Specific Notions of Ultrasound in the Critically Ill
time, the team should place the electrodes on non- strategic areas such as the shoulders and sternum), the tracheal tube is gently removed in order to free the cervical areas, the elbows are spread from the chest in order to study the lateral areas (lung, spleen, etc.).
Apnea is difficult to obtain because the patient is mechanically ventilated and cannot hold his breath.A nonventilated patient is often dyspneic or encephalopathic. Experience is sometimes required for this examination, but solutions do exist.
Lung ultrasound of a dyspneic patient is perfectly feasible (see Chap. 28). With a little experience, it is even possible to follow the respiratory move- ments by slight pivoting movements of the probe, and the image will remain stable. In ventilated patients, we rarely need absolute immobility. If needed, lowering the respiratory cycles to a mini- mum (or simply disconnecting the tube) will be fully effective.
Other Limitations
A sedated patient cannot show pain. Thus, this basic clinical sign will be absent when, for instance, cholecystitis is suspected. One could envisage interrupting the sedation for the duration of the examination, but this procedure remains extreme- ly theoretical. It is better to approach the patient with a different attitude: ultrasound patterns must speak for the patient. This step requires experience as well as a good clinical sense, especially true for the gallbladder.
The Advantages of Ultrasound in a Critically Ill Patient
The critically ill patient is – in a way – a privileged patient with respect to ultrasound. This patient is already sedated, and all interventional procedures From the ultrasound perspective, the critically ill
patient differs from other patients on two levels.
First, since most often comatose and immobilized in the supine position, the patient cannot partici- pate in the examination, maintain apnea, etc. Sec- ond, this patient depends more than others on optimal initial management.
The intensive care environment includes both limitations and advantages.
Limitations Due to the Patient’s Position
An ambulatory patient can easily be positioned in lateral decubitus with inspiratory apnea for study- ing the liver, or sitting for studying pleural effusions, or again with legs hanging down for venous analy- sis, etc. The problem of the critically ill patient has rarely been dealt with in the literature. In this venti- lated, sedated patient, the supine position must be exploited to its maximum. The ultrasound approach must be adapted to this position. As a consequence, the procedures described in the following pages are not always purely academic. Their sole ambition is to provide answers to critical clinical questions.
Intensivists performing echocardiography have long adapted their technique by an extensive use of the subcostal route, often the only available route.
Limitations Due to the Material
The critically ill patient is surrounded by impres- sive life-support materials: ventilator, hemodialy- sis device, pleural drainage kits, and others. The operator must make sufficient room to work com- fortably, a mandatory step for the examination to contribute fully to diagnosis. However, this obsta- cle can already be minimized by adopting a small ultrasound unit.
The barrier is lowered, thoracic electrodes are withdrawn for heart and lung study (or, to save
will be facilitated. Other remarkable features should render an ultrasound examination optimal.
For instance, mechanical ventilation can allow exploration of organs that were previously hidden, such as an inaccessible gallbladder. When the sub- costal approach is limited, it is possible to lower the diaphragm by increasing the tidal volume during a few cycles, as long as there is no risk of barotrauma.
Prolonged intensive care with parenteral feed- ing can result in a progressive decrease in digestive gas, a feature which considerably increases ultra- sound performance.
A hydric surcharge is frequent in septic patients with impaired capillary permeability. This is not an obstacle, since water is a good ultrasound con- ductor.
The feasibility of ultrasound varies with the patient and with the area. Some examinations are feasible, others are not. Among the feasible ones, some fully answer the clinical question, others do not. In our institution, a study showed a 92% feasi- bility, all areas combined [1]. The examination was classified as difficult in 29% of feasible cases. The pancreas and abdominal aorta were the main organs that could not be visualized, mainly because of gas (Table 3.1).We should immediately note that in some instances, conditions reputed to make an examination unfeasible can provide precious infor-
mation. As a simple example, a gas barrier pre- venting abdominal analysis can indicate pneu- moperitoneum perfectly. All in all, one idea should be highlighted: ultrasound examination is always indicated, since only beneficial information can emerge from this policy. To our knowledge, other studies have also found positive data [2].
Developing an efficient system to eradicate bowel gas in any critically ill patient can be of major interest. The idea is to give the physician the best conditions allowing permanent ultrasound access to the abdomen at any time. If such a method exists, is simple and nontoxic, a great step forward will be made in abdominal ultrasonography.
A supine patient offers wide access to the abdomen, the lungs, the majority of the deep veins, the maxillary sinuses, etc. The hidden side of the patient conceals information on very posterior alveolar consolidations, some small pleural effu- sions, abdominal aorta (lumbar approach), and calf veins. All these areas can, however, be basically assessed without moving the patient, since turning a critically ill patient may sometimes be harmful.
To sum up, a whole-body investigation can be performed in the supine position with maximal results.
