Safe and effective bedside thoracentesis: A review of the evidence for practicing clinicians
BACKGROUND
Physicians often care for patients with pleural effusion, a condition that requires thoracentesis for evaluation and treatment. We aim to identify the most recent advances related to safe and effective performance of thoracentesis.
METHODS
We performed a narrative review with a systematic search of the literature. Two authors independently reviewed search results and selected studies based on relevance to thoracentesis; disagreements were resolved by consensus. Articles were categorized as those related to the pre-, intra- and postprocedural aspects of thoracentesis.
RESULTS
Sixty relevant studies were identified and included. Pre-procedural topics included methods for physician training and maintenance of skills, such as simulation with direct observation. Additionally, pre-procedural topics included the finding that moderate coagulopathies (international normalized ratio less than 3 or a platelet count greater than 25,000/µL) and mechanical ventilation did not increase risk of postprocedural complications. Intraprocedurally, ultrasound use was associated with lower risk of pneumothorax, while pleural manometry can identify a nonexpanding lung and may help reduce risk of re-expansion pulmonary edema. Postprocedurally, studies indicate that routine chest X-ray is unwarranted, because bedside ultrasound can identify pneumothorax.
CONCLUSIONS
While the performance of thoracentesis is not without risk, clinicians can incorporate recent advances into practice to mitigate patient harm and improve effectiveness. Journal of Hospital Medicine 2017;12:266-276. © 2017 Society of Hospital Medicine
© 2017 Society of Hospital Medicine
Skin Disinfection and Antisepsis Precautions
The 2010 BTS guidelines list empyema and wound infection as possible complications of thoracentesis.19 However, no data regarding incidence are provided. Additionally, an alcohol-based skin cleanser (such as 2% chlorhexidine gluconate/70% isopropyl alcohol), along with sterile gloves, field, and dressing are suggested as precautionary measures.19 In 1 single-center registry of 2489 thoracenteses performed using alcohol or iodine-based antiseptic and sterile drapes, no postprocedure infections were identified.27 Of note, we did not find other studies (including case reports) that reported either incidence or rate of infectious complications such as wound infection and empyema. In an era of modern skin antiseptics that have effectively reduced complications such as catheter-related bloodstream infection,28 the incidence of this event is thus likely to be low.
INTRAPROCEDURAL CONSIDERATIONS
Use of Bedside Ultrasound
Portable US has particular advantages for evaluation of pleural effusion vs other imaging modalities. Compared with computerized tomography (CT), bedside US offers similar performance but is less costly, avoids both radiation exposure and need for patient transportation, and provides results instantaneously.29,30 Compared to chest x-ray (CXR), US is more sensitive at detecting the presence, volume, and characteristics of pleural fluid30,31 and can be up to 100% sensitive for effusions greater than 100 mL.29 Furthermore, whereas CXR typically requires 200 mL of fluid to be present for detection of an effusion, US can reliably detect as little as 20 mL of fluid.29 When US was used to confirm thoracentesis puncture sites in a study involving 30 physicians of varying experience and 67 consecutive patients, 15% of sites found by clinical exam were inaccurate (less than 10 mm fluid present), 10% were at high risk for organ puncture, and a suitable fluid pocket was found 54% of times when exam could not.4
A 2010 meta-analysis of 24 studies and 6605 thoracenteses estimated the overall rate of pneumothorax at 6%; however, procedures performed with US guidance were associated with a 70% reduced risk of this event (odds ratio, 0.30; 95% confidence interval, 0.20 - 0.70).32 In a 2014 randomized control trial of 160 patients that compared thoracentesis with US guidance for site marking vs no US use, 10 pneumothoraces occurred in the control group vs 1 in the US group (12.5% vs 1.25%, P = 0.009).33 Similarly, another retrospective review of 445 consecutive patients with malignant effusions revealed a pneumothorax rate of 0.97% using US in real time during needle insertion compared to 8.89% for unguided thoracenteses (P < 0.0001).34 Several other studies using US guidance for either site markup or in real time reported similar pneumothorax rates, ranging from 1.1% - 4.8%.35-37 However, it is unclear if real-time US specifically provides an additive effect vs site marking alone, as no studies directly comparing the 2 methods were found.
Benefits of US also include a higher rate of procedural success, with 1 study demonstrating a 99% success rate when using US vs. 90% without (P = 0.030).33 A larger volume of fluid removed has been observed with US use as well, and methods have been described using fluid-pocket depth to guide puncture site localization and maximize drainage.38 Finally, US use for thoracentesis has been associated with lower costs and length of stay.39,40
Intercostal Artery Localization
Although rare (incidence, 0.18%-2%20,21,39), the occurrence of hemothorax following thoracentesis is potentially catastrophic. This serious complication is often caused by laceration of the intercostal artery (ICA) or 1 of its branches during needle insertion.41
While risk of injury is theoretically reduced by needle insertion superior to the rib, studies using cadaver dissection and 3D angiography show significant tortuosity of the ICA.6,41-43 The degree of tortuosity is increased within 6 cm of the midline, in more cephalad rib spaces, and in the elderly (older than 60 years).41-43 Furthermore, 1 cadaveric study also demonstrated the presence of arterial collaterals branching off the ICA at multiple intercostal spaces, ranging between 8 cm and 11 cm from the midline.41 This anatomic variability may explain why some have observed low complication and hemothorax rates with an extreme lateral approach.35 Bedside US with color flow Doppler imaging has been used to identify the ICA, with 88% sensitivity compared to CT imaging while adding little to exam time.44,45 Of note, a 37% drop in the rate of hemothorax was observed in 1 study with routine US guidance alone.39
Pleural Pressure Monitoring and Large-Volume Thoracentesis
While normal intrapleural pressures are approximately -5 to -10 cm H2O,46 the presence of a pleural effusion creates a complex interaction between fluid, compressed lung, and chest wall that can increase these pressures.47 During drainage of an effusion, pleural pressures may rapidly drop, provoking re-expansion pulmonary edema (REPE). While rare (0 -1%), clinically-diagnosed REPE is a serious complication that can lead to rapid respiratory failure and death.20,48 REPE is postulated to be caused by increased capillary permeability resulting from inflammation, driven by rapid re-inflation of the lung when exposed to highly negative intrapleural pressures.47,49
