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    Thoracentesis / Pleurocentesis – Ultrasound Guided


    Last Updated Mar 04, 2021
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    • Definition: Percutaneous procedure to remove pleural fluid.
    • Use of either needle (smaller volumes, <30 mL), needle over catheter, or small-bore catheter.
    • Can be performed at bedside in emergency departments.



    • Presentation of new pleural effusion – determining cause.
    • Exceptions:
      • Small volume pleural effusion with clear diagnosis – eg. viral pleurisy,
      • Clinical CHF with typical features.
        • Atypical Features suggest alternate diagnosis:
          • bilateral effusions that are very different in size – especially when left >> right
          • Features of pleurisy
          • Fever
          • Features indicative of infection or cancer
          • Echocardiogram inconsistent with CHF
          • Poor improvement of effusion with effective CHF therapy.


    • Symptom relief, eg. dyspnea.
    • Complicated pleural effusions, eg. loculations in a parapneumonic pleural effusion.
    • Pleural conditions that can potentially lead to pleural thickening and restrictive functional impairment, eg. effusions as result of post-primary or reactivation tuberculosis, hemothorax.
    • Multiple factors determine duration of drainage.
      • Size of effusion, locations, whether complete drainage is needed, institutional factors, etc.


    • Small volume of pleural fluid.
    • Skin infection at site.
    • Bleeding diathesis.
      • limited data on safety of thoracentesis when taking anticoagulants, coagulopathy, or thrombocytopenia.
        • Individualized approach needed.
        • Interventional Radiology (IR) Thoracentesis (Society of Interventional Radiology Consensus Guidelines in Image-Guided Interventions):
          • Thoracentesis considered low risk bleeding procedure in IR.
            • If patient has low bleeding risk, generally safe to continue current anticoagulation. Please see guidelines in reference to all specific anticoagulants (and antiplatelets).
        • Patel et al:
          • Retrospective, Single Center (low-quality study).
          • Conclusion: Overall risk of major bleed with patients taking DOAC and/or clopidogrel in Ultrasound-Guided Thoracentesis is very low.

    Mechanical ventilation is not considered a contraindication to thoracentesis (PEEP doesn’t increase risk of pneumothorax).

    Should I Refer to Interventional Radiology?

    • Consider if difficult patient, patient with limiting comorbidities, provider lacks skills, or lack of adequate equipment/bedside ultrasound.
    • Kozmic et al: Bedside thoracentesis with portable ultrasound is as safe as IR procedures and less costly.

    Recommended Treatment


    • Sterile gloves, gown, drapes, chlorhexidine, wound dressing.
    • Local anesthetic agent, 25 gauge needle, syringe.
    • Thoracentesis kit: Can include:  8-Fr over the needle catheter, 18-gauge needle, stopcock, large syringe, drainage bag.
      • Consideration:
        • Diagnostic purposes where only small volume needed (eg. 30 mL), 18-gauge needle without catheter may be used.
        • Any larger volume aspiration risk visceral pleural laceration.
          • In these cases use an over-the-needle catheter or Seldinger technique (wire / dilator / catheter).
          • Typically 8 Fr catheter can suffice for large volume drainages.
          • Note: with Seldinger technique, catheters can range from 6 – 14 Fr.
        • Otherwise for diagnostic needle thoracentesis consider 50 mL syringe with small gauge needle (21-22 gauge), 40 mm length.
          • Larger bore needles possibly associated with increased pneumothorax rate (weak evidence).
          • Larger body habitus may necessitate longer needles – eg. 20-gauge lumbar puncture needle (generally 100 mm length) can be considered if your kit doesn’t already supply 100 mm needles.
    • Sedation typically not required.
    • Bedside ultrasound.
      • Sterile cover and gel not typically needed for simple thoracentesis.
        • Consider use in more complicated cases.
          • When using guide wires (eg. Seldinger technique).
          • Loculated effusions.
          • Body habitus that may require site selection reconfirmation during procedure.
    • Informed consent.

    Technique (Over the Needle Catheter)

    • Identify anatomical structures with ultrasound and locations of lung sliding.
      • Pleural effusions can be free-flowing or loculated.
      • Identify effusion, and choose safe intercostal space – generally 1 intercostal space below superior margin of small effusions, and 2-3 spaces below larger ones (beware diaphragm).
        If ultrasound not available, perform only if evidence of free-flowing pleural effusion.  Use clinical landmarks in conjunction with CXR or CT findings – eg. one or two interspaces below decreased breath sounds, above 9th rib as it avoids diaphragmatic puncture.
      • Use needle cap to mark site before applying chlorhexidine.
    • Determine appropriate angle and depth of needle.
      • Adjust needle length as needed per depth of fluid seen.
    • Sterilize with chlorhexidine and sterile drapes.
    • Local anesthetic (eg. 1 or 2 % lidocaine without epinephrine).
      • Infiltrate with local: epidermis, upper border rib, parietal pleura.
        • When advancing forward, retract plunger of syringe to watch for bloody aspiration and to confirm the point of reaching the pleural effusion.
        • Ensure anesthetization of the parietal pleura, as it produces significant pain in the procedure.
    • Cut through skin with scalpel.
    • Insert over-the-needle catheter through skin and provide continuous negative pressure.
      • Advance until fluid aspirated, and then advance approx. 5 mm further to ensure depth.
      • Hold needle, and advance catheter. Then remove needle.
        • Ensure stopcock attached – this prevents pneumothorax on patient inspirations.
    • Withdraw 50 mL of pleural fluid and send for analysis.
      • Cell count, protein, LDH, pH, glucose, amylase, gram stain, culture, cytology.
    • Drainage techniques (use sutures to stabilize catheter in place, see video 3 below):
      • Gravity Drainage
      • Syringe Drainage
      • Vacuum Bottle Drainage|
        Drain generally until flow slows or stops.
    • Removal technique:
      • Remove catheter while patient holds breath at end expiration. Place an occlusive dressing. Video: Chest Tube Removal (HealthPartnersMedEd).

    Reasons For a ‘Dry’ Tap

    • Errors in skin land-marking
    • Poor angle replication
    • Patient movement
    • Needle blockage
    • Short needle
    • Unexpandable lung – entrapped or trapped fluid.

    Criteria For Hospital Admission


    • Consider post-procedure chest x-ray.
    • Post-procedure ultrasound demonstrating multiple sites of lung sliding may adequately exclude procedure associated pneumothorax.


    • Several: pain at puncture site, bleeding, pneumothorax, empyema, spleen or liver injury, re-expansion pulmonary edema.
      • Pneumothorax:
        • Most common, decreased incidence with ultrasound use.
    • Risk factors: effusions < 250 mL, obesity, multiple loculations, coagulopathy, mechanical ventilation, large volume drainages.

    Tips to Avoid Complications

    • Understand equipment, especially three-way stop cock.
    • Establish level of effusion. Lateral decubitus radiography can distinguish free-flowing from loculated effusions.
    • Check for coagulopathy and/or thrombocytopenia prior to procedure.
    • Always advanced used needles on superior surface of the rib – avoids intercostal vessel injury.
    • Limit drainage to under 1500 mL – avoids post-expansion pulmonary edema.
    • Remove needle with patient at end expiration (negative intrathoracic pressure during inspiration can cause pneumothorax).
      • Otherwise, if stop-cock is affixed to catheter, ensure it is in a position that is closed to the patient.

    Quality Of Evidence?


    We are highly confident that the true effect lies close to that of the estimate of the effect. There is a wide range of studies included in the analyses with no major limitations, there is little variation between studies, and the summary estimate has a narrow confidence interval.


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