This study describes a different technique for echoguided thoracentesis including a case series with an analysis of success and complications. Major advantages of this technique are patient comfort, the possibility to be carried out in all types of patients, short procedural time and a reduction of risks and complications due to constant atraumatic needle puncture.
Thoracentesis is to date generally performed with the patient sitting at the edge of the bed and leaning forward with arms resting on a bedside table . Lateral recumbent or supine positions are limited to patients unable to sit. The advantage of the above described technique is being easily performed in the lying position thus increasing patient comfort and reducing vasovagal syncope rate and being as well easily performed in patients with obligate decubitus for example in Intensive Care Unit beds.
The lateral recumbent or supine position with head and chest elevated at 30-45° allows fluid to accumulate in the deepest part of the pleural space following gravity as it would be in the “usual” position (patient sitting at the edge of the bed and leaning forward) making it easily detectable by ultrasound and available for pleural procedures even if in small quantity.
Lung sonography allows a preliminary estimate of effusion volume and characteristics and this is, in our opinion, important for clinical purposes . A small effusion occupying the costo-phrenic sinus is not visible on chest radiography and is no more than 150 ml. A retroparietal effusion able to be seen in a single scan (a lateral height of 5–7 cm) corresponds to 500–600 ml of fluid. Any further scan necessary to include the entire effusion to be seen, adds about 500–600 ml. Therefore an effusion classified as massive (three or more scans, 21–24 cm in height) will refer to over 1800 ml of fluid. These data are in line with Reuss e coll. .
The echographic aspect of the effusion is important in the choice of draining system, its caliber, and in the timing of the procedure. In fact an exudative effusion and in particular an areolar complex effusion is most often associated to infective or neoplastic disease and usually requires a large bore drainage [8, 17].
Most studies on echo-supported thoracentesis do not provide details on the technique used and are not able to associate patient comfort in the lying position with a complete real time visualization of each operating phase. Correct echographic guiding should allow constant monitoring of needle point position and this, for physical reasons, is only possible if the needle is positioned in the same scanning plane as the probe . In the thorax in particular, this is only feasible if the probe is placed along an intercostal space with the needle penetrating inside the scan plane (in-plane). With the in-plane approach, the needle enters the skin at the side of the probe. Then the needle crosses the plane and the whole shaft is visualized as it progresses towards the target. For this reason, the costophrenic angle is the perfect position for this echoguided acquisition.
Iatrogenic PNX is the most common and important complication following pleural puncture . Several risk factors have been identified as the type of needle used , the presence of mechanical ventilation, characteristics of the patient as the presence of pulmonary emphysema, operator experience and even the absence of an echographic guide [21, 22]. It has been recently confirmed how programs of ‘best practice’ may reduce the risk of post-procedural PNX  and regarding this discussion we believe that in addition to operator training, it is important to standardize the materials and methods used. Following these recommendations, in fact, iatrogenic PNX rate, which is reported in literature to be between 5-10% and 28% [24–26], may be reduced to around 2% . This risk reduction is particularly evident when using echography.
Other reported complications are not very significant both clinically and in terms of numbers (vasovagal events 3%, pain 5%, cough 24%), or are very rare (hemothorax, abdominal organ lesions) .
PNX can develop during thoracentesis if a communication between atmosphere and pleural space is established because of negative pleural pressure, that occurs when the needle for thoracentesis lacerates the lung and allows air to enter the pleural space from the alveoli, or if a rapid decompression of pleural space due to fluid removal lacerates the visceral pleura [14, 19, 22, 26]. The latter occurrence is relatively common in patients with neoplastic and chronic effusions, and a chronically atelectatic lung.
In our series, we observed a case of PNX in a patient with lung cancer and a chronic large pleural effusion in whom at no time was the needle in contact with lung parenchyma. Another case of PNX developed as post procedural event in a patient with bullous emphysema and staphylococcal empyema. PNX presented thus as a complication in only 1.4% of cases. In both cases a direct needle contact with lung parenchyma was not seen and it is thus likely that their aetiology is not linked to a predictable procedural lesion but rather to an ‘ex vacuo’ mechanism. Their well documented aetiology is drainage- related rather than due to penetrating lung trauma or external air introduction . In our cases echographic diagnosis was immediate and no drainage was necessary. In fact it has been reported that in ex vacuo PNX following thoracentesis, chest tube placement is not necessary in asymptomatic patients and is unlikely to provide clinical benefit .
In the group of patients treated with a pigtail catheter a small passage of air in the pleural space when inserting the guidewire took place if the effusion volume was less than 1500 ml and the intrapleural pressure presumably low. This often created a small anterior pneumothorax easily detected by lung ultrasonography and always drained through the inserted catheter without any clinical consequence. In no case there was evidence of a contact between the needle and lung parenchyma, echographic evidence of air filtration from the lung, or persistent or progressive PNX after air aspiration. For this reason it is not usually considered as complication of pleural puncture, and we considered it as a complication only in the two cases described.
It is possible that our technique reduced complications both because of the features of the Veres needle and for the constant direct real time view of the needle in the costophrenic sinus. Veres atraumatic needle was introduced in clinical practice in 1932 by Janos Veres  to create an artificial PNX. Curiously, its recent and actual use is almost entirely dedicated to laparoscopic procedures. To the best of our knowledge the only study considering this type of needle for thoracentesis is that by Jenkins et al. . Our study is therefore the first study using Veres needle for echoguided thoracentesis procedures.
As far as cough onset is concerned, previous studies report a rate of 9 to 24% [21, 30]. In our patients, transitory cough not requiring procedural stop was frequent (55.7%), and without difference among patients undergoing thoracentesis or pigtail catheter drainage, while the onset of cough as a complication leading to procedure interruption was only 1.5%. We agree with Jones et al. that the onset of persistent cough should represent an indication to stop the procedure . In fact, cough onset is a risk factor for needle contact with lung parenchyma causing a possible lung lesion. Since in our proposed technique the needle point may easily be moved toward thoracic wall, any sudden patient movement may be anticipated becoming less dangerous.
Regarding vasovagal events, the literature indicates a rate of occurrence from 2 to 3.9% . We report a much smaller rate of 0.7% possibly due to a more comfortable patient positioning. Presyncopal symptoms in one of our patients led to the interruption of the procedure.
No case of re-expansion pulmonary oedema (a complication of thoracentesis described in literature [32, 33]) occurred in our series. Slow removal of pleural fluid associated with the previously defined limits of the procedure allowed us to reduce the risk of this complication.
The small number of complications reported in our series is, in our opinion, due to the particular choice of the point of puncture, the real time echographic acquisition and following of the needle point through all steps, and again the use of a Veres needle.
Recently, Patel and coll. highlighted the importance of US guidance for thoracentesis in terms of lower total hospital stay costs and lower incidence of PNX and hemorrhage . Although Veres needle assembly is more expensive than commonly used needles, the low rate of complications observed in this study makes our procedure cost-effective, and it is possible that the low rate of complications observed in the present study can match the cost of the needle in comparison with other reports.
This is an observational study describing a new technique to perform thoracentesis. Although in literature there are no prospective studies comparing ‘blind’ to ‘echoguided’ pleural drainage, evidence exists regarding how echographic support reduces thoracentesis risks and complications both in the spontaneously breathing patient and in the mechanically ventilated patient [23, 34–36]. The purpose of this study, in fact, was not a comparison between blind and echoguided techniques as advantages of the second one have already been well appointed and would not be ethically supportable at this time.