Large volume (therapeutic) thoracentesis: Procedure and complications

INTRODUCTION — Large volume thoracentesis refers to the removal of more than one liter of pleural fluid during a therapeutic thoracentesis. Although this definition is somewhat arbitrary, we define it as such for the purposes of this topic.  

The technique for large volume thoracentesis will be reviewed here. The diagnostic evaluation of pleural fluid and the techniques for pleural manometry and diagnostic thoracentesis are discussed separately. (See "Measurement and interpretation of pleural pressure (manometry): Indications and technique" and "Ultrasound-guided thoracentesis" and "Pleural fluid analysis in adults with a pleural effusion" and "Diagnostic evaluation of the hemodynamically stable adult with a pleural effusion".)

INDICATIONS AND CONTRAINDICATIONS

●Indications – The indication for large volume thoracentesis is dyspnea due to a moderate to large pleural effusion confirmed by physical examination and chest radiography. One study of 145 patients who underwent therapeutic thoracentesis reported improved symptoms and exercise tolerance in most patients with minimal changes in lung spirometry or oxygenation [1].

The exceptions to this rule include the following:

•Hepatic hydrothorax – Transudative pleural effusions due to liver failure are not generally managed with large volume thoracentesis, although it may occasionally be necessary for relief of severe dyspnea or hypoxemia due to the effusion. This is because pleural fluid tends to reaccumulate rapidly following thoracentesis and serial thoracenteses are associated with increased complication rates in this setting [2]. (See "Hepatic hydrothorax", section on 'Management'.)

•Unexpandable lung – If unexpandable lung is suspected or confirmed, large volume thoracentesis is unlikely to be successful and may increase the risk of complications. (See "Diagnosis and management of pleural causes of nonexpandable lung" and "Measurement and interpretation of pleural pressure (manometry): Indications and technique", section on 'Interpretation of pleural pressures'.)

●Contraindications – General contraindications of thoracentesis (eg, severe coagulopathy) which also apply to patients undergoing large volume thoracentesis, are provided separately. (See "Ultrasound-guided thoracentesis", section on 'Indications and contraindications'.)

PROCEDURE

Equipment and technique — The equipment for thoracentesis and also pleural manometry should be available:

●Thoracentesis – The equipment (table 1), preparation, and technique for large volume thoracentesis is identical to that described for diagnostic thoracentesis, the details of which are provided separately. (See "Ultrasound-guided thoracentesis", section on 'Equipment' and "Ultrasound-guided thoracentesis", section on 'Technique'.)

●Manometry – For most patients in whom large volume thoracentesis is planned, and in particular for those with suspected unexpandable lung (ie, trapped lung or lung entrapment), we perform manometry during the procedure based upon the rationale that it can guide the operator in deciding how much fluid may be removed. However, the expertise for pleural manometry is not always available. The equipment and technique for pleural manometry is also provided separately. (See "Measurement and interpretation of pleural pressure (manometry): Indications and technique", section on 'Technique'.)

Determining the volume of fluid to be removed — When large volume thoracentesis is planned, we monitor symptoms and in those with suspected unexpandable lung (ie, trapped lung or lung entrapment), we additionally use pleural manometry to guide the volume of fluid removal (picture 1). Fluid removal should be stopped if the patient develops intractable chest pain or becomes hypotensive or if no more fluid can be aspirated [3-8]. When manometry is being used, thoracentesis may also be discontinued if the pleural pressure decreases by no more than 10 cm H₂O between two measurement to a value less than or equal to -10 cm H₂O (relative to the position of the left atrium). If a patient experiences persistent anterior vague chest discomfort and manometry is not being used, some experts introduce ambient air or sterile saline (eg, 10 to 20 mL aliquots) into the pleural space until discomfort is relieved. This usually relieves the discomfort immediately when negative pressure is the cause of pain.

There is no single absolute maximum volume of fluid that can be safely removed during therapeutic thoracentesis. Traditionally, fluid removal was discontinued when the total amount of fluid removed reached 1000 to 1500 mL [8]. However, this practice does not always prevent adverse effects and, in fact, many patients do well with removal of more than 1500 mL. In addition, although patients undergoing large volume thoracentesis are at higher risk of re-expansion pulmonary edema (RPE) and procedure-related pneumothorax, these complications do not clearly correlate with the volume of fluid removed [9,10].

The onset of vague chest discomfort generally correlates with development of more negative pleural pressures, which in turn indicates that additional fluid removal may be harmful. In a series of 169 patients, the onset of chest discomfort was associated with lower (more negative) pleural pressures and a greater total change in pleural pressure, while cough did not correlate with lower pressures or the change in pressure [6]. Among those who developed chest discomfort, the majority had pleural pressure more positive than -20 cm H₂O (ie, pressures above which additional removal of fluid is likely safe) and only 22 percent had a potentially unsafe decrease in pleural pressure (ie, more negative than -20 cm H₂O), suggesting that stopping fluid removal at the onset of chest discomfort avoids “unsafe” pleural pressures in the majority.

