PLAPS and Pleural Effusion

(1)

Hôpital Ambroise Paré Service de Réanimation Médicale, Boulogne (Paris-West University), France

Electronic supplementary material

The online version of this chapter (doi:10.1007/978-3-319-15371-1_16) contains supplementary material, which is available to authorized users.

In the usual work of a physician, knowing how to detect a pleural effusion is a conclusion. The interest of the BLUE-protocol is to specify what to do with this information (redundant here, informative there) and how to link it to a cause.

The fast detection of pleural effusions is part of the BLUE-protocol, which simplifies the diagnosis by adding original approaches. This familiar application imagined by Dénier in 1946 and assessed by Joyner in 1967 has for many doctors summarized the interest of thoracic ultrasound [1, 2].

Why to use ultrasound in complement with other tools (physical examination and others) is detailed in Chap. 23.

Ultrasound evaluates the volume and the nature of an effusion and indicates the appropriate area for a thoracentesis, far better than radiography.

For this application, our 5 MHz microconvex probe is perfect.

The Technique of the BLUE-Protocol

From the old school and during decades, pleural effusions were detected during abdominal examinations, using abdominal probes and subcostal approaches. This route can mislead (Fig. 16.1). Our microconvex probe is perfect for direct analysis through the intercostal space. Therefore, new signs adapted to this direct approach will be described.

Fig. 16.1

Pleural effusion and traditional approach. This effusion appears during a transabdominal approach, through the liver (L), in a transversal scan. This does not provide a definite diagnosis with certain lower-lobe consolidations and also does not allow ultrasound-guided thoracentesis. Note that the effusion goes posterior to the inferior vena cava (V), a feature that distinguishes, if necessary, pleural from peritoneal effusion

Pleural effusion collects in dependent areas (principle n°2 – fluid is heavier than air). Any free pleural effusion is therefore in contact with the bed in a supine patient. Rotating the patient laterally is sometimes difficult, and not satisfactory if the effusion moves to inaccessible dependent areas (Fig. 16.2). Scanning only the accessible, lateral wall will result in a loss of sensitivity. We insert the probe at the PLAPS-point, as far as we can (read again carefully the technique of the PLAPS-point in Chap. 5).

Fig. 16.2

PLAPS-point and Earth-sky axis. The lateralization maneuver. Left: the probe explores the lateral zone up to bed level. The bed prevents the probe from scanning further. Note the probe is far from perpendicular to the wall. Using this horizontal axis, the detection of the small effusion (arrowheads) is not obtained. Right: the back of the patient has been slightly raised (lateralization maneuver) (or the bed is soft enough for avoiding this maneuver). The probe gains precious centimeters of exploration and is now pointing to the sky, at a PLAPS-point, not far from perpendicular. Minimal effusion or posterior consolidation can be diagnosed. Note that the effusion has slightly moved toward the medial line (the arrows indicate the maximal thickness of the fluid, the circle the medial line), indicating that the maneuver of turning the patient should be minimal (a wider maneuver could result in locating this effusion at the mediastinal wall)

The principle of the PLAPS-point is simple: if only one “shot” is allowed for determining whether there is, or not, a pleural effusion, this location indicates immediately quite all free pleural effusions, either abundant or minute. Ultrasound can perfectly detect millimetric effusions (Fig. 16.3), provided the probe is applied at the correct spot.

Fig. 16.3

Minimal pleural effusion. Longitudinal scan at the PLAPS-point. This figure indicates several pieces of information.

1. It shows the quad sign: the dark image is an effusion not because it is dark but because it is framed within four regular borders: the pleural line, the shadow of the ribs, and mostly the regular deep border (the lung line – arrows). The quad sign is drawn at the right image

2. It shows the absence of local lung consolidation, since the image beyond the lung line is artifactual

3. It indicates the volume of the effusion. The interpleural expiratory distance is 7 mm. This corresponds to a 20–40 ml effusion.

4. This effusion seems too thin for safe thoracentesis.

5. This figure allows to present the sub-B-lines (artifacts looking like B-lines, arising not from the pleural line but from the lung line, whose meaning is not the same, since only the pleural fluid must be on attention). This notion of sub-B-lines matters for those who want to know the volume of a pleural effusion; read more in Chap. 28

The Signs of Pleural Effusion

Traditionally, the diagnosis is based on an anechoic image. CEURF does not use this criterion in the critically ill. Only anechoic effusions are anechoic. How about the others, which can have all degrees of echogenicity, especially the most life-threatening: hemothorax, pyothorax, etc.? In addition, hard conditions (challenging patients) create parasite echoes with difficulties to affirm the anechoic pattern of the effusion. The CEURF definition has been made independent from the tone of the effusion. We first see a structural image (i.e., not an artifact) at the PLAPS-point. Structural images in the thorax, in critically ill patients, are of either pleural effusions or lung consolidations. What else? For defining the pleural effusion anyway and regardless of its volume, we use two signs of our own.

One Static Sign: The Quad Sign

This is the only static sign we use. A pleural effusion is limited by four regular borders shaping a quad (Fig. 16.3). These borders are the pleural line, from where it arises; the upper and lower shadows of the ribs, regular as any artifact; and the deep border, which is always regular and roughly parallel to the pleural line (15° more or less), as it represents the lung surface. We imagine that apart from irregular pleural tumors that we never yet see, the lung surface is always regular. This line was called the lung line, an ultrasound marker of the visceral pleura. The lung line is visible when the visceral pleura is separated from the parietal pleura by a structure that allows ultrasound transmission, i.e., a fluid effusion. In healthy subjects, the lung line is virtual, making the parietal and the visceral pleura one line (the pleural line).

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