The critically ill patient has benefited from gen- eral ultrasound studies that concluded that this examination was useful [3, 4]. Our hospital is in all 14 Chapter 3 Specific Notions of Ultrasound in the Critically Ill
Table 3.1. Feasibility of general emergency ultrasound (expressed as a percentage of cases where the item was analyzed)
Organ Explorable organ Optimal exploration Exploration with
a risk of error
Liver 96 72 22
Gallbladder 97 82 14
Right kidney 97 87 10
Left kidney 100 63 37
Spleen 98 75 22
Left pleura (via the abdominal route) 86 54 32
Right pleura (via the abdominal route) 71 58 13
Pancreas 70 51 19
Abdominal aorta 84 51 –
Peritoneum 98 NA NA
Femoral veins 98 NA NA
Internal jugular veins 98 95 3
Subclavian veins 93 87 6
Maxillary sinuses 100 100 –
Anterior lung surface 98 98 –
Lateral lung surface 92 86 6
Optic nerve 100 94 6
NA not available.
probability the first to study assessing the useful- ness of general ultrasound, handled by the inten- sivist himself, using a set-up belonging to the ICU [5]. This study showed that, as regards the classic indications of general ultrasound alone, 22% of the patients benefited from a systematic study, with a direct change in the immediate therapeutic man- agement. This study did not take into account negative results (with positive outcome on patient management), cardiac results, interventional pro- cedures and, above all, nonclassic indications such as lungs or maxillary sinuses. If it had, the percent- age of patients benefiting from the ultrasound approach would not have been 22% but a number not far from 100%. As an example, the following pages will show that it is possible to decrease irra- diation in every patient admitted to an ICU.
Conducting an Ultrasound Examination
The region of clinical interest will be studied, of course, but it is often advisable to make a complete examination. The potentials of this noninvasive test are thus exploited as fully as possible. Table 3.2 is a suggestion of an ultrasound report made with this in mind.
In good conditions, in emergency situations, the abdomen, thorax and deep veins can be analyzed in less than 10 min, or even less than 5 min with experience. The examination can be recorded in real-time without losing time taking down figures.
A precise answer to a clinical question such as checking for absence of pneumothorax, absence of thrombosis of the vein to be catheterized, absence or presence of bladder distension, etc., usually require only a few seconds.
Table 3.2. Usual ultrasound report
Ambroise-Paré Hospital Medical intensive care unit
General ultrasound
Name Date and hour
Operator Unit: Hitachi 405 Sumi, 5-MHz probe Age, history Clinical question(s)
Conditions, echogenicity of the patient
Position of the patient: supine half-sitting chair other
Ventilatory status: spontaneous or mechanical ventilation PEP 02 level Eupnea or dyspnea sedation Thorax
Lungs
Anterior analysis (level 1) lung sliding
air artifacts
Lateral analysis up to bed level (level 2) Type of artifacts
Pleural effusion Alveolar consolidation
Lateral analysis with posterior extension (level 3)
Anteroposterior examination in lateral decubitus and apex analysis (level 4):
Hemidiaphragm: location, dynamics (mm) Heart (general two-dimensional analysis)
Easiness:
Pericardium: subnormal or not Left ventricle
Diastolic diameter Systolic diameter
Global contractility: impaired low normal exaggerated Dilatation: absent mild substantial
Wall thickness
Other (asymmetry, etc.) Right ventricle
Dilated or not Free wall thin or not Contractility
Thoracic aorta (initial, arcus, descending aorta) Right pulmonary artery: exposed or not
Disinfection of the Device
Prevention of cross-infections is a major concern in the ICU. It is therefore mandatory to return the ultrasound set-up free of any harmful microbes after examination of a septic patient (or of any patient). One could logically compare an ultra- sound examination with a central venous catheter-
ization. In fact, asepsis in ultrasound is not only mandatory, but is above all very easy to follow. A small intellectual investment is the only require- ment. We must create automatic reflexes based on logic.
The first step is to define septic areas: the probe and the cable, the keyboard, the lower part of the contact product bottle. These areas will be distinct 16 Chapter 3 Specific Notions of Ultrasound in the Critically Ill
Table 3.2(continued) Abdomen
Easiness and difficulties (and reasons) Fluid peritoneal effusion: absent or other
Pneumoperitoneum: absent (present peritoneal sliding and/or splanchnogram) or else Stomach: full empty Gastric tube location
Small bowel: peristalsis present or abolished or not accessible. Wall thickness. Caliper (mm) normal or distended. Content (echoic or anechoic)
Colon: air-fluid level search Aorta: regular or else
Inferior vena cava: expiratory caliper at the left renal vein Search for thrombosis
Gallbladder: Painful or not. Global dimensions. Wall thickness. Content (anechoic or sludge or calculi).
Perivesicular effusion. Other items (wall abnormalities) or absence of these features Liver: no detectable abnormality, no portal gas in partial or exhaustive analysis, or other Intrahepatic and common bile duct: caliper (mm)
Spleen: homogeneous or not, measurement (mm) Portal veins: without anomaly or other
Pancreas: normal size and echostructure or other Kidneys: nondilated cavities or other
Bladder: full empty Uterus
Other
Deep venous trunks
Two-dimensional ultrasound, without Doppler, with the technique of soft compression Internal jugular axes (right or left dominant)
Subclavian axes Inferior vena cava Iliac axes
Femoropopliteal veins
Calf veins: compressible at least partly (%) or other Head
Optic nerves: caliper Distal bulge
Maxillary sinuses (head supine or upright) No signal or presence of sinusogram
If sinusogram present: complete or incomplete Miscellaneous
Muscle/adipose tissue ratio Others
In practice, a practical synthesis is made from these previously detailed data, with immediate management chan- ges to be envisaged. The clearest answer possible must be given to the clinical question. Positive as well as negati- ve items should be specified. Serendipitous items with immediate consequences must be recalled here.