However, relying on symptoms is not fool-proof since some patients may be asymptomatic despite excessively negative pleural pressures and use does not always protect against the development of complications including pneumothorax ex vacuo and re-expansion pulmonary edema (REPE). As an example, one trial of 128 patients with free-flowing effusions estimated to be at least 0.5 L were randomized to symptom-guided or manometry-guided fluid removal [11]. In both groups drainage was discontinued early if patients developed persistent chest discomfort, intractable cough, or other complications, and additionally, in the manometry group, if end-expiratory pleural pressure was lower than -20 cm H₂O or declined by more than 10 cm H₂O between two measurements to a value less than or equal to -10 cm H₂O. Similar symptoms of chest discomfort was reported in both groups at the end of thoracentesis. However, six patients in the control group developed pneumothorax ex vacuo (ie, a sign of unexpandable lung) compared with zero in the patients who underwent manometry. These results further support the value of manometry in detecting unexpandable lung, especially when large volumes of pleural fluid are being removed. Similarly, in a series of 185 large volume thoracenteses, pleural fluid pressure was monitored and fluid removal stopped at the onset of intractable chest discomfort or a pleural pressure of less than -20 cm H₂O [12]. The mean amount of fluid removed was 1670 mL and the range 1000 to 6550 mL. Only one patient developed significant REPE. (See 'Complications' below.)

Assessment after fluid removal

Clinical assessment — Following large volume thoracentesis, all patients should be clinically assessed for improvement in dyspnea and the response documented since this may impact future decisions regarding removal of additional fluid or placement of a chest tube thoracostomy or tunneled catheter. If symptoms improve with removal of fluid (especially in the setting of unexpandable lung) then most experts consider that patients are likely to respond to the additional removal or drainage of any remaining pleural fluid.

Imaging — Similar to patients undergoing diagnostic thoracentesis, post-procedural imaging, usually ultrasound, is performed to assess for a pneumothorax and the amount of residual pleural fluid. The details of this imaging are provided separately. (See "Ultrasound-guided thoracentesis", section on 'Follow-up'.)

For patients with a pleural pressure at the end of thoracentesis that is more negative than -20 cm H₂O or with an abnormally high elastance (>14.5 cm H₂O/L; ie, trapped lung), in whom prior chest computed tomography (CT) does not readily identify a visceral pleural rind to suggest trapped lung, an air contrast CT scan of the chest is sometimes obtained to verify the presence of visceral pleural thickening as a cause of trapped lung physiology. The technique of air contrast CT of the pleura is described separately. (See "Diagnosis and management of pleural causes of nonexpandable lung", section on 'Imaging'.)

Effect on pulmonary function — Pulmonary function tests (PFTs) are not routinely performed after large volume thoracentesis. This is based upon the rationale that, although pulmonary function improves, the degree of improvement does not correlate well with the volume of fluid withdrawn and management is not impacted by the information gained on PFTs [13-15]. In a series of 26 thoracenteses, the improvement in the forced vital capacity (FVC) was small relative to the amount of fluid withdrawn [13]; the mean vital capacity improved 410 +/- 390 mL in patients who had 1740 +/- 900 mL of fluid removed. After the removal of 800 mL of pleural fluid, patients with higher (ie, less negative) pleural pressures and those with smaller decreases in the pleural pressure had greater improvements in their pulmonary function after thoracentesis, likely indicating expandable lung and implying that patients with more negative pleural pressure had unexpandable lung limiting the benefit of fluid removal. A study from Australia, examined 145 patients who underwent thoracentesis for breathlessness associated with the pleural effusion. There was only a small change noticed in spirometry findings and no change in oxygenation after thoracentesis. Abnormal diaphragm shape and movement were significantly associated with relief of breathlessness after thoracentesis [1]. (See "Overview of pulmonary function testing in adults", section on 'Lung volumes' and "Measurement and interpretation of pleural pressure (manometry): Indications and technique", section on 'Interpretation of pleural pressures'.)

COMPLICATIONS — The complications associated with large volume thoracentesis are similar to those associated with diagnostic thoracentesis (eg, pneumothorax, bleeding, infection), which are discussed separately. (See "Ultrasound-guided thoracentesis", section on 'Complications'.).

Although the risk of complications correlates imperfectly with the volume of fluid removed, the risk of re-expansion pulmonary edema (RPE) and pneumothorax are thought to be higher in those undergoing large volume thoracentesis than in those undergoing diagnostic thoracentesis or <1 L thoracentesis.  

