LDH–to–serum LDH ratio, increased immunoglobulins
Systemic Lupus Erythematosus: Similar findings as with rheumatoid disease, except that glucose is usually not decreased

Nursing Implications, Nursing Process, Clinical Judgement ⬆

Before the Study: Planning and Implementation

Teaching the Patient What to Expect

Discuss how this test can assist in identifying the type of fluid being produced within the body cavity.
Explain that the procedure takes about 10 to 20 min and is performed under sterile conditions.
Explain that a pleural fluid sample is needed for the test and that chest x-ray is recommended immediately after a pleural biopsy in order to identify postprocedural complications.
Review the procedure with the patient.
Explain that prior to the procedure, laboratory testing may be required to determine the possibility of bleeding risk (coagulation testing).
Explain that pregnancy testing may be required.
Advise that the HCP may request that a cough suppressant be given before the thoracentesis.
Discuss how there may be moments of discomfort or pain when the IV line or catheter is inserted, allowing for infusion of fluids such as saline, anesthetics, sedatives, medications used in the procedure, or emergency medications.
Explain that a sedative and/or analgesia will be administered to promote relaxation and reduce discomfort prior to needle insertion through the chest wall into the pleural space.
Discuss how reducing health-care-associated infections is an important patient safety goal, and a number of different safety practices will be implemented during the procedure.
Explain that hair in the area near the catheter insertion site may be clipped and the area cleaned with an antiseptic solution to cleanse bacteria from the skin in order to reduce the risk for infection.

Procedural Information

Note: The World Health Organization, Centers for Disease Control and Prevention, and Association of periOperative Registered Nurses recommend that hair not be removed at all unless it interferes with the incision site or other aspects of the procedure because hair removal by any means is associated with increased infection rates.
Hair removal requires facilities to use a protocol that is based on scientific literature or the endorsement of a professional organization.
Clipping immediately before the procedure and in a location outside the procedure area is preferred to shaving with a razor.
Shaving creates a break in skin integrity and provides a way for bacteria on the skin to enter the incision site.
Baseline vital signs are recorded and monitored throughout the procedure.
Positioning for this procedure is in a sitting or side-lying position.
Prior to the administration of local anesthesia, the site is cleansed with an antiseptic solution and draped with sterile towels.
The thoracentesis needle is inserted, and fluid is removed.
The needle is withdrawn, and pressure is applied to the site with a petroleum jelly gauze followed by a pressure dressing.
The purpose of the jelly gauze is to keep the site moist, decrease pain and trauma during future dressing changes, and conform to the shape of the site to provide a seal against air leaks and fluid loss.
Samples are placed in a properly labelled specimen container and promptly transported to the laboratory for processing and analysis.

Potential Nursing Actions

Make sure a written and informed consent has been signed prior to the procedure and before administering any medications.

Safety Considerations

Avoid using morphine sulfate in those with asthma or other pulmonary disease.
Morphine sulfate can further exacerbate bronchospasms and respiratory impairment.
Anticoagulants, aspirin, and other salicylates should be discontinued by medical direction for the appropriate number of days prior to a procedure where bleeding is a potential complication.

After the Study: Implementation & Evaluation Potential Nursing Actions

Avoiding Complications

Monitor the patient for complications related to the procedure.
Establishing an IV site and performing a thoracentesis are invasive procedures that can cause rare complications. For additional information see Appendix A: Patient Preparation and Specimen Collection, subsection: Potential Contraindications and Complications Associated With Diagnostic Procedures.
Observe/assess the patient for signs of respiratory distress or skin color changes.
Discuss the importance of immediately reporting symptoms such as absent breathing sounds, air hunger, excessive coughing, or dyspnea (indications of hemoptysis); elevated WBC count, fever, malaise, or tachycardia (indications of infection); dyspnea, tachypnea, anxiety, decreased breathing sounds, or restlessness (symptoms of developing pneumothorax). A chest x-ray may be ordered to check for the presence of pneumothorax.
Observe/assess the needle insertion site for bleeding, inflammation, or hematoma formation.
Emergency resuscitation equipment should be readily available in the case of respiratory impairment or laryngospasm after the procedure.

Treatment Considerations

Follow postprocedure vital sign and assessment protocol.
Resume the usual medications, as directed by the HCP.
Inform the patient that 1 hr or more of bedrest (lying on the unaffected side) is required after the procedure. Elevate the patient’s head for comfort.
Observe/assess for nausea and pain. Administer antiemetic and analgesic medications as needed and as directed by the HCP.
Administer antibiotics, as ordered, and instruct the patient in the importance of completing the entire course of antibiotic therapy even if no symptoms are present.

Clinical Judgement

Consider how to ensure therapeutic recommendations are adopted improving respiratory health.

Follow-Up and Desired Outcomes

Acknowledges that depending procedure results, additional testing may be necessary to evaluate or monitor disease progression or the need for a change in therapy.