(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_18) contains supplementary material, which is available to authorized users.
A long chapter, but an easy, reasonable procedure, provided some clues are followed.
Vascular probes are not fully suitable for vascular assessment in the critically ill.
Why Is This Chapter Long and Apparently Complicated?
Why is this chapter so long (22 pages), whereas the practical achievement is so short? In practice, the venous step of the BLUE-protocol takes 2 min or less. Half the cases of deep venous thrombosis (DVT) are detected within the first seconds, and the average timing is 55 s (Accessory Note 1).
This contrast is explained mainly because we have to explain what we do not do, more than what we do. Also because, it is true, the venous network is extensive, and nearly each area has some peculiarities. The principle of the BLUE-protocol, i.e., a sequential scanning of the most frequently involved areas, expedites the procedure. Our contact product also enables a really fast protocol.
Our 5 MHz microconvex probe is ideal for assessing almost all deep veins (popliteal, calf, subclavian, including the caval veins – i.e, the superior caval too – a.m.o.).
For the Very Hurried Readers: What Is Seen from the Outside at the Venous Step of the BLUE-Protocol?
The operator applies the probe at the common femoral vein, looks, and then compresses. If this area is thrombosed, the BLUE-protocol is concluded. If not, the superficial femoral vein just above the knee is scanned. If this area is normal, a calf analysis is done. If normal, jugular internal and subclavian veins are scanned. If normal, the operator comes back to the lower extremity: one shot at the midfemoral area, one at the popliteal vein. This sequence, which replaces the laconic term “venous analysis” of the decision tree, results in a larger decision tree, but eventually expedites the venous step.
When to Make Use of Venous Ultrasound in the BLUE-Protocol
The venous assessment is the critical step in the BLUE-protocol, when diagnosing pulmonary embolism. Venous ultrasound is also done in the ICU first (routine assessment in stable patients, cause of a fever in a long-staying patient (Fever-protocol), evaluation of volemia using mainly the caval veins (FALLS-protocol) and first step for venous line insertions) and many other settings (e.g., geriatric dept).
The BLUE-protocol offers a 99 % specificity for the diagnosis of pulmonary embolism in those patients who have a normal anterior lung surface associated with a deep venous thrombosis (DVT). This highlights the importance of the present chapter.
A DVT is able to create sudden death, acute respiratory failure, but also simple fever, multiple so-called pneumoniae delaying the weaning of our ICU patients. Ultrasound can assess the venous network at the bedside, noninvasively, and almost all this network is accessible. Our 5 MHz microconvex probe is perfect for the search for DVT at all areas. In the BLUE-protocol, this is a requirement, since it will be used for any vein and the lung (plus the heart) without any delay.
The decision tree shows that the venous investigation is decided by the BLUE-protocol in the case of an A-profile, i.e., normality of the anterior chest wall in a severely dyspneic patient. We remind the main property of the BLUE-protocol, written in its label: it is only a protocol, not designed for exempting doctors to think. The doctor pilots this protocol, and his/her expertise tells him/her when to go beyond. Once this is understood, the BLUE-protocol gives its best.
Of critical importance (it will be reminded in the text), the BLUE-protocol takes into account only positive findings. In the spirit of the LUCIFLR, it will already allow 80 % of having shorter management with less radiations.
To Who Can This Chapter Provide New Information?
The traditional venous ultrasound did not consider the critically ill, mainly. Little by little since our underground use (1985), we saw that our empiric approach was different from the usual teaching we saw here and there. The differences are substantial and we suspect in actual fact that the same experts who proclaimed that lung ultrasound was unfeasible had developed, in their way, vascular ultrasound.
Here are our ten main differences:
1.
We do not use vascular probes.
2.
We do not use Doppler.
3.
We do not use longitudinal approaches.
4.
We do not use compression – when it is not necessary.
5.
We do not use tough compression – when it is decided.
6.
We use a new sign (the escape sign).
7.
We do not restrict to “two-points” compression.