Re-expansion pulmonary edema — Symptomatic RPE is an uncommon complication of large volume thoracentesis, occurring in less than 1 percent of procedures [12,16-19], while asymptomatic radiographic evidence of pulmonary edema (eg, usually on the side of the thoracentesis but occasionally bilateral) is slightly more common (<2 percent) [8,20]. Rarely, REPE occurs with drainage of smaller volumes of fluid [21-23]. As an example, one study showed that although REPE was very rare during large volume thoracentesis (0.01 percent of cases), for every 1 mL of fluid removed there was a 0.18 percent increase in the risk of REPE [24]. Poor performance status may increase the risk [19]. The clinical presentation, diagnosis, and management of REPE are discussed separately. (See "Noncardiogenic pulmonary edema", section on 'Re-expansion pulmonary edema'.)

Pneumothorax (including pneumothorax ex vacuo) — The risk of post-procedure pneumothorax (from iatrogenic lung puncture, inadvertent introduction of air during the procedure, and pneumothorax ex vacuo) increases with the volume of fluid withdrawn, although some patients appear to tolerate larger volumes of fluid removal than others [7,8,19,25]. In a prospective study of 735 thoracenteses in 471 patients, compared with drainage of 0.8 to 1.2 L, drainage of 1.8 to 2.2 L was associated with a more than threefold increase in risk for pneumothorax and, after drainage of 2.3 L or more, the increase in risk was almost six-fold [25]. In another retrospective study, pneumothorax developed in 4 percent of patients in whom ≥1.5 L was removed, but only 0.3 percent required intervention [19].

While most pneumothoraces are iatrogenic in nature due to lung puncture or the introduction of air into the pleural space, some are indicative of underlying unexpandable lung (ie, pneumothorax ex vacuo). Pneumothorax ex vacuo refers to the development of a pneumothorax (image 1 and image 2 and image 3) due to strongly negative pleural pressure created during pleural fluid removal. The air may enter the pleural space across the visceral pleura of the lung without creation of a lung puncture [7,26]. The causes of pneumothorax ex vacuo are attributed to an unexpandable lung (eg, from chronic atelectasis, endobronchial obstruction, and visceral pleural restriction due to either a trapped lung or lung entrapment by an inflammatory or malignant process), details of which are provided separately. (See "Diagnosis and management of pleural causes of nonexpandable lung".)

Of note, postprocedure radiographs of a pneumothorax ex vacuo may show ipsilateral volume loss (rather than an unchanged or increased volume of the hemithorax), and the pneumothorax may be located at the base of the lung in the area where pleural fluid was withdrawn.

Post-procedure pneumothorax is managed in a similar fashion to spontaneous pneumothorax, with the exception that no intervention is required for pneumothorax ex vacuo. (See "Treatment of secondary spontaneous pneumothorax in adults", section on 'Other pneumothorax types'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Pleural effusion".)

SUMMARY AND RECOMMENDATIONS

●Large volume thoracentesis is a therapeutic procedure that removes 1 liter or more of pleural fluid. (See 'Introduction' above.)

●The indication for large volume thoracentesis is dyspnea due to a moderate to large pleural effusion confirmed by physical examination and chest radiography. Transudative pleural effusions due to liver failure and effusions associated with unexpandable lung are not typically managed with large volume thoracentesis. (See 'Introduction' above and 'Indications and contraindications' above.)

●The equipment (table 1), preparation, and technique for large volume thoracentesis is similar to that described for diagnostic thoracentesis. For most patients, and in particular for those with known or suspected unexpandable lung (ie, trapped lung or lung entrapment), we prefer that pleural manometry be performed during large volume thoracentesis based upon the rationale that it can guide the operator in deciding on the volume of fluid to be removed. (See 'Procedure' above and "Ultrasound-guided thoracentesis", section on 'Equipment' and "Ultrasound-guided thoracentesis", section on 'Technique' and "Measurement and interpretation of pleural pressure (manometry): Indications and technique".)

●Fluid removal should be discontinued when the patient develops intractable chest discomfort or when no more fluid can be aspirated, and, if pleural manometry is available, when the pleural pressure is more negative than -20 cm H₂O, declines by more than 10 cm H₂O between two measurements to a value less than or equal to -10 cm H₂O, or the pleural elastance is greater than 14.5 cm H₂O/L. Following large volume thoracentesis, all patients should be clinically assessed for improvement in dyspnea and imaged with ultrasound for residual fluid and pneumothorax. (See 'Procedure' above and "Measurement and interpretation of pleural pressure (manometry): Indications and technique".)

●The complications associated with large volume thoracentesis are similar to those associated with diagnostic thoracentesis (eg, pneumothorax, bleeding, infection). Although the risk of complications correlates imperfectly with the volume of fluid removed, re-expansion pulmonary edema (REPE) and pneumothorax occur at higher rates in those undergoing large volume thoracentesis compared with patients undergoing diagnostic thoracentesis or when volumes <1 L are removed. (see 'Complications' above and "Ultrasound-guided thoracentesis", section on 'Complications' and "Noncardiogenic pulmonary edema", section on 'Re-expansion pulmonary edema').

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Peter Doelken, MD, FCCP, who contributed to an earlier version of this topic review.