An easier and safe affair, pleural drainage with ultrasound in critical patient: a technical note

Pigtail insertion should be carried out in the safety triangle, almost always at the posterior axillary line if aiming for effusion [11], and performed under image guidance [11, 17]. The safety triangle is bordered by the lateral edge of the pectoralis major, the lateral edge of the latissimus dorsi and a line along the fifth intercostal space at the level of the nipple. However, ultrasound guidance allows the operator to better decide where to insert the pigtail. The best puncture site is, in fact, the place where the operator can visualise each anatomical structure (i.e., diaphragm, pleural, and organs) and where the operator can measure the maximum distance between visceral and parietal pleural (increasing the safety margin). One of the most commonly used US method for estimation of pleural effusion volume (V) is represented by the Balik equation: V (mL) = 20 × Sep (mm) [8]. To obtain separation (Sep), the operator has to measure the maximal vertical distance between the parietal and visceral pleura in end-expiration at the lung base, in supine patient with trunk elevation of 10–15°. The patient’s position greatly influences the extent of PLEFF [18]. In addition, for pleural effusion when measuring the maximal end-expiratory distance between the parietal and visceral pleura at the thoracic base the area under the curve, as reported by Vignon et al. [19], was greater for right-sided pleural effusions, on the left side the heart increases the fluid level, like a stone in a water recipient. The operator should also examine the ultrasound features of the effusion; the presence of hyperechoic material within the effusion indicates an exsudative effusion.

It was once thought that ultrasound was incapable of identifying intercostal vessels [10]. However, some studies have shown that Doppler ultrasound can be used to visualise intercostal vessels [20‐23] helping prevent vessel injury and ensure a procedure with a low risk of bleeding, even in patients with abnormal pre-procedural coagulation parameters [24]. The colour Doppler box should be placed on the bottom edge of the rib and the depth reduced so the rib does not occupy the entire screen. Reduce the pulse repetition frequency (PRF) until pulsation is detected (Fig. 2, Additional file 1: Video S1). Take care the more posteriorly puncture site is performed, the greater the risk of puncture of the intercostal artery which is not covered by the lower rib edge approaching to the paravertebral line [25‐28].

Ultrasound guidance during pigtail insertion is performed using either site marking or direct needle guidance [29]. In the first case, the physician defines the optimal location point and marks it on the skin, then carries out the procedure without using real-time visualisation through US. Remember that patient repositioning can lead to fluid reallocation, so drain insertion has to be performed instantly after “site marking”. In “direct needle guidance” ultrasound is used in real-time to guide the pleural puncture; some operators prefer to perform needle insertion under real-time ultrasound guidance even though this approach is more technically challenging [29]. Advantages and limitations of ultrasound guidance are enlisted in Table 3.

The pigtail catheter is a smaller drain (8–14F) compared to traditional chest tubes. Pigtail catheters insertion includes the following complications:

Insertional complications, dry taps and procedure failure are less common with ultrasound guidance [11].

The main complications linked to small-bore catheters are blockade, dislodgement, malposition, and kinking [30]. The disconnection of the tubing system represents another possible complication. For infected pleural-fluid effusions, the efficacy and safety of intrapleural fibrinolytic agents are still debatable [11, 31].

Wound infection and empyema may occur if the chest tube (a foreign object) introduces bacteria into the pleural space.

The etiopathogenesis of the re-expansion oedema (RPO) is relatively unknown. Over the years different hypotheses have arisen about increased permeability of pulmonary blood vessels damaged by fast re-expansion of lung tissue [32], blood vessels damaging by free oxygen radicals generated by reperfusion of ischemic lung [33], pulmonary hydrostatic pressure caused by increased venous return, pressure-induced disruption of the alveolar capillaries and altered lymphatic clearance [34]. Mokotedi postulated that RPO could be due to decreased pleural and intrathoracic pressure and left ventricular afterload increased after pleural drainage with a detrimental effect on LV performance in patient with more than moderate compromised LV systolic function [35]. Rapid lung re-expansion in the following settings [36] has been described as a risk factor:

Due to the fact that the etiology of re-expansion pulmonary oedema is unclear, there is concern that re-expansion pulmonary oedema may occur if larger volumes of fluid are withdrawn. Despite BTS guidelines, consensus statement of American College of Chest Physicians and most authors advise to drain no more than 1–1.5 L of fluid at one time, the amount of fluid safely removed continues to be debated as in several studies volumes greater than 1.5 L up to 6 L were safely aspirated.

Cause the RPO mortality rate has been quoted as high as 20%, preventive strategies include limiting drainage of pleural fluid, if the patient reports chest pressure or discomfort during thoracentesis, and using low negative pressure (less than − 20 cm H₂O) for suction with serial measures of pleural pressure can lead to prevention and early recognition of complication. Pleural manometry is not currently in clinical practice and there are no randomised controlled trials. Two important warning signs to end the aspiration are if the patient develops a cough or complains of chest discomfort [11].

Remember that pigtails can easily be drawn back, but cannot be inserted farther in after the procedure is completed.