8.
We pay little attention to the popliteal veins.
9.
We pay special attention to the calf level.
10.
The BLUE-protocol invites the first-line physician to provide this service immediately, 24/7/365, since 1989. This allows to bypass the traditional landscape where the expert (the radiologist) is not present on night. Or, if present, not immediately. Or, if immediately present, not accustomed to this kind of patient. Or, if accustomed, not always fully aware of some specific developments (here detailed). This makes many limitations.
We have the satisfaction to see that, in 2015, the point N°10 seems acquired: the tool is now in the right hands. A whole community of clinicians is at last convinced that ultrasound venous scanning is part of their discipline. We still believe, however, that the “rights hands” did not benefit up to now from the “right tool,” hence this long chapter. Let us now, precisely, detail the 9 other points.
1. Vascular Probes Are Not Used
We are not quite sure if “vascular” probes deserve this label. We prefer to call them “linear,” what they are for sure. Yet are we linear? We are not. Critical areas of interest are really not linear, such as the subclavian vein, the superior caval vein, and all veins when various materials surrounding the critically ill (catheters, devices, mechanical ventilation, tracheostomy, renal replacement catheters, any tubes and drains, etc.) prevent traditional approach with large footprint linear probes. The cutaneous availability is highly limited – the ergonomy of vascular probes makes a serious hindrance. Were we snakes, i.e., the most linear living creature, long axis would be fine, but in the short axis, due to the curvature, the probe contact to the skin would be suboptimal. The label “vascular” is not appropriate for probes which are unable to scan nonlinear areas (subclavian, skinny patients), which are unable to scan deep veins (caval vein), and which are condemned to follow anatomic constraints, for example, a short axis of the internal jugular vein if the patient has a short neck.
In other words, we consider that vascular probes are not suitable for studying vessels (we are not studying ambulatory chronic venous insufficiency).
Reminder, the necessity to change probes makes a loss of time, a failure of critical ultrasound, which the BLUE-protocol does not know.
We use a Japanese 5 MHz microconvex probe which makes a universal assessment: all veins in all orientations from all areas, linear or not, superficial and deep (Anecdotal Note 1). This smart probe can be inserted anywhere, at nonlinear areas (subclavian, popliteal, superior caval vein) as well as very linear ones (abdomen for inferior caval vein) and in areas of limited access (devices etc.), everywhere briefly. It can be rotated in long or short axis without increasing the skin contact. With a range from 0.6 to 17 cm, it exposes all the veins we need to see (Fig. 18.1). Of course, some veins can be seen very well with linear probes, but the principle of the BLUE-protocol is to use the same probe for the veins (all), the lungs, and the heart, a.m.o., without losing one second (nor one dollar).
Fig. 18.1
The venous network, anatomical reminder. This figure shows the deep venous axes accessible to ultrasound. The superior caval vein, brachiocephalic trunk, and the primitive iliac veins, inconstantly exposed, are in gray or dotted. The areas where the second hand (“Doppler hand”) is necessary are indicated
Third interest of the microconvex probe, its limited skin contact allows less energy for the compression, focused on the vein.
Colleagues who advocate vascular probes are happy to see nice images (in passing, not so spectacular if low-quality laptop equipment is used), but must acknowledge its limited value (scanning only superficial veins, only linear areas, no choice for orientation between short and long axis). The principle of the optimal compromise shows why our probe is the winning choice (see Chap. 3 devoted on the concept of the optimal compromise).
2. Doppler Is Not Used: What Does the BLUE-Protocol Instead
We promise to buy a Doppler equipment (and throw our Hitachi-405 to the garbage) at the very minute where we will feel blocked – a point not yet reached after our 26/30 years of clinical use. Read Anecdotal Note 2. Increasingly, clinicians admit that Doppler is not that mandatory for assessing the content of a vein [1–5]. Gray-scale ultrasound is a gold standard – a powerful bedside gold standard. The usual craze for Doppler appears ill defined to us; read Anecdotal Note 3.