The style of this report has been adapted for the needs of the book. It contains a maximum of information which will be printed in a minimum of time (a precious advantage in emergency situations). Some data serve as
an initial reference for later examinations. The item
»normal or other« has been created in order to avoid any ambiguity, if for instance the item was not analyzed.
from the clean areas: the cart, the disinfectant product, and the upper part of the contact product bottle. Septic and nonseptic areas should not be confused during an examination.
With a device set up before any contact with the patient, if the operator touches, after patient con- tact, only the probe, the keyboard and the contact product, only these three elements will have to be wiped down after the examination (and after hand-washing).A thousand useless gestures should be avoided, such as nonchalantly putting soiled hands on nonseptic parts of the device. The con- tact product bottle should never lie over the bed;
nor should the disinfectant be held by soiled hands. If the device has to be moved slightly, one will use the elbows, or even a foot, but not soiled hands, unless this area is carefully disinfected after the examination, which would be unnecessarily time-consuming.
The disinfectant must remain in a separate place on the cart, for instance on the lower level.
It should never be held with contaminated hands. The hands must be washed after having recovered the patient, etc. The probe is then cleaned. It should never be inserted onto its stand before being cleaned. Our procedure is to leave the probe on the bed at the end of the examination, wash our hands, then handle the cable by the end (toward the device) and clean it up to the probe itself. Note that the use of more than one probe will cause serious problems, since a contaminating gesture will be unavoidable. All these steps, at all times necessary, should become automatic and be executed in a precise order. Loss of time will be minimal and the device will remain microorgan- ism-free. The only problem will occur in case of multiple operators: each operator must trust the previous operator. We are fully convinced that, more than 150 years after Semmelweis’s first observations, physicians are aware of and take this concern to heart.
Which product should be used? The problem is that the probe must tolerate the product without being damaged. We noted that manufacturers gen- erally provided a vague answer and we have built up experience with the micro-convex, silicone- covered probe of our Hitachi Sumi unit, and a 60°
alcohol-based alkylamine bactericide spray with neutral tensioactive amphoteric pH. We have used this system since 1995, and our probe has not shown the slightest damage. Some authors have proposed 70° alcohol as a simple and efficient pro- cedure [6], but a majority of authors find alcohol
risky for the probes and not effective enough in terms of decontamination. An aldehyde-based and alcohol-based spray has been advocated [7], but this is a questionable approach since this blend fixes the proteins. Some authors again find that withdrawing all marks of gel with an absorbent towel between two patients is a good solution [8].
In hospital atmosphere and particularly in the ICU, this solution seems highly questionable.All in all, we should not forget that very precise proce- dures have been established for material disinfec- tion, but since the major problem is removing the gel (a genuine culture medium for bacteria), if gel is no longer used (see Chap. 2), these complicated and constraining procedures should be, to our opinion, forgotten.
Indications for an Ultrasound Examination
When we see the possible benefits of ultrasound for the patient as well as the drawbacks, extensive use of ultrasound clearly is beneficial. Simply admission to an ICU, regardless of the initial pos- sible diagnosis, is an obvious sign of gravity, and justifies a routine ultrasound examination. The question of whether to perform an ultrasound examination should never be raised in a critically ill patient. Too often we have seen cases evolving unfavorably, where the use of ultrasound was late, although it then immediately clarified so-called difficult diagnoses – but too late.
In practice, in our institution, a whole-body ultrasound approach is taken for each new patient admitted to the ICU. It is repeated as many times as necessary. Schematically, three steps can be described:
∑ The initial step is the initial diagnosis at admis- sion.
∑ The second step is material management. Inter- ventional ultrasound is of prime importance here (puncture of suspect areas, insertion of catheters, etc.).
∑ The third step is the follow-up of long-stay crit- ically ill patients, where complications occur (infections, thromboses, etc.).
In each of these steps, ultrasound will play a deter- mining role.
References
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2. Schunk K, Pohan D, Schild H (1992) The clinical rele- vance of sonography in intensive care units. Aktuelle Radio 2:309–314
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4. Harris RD, Simeone JF, Mueller PR, Butch RJ (1985) Portable ultrasound examinations in intensive care units. J Ultrasound Med 4:463–465
18 Chapter 3 Specific Notions of Ultrasound in the Critically Ill
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6. O’Doherty AJ, Murphy PG, Curran RA (1989) Risk of Staphylococcus aureus transmission during ultra- sound investigation. J Ultrasound Med 8:619–621 7. Pouillard F,Vilgrain V, Sinègre M, Zins M, Bruneau B,
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