Page 300 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

204 PART 2: General Management of the Patient

and the patient bed, but it is well worth the effort. Optimal machine visualization. In obese or very muscular individuals, the subclavian
position is such that the operator can look at the insertion site vessels may be difficult to image. Color Doppler imaging is always
and then the screen with minimal head movement. Gain, depth, and an option, but is usually not required.
screen orientation must be optimized. Real-time guidance of needle 8. Following needle access and insertion of the wire, a standard safety
insertion improves success rate, so that the sterile field must include precaution is to reimage the vein before dilation. The requirement is
the transducer covered with a purpose built full-length sterile cover. to identify the wire lying in longitudinal axis within the vein. This
It is inappropriate to improvise using a sterile glove as a substitute is straightforward in the internal jugular and femoral position, but
for a full-length sterile probe cover. more difficult for the subclavian vein. To check wire placement in the
3. The operator may choose a two-person method, where one person subclavian vein, the transducer may need to be placed in the supra-
holds the transducer, while the other inserts the needle. Alternatively, clavicular fossa and angled downward in coronal scanning plane to
a single operator holds the transducer in one hand and performs the identify the wire as it passes into the great veins of the thorax.
needle insertion under real-time guidance with the other. This is the ■
preferred technique of most operators. SITE-SPECIFIC ISSUES
4. Thoracic, abdominal, and vascular ultrasonography is performed Internal Jugular Vein: As part of the initial ultrasound scan to determine
with the orientation marker placed on the left of the screen and the which side is best for line insertion, the operator should examine the
transducer indicator pointed toward the right side of the patient when anterior chest in order to rule out preprocedure pneumothorax. This
scanning in transverse plane. In this manner, structures on the left precaution holds for the subclavian position as well. This may be done
side of the screen will correspond to the right side of the body. This is with the vascular transducer by identifying sliding lung (see discussion
identical to the projection used with computerized tomography (CT). below). In thick-chested patients, the vascular transducer may have
When performing internal jugular venous access from the head of the insufficient penetration, so that the cardiac transducer is required to
bed, the operator will need to decide on how to orientate the transducer identify sliding lung. Following insertion of the line, the anterior chest
indicator. When scanning from the head of the bed, most operators is again examined. Loss of lung sliding when it was present beforehand
hold the transducer such the indicator that it points toward the patients is strong evidence for procedure-related pneumothorax.
left side, when scanning in transverse plain. In any case, the operator In our experience, the internal jugular vein is best accessed using a
should standardize their approach, so as to be able direct the needle in transverse scanning plane. Optimally, the needle is introduced through
predictable fashion during real-time guidance of needle insertion. the skin at a point above the point of vessel penetration and advanced
5. For central venous access, it is important to scan both sides of the forward with simultaneous forward movement of the transducer such
body in order to select the best target. In the internal jugular posi- that the needle tip is guided into the vessel. This is often difficult to do,
tion, there can be significant variation of vessel size. The presence and many operators rely on watching for movement of the vessel wall as
of a thrombus prohibits cannulation on the ipsilateral side, and evidence of appropriate needle trajectory. This entails the risk of needle
relatively contraindicates insertion contralaterally due to the risk of insertion outside of the scanning plane. Practice on a task trainer is
bilateral thrombus formation. required to refine needle tip control. The proper catheter tip position
15,16
6. In using ultrasonography for real-time needle guidance, the operator may be documented by ultrasonography.
must choose between transverse and longitudinal scanning planes. Subclavian Vein: When using ultrasonography for guidance, the subcla-
This is by personal preference, as there is no literature that favors vian vein is best accessed from lateral chest wall location. The insertion
one or the other approach. The transverse method requires that the site may be as far lateral as the proximal portion of the axillary vein. The
operator be able to track the needle tip as it advances toward the target landmark expert is used to a more medial approach with the clavicle as a
vessel. This requires moving the needle tip forward in tandem with definitive anatomic feature used to guide needle trajectory. With ultraso-
the movement of the transducer scanning plane. The longitudinal nographic guidance, the operator does not use the clavicle as a primary
method requires that the operator keep the entire needle in clear guide, but relies on the ultrasound image. Imaging the needle in its lon-
view throughout the insertion. This is difficult, as the thickness of the gitudinal axis allows the operator to insert the needle in real time with
scanning plane may be only 1 to 2 mm. Even minimal deviation of safety, but care must be taken to visualize the entire needle throughout
8
the needle from this plane causes loss of tip visualization. With either the insertion. An oblique scanning plane may cause the operator to lose
method, repeated practice on an ultrasound mannequin model is an control of the needle tip, as the barrel of the needle may be misinterpreted
essential part of skill acquisition. It is not intuitively obvious how to as the needle tip. Loss of needle tip control may result in a pneumothorax.
track a needle during insertion, and multiple passes on a well-designed
task trainer greatly increase success rate at the bedside. Veins are sur- Femoral Vein: Femoral venous access under ultrasound guidance is
prisingly compressible, so that a frequent problem is that the needle straightforward. One benefit for the operator is that ultrasound examina-
compresses the vein to the extent that the lumen is completely effaced tion allows the operator to insert the needle into the common femoral
without blood return. This is especially common in the internal jugu- vein where it lies medial to the artery. Immediately caudad to the inguinal
lar position. The operator may pass through the back wall of the ves- ligament, the vein (now the superficial femoral vein) rotates to become
sel, and obtain blood return only upon slow withdrawal of needle as deep to the artery. Blind insertion at this point risks arterial injury.
it passes through the now open lumen. This should be avoided in the Ultrasonographic guidance avoids this pitfall of blind insertion technique.
subclavian position, due to the close proximity of the pleural surface. ■ ARTERIAL AND PERIPHERAL VENOUS ACCESS
7. A key element for safe venous access is to distinguish the vein from The principles of ultrasonographic guidance of arterial and peripheral
its paired artery. The vein is easily compressible and thin walled
compared to the adjacent artery. Veins may have mobile thin valves venous access are the same as for central venous access. Skill at difficult
peripheral venous line placement reduces the need for central venous
and exhibit respirophasic size variation. Attention to image orienta-
tion and scanning technique is helpful in identifying the vessels, access and the risks associated with it.
the artery and vein are particularly common in the internal jugular ■ PITFALLS OF ULTRASONOGRAPHY FOR GUIDANCE
but is not sufficient to be certain. Unusual positional relationship of
position. Sometimes it may be difficult to differentiate between the OF VASCULAR ACCESS
artery and the vein. For example, severe hypotension may cause The main pitfall to ultrasonographic guidance of vascular access relates
the artery to be easily compressible. Massive obesity and edema, to operator skill level. The seasoned intensivist with expert-level land-
wounds, and dressings may impair definitive ultrasonographic mark technique will have no trouble in quickly adopting the method.

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