Let us apply our probe on this patient we care to. Let us apply it correctly, i.e., like a fountain pen, at zero pressure. Just enough pressure for having an image on the screen. Holding the probe another way would compress the vein, making it invisible on the screen (see Fig. 1.1). Decreasing the pressure up to the “zero pressure” level would progressively show the collapsed vein. Remember that an external operator must be able to withdraw the probe from the operator’s hand without effort.
Let us apply the probe in the short axis of the vessels (this makes their detection immediate; see next section). Let us first rule out all what is not vascular. Round images can be vessels, but also cysts, lymph nodes, and hematomas (Fig. 18.2). No need for Doppler: just a Carmen maneuver shows that a lymph node has a beginning and an end, whereas a vessel has no end. Now we know we are scanning vessels. Muscles (sternocleidomastoidian for the internal jugular vein) are usually flat, not tubular.
Fig. 18.2
A lymph node. Transverse scan of the neck. This “M” may be a venous thrombosis, a tissue-like mass detected outside the artery. The Carmen maneuver immediately shows this is an enlarged lymph node, egg shaped when scanned. The arrow designates the shifted and flattened internal jugular vein
Then the vascular pair is identified. Apart from rarities (brain, saphenous veins, etc.), there is one vein per artery (Figs. 18.3 and 18.4). Cross-sectional scans immediately show this pair. If the pair is not well seen, the Carmen maneuver is done until the image quality is optimized. Then the probe is held standstill. For keeping ultrasound a simple discipline, we advise to position the probe always perpendicular to the skin, above the area of interest, avoiding these sophisticated oblique approaches (see Fig. 1.1).
Fig. 18.3
Normal right internal jugular vein. Cross-sectional scan. The vein is located outside the artery (A) and has a round shape, a caliper of 13 × 20 mm, and an anechoic content. Note the vagus nerve behind the angle between the two vessels. It is difficult for us to understand what a vascular probe would add in terms of resolution, when compared to our universal microconvex probe
Fig. 18.4
Normal jugular internal vein, long axis. In this scan, the vein lies anterior to the artery (A), a rare (not exceptional) finding. Note this 1982 technology, taken here on purpose for showing that even this system was fully suitable at the bedside
So now, which tube is the vein? A few of the following criteria is sufficient for immediate recognition. This is really easy for central veins, more subtle at distal veins, yet not an issue (read).
1.
Central veins (jugular, subclavian, caval veins)
(i)
The vein is the one which is at the anatomical location of a vein (see again your anatomic lessons).
(ii)
The vein is the one not perfectly round in cross-section: it is more or less ovoid, even concave and sometimes collapsed, whereas the artery is always round (aneurism apart).
(iii)
The vein is the one, in long axis, with walls quite never fully parallel, as opposed to the artery.
(iv)
The vein is the one with ample, respiratory movements – or no movement – whereas the artery has pulsatile systolic variations, visible on real time. On occasion, the vein has a complete inspiratory collapse. On occasion, we see superimposed cardiac-rhythm variations in large veins, especially in the case of tricuspid regurgitation, but these variations are not the abrupt systolic expansion seen in the arteries. The vein flattens on spontaneous inspiration and enlarges on mechanical inspiration.
(v)
The vein is the largest of both, since 2/3 of the blood volume is stocked in the venous compartment.
(vi)
The vein may contain fine valves (see Fig. 12.4 of our 2010 Edition), and the artery may contain coarse calcifications, never the opposite.
(vii)
The normal vein content is rather less echoic than the artery.
(viii)
A particular flow can on occasion be seen in a vein, never in an artery.
(ix)
When all these clues fail, a compression can then be attempted; only a free vein should collapse (see above).
2.
Distal veins (femoral to calf veins) (iliac often)
At these areas, the features from 2 to 8 are increasingly more subtle. In practice, the compression step is more readily done. If one vessel begins to collapse, this vessel tells us it is the vein. If none of the vessels collapses, we know that one of them is a thrombosed vein, the other an artery (read Sophisticated Note 1). No matter which is the vein, the BLUE-protocol is positive. For those willing absolutely to know which one is the vein, a comparison with the other side shows the venous location (provided there is no exceptional bilateral venous thrombosis, of course). The few who will not be convinced will use the Doppler function, i.e., buy a Doppler machine.
3. Long-Axis Scans Are Not Performed
They make ultrasound more difficult. A slight rotation upsets the pattern in a long-axis view, whereas it does not affect a short-axis one (see Fig. 1.2). Let us remind that the words “longitudinal” and “transversal” are anatomical, body landmarks, whereas long axis and short axis regard only a given vessel.
For subclavian vein cannulation, we advocate a long axis (but this is no longer the BLUE-protocol).
We always use the Carmen maneuver, which allows, once a short-axis view of the vein is displayed, to see a centimetric bit of its distal and proximal aspect in a few seconds. In other words, we are short axis and long axis simultaneously in some sort.
4. Compression Is Not Performed: Not Systematically
Teachers have accustomed us to compress the veins for checking if they are thrombosed. This rather popular habit means skipping the first step of the BLUE-protocol, i.e., first observing the vein. This also maybe means that the usual “vascular” probes do not provide such a perfect image resolution. Using our 1982 technology, we are accustomed to see venous thromboses directly (Fig. 18.5). In the BLUE-protocol, “controlled compression” means slight compression, or no compression at all. When a static analysis has detected a DVT, this answered the question, and the compression technique is of no interest, possibly dangerous for no benefit.
Fig. 18.5
Subocclusive thrombosis. Echoic image indicating a thrombosis of the jugular internal vein. The free lumen is reduced to an anechoic moon shape. A slight compression maneuver should make disappear this free lumen; an increased compression should initiate an escape sign. Cross-sectional scan of the cervical vessels (A, artery)
We often see that when young doctors assess a vein, they compress it suddenly, at the moment they see it, without a breath, without a time for observation. The vein will not suddenly jump somewhere else. We must take time to locate it in the gunsight, aim, and then shoot without exaggerated haste (please, just identify the enemy before shooting!).
A normal, free vein appears homogeneous. Sometimes anechoic, sometimes just hypoechoic, mostly depending on the local acoustic conditions, but it appears always homogeneous – apart from ghosts, easily spotted. Like some microclimates, some areas quite always have a favorable surrounding: jugular internal vein in particular. In these cases, the static approach can be considered a gold standard: “black means free.” The compression here is really redundant. Subclavian and femoropopliteal veins are usually black gray.
A visible DVT yields static and dynamic signs. The dynamic signs are striking and would convince any reluctant academician, yet they are redundant to our opinion.
Static Sign: The Anatomical Image
Once we have chosen the correct unit, the correct probe, the correct probe holding, the correct axis (short axis), and the correct pressure, at the chosen location, we can now see the ultrasound image and interpret it. A thrombosis can be nonocclusive or occlusive. When it is nonocclusive, the eye of the operator immediately detects two anomalies:
There is a contrast between the anechoic (or hypoechoic) tone of the circulating fluid, and the more echoic tone of the thrombosis.
The shape of this supposed thrombosis is well defined and convex, with well-defined borders: a shape of cumulus or cauliflower.
This allows an immediate recognition (Figs. 18.5 and 18.6).
Fig. 18.6
Jugular internal vein floating thrombosis. Blatant thrombosis and comparative look. There is no video but such thrombosis, surrounded by the bloodstream, is by definition floating. This figure exploits the concept of the best compromise: this is the reprint of a reprint (original long lost), but in spite of the degradation, this image clearly demonstrates the disease. These patterns were observable at the bedside since 1992. Ultrasound is really a gold standard
When the thrombosis is occlusive, these two patterns are no longer available, but it is sometimes possible to see a tissue-like, heterogeneous, irregular pattern, standstill, striking in Fig. 18.7, and see Fig. 28.8. This semiology is striking when the caliper of the vein is large, increasingly more subtle when this caliper shrinks. Each time this pattern is not easily detected, the compression will confirm the diagnosis.
Fig. 18.7
Occlusive and extensive jugular internal venous thrombosis. Long axis. We can measure at least a 6 cm extension. Note the echoic, tissue-like standstill echogenicity, making the diagnosis of thrombosis
Simple, real-time ultrasound informs that such thromboses are more or less occlusive (Fig. 18.7), more or less extensive (Fig. 18.7), more or less floating (Fig. 28.10 and Video 28.1), and more or less infected (see Fig. 28.11). Extensive, floating, infected cases are probably more severe than others. Really, ultrasound has the power of a gold standard.
Some signs of ours:
The sequel sign: the image of (suspected) thrombosis is prolonged downstream (or upstream) by an image clearly identified as the patent vein.
The echoic flow. In some machines (at least, the old ADR-4000), it was possible to see echoic flows through the veins (see Fig. 13.14 of our 2010 Edition). This informed on the flow (not a big deal in our duties), a possible tricuspid regurgitation (sudden inversion of flow in rhythm with respiration), and mostly the venous patency.
Dynamic Signs
The Floating Thrombosis
The floating character of a DVT, although spectacular, does not add a lot to the diagnosis of DVT; it is rather a prognosis indicator. A blue patient with a floating DVT is, clearly, at the highest risk of sudden death. In the BLUE-protocol, floating patterns are rarely seen. They were likely present just before the sudden drama (i.e., patients we don’t see). They are much more often seen in the ICU, within the CLOT-protocol, presented in Chap. 28, where a video is available (Video 28.1).
For floating DVTs, ultrasound appears to us as a gold standard, making venography fully obsolete, without long descriptions.
The Adynamic Vein
A more subtle dynamic sign is the absence of dynamics. Free upper veins (internal jugular, subclavian) have usually ample movements in spontaneous breathing (negative inspiratory pressure). A standstill upper vein suggests thrombosis (Fig. 18.8).
Fig. 18.8
Occlusive thrombosis of the subclavian vein. Short axis. The vein is incompressible. The right figure, in M-mode, depicts a sensitive sign of occlusive thrombosis: complete absence of respiratory dynamics of the vein
Some Particular Images of Thrombosis
Incipient Thrombosis
Between blood and clot, there is a short transient step. The vein is soft; we are quite sure such a vein can be flattened by the probe pressure, but we never tried (we hesitate to compress). A kind of diaphanous image is visible within the venous lumen, partly fixed against the wall, partly freely floating, and nearly dancing (Fig. 18.9). A day later, a complete thrombosis is usually present.
Fig. 18.9
The Excluded Patients of the BLUE-Protocol: Who Are They? Did Their Exclusion Limit Its Value?
The BLUE-Protocol and the Diagnosis of Pneumonia
Glossary
The Ultrasound Approach of an Acute Respiratory Failure: The BLUE-Protocol
The BLUE-Points: Three Points Allowing Standardization of a BLUE-Protocol
The Extended-BLUE-Protocol
Incipiens thrombosis. Diaphanous curls are floating, dancing likes wreaths, in the lumen of this internal jugular vein. A part is fixed against the wall. This pattern appears as the first step of a rising venous thrombosis. This figure was taken in a night shift in 1989 with the ADR-4000. Just by looking at this potential, we had the feeling that bedside ultrasound was a giant, just (deeply) sleepy
Related posts:
The Excluded Patients of the BLUE-Protocol: Who Are They? Did Their Exclusion Limit Its Value?
The BLUE-Protocol and the Diagnosis of Pneumonia
Glossary
The Ultrasound Approach of an Acute Respiratory Failure: The BLUE-Protocol
The BLUE-Points: Three Points Allowing Standardization of a BLUE-Protocol
The Extended-BLUE-Protocol
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